Predictability effects in auditory scene analysis: a review
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paper_title: Pitch, harmonicity and concurrent sound segregation: Psychoacoustical and neurophysiological findings

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Harmonic complex tones are a particularly important class of sounds found in both speech and music. Although these sounds contain multiple frequency components, they are usually perceived as a coherent whole, with a pitch corresponding to the fundamental frequency (F0). However, when two or more harmonic sounds occur concurrently, e.g., at a cocktail party or in a symphony, the auditory system must separate harmonics and assign them to their respective F0s so that a coherent and veridical representation of the different sounds sources is formed. Here we review both psychophysical and neurophysiological (single-unit and evoked-potential) findings, which provide some insight into how, and how well, the auditory system accomplishes this task. A survey of computational models designed to estimate multiple F0s and segregate concurrent sources is followed by a review of the empirical literature on the perception and neural coding of concurrent harmonic sounds, including vowels, as well as findings obtained using single complex tones with mistuned harmonics.
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paper_title: Temporal coherence in the perception of tone sequences [doctoral dissertation

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A direct reduction apparatus having a means for briquetting oxide ores of iron, manganese, chrome, and copper, with a powdered coal tar pitch, means for caramelizing (hardening) the briquettes for ease of handling, subjecting the caramelized briquettes to a first temperature source until said briquettes are partially reduced to conductivity, their dimensions are substantially reduced and subsequently reducing said briquettes by subjecting them to a frequency electric induction induced heat source.
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paper_title: Contribution of harmonicity and location to auditory object formation in free field: Evidence from event-related brain potentials

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The contribution of location and harmonicity cues in sound segregation was investigated using behavioral reports and source waveforms derived from the scalp-recorded evoked potentials. Participants were presented with sounds composed of multiple harmonics in a free-field environment. The third harmonic was either tuned or mistuned and could be presented from the same or different location from the remaining harmonics. Presenting the third harmonic at a different location than the remaining harmonics increased the likelihood of hearing the tuned or slightly (i.e., 2%) mistuned harmonic as a separate object. Partials mistuned by 16% of their original value “pop out” of the complex and were paralleled by an object-related negativity (ORN) that superimposed the N1 and P2 components. For the 2% mistuned stimuli, the ORN was present only when the mistuned harmonic was presented at a different location than the remaining harmonics. Presenting the tuned harmonic at a different location also yielded changes in neu...
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paper_title: Gestalt psychology : an introduction to new concepts in modern psychology.

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Wolfgang Koehler (1887-1967) was one of the founders of Gestalt psychology, the influential school that argues that perception is best understood as an organized pattern rather than as separate parts. Penetrating in its insights and lucid in presentation, Gestalt Psychology (1947) is Koehler's definitive statement of Gestalt theory.
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paper_title: The Cocktail Party Problem

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This review presents an overview of a challenging problem in auditory perception, the cocktail party phenomenon, the delineation of which goes back to a classic paper by Cherry in 1953. In this review, we address the following issues: (1) human auditory scene analysis, which is a general process carried out by the auditory system of a human listener; (2) insight into auditory perception, which is derived from Marr's vision theory; (3) computational auditory scene analysis, which focuses on specific approaches aimed at solving the machine cocktail party problem; (4) active audition, the proposal for which is motivated by analogy with active vision, and (5) discussion of brain theory and independent component analysis, on the one hand, and correlative neural firing, on the other.
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paper_title: The free-energy principle: a unified brain theory?

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A free-energy principle has been proposed recently that accounts for action, perception and learning. This Review looks at some key brain theories in the biological (for example, neural Darwinism) and physical (for example, information theory and optimal control theory) sciences from the free-energy perspective. Crucially, one key theme runs through each of these theories — optimization. Furthermore, if we look closely at what is optimized, the same quantity keeps emerging, namely value (expected reward, expected utility) or its complement, surprise (prediction error, expected cost). This is the quantity that is optimized under the free-energy principle, which suggests that several global brain theories might be unified within a free-energy framework.
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paper_title: An experimental evaluation of three theories of auditory stream segregation

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Three theories of auditory stream segregation were evaluated. In two-part trials, subjects heard an induction sequence, whose effects upon an immediately subsequent test sequence were measured. The rhythm and total duration of Induction Sequence tones were varied in two experiments. The similarity between induction and test sequences aided segregation, but rhythmic predictability and longer tone durations did not. Frequency alternation during the induction sequence was not necessary to induce segregation in the test sequence. Furthermore, peripheral processes inadequately account for the segregation effects found. The data suggest that, once a distinct percept emerges from an auditory scene, properties derived from the percept (particularly changes) are fed back to control the ongoing analysis of that auditory scene. A neural adaptation to stimuli with constant properties may form part of this analysis.
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paper_title: Modelling the Emergence and Dynamics of Perceptual Organisation in Auditory Streaming

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Many sound sources can only be recognised from the pattern of sounds they emit, and not from the individual sound events that make up their emission sequences. Auditory scene analysis addresses the difficult task of interpreting the sound world in terms of an unknown number of discrete sound sources (causes) with possibly overlapping signals, and therefore of associating each event with the appropriate source. There are potentially many different ways in which incoming events can be assigned to different causes, which means that the auditory system has to choose between them. This problem has been studied for many years using the auditory streaming paradigm, and recently it has become apparent that instead of making one fixed perceptual decision, given sufficient time, auditory perception switches back and forth between the alternatives-a phenomenon known as perceptual bi- or multi-stability. We propose a new model of auditory scene analysis at the core of which is a process that seeks to discover predictable patterns in the ongoing sound sequence. Representations of predictable fragments are created on the fly, and are maintained, strengthened or weakened on the basis of their predictive success, and conflict with other representations. Auditory perceptual organisation emerges spontaneously from the nature of the competition between these representations. We present detailed comparisons between the model simulations and data from an auditory streaming experiment, and show that the model accounts for many important findings, including: the emergence of, and switching between, alternative organisations; the influence of stimulus parameters on perceptual dominance, switching rate and perceptual phase durations; and the build-up of auditory streaming. The principal contribution of the model is to show that a two-stage process of pattern discovery and competition between incompatible patterns can account for both the contents (perceptual organisations) and the dynamics of human perception in auditory streaming.
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paper_title: Concurrent sound segregation based on inharmonicity and onset asynchrony

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Abstract To explore the neural processes underlying concurrent sound segregation, auditory evoked fields (AEFs) were measured using magnetoencephalography (MEG). To induce the segregation of two auditory objects we manipulated harmonicity and onset synchrony. Participants were presented with complex sounds with (i) all harmonics in-tune (ii) the third harmonic mistuned by 8% of its original value (iii) the onset of the third harmonic delayed by 160 ms compared to the other harmonics. During recording, participants listened to the sounds and performed an auditory localisation task whereas in another session they ignored the sounds and performed a visual localisation task. Active and passive listening was chosen to evaluate the contribution of attention on sound segregation. Both cues – inharmonicity and onset asynchrony – elicited sound segregation, as participants were more likely to report correctly on which side they heard the third harmonic when it was mistuned or delayed compared to being in-tune with all other harmonics. AEF activity associated with concurrent sound segregation was identified over both temporal lobes. We found an early deflection at ∼75 ms (P75m) after sound onset, probably reflecting an automatic registration of the mistuned harmonic. Subsequent deflections, the object-related negativity (ORNm) and a later displacement (P230m) seem to be more general markers of concurrent sound segregation, as they were elicited by both mistuning and delaying the third harmonic. Results indicate that the ORNm reflects relatively automatic, bottom-up sound segregation processes, whereas the P230m is more sensitive to attention, especially with inharmonicity as the cue for concurrent sound segregation.
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paper_title: Auditory Scene Analysis: The Perceptual Organization of Sound

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Auditory Scene Analysis addresses the problem of hearing complex auditory environments, using a series of creative analogies to describe the process required of the human auditory system as it analyzes mixtures of sounds to recover descriptions of individual sounds. In a unified and comprehensive way, Bregman establishes a theoretical framework that integrates his findings with an unusually wide range of previous research in psychoacoustics, speech perception, music theory and composition, and computer modeling.
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paper_title: A theory of cortical responses

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This article concerns the nature of evoked brain responses and the principles underlying their generation. We start with the premise that the sensory brain has evolved to represent or infer the causes of changes in its sensory inputs. The problem of inference is well formulated in statistical terms. The statistical fundaments of inference may therefore afford important constraints on neuronal implementation. By formulating the original ideas of Helmholtz on perception, in terms of modern-day statistical theories, one arrives at a model of perceptual inference and learning that can explain a remarkable range of neurobiological facts. It turns out that the problems of inferring the causes of sensory input (perceptual inference) and learning the relationship between input and cause (perceptual learning) can be resolved using exactly the same principle. Specifically, both inference and learning rest on minimizing the brain’s free energy, as defined in statistical physics. Furthermore, inference and learning can proceed in a biologically plausible fashion. Cortical responses can be seen as the brain’s attempt to minimize the free energy induced by a stimulus and thereby encode the most likely cause of that stimulus. Similarly, learning emerges from changes in synaptic efficacy that minimize the free energy, averaged over all stimuli encountered. The underlying scheme rests on empirical Bayes and hierarchical models of how sensory input is caused. The use of hierarchical models enables the brain to construct prior expectations in a dynamic and context-sensitive fashion. This scheme provides a principled way to understand many aspects of cortical organization and responses. The aim of this article is to encompass many apparently unrelated anatomical, physiological and psychophysical attributes of the brain within a single theoretical perspective. In terms of cortical architectures, the theoretical treatment predicts that sensory cortex should be arranged hierarchically, that connections should be reciprocal and that forward and backward connections should show a functional asymmetry (forward connections are driving, whereas backward connections are both driving and modulatory). In terms of synaptic physiology, it predicts associative plasticity and, for dynamic models, spike-timing-dependent plasticity. In terms of electrophysiology, it accounts for classical and extra classical receptive field effects and long-latency or endogenous components of evoked cortical responses. It predicts the attenuation of responses encoding prediction error with perceptual learning and explains many phenomena such as repetition suppression, mismatch negativity (MMN) and the P300 in electroencephalography. In psychophysical terms, it accounts for the behavioural correlates of these physiological phenomena, for example, priming and global precedence. The final focus of this article is on perceptual learning as measured with the MMN and the implications for empirical studies of coupling among cortical areas using evoked sensory responses.
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paper_title: Time, our lost dimension: toward a new theory of perception, attention, and memory

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A theory of perception and attention that emphasizes the relational nature o{ perceptual invariants is developed within the context of auditory pattern research. The theory is divided into two parts. The first part, addresses world pattern structure; the second describes interaction of organisms with pattern structure. Tn the former, world patterns arc subjectively represented as nested relations within a multidimensional space defined by pilch, loudncss, and time. But dependency of these defining dimensions means that a pattern's lime scale determines the serial integrity of its pitch/loudness structure. Second, the theory proposes a time scale for living things that is manifest in graded perceptual rhythms. These rhythms can be synchronized to corresponding nested time zones within world pattern structure. Related assumptions about the deployment of physical energy across time zones and cognitive locations of perceptual rhythms lead to a simple, but general, attentional theory. Theoretical support, found in research with tone patterns, speech, and sequences of noise is died in a final section. Beyond this focal research, the theory offers a general framework for understanding diverse phenomena thai range from speech perception and aphasia to sleep, growth, and time eslimation.
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paper_title: Interpreting the mismatch negativity.

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The widely accepted "memory-mismatch" interpretation of the mismatch negativity (MMN) event-related brain potential (ERP) suggests that an MMN is elicited when an acoustic event deviates from a memory record describing the immediate history of the sound sequence. The first variant of the memory-mismatch theory suggested that the memory underlying MMN generation was a strong auditory sensory memory trace, which encoded the repetitive standard sound. This "trace-mismatch" explanation of MMN has been primarily based on results obtained in the auditory oddball paradigm. However, in recent years, MMN has been observed in stimulus paradigms containing no frequently repeating sound. We now suggest a different variant of the memory-mismatch interpretation of MMN in order to provide a unified explanation of all MMN phenomena. The regularity-violation explanation of MMN assumes that the memory records retaining the history of auditory stimulation are regularity representations. These representations encode rules extracted from the regular intersound relationships, which are mapped to the concrete sound sequence by finely detailed auditory sensory information. Auditory events are compared with temporally aligned predictions drawn from the regularity representations (predictive models) and the observable MMN response reflects a process updating the representations of those detected regularities whose prediction was mismatched by the acoustic input. It is further suggested that the auditory deviance detection system serves to organize sound in the brain: The predictive models maintained by the MMN-generating process provide the basis of temporal grouping, a crucial step in the formation of auditory
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paper_title: Early electrophysiological indicators for predictive processing in audition: a review.

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Abstract The auditory system essentially deals with sequential type of input and thus requires processing that is particularly suited to extract stimulus relations within a sequence. Evidence from a variety of paradigms converges to show that the auditory system automatically uses stimulus predictability for facilitating its sequential processing. This type of predictive processing does not require attentional processing of the sounds or cognitive control of the predictions, nor does it involve the preparation of motor responses to the auditory stimuli. We will present a taxonomy of paradigms and resulting electrophysiological indicators for such automatic predictive processing in terms of event-related potential components and oscillatory activity. These indicators will include signals of fulfilled predictions (match signals such as N1 attenuation, repetition positivity, and early evoked gamma band response enhancement) as well as signals of violated predictions (mismatch signals such as the mismatch negativity and stimulus omission responses). We will show how recent approaches have revealed particularly early indicators of predictive processing down to the level of the auditory middle-latency responses. We will discuss the strength of the various indicators in terms of a truly predictive account of auditory processing (as opposed to, e.g., a retrospective verification of predictions). Finally, we will discuss the benefits of a predictive system within and beyond auditory processing. In conclusion, we argue in favor of the overwhelming evidence for predictions in audition, flexibly instantiated on different levels and timescales, and we aim to provide guidance along a variety of research paradigms illustrating the existence of these predictions.
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paper_title: Brain Generators Implicated in the Processing of Auditory Stimulus Deviance: A Topographic Event-Related Potential Study

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The neurophysiological mechanisms underlying mismatch negativity (MMN) can be inferred from an examination of some of the brain generators involved in the process of this event-related potential (ERP) component. ERPs were recorded in two studies in which the subjects were involved in a selective dichotic listening task. Subjects were required to silently count rare stimuli deviating in pitch from a sequence of standard stimuli in one ear, while ignoring all the stimuli (standards and deviants) delivered randomly to the other ear. The results showed that, in all cases, the negative wave elicited by the deviant stimuli showed the highest amplitudes over the right hemiscalp irrespective of the ear of stimulation or the direction of attention. Scalp radial current density analysis showed that this asymmetric potential distribution could be attributed to the sum of activities of two sets of neural generators: one temporal, located in the vicinity of the primary auditory cortex, predominantly activated in the hemisphere contralateral to the ear of stimulation, and the other frontal, involving mainly the right hemisphere. ::: ::: ::: ::: The results are discussed in light of Naatanen's model: we suggest the dissociation of two functional processes on the basis of activity of distinct brain areas: a sensory memory mechanism related to the temporal generators, and an automatic attention-switching process related to the frontal generators.
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paper_title: Electrophysiological evidence for the hierarchical organization of auditory change detection in the human brain

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Auditory change detection has been associated with mismatch negativity (MMN), an event-related potential (ERP) occurring at 100–250 ms after the onset of an acoustic change. Yet, single-unit recordings in animals suggest much faster novelty-specific responses in the auditory system. To investigate change detection in a corresponding early time range in humans, we measured the Middle Latency Response (MLR) and MMN during a controlled frequency oddball paradigm. In addition to MMN, an early effect of change detection was observed at about 40 ms after change onset reflected in an enhancement of the Nb component of the MLR. Both MMN and the Nb effect were shown to be free from confounding influences such as differences in refractoriness. This finding implies that early change detection processes exist in humans upstream of MMN generation, which supports the emerging view of a hierarchical organization of change detection expanding along multiple levels of the auditory pathway. Descriptors: Middle-latency response, Auditory processing, Deviance detection, MMN
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paper_title: Mismatch negativity (MMN), the deviance-elicited auditory deflection, explained

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The current review constitutes the first comprehensive look at the possibility that the mismatch negativity (MMN, the deflection of the auditory ERP/ERF elicited by stimulus change) might be generated by so-called fresh-afferent neuronal activity. This possibility has been repeatedly ruled out for the past 30 years, with the prevailing theoretical accounts relying on a memory-based explanation instead. We propose that the MMN is, in essence, a latency- and amplitude-modulated expression of the auditory N1 response, generated by fresh-afferent activity of cortical neurons that are under nonuniform levels of adaptation. Descriptors: Mismatch negativity (MMN), N1, N100, Event-related potential, Event-related field, Electroencephalography, Magnetoencephalography, Human, Auditory, Memory, Attention, Computational modeling, Cortex, Adaptation, Lateral inhibition
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paper_title: Automatic auditory intelligence: An expression of the sensory–cognitive core of cognitive processes

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Abstract In this article, we present a new view on the nature of cognitive processes suggesting that there is a common core, viz., automatic sensory–cognitive processes that form the basis for higher-order cognitive processes. It has been shown that automatic sensory–cognitive processes are shared by humans and various other species and occur at different developmental stages and even in different states of consciousness. This evidence, based on the automatic electrophysiological change-detection response mismatch negativity (MMN), its magnetoencephalographic equivalent MMNm, and behavioral data, indicates that in audition surprisingly complex processes occur automatically and mainly in the sensory-specific cortical regions. These processes include, e.g. stimulus anticipation and extrapolation, sequential stimulus–rule extraction, and pattern and pitch-interval encoding. Furthermore, these complex perceptual–cognitive processes, first found in waking adults, occur similarly even in sleeping newborns, anesthetized animals, and deeply sedated adult humans, suggesting that they form the common perceptual–cognitive core of cognitive processes in general. Although the present evidence originates mainly from the auditory modality, it is likely that analogous evidence could be obtained from other sensory modalities when measures corresponding to those used in the study of the auditory modality become available.
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paper_title: Perceptions as Hypotheses

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Perceptions may be compared with hypotheses in science. The methods of acquiring scientific knowledge provide a working paradigm for investigating processes of perception. Much as the information channels of instruments, such as radio telescopes, transmit signals which are processed according to various assumptions to give useful data, so neural signals are processed to give data for perception. To understand perception, the signal codes and the stored knowledge or assumptions used for deriving perceptual hypotheses must be discovered. Systematic perceptual errors are important clues for appreciating signal channel limitations, and for discovering hypothesis-generating procedures. Although this distinction between 'physiological' and 'cognitive' aspects of perception may be logically clear, it is in practice surprisingly difficult to establish which are responsible even for clearly established phenomena such as the classical distortion illusions. Experimental results are presented, aimed at distinguishing between and disconvering what happens when there is mismatch with the neural signal channel, and when neural signals are processed inappropriately for the current situation. This leads us to make some distinctions between perceptual and scientific hypotheses, which raise in a new form the problem: What are 'objects'?
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paper_title: Long-latency evoked potentials to irrelevant, deviant stimuli.

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Occasional shifts of loudness in a repetitive train of clicks elicited a late-positive wave (P3a) in nonattending subjects which peaked at a mean latency of 258 msec and had a fronto-central scalp distribution; and P3a was typically preceded by an “N2” component at 196 msec. The P3a wave was distinguishable from the longer-latency (378 msec) parieto-centrally distributed “P3b” wave, that was evoked by the same stimulus in an actively attending subject, thus confirming the findings of Squires et al . Infrequently presented single sounds did not produce large or consistent N2-P3a components; the critical condition for the generation of an N2-P3a wave seemed to be that the infrequent sounds represent a deviation (intensity increment or decrement) from a repetitive background. Furthermore, increasing the repetition rate of the background clicks drastically reduced Nl-P2 amplitude but had little effect on the amplitude of N2-P3a. This suggests that N2-P3a is not simply a delayed N1-P2 “vertex potential”, but rather reflects the operation of a “mismatch” detector, which registers deviations from an ongoing auditory background.
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paper_title: Attention and brain function

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This book delineates cerebral mechanisms of attention in humans as they presently appear in the light of data obtained by using various modern brain-research techniques. While the book focuses primarily on the ways humans select environmental information, the selectivity manifest in human thinking, consciousness, and motor behavior is also dealt with in the framework of an expanded attention concept. By combining the most recent evidence from diverse fields of human brain research and relating these physiological data to achievements of modern cognitive psychology, the author has developed an integrative view of human information processing. This theory concentrates on mechanisms of attentional selection and on the automatic processing which provides a basis for the selective processes.
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paper_title: I Heard That Coming: Event-Related Potential Evidence for Stimulus-Driven Prediction in the Auditory System

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The auditory system has been shown to detect predictability in a tone sequence, but does it use the extracted regularities for actually predicting the continuation of the sequence? The present study sought to find evidence for the generation of such predictions. Predictability was manipulated in an isochronous series of tones in which every other tone was a repetition of its predecessor. The existence of predictions was probed by occasionally omitting either the first (unpredictable) or the second (predictable) tone of a same-frequency tone pair. Event-related electrical brain activity elicited by the omission of an unpredictable tone differed from the response to the actual tone right from the tone onset. In contrast, early electrical brain activity elicited by the omission of a predictable tone was quite similar to the response to the actual tone. This suggests that the auditory system preactivates the neural circuits for expected input, using sequential predictions to specifically prepare for future acoustic events.
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paper_title: What Re-Enactment Earns Us

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Evidence from both behavioural and brain studies suggests that perception of actions and their outcomes may induce (overt or covert) production of related actions in perceivers. Three views of the proper function of such re-enactment have been suggested: imitation, identification, and anticipation. Here I propose that the proper function of re-enactment is to subserve anticipation of upcoming action. Re-enactment exploits the motor system's inbuilt capacity to anticipate the consequences of action and extends it from the planning of own action to the perception of foreign action.
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paper_title: Attentive novelty detection in humans is governed by pre-attentive sensory memory

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BEING able to detect unusual, possibly dangerous events in the environment is a fundamental ability that helps ensure the survival of biological organisms1–3. Novelty detection requires a memory system that models (builds neural representations of) events in the environment, so that changes are detected because they violate the predictions of the model. The earliest physiologically measurable brain response to novel auditory stimuli is the mismatch negativity4, MMN, a component of the event-related potential. It is elicited when a predictable series of unvarying stimuli is unex-pectedly followed by a deviating stimulus5. As the occurrence of MMN is not usually affected by the direction of attention5–7, MMN reflects the operation of automatic sensory (echoic) memory8, the earliest memory system that builds traces of the acoustic environment against which new stimuli can be compared5. The dependence of attentive novelty detection on earlier, pre-atten-tive processes, however, has remained elusive. Previous, related studies9–12 seem to suggest a relationship between MMN and atten-tive processes, although no conclusive evidence has so far been shown. Here we address novelty detection in humans both on a physiological and behavioural level, and show how attentive novelty detection is governed by a pre-attentive sensory memory mechanism.
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paper_title: The free-energy principle: a unified brain theory?

