Time models and cognitive processes: a review
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paper_title: On the Evolution of Memory: A Time for Clocks

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What was the earliest engram? Biology has evolved to encode representations of past events, and in neuroscience, we are attempting to link experience-dependent changes in molecular signaling with cellular processes that ultimately lead to behavioral output. The theory of evolution has guided biological research for decades, and since phylogenetically conserved mechanisms drive circadian rhythms, these processes may serve as common predecessors underlying more complex behavioral phenotypes. For example, the cAMP/MAPK/CREB cascade is interwoven with the clock to trigger circadian output, and is also known to affect memory formation. Time-of-day dependent changes have been observed in long-term potentiation (LTP) within the mammalian suprachiasmatic nucleus and hippocampus, along with light-induced circadian phase resetting and fear conditioning behaviors. Together this suggests during evolution, similar processes underlying metaplasticity in more simple circuits may have been redeployed in higher-order brain regions. Therefore, this notion predicts a model that LTP and metaplasticity may exist in clock-forming circuits of lower-order species, through phylogenetically conserved pathways, leading to several testable hypotheses.
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paper_title: Self-organized Neural Representation of Time

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Time is crucially involved in most of the activities of humans and animals. However, the cognitive mechanisms that support experiencing and processing time remain largely unknown. In the present work we follow a self-organized connectionist modeling approach to study how time may be encoded in a neural network based cognitive system in order to provide suggestions for possible time processing mechanisms in the brain. A particularly interesting feature of our study regards the implementation of a single computational model to accomplish two different robotic behavioral tasks which assume diverse manipulation of time intervals. Examination of the implemented cognitive systems revealed that it is possible to integrate the main theoretical models of time representation existing today into a new and particularly effective theory that can sufficiently explain a series of neuroscientific observations.
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paper_title: Evolution of temporal order in living organisms

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Circadian clocks are believed to have evolved in parallel with the geological history of the earth, and have since been fine-tuned under selection pressures imposed by cyclic factors in the environment. These clocks regulate a wide variety of behavioral and metabolic processes in many life forms. They enhance the fitness of organisms by improving their ability to efficiently anticipate periodic events in their external environments, especially periodic changes in light, temperature and humidity. Circadian clocks provide fitness advantage even to organisms living under constant conditions, such as those prevailing in the depth of oceans or in subterranean caves, perhaps by coordinating several metabolic processes in the internal milieu. Although the issue of adaptive significance of circadian rhythms has always remained central to circadian biology research, it has never been subjected to systematic and rigorous empirical validation. A few studies carried out on free-living animals under field conditions and simulated periodic and aperiodic conditions of the laboratory suggest that circadian rhythms are of adaptive value to their owners. However, most of these studies suffer from a number of drawbacks such as lack of population-level replication, lack of true controls and lack of adequate control on the genetic composition of the populations, which in many ways limits the potential insights gained from the studies. The present review is an effort to critically discuss studies that directly or indirectly touch upon the issue of adaptive significance of circadian rhythms and highlight some shortcomings that should be avoided while designing future experiments.
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paper_title: Cryptochromes Enabling Plants and Animals to Determine Circadian Time

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Abstract Cryptochromes are flavin-containing blue light photoreceptors related to photolyases—they are found in both plants and animals and have recently been described for bacteria. In plants, cryptochromes perform a variety of functions including the entrainment of circadian rhythms. They serve a similar role in Drosophila and mammals, where the cryptochromes also perform an additional function as an essential component of the circadian clock.
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paper_title: Explorations on Artificial Time Perception

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In the field of biologically inspired cognitive systems, time perception, a fundamental aspect of natural cognition is not sufficiently explored. The majority of existing works ignore the importance of experiencing the flow of time, and the implemented agents are rarely furnished with time processing capacities. The current work aims at shedding light on this largely unexplored issue, focusing on the perception of temporal duration. Specifically, we investigate a rule switching task that consists of repeating trials with dynamic temporal lengths. An evolutionary process is employed to search for neuronal mechanisms that accomplish the underlying task and self-organize time-processing dynamics. Our repeated simulation experiments showed that the capacity of perceiving duration biases the functionality of neural mechanisms with other cognitive responsibilities and additionally that time perception and ordinary cognitive processes may share the same neural resources in the cognitive system. The obtained results are related with previous brain imaging studies on time perception, and they are used to formulate suggestions for the cortical representation of time in biological agents.
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paper_title: An integrated theory of prospective time interval estimation: The role of cognition, attention and learning