paper_content:

A free-energy principle has been proposed recently that accounts for action, perception and learning. This Review looks at some key brain theories in the biological (for example, neural Darwinism) and physical (for example, information theory and optimal control theory) sciences from the free-energy perspective. Crucially, one key theme runs through each of these theories — optimization. Furthermore, if we look closely at what is optimized, the same quantity keeps emerging, namely value (expected reward, expected utility) or its complement, surprise (prediction error, expected cost). This is the quantity that is optimized under the free-energy principle, which suggests that several global brain theories might be unified within a free-energy framework.
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paper_title: Repetition effects to sounds: evidence for predictive coding in the auditory system

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Grill-Spector, Henson and Martin [1] recently reviewed evidence for neural repetition effects in the visual system. They discussed models that account for behavioural facilitation and reduced neural activity after stimulus repetition (‘repetition suppression’), measured using single-unit recording and human ERP and fMRI. Here I discuss studies that support and extend such effects to audition.
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paper_title: Early selective-attention effect on evoked potential reinterpreted ☆

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Abstract In a dichotic listening situation stimuli were presented one at a time and at random to either ear of the subject at constant inter-stimulus intervals of 800 msec. The subject's task was to detect and count occasional slightly different stimuli in one ear. In Experiment 1, these ‘signal’ stimuli were slightly louder, and in Experiment 2 they had a slightly higher pitch, than the much more frequent, ‘standard’, stimuli. In both experiments signals occured randomly at either ear. Separate evoked potentials from three different locations were recorded for each of the four kinds of stimuli (attended signals, unattended signals, attended standards, unattended standards). Contrary to Hillyard et al. (1973), no early (N 1 component) evoked-potential enhancement was observed to stimuli to the attended ear as compared with those to the unattended ear, but there was a later negative shift superimposed on potentials elicited by the former stimuli. This negative shift was considered identical to the N 1 enhancement of Hillyard and his colleagues which in the present study was forced, by the longer inter-stimulus interval used, to demonstrate temporal dissociation with the N 1 component. The ‘Hillyard effect’ was, consequently, explained as being caused by a superimposition of a CNV kind of negative shift on the evoked potential to the attended stimuli rather than by a growth of the ‘real’ N 1 component of the evoked potential.
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paper_title: Memory‐based or afferent processes in mismatch negativity (MMN): A review of the evidence

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AbstractThemismatchnegativity(MMN)isanelectromagneticresponsetoanydiscriminablechangeinregularauditoryinput.This response is usually interpreted as being generated by an automatic cortical change-detection process in which adifference is found between the current input and the representation of the regular aspects of the preceding auditoryinput. Recently, this interpretation was questioned by Ja¨a¨skela¨inen et al. (2004) who proposed that the MMN is aproduct of an N1 (N1a) difference wave emerging in the subtraction procedure used to visualize and quantify theMMN. We now evaluate this ‘‘adaptationhypothesis’’ ofthe MMN inthelightoftheavailable data. It isshown thatthe MMN cannot be accounted for by differential activation of the afferent N1 transient detectors by repetitive(‘‘standard’’)stimulianddeviant(‘‘novel’’)stimuliandthatthepresenceofamemoryrepresentationofthestandardisrequired for the elicitation of MMN.Descriptors: Auditory event-related potential (AERP), Auditory change, Mismatch negativity (MMN),Feature-detector adaptation, N1The Memory-Trace Explanation of the MMNThemismatchnegativity (MMN) isanelectromagneticresponseto a discriminable change in any regular (e.g., repetitive) aspectofauditorystimulation,whichusuallypeaksat150–200msfromchange onset and is elicited even in the absence of attention(Na¨a¨ta¨nen, Gaillard, & Ma¨ntysalo, 1978). A commonly accept-ed interpretation of the MMN is that it is generated by an au-tomatic change-detection process in which a disconcordance isfoundbetweentheinputfromthedeviantauditoryeventandthesensory-memory representationoftheregularaspectsofthepre-ceding auditory stimulation (for reviews, see Na¨a¨ta¨nen, 2001;Na¨a¨ta¨nen & Winkler, 1999). It was further proposed that thischange-detection process occurs preperceptually in the auditorycortices (generating the auditory-cortex subcomponent of theMMN), which in turn triggers frontal-cortex processes (gener-ating the frontal MMN subcomponent and in part the subse-quent P3a; Alho et al., 1998) underlying the possible attentionswitch to and conscious perception of stimulus change (Giard,Perrin, Pernier, & Bouchet, 1990; Na¨a¨ta¨nen, 1990; Na¨a¨ta¨nen M Rinne, Alho, Ilmoniemi, Virtanen, & Na¨a¨ta¨nen,2000).This interpretation postulates an MMN-generator processthat is separate from the afferent processes triggered by both thefrequent (‘‘standard’’) and infrequent (‘‘deviant’’) stimuli (orstimulus events), that is, that separate memory-related neuronalactivity is involved rather than just new (or fresh) afferent ele-ments, those activated by the deviants but not by the standards(see,e.g.,Na¨a¨ta¨nenA for a review,
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paper_title: Mismatch Negativity: Different Water in the Same River

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The mismatch negativity (MMN) is a frontal negative deflection in the human event-related potential that typically occurs when a repeating auditory stimulus changes in some manner. The MMN can be elicited by many kinds of stimulus change, varying from simple changes in a single stimulus feature to abstract changes in the relationship between stimuli. The main intracerebral sources for the MMN are located in the auditory cortices of the temporal lobe. Since it occurs whether or not stimuli are being attended, the MMN represents an automatic cerebral process for detecting change. The MMN is clinically helpful in terms of demonstrating disordered sensory processing or disordered memory in groups of patients. Improvements in the techniques for measuring the MMN and in the paradigms for eliciting it will be needed before the MMN can become clinically useful as an objective measurement of such disorders in individual patients.
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paper_title: Differential Contribution of Frontal and Temporal Cortices to Auditory Change Detection: fMRI and ERP Results

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The present study addresses the functional role of the temporal and frontal lobes in auditory change detection. Prior event-related potential (ERP) research suggested that the mismatch negativity (MMN) reflects the involvement of a temporofrontal network subserving auditory change detection processes and the initiation of an involuntary attention switch. In the present study participants were presented with repetitive spectrally rich sounds. Infrequent changes of either small (10% change), medium (30% change), or large (100% change) magnitude were embedded in the stimulus train. ERPs and fMRI measures were obtained in the same subjects in subsequent sessions. Significant hemodynamic activation in the superior temporal gyri (STG) bilaterally and the opercular part of the right inferior frontal gyrus was observed for large and medium deviants only. ERPs showed that small deviants elicited MMN when presented in silence but not when presented with recorded MR background noise, indicating that small deviants were hardly detected under fMRI conditions. The MR signal change in temporal lobe regions was larger for large than for medium deviants. For the right fronto-opercular cortex the opposite pattern was observed. The strength of the temporal activation correlated with the amplitude of the change-related ERP at around 110 ms from stimulus onset while the frontal activation correlated with the change-related ERP at around 150 ms. These results suggest that the right fronto-opercular cortex is part of the neural network generating the MMN. Three alternative explanations of these findings are discussed. © 2002 Elsevier Science
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paper_title: Adaptive modeling of the unattended acoustic environment reflected in the mismatch negativity event-related potential

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Abstract The mismatch negativity (MMN) event-related potential is elicited by changes in repetitive auditory stimuli. The present paper suggests that: (1) an acoustic model of the auditory environment is maintained even in the absence of attention focussed on auditory stimuli, preattentively detecting repetitive features of the acoustic stimulation; and (2) the MMN reflects modifications to existing parts of this model during incorporation of a new stimulus into the model. MMN responses were investigated during the period when a repetitive stimulus (standard) was replaced by a new standard sound. It was found that whereas the new standard stimulus stopped eliciting an MMN after its third presentation with respect to the old standard, a probe stimulus, differing from both standards, elicited an MMN with respect to the old standard, even when following four presentations of the new standard. The probe stimulus also elicited an MMN with respect to the new standard after four or more presentations of this new standard stimulus, thus eliciting two consecutive MMNs. The comparison (conducted on the basis of the present and some previous findings) of the present hypothesis with alternative explanations of MMN based on the presence and strength of auditory transient memory traces supported the model adjustment hypothesis.
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paper_title: A theory of cortical responses

paper_content:

This article concerns the nature of evoked brain responses and the principles underlying their generation. We start with the premise that the sensory brain has evolved to represent or infer the causes of changes in its sensory inputs. The problem of inference is well formulated in statistical terms. The statistical fundaments of inference may therefore afford important constraints on neuronal implementation. By formulating the original ideas of Helmholtz on perception, in terms of modern-day statistical theories, one arrives at a model of perceptual inference and learning that can explain a remarkable range of neurobiological facts. It turns out that the problems of inferring the causes of sensory input (perceptual inference) and learning the relationship between input and cause (perceptual learning) can be resolved using exactly the same principle. Specifically, both inference and learning rest on minimizing the brain’s free energy, as defined in statistical physics. Furthermore, inference and learning can proceed in a biologically plausible fashion. Cortical responses can be seen as the brain’s attempt to minimize the free energy induced by a stimulus and thereby encode the most likely cause of that stimulus. Similarly, learning emerges from changes in synaptic efficacy that minimize the free energy, averaged over all stimuli encountered. The underlying scheme rests on empirical Bayes and hierarchical models of how sensory input is caused. The use of hierarchical models enables the brain to construct prior expectations in a dynamic and context-sensitive fashion. This scheme provides a principled way to understand many aspects of cortical organization and responses. The aim of this article is to encompass many apparently unrelated anatomical, physiological and psychophysical attributes of the brain within a single theoretical perspective. In terms of cortical architectures, the theoretical treatment predicts that sensory cortex should be arranged hierarchically, that connections should be reciprocal and that forward and backward connections should show a functional asymmetry (forward connections are driving, whereas backward connections are both driving and modulatory). In terms of synaptic physiology, it predicts associative plasticity and, for dynamic models, spike-timing-dependent plasticity. In terms of electrophysiology, it accounts for classical and extra classical receptive field effects and long-latency or endogenous components of evoked cortical responses. It predicts the attenuation of responses encoding prediction error with perceptual learning and explains many phenomena such as repetition suppression, mismatch negativity (MMN) and the P300 in electroencephalography. In psychophysical terms, it accounts for the behavioural correlates of these physiological phenomena, for example, priming and global precedence. The final focus of this article is on perceptual learning as measured with the MMN and the implications for empirical studies of coupling among cortical areas using evoked sensory responses.
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paper_title: Prediction of external events with our motor system : towards a new framework

paper_content:

We cannot, in the proper sense, imitate or re-enact inanimate events, such as ocean waves rolling, or even non-human animate ones, such as dogs walking. However, we can anticipate the way they change and recent studies show that our motor system becomes involved while doing so. A novel framework is presented that accounts for these findings by generalizing a predictive account of the motor system from action to event perception. It is suggested that we predict events that we cannot reproduce ourselves by exploiting an audiomotor or visuomotor representation that never amounts to a real action because it lacks proprioceptive and other interoceptive information. This view inspires thinking beyond our customary conceptualization of a ‘motor' system.
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paper_title: ‘Primitive intelligence’ in the auditory cortex

paper_content:

Abstract The everyday auditory environment consists of multiple simultaneously active sources with overlapping temporal and spectral acoustic properties. Despite the seemingly chaotic composite signal impinging on our ears, the resulting perception is of an orderly ‘auditory scene' that is organized according to sources and auditory events, allowing us to select messages easily, recognize familiar sound patterns, and distinguish deviant or novel ones. Recent data suggest that these perceptual achievements are mainly based on processes of a cognitive nature (‘sensory intelligence') in the auditory cortex. Even higher cognitive processes than previously thought, such as those that organize the auditory input, extract the common invariant patterns shared by a number of acoustically varying sounds, or anticipate the auditory events of the immediate future, occur at the level of sensory cortex (even when attention is not directed towards the sensory input).
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paper_title: Interpreting the mismatch negativity.

paper_content:

The widely accepted "memory-mismatch" interpretation of the mismatch negativity (MMN) event-related brain potential (ERP) suggests that an MMN is elicited when an acoustic event deviates from a memory record describing the immediate history of the sound sequence. The first variant of the memory-mismatch theory suggested that the memory underlying MMN generation was a strong auditory sensory memory trace, which encoded the repetitive standard sound. This "trace-mismatch" explanation of MMN has been primarily based on results obtained in the auditory oddball paradigm. However, in recent years, MMN has been observed in stimulus paradigms containing no frequently repeating sound. We now suggest a different variant of the memory-mismatch interpretation of MMN in order to provide a unified explanation of all MMN phenomena. The regularity-violation explanation of MMN assumes that the memory records retaining the history of auditory stimulation are regularity representations. These representations encode rules extracted from the regular intersound relationships, which are mapped to the concrete sound sequence by finely detailed auditory sensory information. Auditory events are compared with temporally aligned predictions drawn from the regularity representations (predictive models) and the observable MMN response reflects a process updating the representations of those detected regularities whose prediction was mismatched by the acoustic input. It is further suggested that the auditory deviance detection system serves to organize sound in the brain: The predictive models maintained by the MMN-generating process provide the basis of temporal grouping, a crucial step in the formation of auditory
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paper_title: A blackboard architecture for computational auditory scene analysis

paper_content:

Abstract A challenging problem for research in computational auditory scene analysis is the integration of evidence derived from multiple grouping principles. We describe a computational model which addresses this issue through the use of a `blackboard' architecture. The model integrates evidence from multiple grouping principles at several levels of abstraction, and manages competition between principles in a manner that is consistent with psychophysical findings. In addition, the blackboard architecture allows heuristic knowledge to influence the organisation of an auditory scene. We demonstrate that the model can replicate listeners' perception of interleaved melodies, and is also able to segregate melodic lines from polyphonic, multi-timbral audio recordings. The applicability of the blackboard architecture to speech processing tasks is also discussed.
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paper_title: Controlled attending as a function of melodic and temporal context

paper_content:

Melodic and rhythmic context were systematically varied in a pattern recognition task involving pairs (standard-comparison) of nine-tone auditory sequences. The experiment was designed to test the hypothesis that rhythmic context can direct attention toward or away from tones which instantiate higher order melodic rules. Three levels of melodic structure (one, two, no higher order rules) were crossed with four levels of rhythm [isochronous, dactyl (A U U), anapest (U U A), irregular]. Rhythms were designed to shift accent locations on three centrally embedded tones. Listeners were more accurate in detecting violations of higher order melodic rules when the rhythmic context induced accents on tones which instantiated these rules. Effects are discussed in terms of attentional rhythmicity.
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paper_title: Role of predictability of sequence in auditory stream segregation

paper_content:

This study evaluates the role of item predictability in auditory temporal coherence. Thirteen normal-hearing subjects were required to hold together long tonal sequences as single strings of notes. Temporal and spectral predictability of successive notes in a sequence varied as a function of experimental condition. As the frequency separation of the notes in the sequence increased, the subjects found it more difficult to hold the sequence together as a single stream. There was no significant difference in subjects’ abilities in performing this task as a function of experimental condition. That is, the predictability of successive notes appeared not to have a role in temporal coherence.
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paper_title: Modeling the auditory scene: predictive regularity representations and perceptual objects

paper_content:

Predictive processing of information is essential for goal-directed behavior. We offer an account of auditory perception suggesting that representations of predictable patterns, or 'regularities', extracted from the incoming sounds serve as auditory perceptual objects. The auditory system continuously searches for regularities within the acoustic signal. Primitive regularities may be encoded by neurons adapting their response to specific sounds. Such neurons have been observed in many parts of the auditory system. Representations of the detected regularities produce predictions of upcoming sounds as well as alternative solutions for parsing the composite input into coherent sequences potentially emitted by putative sound sources. Accuracy of the predictions can be utilized for selecting the most likely interpretation of the auditory input. Thus in our view, perception generates hypotheses about the causal structure of the world.
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paper_title: The development of rhythmic attending in auditory sequences: attunement, referent period, focal attending

paper_content:

Abstract This paper is divided into three sections. The first section is theoretical; it extends Dynamic Attending Theory (Jones, M. R. Psychological Review 83 (1976) 323; Jones, M. R. Perception and Psychophysics 41(6) (1987) 631; Jones, M. R. Psychomusicology 9(2) (1990) 193; Jones, M. R., & Boltz, M. Psychological Review 96(3) (1989) 459) to developmental questions concerning tempo and time hierarchies. Generally Dynamic Attending Theory proposes that, when listening to a complex auditory sequence, listeners spontaneously focus on events occurring at an intermediate rate (the referent level), and they then may shift attention to events occurring over longer or shorter time spans, that is at lower (faster) or higher (slower) hierarchical levels (focal attending). The second section of the paper is experimental. It examines maturational changes of three dynamic attending activities involving referent period and level, attunement, and focal attending. Tasks involve both motor tapping (including spontaneous motor tempo and synchronization with simple sequences and music) and tempo discrimination. We compare performances by 4-, 6-, 8-, and 10-year-old children and adults, with or without musical training. Results indicate three changes with increased age and musical training: (1) a slowing of the mean spontaneous tapping rate (a reflection of the referent period) and mean synchronization rate (a reflection of the referent level), (2) enhanced ability to synchronize tapping and discriminate tempo (improved attunement), and (3) an enlarged range of tapping rates towards slower rates and higher hierarchical levels (improved focal attending). A final section considers results in light of the theory proposed here. It is suggested that growth trends can be expressed in terms of listeners' engagement of slower attending oscillators with age and experience, accompanied by the passage from the initial use of a single oscillator towards the coupling of multiple oscillators.
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paper_title: Human auditory cortex tracks task-irrelevant sound sources

paper_content:

The brain organizes sound into coherent sequences, termed auditory streams. We asked whether task-irrelevant sounds would be detected as separate auditory streams in a natural listening environment that included three simultaneously active sound sources. Participants watched a movie with sound while street-noise and sequences of naturally varying footstep sounds were presented in the background. Occasional deviations in the footstep sequences elicited the mismatch negativity (MMN) event-related potential. The elicitation of MMN showed that the regular features of the footstep sequences had been registered and their violations detected, which could only occur if the footstep sequence had been detected as a separate auditory stream. Our results demonstrate that sounds are organized into auditory streams irrespective of their relevance to ongoing behavior.
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paper_title: An automatic speech recognition system based on the scene analysis account of auditory perception

paper_content:

Despite many years of concentrated research, the performance gap between automatic speech recognition (ASR) and human speech recognition (HSR) remains large. The difference between ASR and HSR is particularly evident when considering the response to additive noise. Whereas human performance is remarkably robust, ASR systems are brittle and only operate well within the narrow range of noise conditions for which they were designed. This paper considers how humans may achieve noise robustness. We take the view that robustness is achieved because the human perceptual system treats the problems of speech recognition and sound source separation as being tightly coupled. Taking inspiration from Bregman's Auditory Scene Analysis account of auditory organisation, we present a speech recognition system which couples these processes by using a combination of primitive and schema-driven processes: first, a set of coherent spectro-temporal fragments is generated by primitive segmentation techniques; then, a decoder based on statistical ASR techniques performs a simultaneous search for the correct background/foreground segmentation and word sequence hypothesis. Mutually supporting solutions to both the source segmentation and speech recognition problems arise as a result. The decoder is tested on a challenging corpus of connected digit strings mixed monaurally at 0dB and recognition performance is compared with that achieved by listeners using identical data. The results, although preliminary, are encouraging and suggest that techniques which interface ASA and statistical ASR have great potential. The paper concludes with a discussion of future research directions that may further develop this class of perceptually motivated ASR solutions.
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paper_title: Preattentive evaluation of multiple perceptual streams in human audition.

paper_content:

To analyze an auditory scene, the segregation of the input into separate streams of information is necessary. Here, the mismatch negativity (MMN) of the event-related potential was used to trace the number of simultaneously monitored streams in auditory scene analysis. Subjects passively listened to sounds belonging to either one, two, or three auditory streams defined by spatial position and pitch. An MMN was obtained for deviants within either one, two or three auditory streams albeit with a smaller amplitude in the latter condition. Control experiments ruled out that this effect was due to variations in stimulation rate.Thus, a preattentive deviant detection system based on simple auditory features provides the basis for subsequent attentive processing directed to a selected stream.
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paper_title: Automatic auditory intelligence: An expression of the sensory–cognitive core of cognitive processes

paper_content:

Abstract In this article, we present a new view on the nature of cognitive processes suggesting that there is a common core, viz., automatic sensory–cognitive processes that form the basis for higher-order cognitive processes. It has been shown that automatic sensory–cognitive processes are shared by humans and various other species and occur at different developmental stages and even in different states of consciousness. This evidence, based on the automatic electrophysiological change-detection response mismatch negativity (MMN), its magnetoencephalographic equivalent MMNm, and behavioral data, indicates that in audition surprisingly complex processes occur automatically and mainly in the sensory-specific cortical regions. These processes include, e.g. stimulus anticipation and extrapolation, sequential stimulus–rule extraction, and pattern and pitch-interval encoding. Furthermore, these complex perceptual–cognitive processes, first found in waking adults, occur similarly even in sleeping newborns, anesthetized animals, and deeply sedated adult humans, suggesting that they form the common perceptual–cognitive core of cognitive processes in general. Although the present evidence originates mainly from the auditory modality, it is likely that analogous evidence could be obtained from other sensory modalities when measures corresponding to those used in the study of the auditory modality become available.
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paper_title: Evidence for Rhythmic Attention.

paper_content:

Three studies compared effects of different rhythmic contexts on order judgments of targets embedded in auditory patterns designed to manifest auditory stream segregation. Of interest was the effect of rhythmic structure upon the frequency-based captor effect, wherein tones in one stream "capture" those of similar frequencies from another. Three rhythmic structures were studied. Experiment 1 compared a rhythm conducive to pairwise-target stream formation with one conducive to a four-tone stream, and one based on an isochronous rhythm in a within-subjects design. Patterns embedding the target tone pair contained a preliminary string of captor tones at frequencies either close or far from frequencies of distracting tones that flanked the target pair. No effect of captor distance was found. Experiments 2 and 3 varied rhythm between subjects using 9- and 11-tone patterns, respectively. In general, the magnitude of the captor effect was found to vary with temporal predictability of flanking and/or target tones. The pairwise rhythm was most likely to improve order judgments by facilitating frequency-based capture. Results are discussed in terms of a rhythmic attentional hypothesis. Language: en
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paper_title: Using Knowledge to Organize Sound: The Prediction-Driven Approach to Computational Auditory Scene Analysis, and Its Application to Speech/nonspeech Mixtures

paper_content:

Computational auditory scene analysis ‐ modeling the human ability to organize sound mixtures according to their sources ‐ has experienced a rapid evolution as the simple principles suggested by psychological experiments have turned out to be less than the whole story. Phenomena such as the continuity illusion and phonemic restoration show that the brain is able to use a wide range of knowledge-based contextual constraints when interpreting obscured or complex mixtures: To model such processing, we need architectures that operate by confirming hypotheses about the observations rather than relying on directly-extracted descriptions. One such architecture, the ‘prediction-driven’ approach, is presented along with results from its initial implementation. This architecture can be extended to take advantage of the high-level knowledge implicit in today’s speech recognizers by modifying a recognizer to act as one of the ‘component models’ which provide the explanations of the signal mixture. Although this adaptation raises a number of issues, a preliminary investigation supports the argument that successful scene analysis must exploit such abstract knowledge at every level.
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paper_title: Dynamic sound stream formation based on continuity of spectral change

paper_content:

Abstract A proposed computational model that dynamically tracks and predicts changes in spectral shapes was verified in both psychophysical experiments and engineering applications. The results of the psychophysical experiments confirmed the model's validity and suggested that `the rule of good continuity' also held in audition. Furthermore, a stream segregation system was implemented with the proposed model. It was composed of simultaneous grouping and sequential integration processes. An effective integration of two processes was performed by dynamically controlling the sequential integration based on the reliability of the output of the simultaneous grouping. Finally, we applied this system to phonemic restoration and segregation of two simultaneous utterances, showing the proposed model to be effective for such engineering applications.
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paper_title: An experimental evaluation of three theories of auditory stream segregation

paper_content:

Three theories of auditory stream segregation were evaluated. In two-part trials, subjects heard an induction sequence, whose effects upon an immediately subsequent test sequence were measured. The rhythm and total duration of Induction Sequence tones were varied in two experiments. The similarity between induction and test sequences aided segregation, but rhythmic predictability and longer tone durations did not. Frequency alternation during the induction sequence was not necessary to induce segregation in the test sequence. Furthermore, peripheral processes inadequately account for the segregation effects found. The data suggest that, once a distinct percept emerges from an auditory scene, properties derived from the percept (particularly changes) are fed back to control the ongoing analysis of that auditory scene. A neural adaptation to stimuli with constant properties may form part of this analysis.
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paper_title: Schema-based processing in auditory scene analysis.

paper_content:

Laboratoire de Psychologie Experimentale (CNRS), Universite Rene Descartes, Paris, France What is the involvement of what we know in what we perceive? In this article, the contribution of melodic schema-based processes to the perceptual organization of tone sequences is examined. Two unfamiliar six-tone melodies, one of which was interleaved with distractor tones, were presented successively to listeners who were required to decide whether the melodies were identical or different. In one condition, the comparison melody was presented after the mixed sequence: a target melody interleaved with distractor tones. In another condition, it was presented beforehand, so that the listeners had precise knowledge about the melody to be extracted from the mixture. In the latter condition, recognition performance was better and a bias towardsame responses was reduced, as compared with the former condition. A third condition, in which the comparison melody presented beforehand was transposed up in frequency, revealed that whereas the performance improvement was explained in part by absolute pitch or frequency priming, relative pitch representation (interval and/or contour structure) may also have played a role. Differences in performance as a function of mean frequency separation between target and distractor sequences, when listeners did or did not have prior knowledge about the target melody, argue for a functional distinction between primitive and schema-based processes in auditory scene analysis.
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paper_title: ARTSTREAM: a neural network model of auditory scene analysis and source segregation

paper_content:

Multiple sound sources often contain harmonics that overlap and may be degraded by environmental noise. The auditory system is capable of teasing apart these sources into distinct mental objects, or streams. Such an 'auditory scene analysis' enables the brain to solve the cocktail party problem. A neural network model of auditory scene analysis, called the ARTSTREAM model, is presented to propose how the brain accomplishes this feat. The model clarifies how the frequency components that correspond to a given acoustic source may be coherently grouped together into a distinct stream based on pitch and spatial location cues. The model also clarifies how multiple streams may be distinguished and separated by the brain. Streams are formed as spectral-pitch resonances that emerge through feedback interactions between frequency-specific spectral representations of a sound source and its pitch. First, the model transforms a sound into a spatial pattern of frequency-specific activation across a spectral stream layer. The sound has multiple parallel representations at this layer. A sound's spectral representation activates a bottom-up filter that is sensitive to the harmonics of the sound's pitch. This filter activates a pitch category which, in turn, activates a top-down expectation that is also sensitive to the harmonics of the pitch. Resonance develops when the spectral and pitch representations mutually reinforce one another. Resonance provides the coherence that allows one voice or instrument to be tracked through a noisy multiple source environment. Spectral components are suppressed if they do not match harmonics of the top-down expectation that is read-out by the selected pitch, thereby allowing another stream to capture these components, as in the 'old-plus-new heuristic' of Bregman. Multiple simultaneously occurring spectral-pitch resonances can hereby emerge. These resonance and matching mechanisms are specialized versions of Adaptive Resonance Theory, or ART, which clarifies how pitch representations can self-organize during learning of harmonic bottom-up filters and top-down expectations. The model also clarifies how spatial location cues can help to disambiguate two sources with similar spectral cues. Data are simulated from psychophysical grouping experiments, such as how a tone sweeping upwards in frequency creates a bounce percept by grouping with a downward sweeping tone due to proximity in frequency, even if noise replaces the tones at their intersection point. Illusory auditory percepts are also simulated, such as the auditory continuity illusion of a tone continuing through a noise burst even if the tone is not present during the noise, and the scale illusion of Deutsch whereby downward and upward scales presented alternately to the two ears are regrouped based on frequency proximity, leading to a bounce percept. Since related sorts of resonances have been used to quantitatively simulate psychophysical data about speech perception, the model strengthens the hypothesis that ART-like mechanisms are used at multiple levels of the auditory system. Proposals for developing the model to explain more complex streaming data are also provided.
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paper_title: The role of predictive models in the formation of auditory streams

paper_content:

Abstract Sounds provide us with useful information about our environment which complements that provided by other senses, but also poses specific processing problems. How does the auditory system distentangle sounds from different sound sources? And what is it that allows intermittent sound events from the same source to be associated with each other? Here we review findings from a wide range of studies using the auditory streaming paradigm in order to formulate a unified account of the processes underlying auditory perceptual organization. We present new computational modelling results which replicate responses in primary auditory cortex [Fishman, Y.I., Arezzo, J.C., Steinschneider, M., 2004. Auditory stream segregation in monkey auditory cortex: effects of frequency separation, presentation rate, and tone duration. J. Acoust. Soc. Am. 116, 1656–1670; Fishman, Y. I., Reser, D. H., Arezzo, J.C., Steinschneider, M., 2001. Neural correlates of auditory stream segregation in primary auditory cortex of the awake monkey. Hear. Res. 151, 167–187] to tone sequences. We also present the results of a perceptual experiment which confirm the bi-stable nature of auditory streaming, and the proposal that the gradual build-up of streaming may be an artefact of averaging across many subjects [Pressnitzer, D., Hupe, J. M., 2006. Temporal dynamics of auditory and visual bi-stability reveal common principles of perceptual organization. Curr. Biol. 16(13), 1351–1357.]. Finally we argue that in order to account for all of the experimental findings, computational models of auditory stream segregation require four basic processing elements; segregation, predictive modelling, competition and adaptation, and that it is the formation of effective predictive models which allows the system to keep track of different sound sources in a complex auditory environment.
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paper_title: Auditory Scene Analysis: The Perceptual Organization of Sound

paper_content:

Auditory Scene Analysis addresses the problem of hearing complex auditory environments, using a series of creative analogies to describe the process required of the human auditory system as it analyzes mixtures of sounds to recover descriptions of individual sounds. In a unified and comprehensive way, Bregman establishes a theoretical framework that integrates his findings with an unusually wide range of previous research in psychoacoustics, speech perception, music theory and composition, and computer modeling.
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paper_title: Processing of complex stimuli and natural scenes in the auditory cortex

paper_content:

Neuronal responses in auditory cortex show a fascinating mixture of characteristics that span the range from almost perfect copies of physical aspects of the stimuli to extremely complex context-dependent responses. Fast, highly stimulus-specific adaptation and slower plastic mechanisms work together to constantly adjust neuronal response properties to the statistics of the auditory scene. Evidence with converging implications suggests that the neuronal activity in primary auditory cortex represents sounds in terms of auditory objects rather than in terms of invariant acoustic features.
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paper_title: Time, our lost dimension: toward a new theory of perception, attention, and memory

paper_content:

A theory of perception and attention that emphasizes the relational nature o{ perceptual invariants is developed within the context of auditory pattern research. The theory is divided into two parts. The first part, addresses world pattern structure; the second describes interaction of organisms with pattern structure. Tn the former, world patterns arc subjectively represented as nested relations within a multidimensional space defined by pilch, loudncss, and time. But dependency of these defining dimensions means that a pattern's lime scale determines the serial integrity of its pitch/loudness structure. Second, the theory proposes a time scale for living things that is manifest in graded perceptual rhythms. These rhythms can be synchronized to corresponding nested time zones within world pattern structure. Related assumptions about the deployment of physical energy across time zones and cognitive locations of perceptual rhythms lead to a simple, but general, attentional theory. Theoretical support, found in research with tone patterns, speech, and sequences of noise is died in a final section. Beyond this focal research, the theory offers a general framework for understanding diverse phenomena thai range from speech perception and aphasia to sleep, growth, and time eslimation.
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paper_title: Role of predictability of sequence in auditory stream segregation

paper_content:

This study evaluates the role of item predictability in auditory temporal coherence. Thirteen normal-hearing subjects were required to hold together long tonal sequences as single strings of notes. Temporal and spectral predictability of successive notes in a sequence varied as a function of experimental condition. As the frequency separation of the notes in the sequence increased, the subjects found it more difficult to hold the sequence together as a single stream. There was no significant difference in subjects’ abilities in performing this task as a function of experimental condition. That is, the predictability of successive notes appeared not to have a role in temporal coherence.
---
paper_title: An experimental evaluation of three theories of auditory stream segregation

paper_content:

Three theories of auditory stream segregation were evaluated. In two-part trials, subjects heard an induction sequence, whose effects upon an immediately subsequent test sequence were measured. The rhythm and total duration of Induction Sequence tones were varied in two experiments. The similarity between induction and test sequences aided segregation, but rhythmic predictability and longer tone durations did not. Frequency alternation during the induction sequence was not necessary to induce segregation in the test sequence. Furthermore, peripheral processes inadequately account for the segregation effects found. The data suggest that, once a distinct percept emerges from an auditory scene, properties derived from the percept (particularly changes) are fed back to control the ongoing analysis of that auditory scene. A neural adaptation to stimuli with constant properties may form part of this analysis.
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paper_title: A Source Analysis of the Late Human Auditory Evoked Potentials

paper_content:

The intracerebral generators of the human auditory evoked potentials were estimated using dipole source analysis of 14-channel scalp recordings. The response to a 400-msec toneburst presented every 0.9 sec could be explained by three major dipole sources in each temporal lobe. The first was a vertically oriented dipole located on the supratemporal plane in or near the auditory koniocortex. This contributed to the scalp-recorded N1 wave at 100 msec. The second was a vertically oriented dipole source located on the supratemporal plane somewhat anterior to the first. This contributed to both the Nl and the sustained potential (SP). The third was a laterally oriented dipole source that perhaps originated in the magnopyramidal temporal field. This contributed a negative wave to the lateral scalp recordings at the latency of 145 msec. A change in the frequency of the toneburst elicited an additional negativity in the scalp-recording ---the mismatch negativity (MMN). When the frequency change was large, the mismatch negativity was composed of two distinct sources with sequential but partially overlapping activities. The earlier corresponded to the Nl dipole sources and the later to a more anteriorly located dipole with an orientation more lateral than Nl. Only the later source was active when the frequency change was small. MMN source activities peaked about 15 msec earlier in the contralateral hemisphere, while this difference was only 4 msec for the sources of the Nl.
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paper_title: Interpreting the mismatch negativity.

paper_content:

The widely accepted "memory-mismatch" interpretation of the mismatch negativity (MMN) event-related brain potential (ERP) suggests that an MMN is elicited when an acoustic event deviates from a memory record describing the immediate history of the sound sequence. The first variant of the memory-mismatch theory suggested that the memory underlying MMN generation was a strong auditory sensory memory trace, which encoded the repetitive standard sound. This "trace-mismatch" explanation of MMN has been primarily based on results obtained in the auditory oddball paradigm. However, in recent years, MMN has been observed in stimulus paradigms containing no frequently repeating sound. We now suggest a different variant of the memory-mismatch interpretation of MMN in order to provide a unified explanation of all MMN phenomena. The regularity-violation explanation of MMN assumes that the memory records retaining the history of auditory stimulation are regularity representations. These representations encode rules extracted from the regular intersound relationships, which are mapped to the concrete sound sequence by finely detailed auditory sensory information. Auditory events are compared with temporally aligned predictions drawn from the regularity representations (predictive models) and the observable MMN response reflects a process updating the representations of those detected regularities whose prediction was mismatched by the acoustic input. It is further suggested that the auditory deviance detection system serves to organize sound in the brain: The predictive models maintained by the MMN-generating process provide the basis of temporal grouping, a crucial step in the formation of auditory
---
paper_title: Different roles of similarity and predictability in auditory stream segregation

paper_content:

Sound sources often emit trains of discrete sounds, such as a series of footsteps. Previously, two different principles have been suggested for how the human auditory system binds discrete sounds together into perceptual units. The feature similarity principle is based on linking sounds with similar characteristics over time. The predictability principle is based on linking sounds that follow each other in a predictable manner. The present study compared the effects of these two principles. Participants were presented with tone sequences and instructed to continuously indicate whether they perceived a single coherent sequence or two concurrent streams of sound. We investigated the influence of separate manipulations of similarity and predictability on these perceptual reports. Both grouping principles affected perception of the tone sequences, albeit with different characteristics. In particular, results suggest that whereas predictability is only analyzed for the currently perceived sound organization, f...
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paper_title: Role of predictability of sequence in auditory stream segregation

paper_content:

This study evaluates the role of item predictability in auditory temporal coherence. Thirteen normal-hearing subjects were required to hold together long tonal sequences as single strings of notes. Temporal and spectral predictability of successive notes in a sequence varied as a function of experimental condition. As the frequency separation of the notes in the sequence increased, the subjects found it more difficult to hold the sequence together as a single stream. There was no significant difference in subjects’ abilities in performing this task as a function of experimental condition. That is, the predictability of successive notes appeared not to have a role in temporal coherence.
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paper_title: Organization of sequential sounds in auditory memory

paper_content:

A repeating five-tone pattern was presented at several stimulus rates (200, 400, 600, and 800 ms onset-to-onset) to determine at what temporal proximity the five-tone repeating unit would be represented in memory. The mismatch negativity component of event-related brain potentials was used to index how the sounds were organized in memory when participants had no task with the sounds. Only at the 200-ms onset-to-onset pace was the five-tone sequence unitized in memory. At presentation rates of 400 ms and above, the regularity (a different frequency tone occurred every fifth tone) was not detected and mismatch negativity was elicited by these tones in the sequence. The results show that temporal proximity plays a role in unitizing successive sounds in auditory memory. These results also suggest that global relationships between successive sounds are represented at the level of auditory cortices.
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paper_title: Modeling the auditory scene: predictive regularity representations and perceptual objects

paper_content:

Predictive processing of information is essential for goal-directed behavior. We offer an account of auditory perception suggesting that representations of predictable patterns, or 'regularities', extracted from the incoming sounds serve as auditory perceptual objects. The auditory system continuously searches for regularities within the acoustic signal. Primitive regularities may be encoded by neurons adapting their response to specific sounds. Such neurons have been observed in many parts of the auditory system. Representations of the detected regularities produce predictions of upcoming sounds as well as alternative solutions for parsing the composite input into coherent sequences potentially emitted by putative sound sources. Accuracy of the predictions can be utilized for selecting the most likely interpretation of the auditory input. Thus in our view, perception generates hypotheses about the causal structure of the world.
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paper_title: Processing of Complex Auditory Patterns in Musicians and Nonmusicians

paper_content:

In the present study we investigated the capacity of the memory store underlying the mismatch negativity (MMN) response in musicians and nonmusicians for complex tone patterns. While previous studies have focused either on the kind of information that can be encoded or on the decay of the memory trace over time, we studied capacity in terms of the length of tone sequences, i.e., the number of individual tones that can be fully encoded and maintained. By means of magnetoencephalography (MEG) we recorded MMN responses to deviant tones that could occur at any position of standard tone patterns composed of four, six or eight tones during passive, distracted listening. Whereas there was a reliable MMN response to deviant tones in the four-tone pattern in both musicians and nonmusicians, only some individuals showed MMN responses to the longer patterns. This finding of a reliable capacity of the short-term auditory store underlying the MMN response is in line with estimates of a three to five item capacity of the short-term memory trace from behavioural studies, although pitch and contour complexity covaried with sequence length, which might have led to an understatement of the reported capacity. Whereas there was a tendency for an enhancement of the pattern MMN in musicians compared to nonmusicians, a strong advantage for musicians could be shown in an accompanying behavioural task of detecting the deviants while attending to the stimuli for all pattern lengths, indicating that long-term musical training differentially affects the memory capacity of auditory short-term memory for complex tone patterns with and without attention. Also, a left-hemispheric lateralization of MMN responses in the six-tone pattern suggests that additional networks that help structuring the patterns in the temporal domain might be recruited for demanding auditory processing in the pitch domain.
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paper_title: Stability of Perceptual Organisation in Auditory Streaming

paper_content:

In everyday situations, we perceive sounds organised according to their source, and can follow someone’s speech or a musical piece in the presence of other sounds without apparent effort. Thus, it is surprising that recent evidence obtained in the most widely used experimental test-bed of auditory scene analysis, the two-tone streaming paradigm, demonstrated extensive bistability even in regions of the parameter space previously thought to be strongly biased towards a particular organisation. This raises the question of what aspects of the rich natural input allow the auditory system to form stable representations of concurrently active sound sources. Here, we report the results of perceptual studies aimed at testing this issue. It is possible that the extreme repetitiveness of the alternating two-tone sequence, i.e. lack of change, causes perceptual instability. Our first experiment addressed this hypothesis by introducing random changes in the stimulation. It is also possible that under natural conditions, multiple redundant cues stabilise perception. The second experiment tested this hypothesis by adding a second cue which favoured one organisation. Much to our surprise, neither one of these manipulations stabilised the perception of two-tone streaming sequences. We discuss these experimental results in the light of our previous theoretical proposals and findings of significant differences between the first and later perceptual phases. We argue that multi-stability is inherent in perception. However, it is normally hidden by switches of attention, which allow the return of the dominant perceptual organisation resulting in the subjective experience of perceptual stability. In our third experiment, we explored this possibility by inserting short gaps into the sequences, since gaps have been shown to reset auditory streaming in a manner similar to switches in attention.
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paper_title: Temporal coherence in the perception of tone sequences [doctoral dissertation

paper_content:

A direct reduction apparatus having a means for briquetting oxide ores of iron, manganese, chrome, and copper, with a powdered coal tar pitch, means for caramelizing (hardening) the briquettes for ease of handling, subjecting the caramelized briquettes to a first temperature source until said briquettes are partially reduced to conductivity, their dimensions are substantially reduced and subsequently reducing said briquettes by subjecting them to a frequency electric induction induced heat source.
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paper_title: Effect of rhythmic attention on the segregation of interleaved melodies

paper_content:

As previously suggested, attention may increase segregation via enhancement and suppression sensory mechanisms. To test this hypothesis, we proposed an interleaved melody paradigm with two rhythm conditions applied to familiar target melodies and unfamiliar distractor melodies sharing pitch and timbre properties. When rhythms of both target and distractor were irregular, target melodies were identified above chance level. A sensory enhancement mechanism guided by listeners’ knowledge may have helped to extract targets from the interleaved sequence. When the distractor was rhythmically regular, performance was increased, suggesting that the distractor may have been suppressed by a sensory suppression mechanism.
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paper_title: Temporal predictability as a grouping cue in the perception of auditory streams

paper_content:

This study reports a role of temporal regularity on the perception of auditory streams. Listeners were presented with two-tone sequences in an A-B-A-B rhythm that was either regular or had a controlled amount of temporal jitter added independently to each of the B tones. Subjects were asked to report whether they perceived one or two streams. The percentage of trials in which two streams were reported substantially and significantly increased with increasing amounts of temporal jitter. This suggests that temporal predictability may serve as a binding cue during auditory scene analysis.
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paper_title: Age-related changes in the use of regular patterns for auditory scene analysis

paper_content:

Abstract A recent approach to auditory processing suggests a close relationship of regularity processing in auditory sensory memory (ASM) and stream segregation, such that within-stream regularities can be used to stabilize stream segregation. The present study investigates age-related changes in how regular patterns are used for auditory scene analysis (ASA), when the stream containing the regularity is attended or unattended. In order to accomplish an intensity level deviant detection task, participants had to segregate the task-relevant pure tone sequence from an irrelevant distractor pure tone sequence, which randomly varied in level. In three conditions a simple spectro-temporal regularity (“Isochronous”), a more complex spectro-temporal regularity (“Rhythmic”), or no regularity (“Random”) was embedded in either the attended target sequence (Experiment 1), or the unattended distractor sequence (Experiment 2). When the sequence containing the regularity was attended, older participants showed a similar increase of performance to younger adults in the conditions with regular patterns (“Isochronous” and “Rhythmic”) compared to the “Random” condition. In contrast, when the sequence containing the regularity was unattended, older adults showed a specific performance decline compared to younger adults in the “Isochronous” condition. Results suggest a link between impaired automatic processing of regularities in ASM, and age-related deficits in the use of regular patterns for ASA.
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paper_title: Regularity Extraction from Non-Adjacent Sounds

paper_content:

The regular behavior of sound sources helps us to make sense of the auditory environment. Regular patterns may, for instance, convey information on the identity of a sound source (such as the acoustic signature of a train moving on the rails). Yet typically, this signature overlaps in time with signals emitted from other sound sources. It is generally assumed that auditory regularity extraction cannot operate upon this mixture of signals because it only finds regularities between adjacent sounds. In this view, the auditory environment would be grouped into separate entities by means of readily available acoustic cues such as separation in frequency and location. Regularity extraction processes would then operate upon the resulting groups. Our new experimental evidence challenges this view. We presented two interleaved sound sequences which overlapped in frequency range and shared all acoustic parameters. The sequences only differed in their underlying regular patterns. We inserted deviants into one of the sequences to probe whether the regularity was extracted. In the first experiment, we found that these deviants elicited the mismatch negativity (MMN) component. Thus the auditory system was able to find the regularity between the non-adjacent sounds. Regularity extraction was not influenced by sequence cohesiveness as manipulated by the relative duration of tones and silent inter-tone-intervals. In the second experiment, we showed that a regularity connecting non-adjacent sounds was discovered only when the intervening sequence also contained a regular pattern, but not when the intervening sounds were randomly varying. This suggests that separate regular patterns are available to the auditory system as a cue for identifying signals coming from distinct sound sources. Thus auditory regularity extraction is not necessarily confined to a processing stage after initial sound grouping, but may precede grouping when other acoustic cues are unavailable.
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paper_title: Role of pattern, regularity, and silent intervals in auditory stream segregation based on inter-aural time differences

paper_content:

Tone triplets separated by a pause (ABA_) are a popular tone-repetition pattern to study auditory stream segregation. Such triplets produce a galloping rhythm when integrated, but isochronous rhythms when segregated. Other patterns lacking a pause may produce less-prominent rhythmic differences but stronger streaming. Here, we evaluated whether this difference is readily explained by the presence of the pause and potentially associated with the reduction of adaptation, or whether there is contribution of tone pattern per se. Sequences with repetitive ABA_ and ABAA patterns were presented in magnetoencephalography. A and B tones were separated by differences in inter-aural time differences (ΔITD). Results showed that the stronger streaming of ABAA was associated with a more prominent release from the adaptation of the P1m in auditory cortex. We further compared behavioral streaming responses for patterns with and without pauses, and varied the position of the pause and pattern regularity. Results showed a major effect of the pauses’ presence, but no prominent effects of tone pattern or pattern regularity. These results make a case for the existence of an early, primitive streaming mechanism that does not require an analysis of the tone pattern at later stages suggested by predictive-coding models of auditory streaming. The results are better explained by the simpler population-separation model and stress the previously observed role of neural adaptation for streaming perception.
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paper_title: Regular patterns stabilize auditory streams

paper_content:

The auditory system continuously parses the acoustic environment into auditory objects, usually representing separate sound sources. Sound sources typically show characteristic emission patterns. These regular temporal sound patterns are possible cues for distinguishing sound sources. The present study was designed to test whether regular patterns are used as cues for source distinction and to specify the role that detecting these regularities may play in the process of auditory stream segregation. Participants were presented with tone sequences, and they were asked to continuously indicate whether they perceived the tones in terms of a single coherent sequence of sounds (integrated) or as two concurrent sound streams (segregated). Unknown to the participant, in some stimulus conditions, regular patterns were present in one or both putative streams. In all stimulus conditions, participants’ perception switched back and forth between the two sound organizations. Importantly, regular patterns occurring in e...
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paper_title: An experimental evaluation of three theories of auditory stream segregation

paper_content:

Three theories of auditory stream segregation were evaluated. In two-part trials, subjects heard an induction sequence, whose effects upon an immediately subsequent test sequence were measured. The rhythm and total duration of Induction Sequence tones were varied in two experiments. The similarity between induction and test sequences aided segregation, but rhythmic predictability and longer tone durations did not. Frequency alternation during the induction sequence was not necessary to induce segregation in the test sequence. Furthermore, peripheral processes inadequately account for the segregation effects found. The data suggest that, once a distinct percept emerges from an auditory scene, properties derived from the percept (particularly changes) are fed back to control the ongoing analysis of that auditory scene. A neural adaptation to stimuli with constant properties may form part of this analysis.
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paper_title: An investigation of the auditory streaming effect using event-related brain potentials

paper_content:

There is uncertainty concerning the extent to which the auditory streaming effect is a function of attentive or preattentive mechanisms. The mismatch negativity ~MMN!, which indexes preattentive acoustic processing, was used to probe whether the segregation associated with the streaming effect occurs preattentively. In Experiment 1, alternating high and low tones were presented at fast and slow paces while subjects ignored the stimuli. At the slow pace, tones were heard as alternating high and low pitches, and no MMN was elicited. At the fast pace a streaming effect was induced and an MMN was observed for the low stream, indicating a preattentive locus for the streaming effect. The high deviant did not elicit an MMN. MMNs were obtained to both the high and low deviants when the interval between the across-stream deviance was lengthened to more than 250 ms in Experiment 2, indicating that the MMN system is susceptible to processing constraints. Descriptors: Auditory stream segregation, Mismatch negativity, Event-related potentials, Streaming effect, Auditory sensory memory
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paper_title: The role of predictive models in the formation of auditory streams

paper_content:

Abstract Sounds provide us with useful information about our environment which complements that provided by other senses, but also poses specific processing problems. How does the auditory system distentangle sounds from different sound sources? And what is it that allows intermittent sound events from the same source to be associated with each other? Here we review findings from a wide range of studies using the auditory streaming paradigm in order to formulate a unified account of the processes underlying auditory perceptual organization. We present new computational modelling results which replicate responses in primary auditory cortex [Fishman, Y.I., Arezzo, J.C., Steinschneider, M., 2004. Auditory stream segregation in monkey auditory cortex: effects of frequency separation, presentation rate, and tone duration. J. Acoust. Soc. Am. 116, 1656–1670; Fishman, Y. I., Reser, D. H., Arezzo, J.C., Steinschneider, M., 2001. Neural correlates of auditory stream segregation in primary auditory cortex of the awake monkey. Hear. Res. 151, 167–187] to tone sequences. We also present the results of a perceptual experiment which confirm the bi-stable nature of auditory streaming, and the proposal that the gradual build-up of streaming may be an artefact of averaging across many subjects [Pressnitzer, D., Hupe, J. M., 2006. Temporal dynamics of auditory and visual bi-stability reveal common principles of perceptual organization. Curr. Biol. 16(13), 1351–1357.]. Finally we argue that in order to account for all of the experimental findings, computational models of auditory stream segregation require four basic processing elements; segregation, predictive modelling, competition and adaptation, and that it is the formation of effective predictive models which allows the system to keep track of different sound sources in a complex auditory environment.
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paper_title: The role of temporal regularity in auditory segregation.

paper_content:

Abstract The idea that predictive modelling and extraction of regularities plays a pivotal role in auditory segregation has recently attracted considerable attention. The present study investigated the effect of one basic form of regularity, rhythmic regularity, on auditory stream segregation. We departed from the classic streaming paradigm and developed a new stimulus, Rand-AB, consisting of two, concurrently presented, temporally uncorrelated, tone sequences (with frequencies A and B). To evaluate segregation, we used an objective measure of the extent to which listeners are able to selectively attend to one of the sequences in the presence of the other. Performance was quantified on a difficult pattern detection task which involves detecting a rarely occurring pattern of amplitude modulation applied to three consecutive A or B tones. In all cases the attended sequence was temporally irregular (with a random inter-tone-interval (ITI) between 100 and 400 ms) and the regularity status of the competing sequence was set to one of four conditions: (1) random ITI between 100 and 400 ms (2) isochronous with ITI = 400 ms. (3) isochronous with ITI = 250 ms (equal to the mean rate of the attended sequence) (4) isochronous with ITI = 100 ms. For a frequency separation of 2 (but not 4) semi tones we observed improved performance in conditions (3) and (4) relative to (1), suggesting that stream segregation is facilitated when the distracter sequence is temporally regular, but that the effect of temporal regularity as a cue for segregation is limited to relatively fast rates and to situations where frequency separation is insufficient for segregation. These findings provide new evidence to support models of streaming that involve segregation based on the formation of predictive models.
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paper_title: Preattentive auditory context effects

paper_content:

The effects of auditory context on the preattentive and perceptual organization of tone sequences were investigated. Two sets of experiments were conducted in which the pitch of contextual tones was varied, bringing about two different contextual manipulations. Preattentive auditory organization was indexed by the mismatch negativity event-related potential, which is elicited by violations of auditory regularities even when participants ignore the sounds (e.g., by reading a book). The perceptual effects of the contextual manipulations on auditory grouping were assessed using target-detection and orderjudgment tasks. The close correspondence found between the effects of auditory context on the perceptual and preattentive measures of auditory grouping suggests that a large part of contextual processing is preattentive.
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paper_title: Newborn infants can organize the auditory world

paper_content:

The perceptual world of neonates is usually regarded as not yet being fully organized in terms of objects in the same way as it is for adults. Using a recently developed method based on electric brain responses, we found that, similarly to adults, newborn infants segregate concurrent streams of sound, allowing them to organize the auditory input according to the existing sound source. The segregation of concurrent sound streams is a crucial step in the path leading to the identification of objects in the environment. Its presence in newborn infants shows that the basic abilities required for the development of conceptual objects are available already at the time of birth.
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paper_title: Auditory Scene Analysis: The Sweet Music of Ambiguity

paper_content:

In this review paper aimed at the non-specialist, we explore the use that neuroscientists and musicians have made of perceptual illusions based on ambiguity. The pivotal issue is auditory scene analysis (ASA), or what enables us to make sense of complex acoustic mixtures in order to follow, for instance, a single melody in the midst of an orchestra. In general, ASA uncovers the most likely physical causes that account for the waveform collected at the ears. However, the acoustical problem is ill-posed and it must be solved from noisy sensory input. Recently, the neural mechanisms implicated in the transformation of ambiguous sensory information into coherent auditory scenes have been investigated using so-called bistability illusions (where an unchanging ambiguous stimulus evokes a succession of distinct percepts in the mind of the listener). After reviewing some of those studies, we turn to music, which arguably provides some of the most complex acoustic scenes that a human listener will ever encounter. Interestingly, musicians will not always aim at making each physical source intelligible, but rather express one or more melodic lines with a small or large number of instruments. By means of a few musical illustrations and by using a computational model inspired by neuro-physiological principles, we suggest that this relies on a detailed (if perhaps implicit) knowledge of the rules of ASA and of its inherent ambiguity. We then put forward the opinion that some degree perceptual ambiguity may participate in our appreciation of music.
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paper_title: Pattern of BOLD signal in auditory cortex relates acoustic response to perceptual streaming

paper_content:

BackgroundSegregating auditory scenes into distinct objects or streams is one of our brain's greatest perceptual challenges. Streaming has classically been studied with bistable sound stimuli, perceived alternately as a single group or two separate groups. Throughout the last decade different methodologies have yielded inconsistent evidence about the role of auditory cortex in the maintenance of streams. In particular, studies using functional magnetic resonance imaging (fMRI) have been unable to show persistent activity within auditory cortex (AC) that distinguishes between perceptual states.ResultsWe use bistable stimuli, an explicit perceptual categorization task, and a focused region of interest (ROI) analysis to demonstrate an effect of perceptual state within AC. We find that AC has more activity when listeners perceive the split percept rather than the grouped percept. In addition, within this ROI the pattern of acoustic response across voxels is significantly correlated with the pattern of perceptual modulation. In a whole-brain exploratory test, we corroborate previous work showing an effect of perceptual state in the intraparietal sulcus.ConclusionsOur results show that the maintenance of auditory streams is reflected in AC activity, directly relating sound responses to perception, and that perceptual state is further represented in multiple, higher level cortical regions.
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paper_title: Different roles of similarity and predictability in auditory stream segregation

paper_content:

Sound sources often emit trains of discrete sounds, such as a series of footsteps. Previously, two different principles have been suggested for how the human auditory system binds discrete sounds together into perceptual units. The feature similarity principle is based on linking sounds with similar characteristics over time. The predictability principle is based on linking sounds that follow each other in a predictable manner. The present study compared the effects of these two principles. Participants were presented with tone sequences and instructed to continuously indicate whether they perceived a single coherent sequence or two concurrent streams of sound. We investigated the influence of separate manipulations of similarity and predictability on these perceptual reports. Both grouping principles affected perception of the tone sequences, albeit with different characteristics. In particular, results suggest that whereas predictability is only analyzed for the currently perceived sound organization, f...
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paper_title: Modeling the auditory scene: predictive regularity representations and perceptual objects

paper_content:

Predictive processing of information is essential for goal-directed behavior. We offer an account of auditory perception suggesting that representations of predictable patterns, or 'regularities', extracted from the incoming sounds serve as auditory perceptual objects. The auditory system continuously searches for regularities within the acoustic signal. Primitive regularities may be encoded by neurons adapting their response to specific sounds. Such neurons have been observed in many parts of the auditory system. Representations of the detected regularities produce predictions of upcoming sounds as well as alternative solutions for parsing the composite input into coherent sequences potentially emitted by putative sound sources. Accuracy of the predictions can be utilized for selecting the most likely interpretation of the auditory input. Thus in our view, perception generates hypotheses about the causal structure of the world.
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paper_title: The role of attention in the formation of auditory streams.

paper_content:

There is controversy over whether stream segregation is an attention-dependent process. Part of the argument is related to the initial formation of auditory streams. It has been suggested that attention is needed only to form the streams, but not to maintain them once they have been segregated. The question of whether covert attention at the beginning of a to-be-ignored set of sounds will be enough to initiate the segregation process remains open. Here, we investigate this question by (1) using a methodology that does not require the participant to make an overt response to assess how the unattended sounds are organized and (2) structuring the test sound sequence to account for the covert attention explanation. The results of four experiments provide evidence to support the view that attention is not always required for the formation of auditory streams.
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paper_title: Temporal coherence in the perception of tone sequences [doctoral dissertation

paper_content:

A direct reduction apparatus having a means for briquetting oxide ores of iron, manganese, chrome, and copper, with a powdered coal tar pitch, means for caramelizing (hardening) the briquettes for ease of handling, subjecting the caramelized briquettes to a first temperature source until said briquettes are partially reduced to conductivity, their dimensions are substantially reduced and subsequently reducing said briquettes by subjecting them to a frequency electric induction induced heat source.
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paper_title: Stable individual characteristics in the perception of multiple embedded patterns in multistable auditory stimuli

paper_content:

The ability of the auditory system to parse complex scenes into component objects in order to extract information from the environment is very robust, yet the processing principles underlying this ability are still not well understood. This study was designed to investigate the proposal that the auditory system constructs multiple interpretations of the acoustic scene in parallel, based on the finding that when listening to a long repetitive sequence listeners report switching between different perceptual organizations. Using the ‘ABA-’ auditory streaming paradigm we trained listeners until they could reliably recognise all possible embedded patterns of length four which could in principle be extracted from the sequence, and in a series of test sessions investigated their spontaneous reports of those patterns. With the training allowing them to identify and mark a wider variety of possible patterns, participants spontaneously reported many more patterns than the ones traditionally assumed (Integrated vs. Segregated). Despite receiving consistent training and despite the apparent randomness of perceptual switching, we found individual switching patterns were idiosyncratic; i.e. the perceptual switching patterns of each participant were more similar to their own switching patterns in different sessions than to those of other participants. These individual differences were found to be preserved even between test sessions held a year after the initial experiment. Our results support the idea that the auditory system attempts to extract an exhaustive set of embedded patterns which can be used to generate expectations of future events and which by competing for dominance give rise to (changing) perceptual awareness, with the characteristics of pattern discovery and perceptual competition having a strong idiosyncratic component. Perceptual multistability thus provides a means for characterizing both general mechanisms and individual differences in human perception.
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paper_title: Measuring target detection performance in paradigms with high event rates

paper_content:

Abstract Objectives Combining behavioral and neurophysiological measurements inevitably implies mutual constraints, such as when the neurophysiological measurement requires fast-paced stimulus presentation and hence the attribution of a behavioral response to a particular preceding stimulus becomes ambiguous. We develop and test a method for validly assessing behavioral detection performance in spite of this ambiguity. Methods We examine four approaches taken in the literature to treat such situations. We analytically derive a new variant of computing the classical parameters of signal detection theory, hit and false alarm rates, adapted to fast-paced paradigms. Results Each of the previous approaches shows specific shortcomings (susceptibility towards response window choice, biased estimates of behavioral detection performance). Superior performance of our new approach is demonstrated for both simulated and empirical behavioral data. Further evidence is provided by reliable correspondence between behavioral performance and the N2b component as an electrophysiological indicator of target detection. Conclusions The appropriateness of our approach is substantiated by both theoretical and empirical arguments. Significance We demonstrate an easy-to-implement solution for measuring target detection performance independent of the rate of event presentation. Thus overcoming the measurement bias of previous approaches, our method will help to clarify the behavioral relevance of different measures of cortical activation.
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paper_title: Temporal Dynamics of Auditory and Visual Bistability Reveal Common Principles of Perceptual Organization

paper_content:

When dealing with natural scenes, sensory systems have to process an often messy and ambiguous flow of information. A stable perceptual organization nevertheless has to be achieved in order to guide behavior. The neural mechanisms involved can be highlighted by intrinsically ambiguous situations. In such cases, bistable perception occurs: distinct interpretations of the unchanging stimulus alternate spontaneously in the mind of the observer. Bistable stimuli have been used extensively for more than two centuries to study visual perception. Here we demonstrate that bistable perception also occurs in the auditory modality. We compared the temporal dynamics of percept alternations observed during auditory streaming with those observed for visual plaids and the susceptibilities of both modalities to volitional control. Strong similarities indicate that auditory and visual alternations share common principles of perceptual bistability. The absence of correlation across modalities for subject-specific biases, however, suggests that these common principles are implemented at least partly independently across sensory modalities. We propose that visual and auditory perceptual organization could rely on distributed but functionally similar neural competition mechanisms aimed at resolving sensory ambiguities.
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paper_title: Using a staircase procedure for the objective measurement of auditory stream integration and segregation thresholds

paper_content:

Auditory scene analysis describes the ability to segregate relevant sounds out from the environment and to integrate them into a single sound stream using the characteristics of the sounds to determine whether or not they are related. This study aims to contrast task performances in objective threshold measurements of segregation and integration using identical stimuli, manipulating two variables known to influence streaming, inter-stimulus-interval (ISI) and frequency difference (Δf). For each measurement, one parameter (either ISI or Δf) was held constant while the other was altered in a staircase procedure. By using this paradigm, it is possible to test within-subject across multiple conditions, covering a wide Δf and ISI range in one testing session. The objective tasks were based on across-stream temporal judgments (facilitated by integration) and within-stream deviance detection (facilitated by segregation). Results show the objective integration task is well suited for combination with the staircase procedure, as it yields consistent threshold measurements for separate variations of ISI and Δf, as well as being significantly related to the subjective thresholds. The objective segregation task appears less suited to the staircase procedure. With the integration-based staircase paradigm, a comprehensive assessment of streaming thresholds can be obtained in a relatively short space of time. This permits efficient threshold measurements particularly in groups for which there is little prior knowledge on the relevant parameter space for streaming perception.
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paper_title: Aiming attention in pitch and time in the perception of interleaved melodies

paper_content:

Listeners succeeded in following a melody interleaved at 6 or 8 notes/sec with distractor notes in the same pitch range and of the same timbre. Their ability to perform this auditory “hidden-figures” task depended on the rhythmic control of attention on the basis of expectancies dew, loped through perceptual learning with melodies in the listeners’ culture. Listeners appear to have aimed expectancies in pitch and time at regions where events critical to the identification of melodies are likely to occur—regions defining “expectancy windows” through which target notes are perceived. Events in pitch and time regions outside these expectancy windows were not perceived as accurately as events within the window. Listeners discerned interleaved melodies whose notes fellon the consistent temporal beat of a pattern better than they did melodies whose notes fell off the beat. Expectancies could also be aimedoffthe beat: expected target notes occurringoff the beat in a syncopated rhythm were judged more accurately than unexpected notes occurringon the beat. Listeners found it more difficult to judge the pitch of target notes that fell outside the expected pitch region than that of notes within the expected region. The interleaved distractor notes appear to be instrumental in narrowing attention to within the expectancy windows. When the interleaved distractors were removed, unexpected notes becamemore salient than expected ones.
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paper_title: Objective and Subjective Psychophysical Measures of Auditory Stream Integration and Segregation

paper_content:

The perceptual organization of sound sequences into auditory streams involves the integration of sounds into one stream and the segregation of sounds into separate streams. “Objective” psychophysical measures of auditory streaming can be obtained using behavioral tasks where performance is facilitated by segregation and hampered by integration, or vice versa. Traditionally, these two types of tasks have been tested in separate studies involving different listeners, procedures, and stimuli. Here, we tested subjects in two complementary temporal-gap discrimination tasks involving similar stimuli and procedures. One task was designed so that performance in it would be facilitated by perceptual integration; the other, so that performance would be facilitated by perceptual segregation. Thresholds were measured in both tasks under a wide range of conditions produced by varying three stimulus parameters known to influence stream formation: frequency separation, tone-presentation rate, and sequence length. In addition to these performance-based measures, subjective judgments of perceived segregation were collected in the same listeners under corresponding stimulus conditions. The patterns of results obtained in the two temporal-discrimination tasks, and the relationships between thresholds and perceived-segregation judgments, were mostly consistent with the hypothesis that stream segregation helped performance in one task and impaired performance in the other task. The tasks and stimuli described here may prove useful in future behavioral or neurophysiological experiments, which seek to manipulate and measure neural correlates of auditory streaming while minimizing differences between the physical stimuli.
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paper_title: The initial phase of auditory and visual scene analysis

paper_content:

Auditory streaming and visual plaids have been used extensively to study perceptual organization in each modality. Both stimuli can produce bistable alternations between grouped (one object) and split (two objects) interpretations. They also share two peculiar features: (i) at the onset of stimulus presentation, organization starts with a systematic bias towards the grouped interpretation; (ii) this first percept has 'inertia'; it lasts longer than the subsequent ones. As a result, the probability of forming different objects builds up over time, a landmark of both behavioural and neurophysiological data on auditory streaming. Here we show that first percept bias and inertia are independent. In plaid perception, inertia is due to a depth ordering ambiguity in the transparent (split) interpretation that makes plaid perception tristable rather than bistable: experimental manipulations removing the depth ambiguity suppressed inertia. However, the first percept bias persisted. We attempted a similar manipulation for auditory streaming by introducing level differences between streams, to bias which stream would appear in the perceptual foreground. Here both inertia and first percept bias persisted. We thus argue that the critical common feature of the onset of perceptual organization is the grouping bias, which may be related to the transition from temporally/spatially local to temporally/spatially global computation.
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paper_title: Regular patterns stabilize auditory streams

paper_content:

The auditory system continuously parses the acoustic environment into auditory objects, usually representing separate sound sources. Sound sources typically show characteristic emission patterns. These regular temporal sound patterns are possible cues for distinguishing sound sources. The present study was designed to test whether regular patterns are used as cues for source distinction and to specify the role that detecting these regularities may play in the process of auditory stream segregation. Participants were presented with tone sequences, and they were asked to continuously indicate whether they perceived the tones in terms of a single coherent sequence of sounds (integrated) or as two concurrent sound streams (segregated). Unknown to the participant, in some stimulus conditions, regular patterns were present in one or both putative streams. In all stimulus conditions, participants’ perception switched back and forth between the two sound organizations. Importantly, regular patterns occurring in e...
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paper_title: Involvement of the Thalamocortical Loop in the Spontaneous Switching of Percepts in Auditory Streaming

paper_content:

Perceptual grouping of successive frequency components, namely, auditory streaming, is essential for auditory scene analysis. Prolonged listening to an unchanging triplet-tone sequence produces a series of illusory switches between a single coherent stream (S1) and two distinct streams (S2). The predominant percept depends on the frequency difference (Δf) between high and low tones. Here, we combined the use of different Δfs with an event-related fMRI design to identify whether the temporal dynamics of brain activity differs depending on the direction of perceptual switches. The results demonstrated that the activity of the medial geniculate body (MGB) in the thalamus occurred earlier during switching from nonpredominant to predominant percepts, whereas that of the auditory cortex (AC) occurred earlier during switching from predominant to nonpredominant percepts, regardless of Δf. The asymmetry of temporal precedence indicates that the MGB and AC activations play different roles in perceptual switching and depend on perceptual predominance rather than on S1 and S2 percepts per se. Our results suggest that feedforward and feedback processes in the thalamocortical loop are involved in the formation of percepts in auditory streaming.
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paper_title: Neuromagnetic Correlates of Streaming in Human Auditory Cortex

paper_content:

The brain is constantly faced with the challenge of organizing acoustic input from multiple sound sources into meaningful auditory objects or perceptual streams. The present study examines the neural bases of auditory stream formation using neuromagnetic and behavioral measures. The stimuli were sequences of alternating pure tones, which can be perceived as either one or two streams. In the first experiment, physical stimulus parameters were varied between values that promoted the perceptual grouping of the tone sequence into one coherent stream and values that promoted its segregation into two streams. In the second experiment, an ambiguous tone sequence produced a bistable percept that switched spontaneously between one- and two-stream percepts. The first experiment demonstrated a strong correlation between listeners' perception and long-latency (>60 ms) activity that likely arises in nonprimary auditory cortex. The second demonstrated a covariation between this activity and listeners' perception in the absence of physical stimulus changes. Overall, the results indicate a tight coupling between auditory cortical activity and streaming perception, suggesting that an explicit representation of auditory streams may be maintained within nonprimary auditory areas.
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paper_title: The role of predictive models in the formation of auditory streams

paper_content:

Abstract Sounds provide us with useful information about our environment which complements that provided by other senses, but also poses specific processing problems. How does the auditory system distentangle sounds from different sound sources? And what is it that allows intermittent sound events from the same source to be associated with each other? Here we review findings from a wide range of studies using the auditory streaming paradigm in order to formulate a unified account of the processes underlying auditory perceptual organization. We present new computational modelling results which replicate responses in primary auditory cortex [Fishman, Y.I., Arezzo, J.C., Steinschneider, M., 2004. Auditory stream segregation in monkey auditory cortex: effects of frequency separation, presentation rate, and tone duration. J. Acoust. Soc. Am. 116, 1656–1670; Fishman, Y. I., Reser, D. H., Arezzo, J.C., Steinschneider, M., 2001. Neural correlates of auditory stream segregation in primary auditory cortex of the awake monkey. Hear. Res. 151, 167–187] to tone sequences. We also present the results of a perceptual experiment which confirm the bi-stable nature of auditory streaming, and the proposal that the gradual build-up of streaming may be an artefact of averaging across many subjects [Pressnitzer, D., Hupe, J. M., 2006. Temporal dynamics of auditory and visual bi-stability reveal common principles of perceptual organization. Curr. Biol. 16(13), 1351–1357.]. Finally we argue that in order to account for all of the experimental findings, computational models of auditory stream segregation require four basic processing elements; segregation, predictive modelling, competition and adaptation, and that it is the formation of effective predictive models which allows the system to keep track of different sound sources in a complex auditory environment.
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paper_title: Auditory Scene Analysis: The Perceptual Organization of Sound

paper_content:

Auditory Scene Analysis addresses the problem of hearing complex auditory environments, using a series of creative analogies to describe the process required of the human auditory system as it analyzes mixtures of sounds to recover descriptions of individual sounds. In a unified and comprehensive way, Bregman establishes a theoretical framework that integrates his findings with an unusually wide range of previous research in psychoacoustics, speech perception, music theory and composition, and computer modeling.
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paper_title: Event-related brain potentials reveal multiple stages in the perceptual organization of sound.

paper_content:

Auditory stream segregation has been suggested to include two distinct processing stages: (1) forming representations for alternative organizations of the acoustic input and (2) choosing one organization for perception after weighing the evidence that supports the different alternatives. The current study tested the possibility that auditory event-related potentials (ERP) could be used to index both stages of the stream-segregation process. Sequences of tones that could be perceived either as a single coherent auditory stream (integrated organization) or as two separate streams of sounds (segregated organization) were presented to subjects. The stimulus configuration encouraged perception to fluctuate between these alternative organizations. Subjects were instructed to continuously indicate whether they perceived one or the other organization of the tone sequence. Occasionally, a tone was omitted from the otherwise regular sequence. This deviance was expected to be processed differently depending on the perceptual organization of the sequence at the time of the omission. We found an early ERP response to omission, which was fully determined by parameters of the stimulation and was not sensitive to the perceived sound organization. In contrast, modulation of two ERP components elicited by the regular tone patterns as well as later responses elicited by deviants correlated with the perceived sound organization. These results suggest that sound organization goes through at least two distinct stages, the first being fully stimulus driven, whereas the second is partly under top-down control.
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paper_title: Separability and Commonality of Auditory and Visual Bistable Perception

paper_content:

It is unclear what neural processes induce individual differences in perceptual organization in different modalities. To examine this issue, the present study used different forms of bistable perception: auditory streaming, verbal transformations, visual plaids, and reversible figures. We performed factor analyses on the number of perceptual switches in the tasks. A 3-factor model provided a better fit to the data than the other possible models. These factors, namely the ‘‘auditory,’’ ‘‘shape,’’ and ‘‘motion’’ factors, were separable but correlated with each other. We compared the number of perceptual switches among genotype groups to identify the effects of neurotransmitter functions on the factors. We focused on polymorphisms of catechol-O-methyltransferase (COMT) Val 158 Met and serotonin 2A receptor (HTR2A) -1438G/A genes, which are involved in the modulation of dopamine and serotonin, respectively. The number of perceptual switches in auditory streaming and verbal transformations differed among COMT genotype groups, whereas that in reversible figures differed among HTR2A genotype groups. The results indicate that the auditory and shape factors reflect the functions of the dopamine and serotonin systems, respectively. Our findings suggest that the formation and selection of percepts involve neural processes in cortical and subcortical areas.
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paper_title: Different roles of similarity and predictability in auditory stream segregation

paper_content:

Sound sources often emit trains of discrete sounds, such as a series of footsteps. Previously, two different principles have been suggested for how the human auditory system binds discrete sounds together into perceptual units. The feature similarity principle is based on linking sounds with similar characteristics over time. The predictability principle is based on linking sounds that follow each other in a predictable manner. The present study compared the effects of these two principles. Participants were presented with tone sequences and instructed to continuously indicate whether they perceived a single coherent sequence or two concurrent streams of sound. We investigated the influence of separate manipulations of similarity and predictability on these perceptual reports. Both grouping principles affected perception of the tone sequences, albeit with different characteristics. In particular, results suggest that whereas predictability is only analyzed for the currently perceived sound organization, f...
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paper_title: Effect of rhythmic attention on the segregation of interleaved melodies

paper_content:

As previously suggested, attention may increase segregation via enhancement and suppression sensory mechanisms. To test this hypothesis, we proposed an interleaved melody paradigm with two rhythm conditions applied to familiar target melodies and unfamiliar distractor melodies sharing pitch and timbre properties. When rhythms of both target and distractor were irregular, target melodies were identified above chance level. A sensory enhancement mechanism guided by listeners’ knowledge may have helped to extract targets from the interleaved sequence. When the distractor was rhythmically regular, performance was increased, suggesting that the distractor may have been suppressed by a sensory suppression mechanism.
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paper_title: Temporal predictability as a grouping cue in the perception of auditory streams

paper_content:

This study reports a role of temporal regularity on the perception of auditory streams. Listeners were presented with two-tone sequences in an A-B-A-B rhythm that was either regular or had a controlled amount of temporal jitter added independently to each of the B tones. Subjects were asked to report whether they perceived one or two streams. The percentage of trials in which two streams were reported substantially and significantly increased with increasing amounts of temporal jitter. This suggests that temporal predictability may serve as a binding cue during auditory scene analysis.
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paper_title: Age-related changes in the use of regular patterns for auditory scene analysis

paper_content:

Abstract A recent approach to auditory processing suggests a close relationship of regularity processing in auditory sensory memory (ASM) and stream segregation, such that within-stream regularities can be used to stabilize stream segregation. The present study investigates age-related changes in how regular patterns are used for auditory scene analysis (ASA), when the stream containing the regularity is attended or unattended. In order to accomplish an intensity level deviant detection task, participants had to segregate the task-relevant pure tone sequence from an irrelevant distractor pure tone sequence, which randomly varied in level. In three conditions a simple spectro-temporal regularity (“Isochronous”), a more complex spectro-temporal regularity (“Rhythmic”), or no regularity (“Random”) was embedded in either the attended target sequence (Experiment 1), or the unattended distractor sequence (Experiment 2). When the sequence containing the regularity was attended, older participants showed a similar increase of performance to younger adults in the conditions with regular patterns (“Isochronous” and “Rhythmic”) compared to the “Random” condition. In contrast, when the sequence containing the regularity was unattended, older adults showed a specific performance decline compared to younger adults in the “Isochronous” condition. Results suggest a link between impaired automatic processing of regularities in ASM, and age-related deficits in the use of regular patterns for ASA.
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paper_title: Evidence for Rhythmic Attention.

paper_content:

Three studies compared effects of different rhythmic contexts on order judgments of targets embedded in auditory patterns designed to manifest auditory stream segregation. Of interest was the effect of rhythmic structure upon the frequency-based captor effect, wherein tones in one stream "capture" those of similar frequencies from another. Three rhythmic structures were studied. Experiment 1 compared a rhythm conducive to pairwise-target stream formation with one conducive to a four-tone stream, and one based on an isochronous rhythm in a within-subjects design. Patterns embedding the target tone pair contained a preliminary string of captor tones at frequencies either close or far from frequencies of distracting tones that flanked the target pair. No effect of captor distance was found. Experiments 2 and 3 varied rhythm between subjects using 9- and 11-tone patterns, respectively. In general, the magnitude of the captor effect was found to vary with temporal predictability of flanking and/or target tones. The pairwise rhythm was most likely to improve order judgments by facilitating frequency-based capture. Results are discussed in terms of a rhythmic attentional hypothesis. Language: en
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paper_title: Regular patterns stabilize auditory streams

paper_content:

The auditory system continuously parses the acoustic environment into auditory objects, usually representing separate sound sources. Sound sources typically show characteristic emission patterns. These regular temporal sound patterns are possible cues for distinguishing sound sources. The present study was designed to test whether regular patterns are used as cues for source distinction and to specify the role that detecting these regularities may play in the process of auditory stream segregation. Participants were presented with tone sequences, and they were asked to continuously indicate whether they perceived the tones in terms of a single coherent sequence of sounds (integrated) or as two concurrent sound streams (segregated). Unknown to the participant, in some stimulus conditions, regular patterns were present in one or both putative streams. In all stimulus conditions, participants’ perception switched back and forth between the two sound organizations. Importantly, regular patterns occurring in e...
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paper_title: The role of temporal regularity in auditory segregation.

paper_content:

Abstract The idea that predictive modelling and extraction of regularities plays a pivotal role in auditory segregation has recently attracted considerable attention. The present study investigated the effect of one basic form of regularity, rhythmic regularity, on auditory stream segregation. We departed from the classic streaming paradigm and developed a new stimulus, Rand-AB, consisting of two, concurrently presented, temporally uncorrelated, tone sequences (with frequencies A and B). To evaluate segregation, we used an objective measure of the extent to which listeners are able to selectively attend to one of the sequences in the presence of the other. Performance was quantified on a difficult pattern detection task which involves detecting a rarely occurring pattern of amplitude modulation applied to three consecutive A or B tones. In all cases the attended sequence was temporally irregular (with a random inter-tone-interval (ITI) between 100 and 400 ms) and the regularity status of the competing sequence was set to one of four conditions: (1) random ITI between 100 and 400 ms (2) isochronous with ITI = 400 ms. (3) isochronous with ITI = 250 ms (equal to the mean rate of the attended sequence) (4) isochronous with ITI = 100 ms. For a frequency separation of 2 (but not 4) semi tones we observed improved performance in conditions (3) and (4) relative to (1), suggesting that stream segregation is facilitated when the distracter sequence is temporally regular, but that the effect of temporal regularity as a cue for segregation is limited to relatively fast rates and to situations where frequency separation is insufficient for segregation. These findings provide new evidence to support models of streaming that involve segregation based on the formation of predictive models.
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paper_title: Selective Attention in Normal and Impaired Hearing

paper_content:

Imagine yourself at a restaurant with a group of friends. Conversation trades off from one talker to another. Especially when the topic under discussion is interesting and emotions are high, interruptions are common. Quips and gentle barbs punctuate the conversation, short bursts of levity that add to the feeling of camaraderie. Topics change quickly as one anecdote reminds another talker of some vaguely related idea. In the background, laughter and conversation from nearby tables swirls by. A common complaint among listeners with hearing loss (HL) is that they have difficulty communicating in common social settings. This article reviews how normal-hearing listeners cope in such settings, especially how they focus attention on a source of interest. Results of experiments with normal-hearing listeners suggest that the ability to selectively attend depends on the ability to analyze the acoustic scene and to form perceptual auditory objects properly. Unfortunately, sound features important for auditory object formation may not be robustly encoded in the auditory periphery of HL listeners. In turn, impaired auditory object formation may interfere with the ability to filter out competing sound sources. Peripheral degradations are also likely to reduce the salience of higher-order auditory cues such as location, pitch, and timbre, which enable normal-hearing listeners to select a desired sound source out of a sound mixture. Degraded peripheral processing is also likely to increase the time required to form auditory objects and focus selective attention so that listeners with HL lose the ability to switch attention rapidly (a skill that is particularly important when trying to participate in a lively conversation). Finally, peripheral deficits may interfere with strategies that normal-hearing listeners employ in complex acoustic settings, including the use of memory to fill in bits of the conversation that are missed. Thus, peripheral hearing deficits are likely to cause a number of interrelated problems that challenge the ability of HL listeners to communicate in social settings requiring selective attention.
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paper_title: Age-related changes in the use of regular patterns for auditory scene analysis

paper_content:

Abstract A recent approach to auditory processing suggests a close relationship of regularity processing in auditory sensory memory (ASM) and stream segregation, such that within-stream regularities can be used to stabilize stream segregation. The present study investigates age-related changes in how regular patterns are used for auditory scene analysis (ASA), when the stream containing the regularity is attended or unattended. In order to accomplish an intensity level deviant detection task, participants had to segregate the task-relevant pure tone sequence from an irrelevant distractor pure tone sequence, which randomly varied in level. In three conditions a simple spectro-temporal regularity (“Isochronous”), a more complex spectro-temporal regularity (“Rhythmic”), or no regularity (“Random”) was embedded in either the attended target sequence (Experiment 1), or the unattended distractor sequence (Experiment 2). When the sequence containing the regularity was attended, older participants showed a similar increase of performance to younger adults in the conditions with regular patterns (“Isochronous” and “Rhythmic”) compared to the “Random” condition. In contrast, when the sequence containing the regularity was unattended, older adults showed a specific performance decline compared to younger adults in the “Isochronous” condition. Results suggest a link between impaired automatic processing of regularities in ASM, and age-related deficits in the use of regular patterns for ASA.
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paper_title: Aging and auditory temporal sequencing: Ordering the elements of repeating tone patterns

paper_content:

In a series of experiments, we examined age-related differences in adults’ ability to order sequences of tones presented at various speeds and in contexts designed to promote or to impede stream segregation. In Experiment 1, 32 listeners (16 young, 16 old) were required to identify two repeating sequences that consisted of four tones (two from a high and two from a low frequency range) in different order. In Experiment 2, 32 listeners were required to judge whether the two recycled patterns from Experiment 1 were the same or different. In Experiment 3, four young and four old listeners were tested on the tasks of Experiment 2 over an extended period. In Experiment 4, 16 young and 16 old listeners were tested with sequences that were not recycled and were composed of tones drawn from a narrow frequency range. Elderly adults were less able than young adults to distinguish between tone sequences with contrasting order, regardless of the speed of presentation, the nature of the task (identification vs. same/different), the amount of practice, the frequency separation of the tones, or the presence or absence of recycling. These findings provide evidence of a temporal sequencing impairment in elderly listeners but reveal no indication of age differences in streaming processes.
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paper_title: Mismatch Negativity in Aging and in Alzheimer’s and Parkinson’s Diseases

paper_content:

Mismatch negativity (MMN) is an auditory event-related potential (ERP) that reflects automatic stimulus discrimination in the human auditory system. By varying the interstimulus intervals (ISIs), the MMN can be used as an index of auditory sensory memory. This paper focuses on MMN findings in aging and in Alzheimer’s (AD) and Parkinson’s diseases (PD). The accumulated data suggest that MMN to duration deviance, unlike MMN to frequency deviance, is reduced in amplitude in aging at short ISIs. The attenuated MMN to frequency deviance observed at long ISIs in elderly subjects seems to be caused by age-related memory trace decay. Existing results suggest that automatic discrimination for the frequency change is not affected in the early phase of AD, whereas the memory trace seems to decay faster in AD patients. The present findings on PD are not as conclusive, although they tentatively suggest deteriorated automatic change detection. The MMN appears to offer an objective tool for studying auditory processing and memory trace decay in different neurological disorders.
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paper_title: Revision, extension, and evaluation of a binaural speech intelligibility model.

paper_content:

This study presents revision, extension, and evaluation of a binaural speech intelligibility model (Beutelmann, R., and Brand, T. (2006). J. Acoust. Soc. Am. 120, 331-342) that yields accurate predictions of speech reception thresholds (SRTs) in the presence of a stationary noise source at arbitrary azimuths and in different rooms. The modified model is based on an analytical expression of binaural unmasking for arbitrary input signals and is computationally more efficient, while maintaining the prediction quality of the original model. An extension for nonstationary interferers was realized by applying the model to short time frames of the input signals and averaging over the predicted SRT results. Binaural SRTs from 8 normal-hearing and 12 hearing-impaired subjects, incorporating all combinations of four rooms, three source setups, and three noise types were measured and compared to the model's predictions. Depending on the noise type, the parametric correlation coefficients between observed and predicted SRTs were 0.80-0.93 for normal-hearing subjects and 0.59-0.80 for hearing-impaired subjects. The mean absolute prediction error was 3 dB for the mean normal-hearing data and 4 dB for the individual hearing-impaired data. 70% of the variance of the SRTs of hearing-impaired subjects could be explained by the model, which is based only on the audiogram.
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paper_title: Listening in aging adults: From discourse comprehension to psychoacoustics.

paper_content:

Abstract Older adults, whether or not they have clinically significant hearing loss, have more trouble than their younger counterparts understanding speech in everyday life. These age-related difficulties in speech understanding may be attributed to changes in higher-- level cognitive processes such as language comprehension, memory, attention, and cognitive slowing, or to lower-level sensory and perceptual processes. A complicating factor in determining how these sources might contribute to age-related declines in speech understanding is that they are highly correlated. Experimenters have typically focused either on cognitive declines or sensory declines in artificially optimized test conditions. In contrast, our approach focuses on the complex interactions between age-related changes in cognitive and perceptual factors that affect spoken language comprehension, especially in nonideal, realistic conditions. In this article, we describe our attempts to systematically investigate sensory-cognitive interactions in controlled experimental situations. We begin by looking at experimental conditions that closely approximate everyday listening, and show that older adults do indeed experience deficits in spoken language comprehension relative to younger adults in these conditions. We then review further experiments designed to isolate more precisely the cognitive and perceptual sources of these age-related differences and how they vary with listening condition. in large part, we find that agerelated changes in speech understanding are a consequence of auditory declines. As many as one-third of seniors find that it is difficult to understand conversations in everyday listening situations (Hamilton-Wentworth District Health Council, 1988; see also CHABA, 1988). Among the more common complaints are that talkers seem to mumble or talk too fast and that it is hard to hear when it is noisy. In general, it is especially difficult for older adults to follow a conversation when there are multiple talkers, or when talkers or topics change. Because they miss parts of what is said and lack confidence in the accuracy of their understanding of the parts they do hear, older communicators are prone to anxiety or frustration, and may avoid or be excluded from social interactions. The speech understanding difficulties of older listeners may arise from a number of possible sources. The difficulties could be in higher-level cognitive processes such as language comprehension, memory, attention, and cognitive slowing, or they could be in lower-level sensory and perceptual processes. A complicating factor in determining how these sources might contribute to age-related declines in speech understanding is that they are highly correlated. Perceptual declines in older adults are highly associated with declines in cognition (e.g., Baltes & Lindenberger, 1997; Lindenberger & Baltes, 1994; Uhlmann, Larson, Rees, Koepsell, & Duckert, 1989). In turn, both perceptual and cognitive declines are linked to emotional and social problems and even to mortality (e.g., Appolonio, Carabellese, Frattola, & Trabucchi, 1996; Cacciatore, Napoli, Abete, Marciano, Triassi, & Rengo, 1999; Naramura, Nakanishi, Tatara, Ishiyama, Shiraishi, & Yamamoto, 1999; Seniors Research Group, 1999). Thus, it is very important to understand how the interplay of perceptual and cognitive factors contributes to the speech understanding difficulties of older listeners so that they can be remediated. The need to consider each of these levels and how they inter-relate has received increasing recognition over the last decade (e.g., Baltes & Lindenberger, 1994; CHABA, 1988). Furthermore, the need to determine how older adults perform in naturalistic, as opposed to laboratory, conditions has also been highlighted (e.g., Stern & Carstensen, 2000; WHO, 2001). Nevertheless, up until now, experimenters have typically focused either on cognitive declines or sensory declines in artificially optimized test conditions. …
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paper_title: The mismatch negativity (MMN) – A unique window to disturbed central auditory processing in ageing and different clinical conditions

paper_content:

Abstract In this article, we review clinical research using the mismatch negativity (MMN), a change-detection response of the brain elicited even in the absence of attention or behavioural task. In these studies, the MMN was usually elicited by employing occasional frequency, duration or speech-sound changes in repetitive background stimulation while the patient was reading or watching videos. It was found that in a large number of different neuropsychiatric, neurological and neurodevelopmental disorders, as well as in normal ageing, the MMN amplitude was attenuated and peak latency prolonged. Besides indexing decreased discrimination accuracy, these effects may also reflect, depending on the specific stimulus paradigm used, decreased sensory-memory duration, abnormal perception or attention control or, most importantly, cognitive decline. In fact, MMN deficiency appears to index cognitive decline irrespective of the specific symptomatologies and aetiologies of the different disorders involved.
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paper_title: The ups and downs of temporal orienting: a review of auditory temporal orienting studies and a model associating the heterogeneous findings on the auditory N1 with opposite effects of attention and prediction

paper_content:

The temporal orienting of attention refers to the process of focusing (neural) resources on a particular time point in order to boost the processing of and the responding to sensory events. Temporal attention is manipulated by varying the task-relevance of events at different time points or by inducing expectations that an event occurs at a particular time point. Notably, the electrophysiological correlates of these manipulations at early processing stages are not identical: Auditory studies operationalizing temporal attention through task-relevance consistently found enhancements of early, sensory processing, as shown in the N1 component of the auditory event-related potential (ERP). By contrast, previous work on temporal orienting based on expectations showed mixed results: early, sensory processing was either enhanced or attenuated or not affected at all. In the present work, I will review existing findings on temporal orienting with a special focus on the auditory modality and present a working model to reconcile the previously heterogeneous results. Specifically, I will suggest that when expectations are used to manipulate attention, this will lead both to an orienting of attention and to the generation of precise predictions about the upcoming event. Attention and prediction are assumed to have opposite effects on early auditory processing, with temporal attention increasing and temporal predictions decreasing the associated ERP correlate, the auditory N1. The heterogeneous findings of studies manipulating temporal orienting by inducing expectations may thus be the consequence of differences in the relative contribution of attention and prediction processes. The model’s predictions will be discussed in the context of a functional interpretation of the auditory N1 as an attention call signal, as presented in a recent model on auditory processing.
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paper_title: A New View on the MMN and Attention Debate The Role of Context in Processing Auditory Events

paper_content:

The question of whether the mismatch negativity (MMN) is modulated by attention has been debated for over a decade. Although the MMN is widely regarded as reflecting a preattentive auditory process, many studies have shown attention effects on MMN. So, what does preattentive mean if attention can modulate the MMN? To understand the function of MMN in auditory processing, we need to shed new light on the "MMN and attention" debate. This review will discuss the apparent paradox that MMN can be modulated by attention and still be considered an attention-independent process, and provide a new framework for viewing the MMN system. The new model proposes that the principal factor governing MMN is the sound context. MMN generation relies on multiple processing mechanisms that are part of a larger system of auditory scene analysis.
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paper_title: Effect of rhythmic attention on the segregation of interleaved melodies

paper_content:

As previously suggested, attention may increase segregation via enhancement and suppression sensory mechanisms. To test this hypothesis, we proposed an interleaved melody paradigm with two rhythm conditions applied to familiar target melodies and unfamiliar distractor melodies sharing pitch and timbre properties. When rhythms of both target and distractor were irregular, target melodies were identified above chance level. A sensory enhancement mechanism guided by listeners’ knowledge may have helped to extract targets from the interleaved sequence. When the distractor was rhythmically regular, performance was increased, suggesting that the distractor may have been suppressed by a sensory suppression mechanism.
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paper_title: Age-related changes in the use of regular patterns for auditory scene analysis

paper_content:

Abstract A recent approach to auditory processing suggests a close relationship of regularity processing in auditory sensory memory (ASM) and stream segregation, such that within-stream regularities can be used to stabilize stream segregation. The present study investigates age-related changes in how regular patterns are used for auditory scene analysis (ASA), when the stream containing the regularity is attended or unattended. In order to accomplish an intensity level deviant detection task, participants had to segregate the task-relevant pure tone sequence from an irrelevant distractor pure tone sequence, which randomly varied in level. In three conditions a simple spectro-temporal regularity (“Isochronous”), a more complex spectro-temporal regularity (“Rhythmic”), or no regularity (“Random”) was embedded in either the attended target sequence (Experiment 1), or the unattended distractor sequence (Experiment 2). When the sequence containing the regularity was attended, older participants showed a similar increase of performance to younger adults in the conditions with regular patterns (“Isochronous” and “Rhythmic”) compared to the “Random” condition. In contrast, when the sequence containing the regularity was unattended, older adults showed a specific performance decline compared to younger adults in the “Isochronous” condition. Results suggest a link between impaired automatic processing of regularities in ASM, and age-related deficits in the use of regular patterns for ASA.
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paper_title: Age-related differences in distraction and reorientation in an auditory task

paper_content:

Abstract Behavioral and event-related potential measures of distraction and reorientation were obtained from children (6 years), young (19–24 years) and elderly adults (62–82 years) in an auditory distraction-paradigm. Participants performed a go/nogo duration discrimination task on a sequence of short and long (50–50%) tones. In children, reaction times were longer and discrimination ( d ′) scores were lower than in adults. Occasionally (15%), the pitch of the presented tones was changed. The task-irrelevant feature variation resulted in longer reaction times and lower d ′ scores with no significant differences between the three groups. Task-irrelevant changes affected the N1 amplitude and elicited the mismatch negativity, N2b, P3 and reorienting negativity (RON) sequence of event-related brain potentials. In children, the P3 latency was the same as in young adults. However the RON component was delayed by about 100 ms. In the elderly, P3 and RON were uniformly delayed by about 80 ms compared to young adults. This pattern of results provides evidence that distraction influences different processing stages in the three groups. Restoration of the task-optimal attention set was delayed in children, whereas in the elderly, the triggering of involuntary attention-switching required longer time.
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paper_title: Auditory distraction in young and middle-aged adults: a behavioural and event-related potential study

paper_content:

Cognitive tasks involving distraction are associated with an early age-related decline in performance. Involuntary shifts in attention to irrelevant stimulus features and subsequent reorientation were studied in young and middle-aged subjects focussing on behavioural and event-related potential (ERP) measures. Subjects were asked to discriminate between equiprobable short and long auditory stimuli. Irrelevant rare frequency deviations prolonged reaction times (RT’s), while an age-related effect on RT’s was not observed. In contrast, notably after short deviant tones the error rate was considerably increased in the middle-aged subjects. ERP measures after deviant stimuli elicited a sequence of mismatch negativity (MMN), P3a and reorienting negativity (RON). The latency and amplitude of the MMN did not differ between age groups indicating an unchanged deviance detection. However, the consecutive process of attention orientation (P3a) was delayed and the subsequent reorienting (RON) to the primary task was strongly attenuated in the middle-aged subjects. After short deviants the RON was virtually absent in the middle-aged subjects, which might account for the observed decline of accuracy.
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paper_title: Regularity Extraction from Non-Adjacent Sounds

paper_content:

The regular behavior of sound sources helps us to make sense of the auditory environment. Regular patterns may, for instance, convey information on the identity of a sound source (such as the acoustic signature of a train moving on the rails). Yet typically, this signature overlaps in time with signals emitted from other sound sources. It is generally assumed that auditory regularity extraction cannot operate upon this mixture of signals because it only finds regularities between adjacent sounds. In this view, the auditory environment would be grouped into separate entities by means of readily available acoustic cues such as separation in frequency and location. Regularity extraction processes would then operate upon the resulting groups. Our new experimental evidence challenges this view. We presented two interleaved sound sequences which overlapped in frequency range and shared all acoustic parameters. The sequences only differed in their underlying regular patterns. We inserted deviants into one of the sequences to probe whether the regularity was extracted. In the first experiment, we found that these deviants elicited the mismatch negativity (MMN) component. Thus the auditory system was able to find the regularity between the non-adjacent sounds. Regularity extraction was not influenced by sequence cohesiveness as manipulated by the relative duration of tones and silent inter-tone-intervals. In the second experiment, we showed that a regularity connecting non-adjacent sounds was discovered only when the intervening sequence also contained a regular pattern, but not when the intervening sounds were randomly varying. This suggests that separate regular patterns are available to the auditory system as a cue for identifying signals coming from distinct sound sources. Thus auditory regularity extraction is not necessarily confined to a processing stage after initial sound grouping, but may precede grouping when other acoustic cues are unavailable.
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paper_title: Low-Frequency Neural Oscillations Support Dynamic Attending in Temporal Context

paper_content:

Behaviorally relevant environmental stimuli are often characterized by some degree of temporal regularity. Dynamic attending theory provides a framework for explaining how perception of stimulus events is affected by the temporal context within which they occur. However, the precise neural implementation of dynamic attending remains unclear. Here, we provide a suggestion for a potential neural implementation of dynamic attending by appealing to low-frequency neural oscillations. The current review will familiarize the reader with the basic theoretical tenets of dynamic attending theory, and review empirical work supporting predictions derived from the theory. The potential neural implementation of dynamic attending theory with respect to low-frequency neural oscillations will be outlined, covering stimulus processing in regular and irregular contexts. Finally, we will provide some more speculative connections between dynamic attending and neural oscillations, and suggest further avenues for future research.
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paper_title: The free-energy principle: a unified brain theory?

paper_content:

A free-energy principle has been proposed recently that accounts for action, perception and learning. This Review looks at some key brain theories in the biological (for example, neural Darwinism) and physical (for example, information theory and optimal control theory) sciences from the free-energy perspective. Crucially, one key theme runs through each of these theories — optimization. Furthermore, if we look closely at what is optimized, the same quantity keeps emerging, namely value (expected reward, expected utility) or its complement, surprise (prediction error, expected cost). This is the quantity that is optimized under the free-energy principle, which suggests that several global brain theories might be unified within a free-energy framework.
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paper_title: Auditory Scene Analysis: The Perceptual Organization of Sound

paper_content:

Auditory Scene Analysis addresses the problem of hearing complex auditory environments, using a series of creative analogies to describe the process required of the human auditory system as it analyzes mixtures of sounds to recover descriptions of individual sounds. In a unified and comprehensive way, Bregman establishes a theoretical framework that integrates his findings with an unusually wide range of previous research in psychoacoustics, speech perception, music theory and composition, and computer modeling.
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paper_title: A theory of cortical responses

paper_content:

This article concerns the nature of evoked brain responses and the principles underlying their generation. We start with the premise that the sensory brain has evolved to represent or infer the causes of changes in its sensory inputs. The problem of inference is well formulated in statistical terms. The statistical fundaments of inference may therefore afford important constraints on neuronal implementation. By formulating the original ideas of Helmholtz on perception, in terms of modern-day statistical theories, one arrives at a model of perceptual inference and learning that can explain a remarkable range of neurobiological facts. It turns out that the problems of inferring the causes of sensory input (perceptual inference) and learning the relationship between input and cause (perceptual learning) can be resolved using exactly the same principle. Specifically, both inference and learning rest on minimizing the brain’s free energy, as defined in statistical physics. Furthermore, inference and learning can proceed in a biologically plausible fashion. Cortical responses can be seen as the brain’s attempt to minimize the free energy induced by a stimulus and thereby encode the most likely cause of that stimulus. Similarly, learning emerges from changes in synaptic efficacy that minimize the free energy, averaged over all stimuli encountered. The underlying scheme rests on empirical Bayes and hierarchical models of how sensory input is caused. The use of hierarchical models enables the brain to construct prior expectations in a dynamic and context-sensitive fashion. This scheme provides a principled way to understand many aspects of cortical organization and responses. The aim of this article is to encompass many apparently unrelated anatomical, physiological and psychophysical attributes of the brain within a single theoretical perspective. In terms of cortical architectures, the theoretical treatment predicts that sensory cortex should be arranged hierarchically, that connections should be reciprocal and that forward and backward connections should show a functional asymmetry (forward connections are driving, whereas backward connections are both driving and modulatory). In terms of synaptic physiology, it predicts associative plasticity and, for dynamic models, spike-timing-dependent plasticity. In terms of electrophysiology, it accounts for classical and extra classical receptive field effects and long-latency or endogenous components of evoked cortical responses. It predicts the attenuation of responses encoding prediction error with perceptual learning and explains many phenomena such as repetition suppression, mismatch negativity (MMN) and the P300 in electroencephalography. In psychophysical terms, it accounts for the behavioural correlates of these physiological phenomena, for example, priming and global precedence. The final focus of this article is on perceptual learning as measured with the MMN and the implications for empirical studies of coupling among cortical areas using evoked sensory responses.
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paper_title: Effects of Location, Frequency Region, and Time Course of Selective Attention on Auditory Scene Analysis

paper_content:

Often, the sound arriving at the ears is a mixture from many different sources, but only 1 is of interest. To assist with selection, the auditory system structures the incoming input into streams, each of which ideally corresponds to a single source. Some authors have argued that this process of streaming is automatic and invariant, but recent evidence suggests it is affected by attention. In Experiments 1 and 2, it is shown that the effect of attention is not a general suppression of streaming on an unattended side of the ascending auditory pathway or in unattended frequency regions. Experiments 3 and 4 investigate the effect on streaming of physical gaps in the sequence and of brief switches in attention away from a sequence. The results demonstrate that after even short gaps or brief switches in attention, streaming is reset. The implications are discussed, and a hierarchical decomposition model is proposed. The sound arriving at a listener’s ears is often a mixture from many different sources, but usually only one will be of interest at any one time. Several different processes might help listeners in the task of selecting the sound from the source(s) in which they are interested. If listeners have a clear idea of the properties of the sound they wish to listen to, then they might be able to selectively attend and devote greater processing resources to sounds with characteristics like the target source. This selection might be based on primitive acoustic properties that are known to be resolved early in auditory processing, such as place of excitation on the
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paper_title: Different roles of similarity and predictability in auditory stream segregation

paper_content:

Sound sources often emit trains of discrete sounds, such as a series of footsteps. Previously, two different principles have been suggested for how the human auditory system binds discrete sounds together into perceptual units. The feature similarity principle is based on linking sounds with similar characteristics over time. The predictability principle is based on linking sounds that follow each other in a predictable manner. The present study compared the effects of these two principles. Participants were presented with tone sequences and instructed to continuously indicate whether they perceived a single coherent sequence or two concurrent streams of sound. We investigated the influence of separate manipulations of similarity and predictability on these perceptual reports. Both grouping principles affected perception of the tone sequences, albeit with different characteristics. In particular, results suggest that whereas predictability is only analyzed for the currently perceived sound organization, f...
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paper_title: Simple and complex acoustic regularities are encoded at different levels of the auditory hierarchy

paper_content:

The detection of auditory stimuli that deviate from a simple or complex auditory regularity is reflected by the mismatch negativity component of the human auditory evoked potential. Moreover, simple deviants of an oddball paradigm modulate the preceding middle-latency response of the auditory evoked potential. For the frequency oddball paradigms it has been shown that the Nb wave, at approximately 40 ms from stimulus onset, is enhanced in response to deviant compared with standard stimuli. In this study we tested whether the detection of auditory deviants in a (frequency-location) feature-conjunction paradigm is reflected by modulations of the Na, Pa or Nb wave of healthy human participants. In addition, a frequency oddball paradigm was applied to directly contrast the results of a simple and a complex invariance. Feature-conjunction deviants did not elicit any modulations of the tested middle-latency waves. Deviants of the frequency oddball paradigm, by contrast, elicited an enhancement of the Nb wave, confirming the outcome of precedent studies. In both conditions a significant mismatch negativity component was elicited, which showed larger amplitudes and shorter latencies in the oddball condition than in the feature-conjunction condition. These findings corroborate the idea that simple auditory regularities are encoded upstream of those of more complex auditory features and are in line with the idea of a hierarchically working auditory novelty system.
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paper_title: Perceptual Organization of Sound Begins in the Auditory Periphery

paper_content:

Summary Segmenting the complex acoustic mixture that makes a typical auditory scene into relevant perceptual objects is one of the main challenges of the auditory system [1], for both human and nonhuman species. Several recent studies indicate that perceptual auditory object formation, or "streaming," may be based on neural activity within the auditory cortex and beyond [2, 3]. Here, we find that scene analysis starts much earlier in the auditory pathways. Single units were recorded from a peripheral structure of the mammalian auditory brainstem, the cochlear nucleus. Peripheral responses were similar to cortical responses and displayed all of the functional properties required for streaming, including multisecond adaptation. Behavioral streaming was also measured in human listeners. Neurometric functions derived from the peripheral responses predicted accurately behavioral streaming. This reveals that subcortical structures may already contribute to the analysis of auditory scenes. This finding is consistent with the observation that species lacking a neocortex can still achieve and benefit from behavioral streaming [4]. For humans, we argue that auditory scene analysis of complex scenes is probably based on interactions between subcortical and cortical neural processes, with the relative contribution of each stage depending on the nature of the acoustic cues forming the streams.
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paper_title: What is an auditory object?

paper_content:

Objects are the building blocks of experience, but what do we mean by an object? Increasingly, neuroscientists refer to 'auditory objects', yet it is not clear what properties these should possess, how they might be represented in the brain, or how they might relate to the more familiar objects of vision. The concept of an auditory object challenges our understanding of object perception. Here, we offer a critical perspective on the concept and its basis in the brain.
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paper_title: Regularity Extraction from Non-Adjacent Sounds

paper_content:

The regular behavior of sound sources helps us to make sense of the auditory environment. Regular patterns may, for instance, convey information on the identity of a sound source (such as the acoustic signature of a train moving on the rails). Yet typically, this signature overlaps in time with signals emitted from other sound sources. It is generally assumed that auditory regularity extraction cannot operate upon this mixture of signals because it only finds regularities between adjacent sounds. In this view, the auditory environment would be grouped into separate entities by means of readily available acoustic cues such as separation in frequency and location. Regularity extraction processes would then operate upon the resulting groups. Our new experimental evidence challenges this view. We presented two interleaved sound sequences which overlapped in frequency range and shared all acoustic parameters. The sequences only differed in their underlying regular patterns. We inserted deviants into one of the sequences to probe whether the regularity was extracted. In the first experiment, we found that these deviants elicited the mismatch negativity (MMN) component. Thus the auditory system was able to find the regularity between the non-adjacent sounds. Regularity extraction was not influenced by sequence cohesiveness as manipulated by the relative duration of tones and silent inter-tone-intervals. In the second experiment, we showed that a regularity connecting non-adjacent sounds was discovered only when the intervening sequence also contained a regular pattern, but not when the intervening sounds were randomly varying. This suggests that separate regular patterns are available to the auditory system as a cue for identifying signals coming from distinct sound sources. Thus auditory regularity extraction is not necessarily confined to a processing stage after initial sound grouping, but may precede grouping when other acoustic cues are unavailable.
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paper_title: Detection of Simple and Pattern Regularity Violations Occurs at Different Levels of the Auditory Hierarchy

paper_content:

Auditory deviance detection in humans is indexed by the mismatch negativity (MMN), a component of the auditory evoked potential (AEP) of the electroencephalogram (EEG) occurring at a latency of 100-250 ms after stimulus onset. However, by using classic oddball paradigms, differential responses to regularity violations of simple auditory features have been found at the level of the middle latency response (MLR) of the AEP occurring within the first 50 ms after stimulus (deviation) onset. These findings suggest the existence of fast deviance detection mechanisms for simple feature changes, but it is not clear whether deviance detection among more complex acoustic regularities could be observed at such early latencies. To test this, we examined the pre-attentive processing of rare stimulus repetitions in a sequence of tones alternating in frequency in both long and middle latency ranges. Additionally, we introduced occasional changes in the interaural time difference (ITD), so that a simple-feature regularity could be examined in the same paradigm. MMN was obtained for both repetition and ITD deviants, occurring at 150 ms and 100 ms after stimulus onset respectively. At the level of the MLR, a difference was observed between standards and ITD deviants at the Na component (20-30 ms after stimulus onset), for 800 Hz tones, but not for repetition deviants. These findings suggest that detection mechanisms for deviants to simple regularities, but not to more complex regularities, are already activated in the MLR range, supporting the view that the auditory deviance detection system is organized in a hierarchical manner.
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paper_title: Regular patterns stabilize auditory streams

paper_content:

The auditory system continuously parses the acoustic environment into auditory objects, usually representing separate sound sources. Sound sources typically show characteristic emission patterns. These regular temporal sound patterns are possible cues for distinguishing sound sources. The present study was designed to test whether regular patterns are used as cues for source distinction and to specify the role that detecting these regularities may play in the process of auditory stream segregation. Participants were presented with tone sequences, and they were asked to continuously indicate whether they perceived the tones in terms of a single coherent sequence of sounds (integrated) or as two concurrent sound streams (segregated). Unknown to the participant, in some stimulus conditions, regular patterns were present in one or both putative streams. In all stimulus conditions, participants’ perception switched back and forth between the two sound organizations. Importantly, regular patterns occurring in e...
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paper_title: Auditory deviance detection revisited: Evidence for a hierarchical novelty system

paper_content:

Abstract The fast detection of novel or deviant stimuli is a striking property of the auditory processing which reflects basic organizational principles of the auditory system and at the same time is of high practical significance. In human electrophysiology, deviance detection has been related to the occurrence of the mismatch negativity (MMN) — a component of the event-related potential (ERP) evoked 100 to 250 ms after the occurrence of a rare irregular sound. Recently, it has been shown in animal studies that a considerable portion of neurons in the auditory pathway exhibits a property called stimulus-specific adaptation enabling them to encode inter-sound relationships and to discharge at higher rates to rare changes in the acoustic stimulation. These neural responses have been linked to the deviant-evoked potential measured at the human scalp, but such responses occur at lower levels anatomically (e.g. the primary auditory cortex as well as the inferior colliculi) and are elicited earlier (20–30 ms after sound onset) in comparison to MMN. Further, they are not considerable enough in size to be interpreted as a direct neural correlate of the MMN. We review here a series of recent findings that provides a first step toward filling this gap between animal and human recordings by showing that comparably early modulations due to a sound's deviancy can be observed in humans, particularly in the middle-latency portion of the ERP within the first 50 ms after sound onset. The existence of those early indices of deviance detection preceding the well-studied MMN component strongly supports the idea that the encoding of regularities and the detection of violations is a basic principle of human auditory processing acting on multiple levels. This sustains the notion of a hierarchically organized novelty and deviance detection system in the human auditory system.
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paper_title: The free-energy principle: a unified brain theory?

paper_content:

A free-energy principle has been proposed recently that accounts for action, perception and learning. This Review looks at some key brain theories in the biological (for example, neural Darwinism) and physical (for example, information theory and optimal control theory) sciences from the free-energy perspective. Crucially, one key theme runs through each of these theories — optimization. Furthermore, if we look closely at what is optimized, the same quantity keeps emerging, namely value (expected reward, expected utility) or its complement, surprise (prediction error, expected cost). This is the quantity that is optimized under the free-energy principle, which suggests that several global brain theories might be unified within a free-energy framework.
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paper_title: Toward a Neurophysiological Theory of Auditory Stream Segregation.

paper_content:

Auditory stream segregation (or streaming) is a phenomenon in which 2 or more repeating sounds differing in at least 1 acoustic attribute are perceived as 2 or more separate sound sources (i.e., streams). This article selectively reviews psychophysical and computational studies of streaming and comprehensively reviews more recent neurophysiological studies that have provided important insights into the mechanisms of streaming. On the basis of these studies, segregation of sounds is likely to occur beginning in the auditory periphery and continuing at least to primary auditory cortex for simple cues such as pure-tone frequency but at stages as high as secondary auditory cortex for more complex cues such as periodicity pitch. Attention-dependent and perception-dependent processes are likely to take place in primary or secondary auditory cortex and may also involve higher level areas outside of auditory cortex. Topographic maps of acoustic attributes, stimulus-specific suppression, and competition between representations are among the neurophysiological mechanisms that likely contribute to streaming. A framework for future research is proposed.
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paper_title: The role of temporal regularity in auditory segregation.