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A theory of prospective time perception is introduced and incorporated as a module in an integrated theory of cognition, thereby extending existing theories and allowing predictions about attention and learning. First, a time perception module is established by fitting existing datasets (interval estimation and bisection and impact of secondary tasks on attention). The authors subsequently used the module as a part of the adaptive control of thought-rational (ACT-R) architecture to model a new experiment that combines attention, learning, dual tasking, and time perception. Finally, the model predicts time estimation, learning, and attention in a new experiment. The model predictions and fits demonstrate that the proposed integrated theory of prospective time interval estimation explains detailed effects of attention and learning during time interval estimation.
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paper_title: The inner sense of time: how the brain creates a representation of duration

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A large number of competing models exist for how the brain creates a representation of time. However, several human and animal studies point to 'climbing neural activation' as a potential neural mechanism for the representation of duration. Neurophysiological recordings in animals have revealed how climbing neural activation that peaks at the end of a timed interval underlies the processing of duration, and, in humans, climbing neural activity in the insular cortex, which is associated with feeling states of the body and emotions, may be related to the cumulative representation of time.
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paper_title: Cortical Networks Underlying Mechanisms of Time Perception

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Precise timing of sensory information from multiple sensory streams is essential for many aspects of human perception and action. Animal and human research implicates the basal ganglia and cerebellar systems in timekeeping operations, but investigations into the role of the cerebral cortex have been limited. Individuals with focal left (LHD) or right hemisphere (RHD) lesions and control subjects performed two time perception tasks (duration perception, wherein the standard tone pair interval was 300 or 600 msec) and a frequency perception task, which controlled for deficits in time-independent processes shared by both tasks. When frequency perception deficits were controlled, only patients with RHD showed time perception deficits. Time perception competency was correlated with an independent test of switching nonspatial attention in the RHD but not the LHD patients, despite attention deficits in both groups. Lesion overlays of patients with RHD and impaired timing showed that 100% of the patients with anterior damage had lesions in premotor and prefrontal cortex (Brodmann areas 6, 8, 9, and 46), and 100% with posterior damage had lesions in the inferior parietal cortex. All LHD patients with normal timing had damage in these same regions, whereas few, if any, RHD patients with normal timing had similar lesion distributions. These results implicate a right hemisphere prefrontal–inferior parietal network in timing. Time-dependent attention and working memory functions may contribute to temporal perception deficits observed after damage to this network.
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paper_title: The neural representation of time

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This review summarizes recent investigations of temporal processing. We focus on motor and perceptual tasks in which crucial events span hundreds of milliseconds. One key question concerns whether the representation of temporal information is dependent on a specialized system, distributed across a network of neural regions, or computed in a local task-dependent manner. Consistent with the specialized system framework, the cerebellum is associated with various tasks that require precise timing. Computational models of timing mechanisms within the cerebellar cortex are beginning to motivate physiological studies. Emphasis has also been placed on the basal ganglia as a specialized timing system, particularly for longer intervals. We outline an alternative hypothesis in which this structure is associated with decision processes.
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paper_title: Spatial–temporal interactions in the human brain

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The review summarises current evidence on the cognitive mechanisms for the integration of spatial and temporal representations and of common brain structures to process the where and when of stimuli. Psychophysical experiments document the presence of spatially localised distortions of sub-second time intervals and suggest that visual events are timed by neural mechanisms that are spatially selective. On the other hand, experiments with supra-second intervals suggest that time could be represented on a mental time-line ordered from left-to-right, similar to what is reported for other ordered quantities, such as numbers. Neuroimaging and neuropsychological findings point towards the posterior parietal cortex as the main site where spatial and temporal information converge and interact with each other.
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paper_title: Emotional moments across time: a possible neural basis for time perception in the anterior insula