paper_content:

Abstract The idea that predictive modelling and extraction of regularities plays a pivotal role in auditory segregation has recently attracted considerable attention. The present study investigated the effect of one basic form of regularity, rhythmic regularity, on auditory stream segregation. We departed from the classic streaming paradigm and developed a new stimulus, Rand-AB, consisting of two, concurrently presented, temporally uncorrelated, tone sequences (with frequencies A and B). To evaluate segregation, we used an objective measure of the extent to which listeners are able to selectively attend to one of the sequences in the presence of the other. Performance was quantified on a difficult pattern detection task which involves detecting a rarely occurring pattern of amplitude modulation applied to three consecutive A or B tones. In all cases the attended sequence was temporally irregular (with a random inter-tone-interval (ITI) between 100 and 400 ms) and the regularity status of the competing sequence was set to one of four conditions: (1) random ITI between 100 and 400 ms (2) isochronous with ITI = 400 ms. (3) isochronous with ITI = 250 ms (equal to the mean rate of the attended sequence) (4) isochronous with ITI = 100 ms. For a frequency separation of 2 (but not 4) semi tones we observed improved performance in conditions (3) and (4) relative to (1), suggesting that stream segregation is facilitated when the distracter sequence is temporally regular, but that the effect of temporal regularity as a cue for segregation is limited to relatively fast rates and to situations where frequency separation is insufficient for segregation. These findings provide new evidence to support models of streaming that involve segregation based on the formation of predictive models.
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paper_title: Auditory Scene Analysis: The Perceptual Organization of Sound

paper_content:

Auditory Scene Analysis addresses the problem of hearing complex auditory environments, using a series of creative analogies to describe the process required of the human auditory system as it analyzes mixtures of sounds to recover descriptions of individual sounds. In a unified and comprehensive way, Bregman establishes a theoretical framework that integrates his findings with an unusually wide range of previous research in psychoacoustics, speech perception, music theory and composition, and computer modeling.
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paper_title: A theory of cortical responses

paper_content:

This article concerns the nature of evoked brain responses and the principles underlying their generation. We start with the premise that the sensory brain has evolved to represent or infer the causes of changes in its sensory inputs. The problem of inference is well formulated in statistical terms. The statistical fundaments of inference may therefore afford important constraints on neuronal implementation. By formulating the original ideas of Helmholtz on perception, in terms of modern-day statistical theories, one arrives at a model of perceptual inference and learning that can explain a remarkable range of neurobiological facts. It turns out that the problems of inferring the causes of sensory input (perceptual inference) and learning the relationship between input and cause (perceptual learning) can be resolved using exactly the same principle. Specifically, both inference and learning rest on minimizing the brain’s free energy, as defined in statistical physics. Furthermore, inference and learning can proceed in a biologically plausible fashion. Cortical responses can be seen as the brain’s attempt to minimize the free energy induced by a stimulus and thereby encode the most likely cause of that stimulus. Similarly, learning emerges from changes in synaptic efficacy that minimize the free energy, averaged over all stimuli encountered. The underlying scheme rests on empirical Bayes and hierarchical models of how sensory input is caused. The use of hierarchical models enables the brain to construct prior expectations in a dynamic and context-sensitive fashion. This scheme provides a principled way to understand many aspects of cortical organization and responses. The aim of this article is to encompass many apparently unrelated anatomical, physiological and psychophysical attributes of the brain within a single theoretical perspective. In terms of cortical architectures, the theoretical treatment predicts that sensory cortex should be arranged hierarchically, that connections should be reciprocal and that forward and backward connections should show a functional asymmetry (forward connections are driving, whereas backward connections are both driving and modulatory). In terms of synaptic physiology, it predicts associative plasticity and, for dynamic models, spike-timing-dependent plasticity. In terms of electrophysiology, it accounts for classical and extra classical receptive field effects and long-latency or endogenous components of evoked cortical responses. It predicts the attenuation of responses encoding prediction error with perceptual learning and explains many phenomena such as repetition suppression, mismatch negativity (MMN) and the P300 in electroencephalography. In psychophysical terms, it accounts for the behavioural correlates of these physiological phenomena, for example, priming and global precedence. The final focus of this article is on perceptual learning as measured with the MMN and the implications for empirical studies of coupling among cortical areas using evoked sensory responses.
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paper_title: Interpreting the mismatch negativity.

paper_content:

The widely accepted "memory-mismatch" interpretation of the mismatch negativity (MMN) event-related brain potential (ERP) suggests that an MMN is elicited when an acoustic event deviates from a memory record describing the immediate history of the sound sequence. The first variant of the memory-mismatch theory suggested that the memory underlying MMN generation was a strong auditory sensory memory trace, which encoded the repetitive standard sound. This "trace-mismatch" explanation of MMN has been primarily based on results obtained in the auditory oddball paradigm. However, in recent years, MMN has been observed in stimulus paradigms containing no frequently repeating sound. We now suggest a different variant of the memory-mismatch interpretation of MMN in order to provide a unified explanation of all MMN phenomena. The regularity-violation explanation of MMN assumes that the memory records retaining the history of auditory stimulation are regularity representations. These representations encode rules extracted from the regular intersound relationships, which are mapped to the concrete sound sequence by finely detailed auditory sensory information. Auditory events are compared with temporally aligned predictions drawn from the regularity representations (predictive models) and the observable MMN response reflects a process updating the representations of those detected regularities whose prediction was mismatched by the acoustic input. It is further suggested that the auditory deviance detection system serves to organize sound in the brain: The predictive models maintained by the MMN-generating process provide the basis of temporal grouping, a crucial step in the formation of auditory
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paper_title: Different roles of similarity and predictability in auditory stream segregation

paper_content:

Sound sources often emit trains of discrete sounds, such as a series of footsteps. Previously, two different principles have been suggested for how the human auditory system binds discrete sounds together into perceptual units. The feature similarity principle is based on linking sounds with similar characteristics over time. The predictability principle is based on linking sounds that follow each other in a predictable manner. The present study compared the effects of these two principles. Participants were presented with tone sequences and instructed to continuously indicate whether they perceived a single coherent sequence or two concurrent streams of sound. We investigated the influence of separate manipulations of similarity and predictability on these perceptual reports. Both grouping principles affected perception of the tone sequences, albeit with different characteristics. In particular, results suggest that whereas predictability is only analyzed for the currently perceived sound organization, f...
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paper_title: Role of predictability of sequence in auditory stream segregation

paper_content:

This study evaluates the role of item predictability in auditory temporal coherence. Thirteen normal-hearing subjects were required to hold together long tonal sequences as single strings of notes. Temporal and spectral predictability of successive notes in a sequence varied as a function of experimental condition. As the frequency separation of the notes in the sequence increased, the subjects found it more difficult to hold the sequence together as a single stream. There was no significant difference in subjects’ abilities in performing this task as a function of experimental condition. That is, the predictability of successive notes appeared not to have a role in temporal coherence.
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paper_title: Modeling the auditory scene: predictive regularity representations and perceptual objects

paper_content:

Predictive processing of information is essential for goal-directed behavior. We offer an account of auditory perception suggesting that representations of predictable patterns, or 'regularities', extracted from the incoming sounds serve as auditory perceptual objects. The auditory system continuously searches for regularities within the acoustic signal. Primitive regularities may be encoded by neurons adapting their response to specific sounds. Such neurons have been observed in many parts of the auditory system. Representations of the detected regularities produce predictions of upcoming sounds as well as alternative solutions for parsing the composite input into coherent sequences potentially emitted by putative sound sources. Accuracy of the predictions can be utilized for selecting the most likely interpretation of the auditory input. Thus in our view, perception generates hypotheses about the causal structure of the world.
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paper_title: Stability of Perceptual Organisation in Auditory Streaming

paper_content:

In everyday situations, we perceive sounds organised according to their source, and can follow someone’s speech or a musical piece in the presence of other sounds without apparent effort. Thus, it is surprising that recent evidence obtained in the most widely used experimental test-bed of auditory scene analysis, the two-tone streaming paradigm, demonstrated extensive bistability even in regions of the parameter space previously thought to be strongly biased towards a particular organisation. This raises the question of what aspects of the rich natural input allow the auditory system to form stable representations of concurrently active sound sources. Here, we report the results of perceptual studies aimed at testing this issue. It is possible that the extreme repetitiveness of the alternating two-tone sequence, i.e. lack of change, causes perceptual instability. Our first experiment addressed this hypothesis by introducing random changes in the stimulation. It is also possible that under natural conditions, multiple redundant cues stabilise perception. The second experiment tested this hypothesis by adding a second cue which favoured one organisation. Much to our surprise, neither one of these manipulations stabilised the perception of two-tone streaming sequences. We discuss these experimental results in the light of our previous theoretical proposals and findings of significant differences between the first and later perceptual phases. We argue that multi-stability is inherent in perception. However, it is normally hidden by switches of attention, which allow the return of the dominant perceptual organisation resulting in the subjective experience of perceptual stability. In our third experiment, we explored this possibility by inserting short gaps into the sequences, since gaps have been shown to reset auditory streaming in a manner similar to switches in attention.
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paper_title: Evidence from auditory and visual event-related potential (ERP) studies of deviance detection (MMN and vMMN) linking predictive coding theories and perceptual object representations

paper_content:

Abstract Predictive coding theories posit that the perceptual system is structured as a hierarchically organized set of generative models with increasingly general models at higher levels. The difference between model predictions and the actual input (prediction error) drives model selection and adaptation processes minimizing the prediction error. Event-related brain potentials elicited by sensory deviance are thought to reflect the processing of prediction error at an intermediate level in the hierarchy. We review evidence from auditory and visual studies of deviance detection suggesting that the memory representations inferred from these studies meet the criteria set for perceptual object representations. Based on this evidence we then argue that these perceptual object representations are closely related to the generative models assumed by predictive coding theories.
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paper_title: Auditory streaming affects the processing of successive deviant and standard sounds

paper_content:

This study investigated the temporal relation between two early mechanisms of auditory information processing: the segregation of the auditory input into streams and the automatic deviance detection indicated by the mismatch negativity (MMN). To address this question the processing of successive deviant and standard tones within streaming and nonstreaming conditions was analyzed. In the streaming condition the amplitude reduction of MMN elicited by the second of two successive deviants was found to be smaller for successive deviants presented in different than in same streams. No corresponding MMN differences were obtained in a nonstreaming condition. These results demonstrate that stream segregation precedes deviance detection. Moreover, modulations of the N1 amplitudes elicited by successive standard tones in the streaming condition demonstrate that not only deviance-related processing but even initial sound processing is affected by streaming.
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paper_title: Role of pattern, regularity, and silent intervals in auditory stream segregation based on inter-aural time differences

paper_content:

Tone triplets separated by a pause (ABA_) are a popular tone-repetition pattern to study auditory stream segregation. Such triplets produce a galloping rhythm when integrated, but isochronous rhythms when segregated. Other patterns lacking a pause may produce less-prominent rhythmic differences but stronger streaming. Here, we evaluated whether this difference is readily explained by the presence of the pause and potentially associated with the reduction of adaptation, or whether there is contribution of tone pattern per se. Sequences with repetitive ABA_ and ABAA patterns were presented in magnetoencephalography. A and B tones were separated by differences in inter-aural time differences (ΔITD). Results showed that the stronger streaming of ABAA was associated with a more prominent release from the adaptation of the P1m in auditory cortex. We further compared behavioral streaming responses for patterns with and without pauses, and varied the position of the pause and pattern regularity. Results showed a major effect of the pauses’ presence, but no prominent effects of tone pattern or pattern regularity. These results make a case for the existence of an early, primitive streaming mechanism that does not require an analysis of the tone pattern at later stages suggested by predictive-coding models of auditory streaming. The results are better explained by the simpler population-separation model and stress the previously observed role of neural adaptation for streaming perception.
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paper_title: Regular patterns stabilize auditory streams

paper_content:

The auditory system continuously parses the acoustic environment into auditory objects, usually representing separate sound sources. Sound sources typically show characteristic emission patterns. These regular temporal sound patterns are possible cues for distinguishing sound sources. The present study was designed to test whether regular patterns are used as cues for source distinction and to specify the role that detecting these regularities may play in the process of auditory stream segregation. Participants were presented with tone sequences, and they were asked to continuously indicate whether they perceived the tones in terms of a single coherent sequence of sounds (integrated) or as two concurrent sound streams (segregated). Unknown to the participant, in some stimulus conditions, regular patterns were present in one or both putative streams. In all stimulus conditions, participants’ perception switched back and forth between the two sound organizations. Importantly, regular patterns occurring in e...
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paper_title: Modelling the Emergence and Dynamics of Perceptual Organisation in Auditory Streaming

paper_content:

Many sound sources can only be recognised from the pattern of sounds they emit, and not from the individual sound events that make up their emission sequences. Auditory scene analysis addresses the difficult task of interpreting the sound world in terms of an unknown number of discrete sound sources (causes) with possibly overlapping signals, and therefore of associating each event with the appropriate source. There are potentially many different ways in which incoming events can be assigned to different causes, which means that the auditory system has to choose between them. This problem has been studied for many years using the auditory streaming paradigm, and recently it has become apparent that instead of making one fixed perceptual decision, given sufficient time, auditory perception switches back and forth between the alternatives-a phenomenon known as perceptual bi- or multi-stability. We propose a new model of auditory scene analysis at the core of which is a process that seeks to discover predictable patterns in the ongoing sound sequence. Representations of predictable fragments are created on the fly, and are maintained, strengthened or weakened on the basis of their predictive success, and conflict with other representations. Auditory perceptual organisation emerges spontaneously from the nature of the competition between these representations. We present detailed comparisons between the model simulations and data from an auditory streaming experiment, and show that the model accounts for many important findings, including: the emergence of, and switching between, alternative organisations; the influence of stimulus parameters on perceptual dominance, switching rate and perceptual phase durations; and the build-up of auditory streaming. The principal contribution of the model is to show that a two-stage process of pattern discovery and competition between incompatible patterns can account for both the contents (perceptual organisations) and the dynamics of human perception in auditory streaming.
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paper_title: The role of predictive models in the formation of auditory streams

paper_content:

Abstract Sounds provide us with useful information about our environment which complements that provided by other senses, but also poses specific processing problems. How does the auditory system distentangle sounds from different sound sources? And what is it that allows intermittent sound events from the same source to be associated with each other? Here we review findings from a wide range of studies using the auditory streaming paradigm in order to formulate a unified account of the processes underlying auditory perceptual organization. We present new computational modelling results which replicate responses in primary auditory cortex [Fishman, Y.I., Arezzo, J.C., Steinschneider, M., 2004. Auditory stream segregation in monkey auditory cortex: effects of frequency separation, presentation rate, and tone duration. J. Acoust. Soc. Am. 116, 1656–1670; Fishman, Y. I., Reser, D. H., Arezzo, J.C., Steinschneider, M., 2001. Neural correlates of auditory stream segregation in primary auditory cortex of the awake monkey. Hear. Res. 151, 167–187] to tone sequences. We also present the results of a perceptual experiment which confirm the bi-stable nature of auditory streaming, and the proposal that the gradual build-up of streaming may be an artefact of averaging across many subjects [Pressnitzer, D., Hupe, J. M., 2006. Temporal dynamics of auditory and visual bi-stability reveal common principles of perceptual organization. Curr. Biol. 16(13), 1351–1357.]. Finally we argue that in order to account for all of the experimental findings, computational models of auditory stream segregation require four basic processing elements; segregation, predictive modelling, competition and adaptation, and that it is the formation of effective predictive models which allows the system to keep track of different sound sources in a complex auditory environment.
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paper_title: Auditory Scene Analysis: The Perceptual Organization of Sound

paper_content:

Auditory Scene Analysis addresses the problem of hearing complex auditory environments, using a series of creative analogies to describe the process required of the human auditory system as it analyzes mixtures of sounds to recover descriptions of individual sounds. In a unified and comprehensive way, Bregman establishes a theoretical framework that integrates his findings with an unusually wide range of previous research in psychoacoustics, speech perception, music theory and composition, and computer modeling.
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paper_title: The effect of small variation of the frequent auditory stimulus on the event-related brain potential to the infrequent stimulus

paper_content:

We investigated whether the mismatch process between a rare stimulus and the trace of frequent stimulus, which generates the mismatch-negativity component of the event-related potential, can tolerate a small variation in the intensity of the frequent stimulus. Series of short tone pips were presented to 10 subjects while they were reading a book and ignoring the auditory stimuli. The intensity (mean 80dB) of the frequent stimulus (600 Hz) varied within a range that was different in different blocks. The probability of the infrequent stimuli which were, in different blocks, either intensity deviants (600 Hz/70dB) or frequency deviants (650 Hz/80dB) was 10%. Both deviant stimuli elicited mismatch negativity even when the intensity of the frequent stimulus varied, although the amplitude of this component decreased with the increasing variability of the frequent stimulus. These results show that the generator process of mismatch negativity tolerates some variation in the repetitive stimulus, thus indicating that this process is also activated in ecologically more valid conditions. This is crucial to the interpretation of the generator process of mismatch negativity as a biologically vital warning mechanism.
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paper_title: Responses to deviants are modulated by subthreshold variability of the standard

paper_content:

Auditory mechanisms automatically detect both basic features of sounds and the rules governing their presentation. In the oddball paradigm, the auditory system detects the sameness (or no-variability) rule when the same reference tone is consistently repeated. We used two oddball protocols, the classical one with a fixed reference and a modified one with a jittered reference, to determine whether the auditory system can detect subthreshold violations of sameness. We found that the response to the repeated standard was not modified by the small jitter. However, the response to the frequency oddball was smaller under the jittered protocol, indicating hypersensitivity to sameness. The sensitivity to jitter was largest when the oddball deviated by 8%, was smaller for 40%, and disappeared at 100% deviation, indicating that sensitivity to sameness is context dependent; namely, it is scaled with respect to the overall range of stimuli.
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paper_title: It all sounds the same to me: Sequential ERP and behavioral effects during pitch and harmonicity judgments

paper_content:

The representation of complex sounds was examined by comparing both behavioral and event-related brain potentials (ERPs) to the change or repetition of fundamental frequency (f 0) and harmonicity. In the pitch task, participants were asked to categorize the incoming stimulus as either low or high, regardless of harmonicity, and in the harmonicity task, participants indicated whether the stimulus was tuned or mistuned, regardless of pitch. Over three experiments, participants were faster in responding to pitch than to harmonicity. As a result of this asymmetry, behavioral and ERP data showed that irrelevant changes in harmonicity had little impact on performance during the pitch task, whereas harmonicity judgments were impeded by irrelevant changes in f 0. These data are consistent with both general horse-race accounts of processing and specific accounts of mistuning detection that posit prior f 0 registration. In addition, ERP components N2 and P3 were modulated by both intertrial contingency and task instructions, revealing the further influence of top-down mechanisms on concurrent sound segregation.
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paper_title: Temporal coherence and attention in auditory scene analysis

paper_content:

Humans and other animals can attend to one of multiple sounds and follow it selectively over time. The neural underpinnings of this perceptual feat remain mysterious. Some studies have concluded that sounds are heard as separate streams when they activate well-separated populations of central auditory neurons, and that this process is largely pre-attentive. Here, we argue instead that stream formation depends primarily on temporal coherence between responses that encode various features of a sound source. Furthermore, we postulate that only when attention is directed towards a particular feature (e.g. pitch) do all other temporally coherent features of that source (e.g. timbre and location) become bound together as a stream that is segregated from the incoherent features of other sources.
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paper_title: A sound element gets lost in perceptual competition

paper_content:

Our ability to understand auditory signals depends on properly separating the mixture of sound arriving from multiple sources. Sound elements tend to belong to only one object at a time, consistent with the principle of disjoint allocation, although there are instances of duplex perception or coallocation, in which two sound objects share one sound element. Here we report an effect of “nonallocation,” in which a sound element “disappears” when two ongoing objects compete for its ownership. When a target tone is presented either as one of a sequence of tones or simultaneously with a harmonic vowel complex, it is heard as part of the corresponding object. However, depending on the spatial configuration of the scene, if the target, the tones, and the vowel are all presented together, the target may not be perceived in either the tones or the vowel, even though it is not perceived as a separate entity. This finding suggests an asymmetry in the strength of the perceptual evidence required to reject vs. to include an element within the auditory foreground, a result with important implications for how we process complex auditory scenes containing ambiguous information.
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paper_title: Neural representations of auditory input accommodate to the context in a dynamically changing acoustic environment

paper_content:

The auditory scene is dynamic, changing from 1 min to the next as sound sources enter and leave our space. How does the brain resolve the problem of maintaining neural representations of the distinct yet changing sound sources? We used an auditory streaming paradigm to test the dynamics of multiple sound source representation, when switching between integrated and segregated sound streams. The mismatch negativity (MMN) component of event-related potentials was used as index of change detection to observe stimulus-driven modulation of the ongoing sound organization. Probe tones were presented randomly within ambiguously organized sound sequences to reveal whether the neurophysiological representation of the sounds was integrated (no MMN) or segregated (MMN). The pattern of results demonstrated context-dependent responses to a single tone that was modulated in dynamic fashion as the auditory environment rapidly changed from integrated to segregated sounds. This suggests a rapid form of auditory plasticity in which the longer-term sound context influences the current state of neural activity when it is ambiguous. These results demonstrate stimulus-driven modulation of neural activity that accommodates to the dynamically changing acoustic environment.
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paper_title: Neurophysiological evidence for context-dependent encoding of sensory input in human auditory cortex

paper_content:

Attention biases the way in which sound information is stored in auditory memory. Little is known, however, about the contribution of stimulus-driven processes in forming and storing coherent sound events. An electrophysiological index of cortical auditory change detection (mismatch negativity [MMN]) was used to assess whether sensory memory representations could be biased toward one organization over another (one or two auditory streams) without attentional control. Results revealed that sound representations held in sensory memory biased the organization of subsequent auditory input. The results demonstrate that context-dependent sound representations modulate stimulus-dependent neural encoding at early stages of auditory cortical processing.
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paper_title: Role of masker predictability in the cocktail party problem

paper_content:

In studies of the cocktail party problem, the number and locations of maskers are typically fixed throughout a block of trials, which leaves out uncertainty that exists in real-world environments. The current experiments examined whether there is (1) improved speech intelligibility and (2) increased spatial release from masking (SRM), as predictability of the number/locations of speech maskers is increased. In the first experiment, subjects identified a target word presented at a fixed level in the presence of 0, 1, or 2 maskers as predictability of the masker configuration ranged from 10% to 80%. The second experiment examined speech reception thresholds and SRM as (a) predictability of the masker configuration is increased from 20% to 80% and/or (b) the complexity of the listening environment is decreased. In the third experiment, predictability of the masker configuration was increased from 20% up to 100% while minimizing the onset delay between maskers and the target. All experiments showed no effect of predictability of the masker configuration on speech intelligibility or SRM. These results suggest that knowing the number and location(s) of maskers may not necessarily contribute significantly to solving the cocktail party problem, at least not when the location of the target is known.
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paper_title: Object continuity enhances selective auditory attention

paper_content:

In complex scenes, the identity of an auditory object can build up across seconds. Given that attention operates on perceptual objects, this perceptual buildup may alter the efficacy of selective auditory attention over time. Here, we measured identification of a sequence of spoken target digits presented with distracter digits from other directions to investigate the dynamics of selective attention. Performance was better when the target location was fixed rather than changing between digits, even when listeners were cued as much as 1 s in advance about the position of each subsequent digit. Spatial continuity not only avoided well known costs associated with switching the focus of spatial attention, but also produced refinements in the spatial selectivity of attention across time. Continuity of target voice further enhanced this buildup of selective attention. Results suggest that when attention is sustained on one auditory object within a complex scene, attentional selectivity improves over time. Similar effects may come into play when attention is sustained on an object in a complex visual scene, especially in cases where visual object formation requires sustained attention.
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paper_title: Regularity Extraction from Non-Adjacent Sounds

paper_content:

The regular behavior of sound sources helps us to make sense of the auditory environment. Regular patterns may, for instance, convey information on the identity of a sound source (such as the acoustic signature of a train moving on the rails). Yet typically, this signature overlaps in time with signals emitted from other sound sources. It is generally assumed that auditory regularity extraction cannot operate upon this mixture of signals because it only finds regularities between adjacent sounds. In this view, the auditory environment would be grouped into separate entities by means of readily available acoustic cues such as separation in frequency and location. Regularity extraction processes would then operate upon the resulting groups. Our new experimental evidence challenges this view. We presented two interleaved sound sequences which overlapped in frequency range and shared all acoustic parameters. The sequences only differed in their underlying regular patterns. We inserted deviants into one of the sequences to probe whether the regularity was extracted. In the first experiment, we found that these deviants elicited the mismatch negativity (MMN) component. Thus the auditory system was able to find the regularity between the non-adjacent sounds. Regularity extraction was not influenced by sequence cohesiveness as manipulated by the relative duration of tones and silent inter-tone-intervals. In the second experiment, we showed that a regularity connecting non-adjacent sounds was discovered only when the intervening sequence also contained a regular pattern, but not when the intervening sounds were randomly varying. This suggests that separate regular patterns are available to the auditory system as a cue for identifying signals coming from distinct sound sources. Thus auditory regularity extraction is not necessarily confined to a processing stage after initial sound grouping, but may precede grouping when other acoustic cues are unavailable.
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paper_title: Recovering sound sources from embedded repetition

paper_content:

Cocktail parties and other natural auditory environments present organisms with mixtures of sounds. Segregating individual sound sources is thought to require prior knowledge of source properties, yet these presumably cannot be learned unless the sources are segregated first. Here we show that the auditory system can bootstrap its way around this problem by identifying sound sources as repeating patterns embedded in the acoustic input. Due to the presence of competing sounds, source repetition is not explicit in the input to the ear, but it produces temporal regularities that listeners detect and use for segregation. We used a simple generative model to synthesize novel sounds with naturalistic properties. We found that such sounds could be segregated and identified if they occurred more than once across different mixtures, even when the same sounds were impossible to segregate in single mixtures. Sensitivity to the repetition of sound sources can permit their recovery in the absence of other segregation cues or prior knowledge of sounds, and could help solve the cocktail party problem.
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paper_title: Exploring the benefit of auditory spatial continuity

paper_content:

Continuity of spatial location was recently shown to improve the ability to identify and recall a sequence of target digits presented in a mixture of confusable maskers [Best et al. (2008). Proc. Natl. Acad. Sci. U.S.A. 105, 13174–13178]. Three follow-up experiments were conducted to explore the basis of this improvement. The results suggest that the benefits of spatial continuity cannot be attributed to (a) the ability to plan where to direct attention in advance; (b) freedom from having to redirect attention across large distances; or (c) the challenge of filtering out signals that are confusable with the target.
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paper_title: Effects of prior stimulus and prior perception on neural correlates of auditory stream segregation

paper_content:

We examined whether effects of prior experience are mediated by distinct brain processes from those processing current stimulus features. We recorded event-related potentials (ERPs) during an auditory stream segregation task that presented an adaptation sequence with a small, intermediate, or large frequency separation between low and high tones (Df), followed by a test sequence with intermediateDf. Perception of two streams during the test was facilitated by small priorDf and by prior perception of two streams and was accompanied by more positive ERPs. The scalp topography of these perception-related changes in ERPs was different from that observed for ERP modulations due to increasing the current Df. These results reveal complex interactions between stimulus-driven activity and temporal-context-based processes and suggest a complex set of brain areas involved in modulating perception based on current and previous experience. Descriptors: Auditory scene analysis, Auditory cortex, Context, Sensory memory, Event-related potentials, Scalp topography
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paper_title: Effects of frequency disparities on trading of an ambiguous tone between two competing auditory objects

paper_content:

Listeners are relatively good at estimating the true content of each physical source in a sound mixture in most everyday situations. However, if there is a spectrotemporal element that logically could belong to more than one object, the correct way to group that element can be ambiguous. Many psychoacoustic experiments have implicitly assumed that when a sound mixture contains ambiguous sound elements, the ambiguous elements “trade” between competing sources, such that the elements contribute more to one object in conditions when they contribute less to others. However, few studies have directly tested whether such trading occurs. While some studies found trading, trading failed in some recent studies in which spatial cues were manipulated to alter the perceptual organization. The current study extended this work by exploring whether trading occurs for similar sound mixtures when frequency content, rather than spatial cues, was manipulated to alter grouping. Unlike when spatial cues were manipulated, resu...
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paper_title: Auditory Scene Analysis: The Perceptual Organization of Sound

paper_content:

Auditory Scene Analysis addresses the problem of hearing complex auditory environments, using a series of creative analogies to describe the process required of the human auditory system as it analyzes mixtures of sounds to recover descriptions of individual sounds. In a unified and comprehensive way, Bregman establishes a theoretical framework that integrates his findings with an unusually wide range of previous research in psychoacoustics, speech perception, music theory and composition, and computer modeling.
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paper_title: The N1 wave of the human electric and magnetic response to sound: a review and an analysis of the component structure.

paper_content:

This paper reviews the literature on the Nl wave of the human auditory evoked potential. It concludes that at least six different cerebral processes can contribute to (he negative wave recorded from the scalp with a peak latency between 50 and 150 ms: a component generated in the auditory-cortex on the supratemporal plane, a component generated in the association cortex on the lateral aspect of the temporal and parietal cortex, a component generated in the motor and premotor cortices, the mismatch negativity, a temporal component of the processing negativity, and a frontal component of the processing negativity, The first three, which can be considered ‘true’ N1 components, are controlled by the physical and temporal aspects of the stimulus and by the general state of the subject. The other three components are not necessarily elicited by a stimulus but depend on the conditions in which the stimulus occurs. They often last much longer than the true N1 components that they overlap.
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paper_title: Dissociation of perceptual judgments of “what” and “where” in an ambiguous auditory scene

paper_content:

Whenever an acoustic scene contains a mixture of sources, listeners must segregate the mixture in order to compute source content and/or location. Some past studies have explored whether perceived location depends on which sound elements are perceived within a source. However, no direct comparisons have been made of “what” and “where” judgments for the same sound mixtures using the same listeners. The current study tested if the sound elements making up an auditory object predict that object’s perceived location. Listeners were presented with an auditory scene containing competing “target” and “captor” sources, each of which could logically contain a “promiscuous” tone complex. In separate blocks, the same listeners matched the perceived spectro-temporal content (“what”) and location (“where”) of the target. Generally, as the captor intensity decreased, the promiscuous complex contributed more to both what and where judgments of the target. However judgments did not agree either quantitatively or qualitatively. For some subjects, the promiscuous complex consistently contributed more to the spectro-temporal content of the target than to its location while for some it consistently contributed more to target location. These results show a dissociation between the perceived spectro-temporal content of an auditory object and where that object is perceived.
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paper_title: Mechanisms of intentional binding and sensory attenuation: The role of temporal prediction, temporal control, identity prediction, and motor prediction.

paper_content:

Sensory processing of action effects has been shown to differ from that of externally triggered stimuli, with respect both to the perceived timing of their occurrence (intentional binding) and to their intensity (sensory attenuation). These phenomena are normally attributed to forward action models, such that when action prediction is consistent with changes in our environment, our experience of these effects is altered. Although much progress has been made in recent years in understanding sensory attenuation and intentional binding, a number of important questions regarding the precise nature of the predictive mechanisms involved remain unanswered. Moreover, these mechanisms are often not discussed in empirical papers, and a comprehensive review of these issues is yet to appear. This review attempts to fill this void. We systematically investigated the role of temporal prediction, temporal control, identity prediction, and motor prediction in previous published reports of sensory attenuation and intentional binding. By isolating the individual processes that have previously been contrasted and incorporating these experiments with research in the related fields of temporal attention and stimulus expectation, we assessed the degree to which existing data provide evidence for the role of forward action models in these phenomena. We further propose a number of avenues for future research, which may help to better determine the role of motor prediction in processing of voluntary action effects, as well as to improve understanding of how these phenomena might fit within a general predictive processing framework. Furthermore, our analysis has important implications for understanding disorders of agency in schizophrenia.
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paper_title: Cortical oscillations and sensory predictions

paper_content:

Many theories of perception are anchored in the central notion that the brain continuously updates an internal model of the world to infer the probable causes of sensory events. In this framework, the brain needs not only to predict the causes of sensory input, but also when they are most likely to happen. In this article, we review the neurophysiological bases of sensory predictions of "what' (predictive coding) and ‘when' (predictive timing), with an emphasis on low-level oscillatory mechanisms. We argue that neural rhythms offer distinct and adapted computational solutions to predicting ‘what' is going to happen in the sensory environment and ‘when'.
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paper_title: Time is more than a sensory feature: Attending to duration triggers specific anticipatory activity

paper_content:

Time processing requires the estimation of events' duration per se, but also seems to trigger attentional and memory processes. To isolate attentional processes, we investigated neural correlates of anticipatory attention when estimating stimulus duration. Magneto-encephalographic (MEG) activity was recorded in fourteen healthy right-handed volunteers, who were cued to attend to either the duration or the intensity of a visual stimulus. We report an increase of gamma-band oscillations over right fronto-central and parietal regions when subjects are prompted to attend to duration, which is not present when subjects are cued to attend to intensity. Cue-related alpha power decreases over occipito-parietal regions were similar in the two conditions. Our results support the hypothesis that the right fronto-parietal network observed repeatedly in time estimation imaging studies is indeed involved in attentional control rather than stimulus processing. Moreover, they underline the supramodal property of time dim...
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paper_title: Benefits of knowing who, where, and when in multi-talker listening.

paper_content:

The benefits of prior information about who would speak, where they would be located, and when they would speak were measured in a multi-talker spatial-listening task. On each trial, a target phrase and several masker phrases were allocated to 13 loudspeakers in a 180 degrees arc, and to 13 overlapping time slots, which started every 800 ms. Speech-reception thresholds (SRTs) were measured as the level of target relative to masker phrases at which listeners reported key words at 71% correct. When phases started in pairs all three cues were beneficial ("who" 3.2 dB, "where" 5.1 dB, and "when" 0.3 dB). Over a range of onset asynchronies, SRTs corresponded consistently to a signal-to-noise ratio (SNR) of -2 dB at the start of the target phrase. When phrases started one at a time, SRTs fell to a SNR of -8 dB and were improved significantly, but only marginally, by constraining "who" (1.9 dB), and not by constraining "where" (1.0 dB) or "when" (0.01 dB). Thus, prior information about "who," "where," and "when" was beneficial, but only when talkers started speaking in pairs. Low SRTs may arise when talkers start speaking one at a time because of automatic orienting to phrase onsets and/or the use of loudness differences to distinguish target from masker phrases.
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paper_title: Dissociation of formal and temporal predictability in early auditory evoked potentials

paper_content:

Perceived regularity among events in the environment allows predictions regarding the “when” and the “what” dimensions of future events. In this context, one crucial question concerns the impact and the potentially optimizing effect, of regular temporal structure on the processing of “what”, or formal, information. The current study addresses this issue by investigating whether temporal and formal structure interact during early stages of sensory processing, and by relating the respective findings to the concept of a predictive bias in brain function. Analyses were performed on two components of the auditory event-related-potential of the electroencephalogram, namely the P50 and the N100. Oddball sequences consisting of frequent standard and infrequent deviant sinusoidal tones were presented with either regular or irregular temporal structure in pre-attentive and attentive experimental settings (Schwartze, Rothermich, Schmidt-Kassow, & Kotz, 2011). Temporal regularity effects on pre-attentive and attentive processing of deviance. Biological Psychology, 87, 146–151). The results confirm that the P50 and the N100 amplitudes reliably encode formal and temporal predictability. Similar patterns of results obtained with pre-attentive and attentive task instructions, as well as the absence of a significant interaction of formal and temporal structure suggest that the P50 response may be interpreted as an automatic marker of predictability, whereas the N100 may represent a more complex marker, in which formal and temporal structure start interacting as a function of attention.
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paper_title: Mechanisms and streams for processing of “what” and “where” in auditory cortex

paper_content:

The functional specialization and hierarchical organization of multiple areas in rhesus monkey auditory cortex were examined with various types of complex sounds. Neurons in the lateral belt areas of the superior temporal gyrus were tuned to the best center frequency and bandwidth of band-passed noise bursts. They were also selective for the rate and direction of linear frequency modulated sweeps. Many neurons showed a preference for a limited number of species-specific vocalizations (“monkey calls”). These response selectivities can be explained by nonlinear spectral and temporal integration mechanisms. In a separate series of experiments, monkey calls were presented at different spatial locations, and the tuning of lateral belt neurons to monkey calls and spatial location was determined. Of the three belt areas the anterolateral area shows the highest degree of specificity for monkey calls, whereas neurons in the caudolateral area display the greatest spatial selectivity. We conclude that the cortical auditory system of primates is divided into at least two processing streams, a spatial stream that originates in the caudal part of the superior temporal gyrus and projects to the parietal cortex, and a pattern or object stream originating in the more anterior portions of the lateral belt. A similar division of labor can be seen in human auditory cortex by using functional neuroimaging.
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paper_title: Tuning of the Human Neocortex to the Temporal Dynamics of Attended Events

paper_content:

Previous studies raise the hypothesis that attentional bias in the phase of neocortical excitability fluctuations (oscillations) represents a fundamental mechanism for tuning the brain to the temporal dynamics of task-relevant event patterns. To evaluate this hypothesis, we recorded intracranial electrocortical activity in human epilepsy patients while they performed an audiovisual stream selection task. Consistent with our hypothesis, (1) attentional modulation of oscillatory entrainment operates in a distinct network of areas including auditory, visual, posterior parietal, inferior motor, inferior frontal and superior midline frontal cortex, (2) the degree of oscillatory entrainment depends on the predictability of the stimulus stream, and (3) the attentional phase shift of entrained oscillation cooccurs with classical attentional effects observed on phase-locked evoked activity in sensory-specific areas but seems to operate on entrained low-frequency oscillations that cannot be explained by sensory activity evoked at the rate of stimulation. Thus, attentional entrainment appears to tune a network of brain areas to the temporal dynamics of behaviorally relevant event streams, contributing to its perceptual and behavioral selection.
---
paper_title: Cortical oscillations and sensory predictions

paper_content:

Many theories of perception are anchored in the central notion that the brain continuously updates an internal model of the world to infer the probable causes of sensory events. In this framework, the brain needs not only to predict the causes of sensory input, but also when they are most likely to happen. In this article, we review the neurophysiological bases of sensory predictions of "what' (predictive coding) and ‘when' (predictive timing), with an emphasis on low-level oscillatory mechanisms. We argue that neural rhythms offer distinct and adapted computational solutions to predicting ‘what' is going to happen in the sensory environment and ‘when'.
---
paper_title: Swinging at a Cocktail Party Voice Familiarity Aids Speech Perception in the Presence of a Competing Voice

paper_content:

People often have to listen to someone speak in the presence of competing voices. Much is known about the acoustic cues used to overcome this challenge, but almost nothing is known about the utility of cues derived from experience with particular voices—cues that may be particularly important for older people and others with impaired hearing. Here, we use a version of the coordinate-response-measure procedure to show that people can exploit knowledge of a highly familiar voice (their spouse's) not only to track it better in the presence of an interfering stranger's voice, but also, crucially, to ignore it so as to comprehend a stranger's voice more effectively. Although performance declines with increasing age when the target voice is novel, there is no decline when the target voice belongs to the listener's spouse. This finding indicates that older listeners can exploit their familiarity with a speaker's voice to mitigate the effects of sensory and cognitive decline.
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paper_title: Prediction filter design for active noise cancellation headphones

paper_content:

Digital active noise control (ANC) for headphones usually has to predict the noise because of the latency of common audio converters. In adaptive feedback ANC, the prediction is based on the noise that entered the headphone. This noise is low-pass filtered because of the physical barrier of the ear cups. In this study, this low-pass characteristic is exploited to define a prediction filter which does not require real-time updates. For broadband noises, the prediction filter performs better than adaptive prediction methods like the least mean squares algorithm or iterated one-step predictions in the relevant frequency band. This is shown in simulations as well as in measurements. In addition, the authors show that their prediction filter is more robust against changes in the acoustics of the headphone.
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paper_title: The effect of small variation of the frequent auditory stimulus on the event-related brain potential to the infrequent stimulus

paper_content:

We investigated whether the mismatch process between a rare stimulus and the trace of frequent stimulus, which generates the mismatch-negativity component of the event-related potential, can tolerate a small variation in the intensity of the frequent stimulus. Series of short tone pips were presented to 10 subjects while they were reading a book and ignoring the auditory stimuli. The intensity (mean 80dB) of the frequent stimulus (600 Hz) varied within a range that was different in different blocks. The probability of the infrequent stimuli which were, in different blocks, either intensity deviants (600 Hz/70dB) or frequency deviants (650 Hz/80dB) was 10%. Both deviant stimuli elicited mismatch negativity even when the intensity of the frequent stimulus varied, although the amplitude of this component decreased with the increasing variability of the frequent stimulus. These results show that the generator process of mismatch negativity tolerates some variation in the repetitive stimulus, thus indicating that this process is also activated in ecologically more valid conditions. This is crucial to the interpretation of the generator process of mismatch negativity as a biologically vital warning mechanism.
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paper_title: Responses to deviants are modulated by subthreshold variability of the standard

paper_content:

Auditory mechanisms automatically detect both basic features of sounds and the rules governing their presentation. In the oddball paradigm, the auditory system detects the sameness (or no-variability) rule when the same reference tone is consistently repeated. We used two oddball protocols, the classical one with a fixed reference and a modified one with a jittered reference, to determine whether the auditory system can detect subthreshold violations of sameness. We found that the response to the repeated standard was not modified by the small jitter. However, the response to the frequency oddball was smaller under the jittered protocol, indicating hypersensitivity to sameness. The sensitivity to jitter was largest when the oddball deviated by 8%, was smaller for 40%, and disappeared at 100% deviation, indicating that sensitivity to sameness is context dependent; namely, it is scaled with respect to the overall range of stimuli.
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Title: Predictability effects in auditory scene analysis: a review

Section 1: INTRODUCTION: AUDITORY SCENE ANALYSIS PRINCIPLES
Description 1: This section introduces the principles of auditory scene analysis (ASA), its theoretical background, and the role of predictability in sound source segregation and integration.

Section 2: PREDICTIVE AUDITORY PROCESSING
Description 2: This section discusses the concept of predictive processing in the auditory system, including empirical findings like the mismatch negativity (MMN) and its implications for detecting deviations in auditory sequences.

Section 3: IMPLICATIONS OF PREDICTIVE PROCESSING FOR AUDITORY SCENE ANALYSIS
Description 3: This section explores how the early availability of predictability information could theoretically impact ASA, and reviews past theories and recent insights on the topic.

Section 4: EARLY STUDIES ON PREDICTABILITY EFFECTS IN AUDITORY SCENE ANALYSIS
Description 4: This section reviews initial studies on the impact of sound predictability on ASA, highlighting methodological approaches and their constraints as well as conclusions drawn from early findings.

Section 5: DE-CONFOUNDING PREDICTABILITY EFFECTS ON STREAM SEGREGATION AND INTEGRATION
Description 5: This section details newer studies that have taken steps to eliminate confounds in manipulating predictability, allowing clearer insights into how predictability affects stream segregation and integration.

Section 6: METHODOLOGICAL ASPECTS OF MEASURING AUDITORY SCENE ANALYSIS
Description 6: This section outlines various methodologies employed in studying ASA, including subjective-report procedures and objective-listening tests, and advances in these techniques.

Section 7: RECENT STUDIES ON PREDICTABILITY EFFECTS IN AUDITORY SCENE ANALYSIS
Description 7: This section revisits the predictability effects in ASA through recent studies, summarizing findings that support predictability as a cue in auditory scene analysis.

Section 8: UNDERSTANDING PREDICTABILITY EFFECTS: PERCEPTION OR ATTENTION?
Description 8: This section investigates whether predictability effects on ASA are due to changes in perception or attentional processes, including evidence from objective and subjective listening procedures.

Section 9: UNDERSTANDING PREDICTABILITY EFFECTS: EARLY OR LATE?
Description 9: This section delves into whether predictability acts as an early or late grouping cue in ASA, examining studies that analyze switching characteristics and potential interactions between different types of predictability.

Section 10: PUTTING THE ROLE OF PREDICTABILITY INTO PERSPECTIVE
Description 10: This section contextualizes the role of predictability within broader frameworks of ASA, comparing it to other established principles like the Gestalt principles of similarity and continuity.

Section 11: PREDICTABILITY AS A SEQUENTIAL ANALOGUE TO THE SIMULTANEOUS OLD-PLUS-NEW HEURISTIC?
Description 11: This section explores the analogy between predictability in sequential ASA and the old-plus-new heuristic in simultaneous ASA, considering theoretical and empirical evidence.

Section 12: OUTSTANDING ISSUES
Description 12: This section outlines open questions and future research directions for further exploring predictability effects in ASA, including the types of predictability, underlying mechanisms, and age-related changes.

Section 13: CONCLUSIONS
Description 13: This section summarizes the key findings from the review, emphasizing the impact of predictability on ASA and noting areas that require further investigation.