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A model of awareness based on interoceptive salience is described, which has an endogenous time base that might provide a basis for the human capacity to perceive and estimate time intervals in the range of seconds to subseconds. The model posits that the neural substrate for awareness across time is located in the anterior insular cortex, which fits with recent functional imaging evidence relevant to awareness and time perception. The time base in this model is adaptive and emotional, and thus it offers an explanation for some aspects of the subjective nature of time perception. This model does not describe the mechanism of the time base, but it suggests a possible relationship with interoceptive afferent activity, such as heartbeat-related inputs.
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paper_title: The inner experience of time

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The striking diversity of psychological and neurophysiological models of ‘time perception’ characterizes the debate on how and where in the brain time is processed. In this review, the most prominent models of time perception will be critically discussed. Some of the variation across the proposed models will be explained, namely (i) different processes and regions of the brain are involved depending on the length of the processed time interval, and (ii) different cognitive processes may be involved that are not necessarily part of a core timekeeping system but, nevertheless, influence the experience of time. These cognitive processes are distributed over the brain and are difficult to discern from timing mechanisms. Recent developments in the research on emotional influences on time perception, which succeed decades of studies on the cognition of temporal processing, will be highlighted. Empirical findings on the relationship between affect and time, together with recent conceptualizations of self- and body processes, are integrated by viewing time perception as entailing emotional and interoceptive (within the body) states. To date, specific neurophysiological mechanisms that would account for the representation of human time have not been identified. It will be argued that neural processes in the insular cortex that are related to body signals and feeling states might constitute such a neurophysiological mechanism for the encoding of duration.
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paper_title: An integrated theory of prospective time interval estimation: The role of cognition, attention and learning

paper_content:

A theory of prospective time perception is introduced and incorporated as a module in an integrated theory of cognition, thereby extending existing theories and allowing predictions about attention and learning. First, a time perception module is established by fitting existing datasets (interval estimation and bisection and impact of secondary tasks on attention). The authors subsequently used the module as a part of the adaptive control of thought-rational (ACT-R) architecture to model a new experiment that combines attention, learning, dual tasking, and time perception. Finally, the model predicts time estimation, learning, and attention in a new experiment. The model predictions and fits demonstrate that the proposed integrated theory of prospective time interval estimation explains detailed effects of attention and learning during time interval estimation.
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paper_title: A right hemispheric frontocerebellar network for time discrimination of several hundreds of milliseconds

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Abstract Debate still surrounds the nature of the role of the dorsolateral prefrontal gyrus (DLPFC) in time perception. This region is frequently associated with working memory and is thus implicated as a so-called “accumulator” within a hypothesized internal clock model. However, we hypothesized that this region may have a more primary role in time perception. To test this hypothesis we used functional magnetic resonance imaging (fMRI) to examine the neural correlates of relatively pure time perception with a temporal discrimination task where intervals of 1 s had to be discriminated from those of 1.3, 1.4, and 1.5 s. Time perception in this particular time domain within the “perceived present” has not previously been investigated using fMRI. By using relatively short time periods to be discriminated and also contrasting activation with an order judgment task, we aimed to minimize the confounding aspects of sustained attention and working memory. In a group of 20 healthy right-handed adult males, neural activation associated with time discrimination was found in a predominantly right hemispheric network of right dorsolateral and inferior prefrontal cortices, right supplementary motor area, and left cerebellum. We conclude that right DLPFC, rather than having a purely working memory function, might be more centrally involved in time perception than previously thought.
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paper_title: Frontal–striatal circuitry activated by human peak-interval timing in the supra-seconds range

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Abstract Functional magnetic resonance imaging (fMRI) was used to measure the location and intensity of brain activations when participants time an 11-s signal duration. The experiment evaluated six healthy adult male participants who performed the peak-interval timing procedure in variants of stimulus modality (auditory or visual) and condition (foreground or background: i.e., whether the presence or absence of the stimulus is the signal to be timed). The complete experimental design called for each signal variant to be used across four behavioral tasks presented in the following order: control, timing+motor, timing, and motor. In the control task, participants passively experienced the stimuli. The timing+motor and timing tasks were preceded by five fixed-time training trials in which participants learned the 11-s signal they would subsequently reproduce. In the timing+motor task, participants made two motor responses centered around their subjective estimate of the criterion time. For the timing task, participants were instructed to time internally without making a motor response. The motor task had participants make two cued responses that were not determined by the participant's sense of the passage of time. Neuroimaging data from the timing+motor and timing tasks showed activation of the frontal cortex, striatum and thalamus—none of which was apparent in the control or motor tasks. These results, combined with other peak-interval procedure data from drug and lesion studies in animals as well as behavioral results in human patient populations with striatal damage, support the involvement of frontal–striatal circuitry in human interval timing.
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paper_title: The evolution of brain activation during temporal processing

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Timing is crucial to many aspects of human performance. To better understand its neural underpinnings, we used event-related fMRI to examine the time course of activation associated with different components of a time perception task. We distinguished systems associated with encoding time intervals from those related to comparing intervals and implementing a response. Activation in the basal ganglia occurred early, and was uniquely associated with encoding time intervals, whereas cerebellar activation unfolded late, suggesting an involvement in processes other than explicit timing. Early cortical activation associated with encoding of time intervals was observed in the right inferior parietal cortex and bilateral premotor cortex, implicating these systems in attention and temporary maintenance of intervals. Late activation in the right dorsolateral prefrontal cortex emerged during comparison of time intervals. Our results illustrate a dynamic network of cortical-subcortical activation associated with different components of temporal information processing.
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paper_title: Time perception: Manipulation of task difficulty dissociates clock functions from other cognitive demands

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Previous studies suggest the involvement in timing functions of a surprisingly extensive network of human brain regions. But it is likely that while some of these regions play a fundamental role in timing, others are activated by associated task demands such as memory and decisionmaking. In two experiments, time perception (duration discrimination) was studied under two conditions of task difficulty and neural activation was compared using fMRI. Brain activation during duration discrimination was contrasted with activation evoked in a control condition (colour discrimination) that used identical stimuli. In the first experiment, the control task was slightly easier than the time task. Multiple brain areas were activated, in line with previous studies. These included the prefrontal cortex, cerebellum, inferior parietal lobule and striatum. In the second experiment, the control task was made more difficult than the time task. Much of the differential time-related activity seen in the first experiment disappeared and in some regions (inferior parietal cortex, pre-SMA and parts of prefrontal cortex) it reversed in polarity. This suggests that such activity is not specifically concerned with timing functions, but reflects the relative cognitive demands of the two tasks. However, three areas of time-related activation survived the task-difficulty manipulation: (i) a small region at the confluence of the inferior frontal gyrus and the anterior insula, bilaterally, (ii) a small portion of the left supramarginal gyrus and (iii) the putamen. We argue that the extent of the timing “network” has been significantly over-estimated in the past and that only these three relatively small regions can safely be regarded as being directly concerned with duration judgements.
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paper_title: Brain activation patterns during measurement of sub- and supra-second intervals

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The possibility that different neural systems are used to measure temporal durations at the sub-second and several second ranges has been supported by pharmacological manipulation, psychophysics, and neural network modelling. Here, we add to this literature by using fMRI to isolate differences between the brain networks which measure 0.6 and 3 s in a temporal discrimination task with visual discrimination for control. We observe activity in bilateral insula and dorsolateral prefrontal cortex, and in right hemispheric pre-supplementary motor area, frontal pole, and inferior parietal cortex during measurement of both intervals, suggesting that these regions constitute a system used in temporal discrimination at both ranges. The frontal operculum, left cerebellar hemisphere and middle and superior temporal gyri, all show significantly greater activity during measurement of the shorter interval, supporting the hypotheses that the motor system is preferentially involved in the measurement of sub-second intervals, and that auditory imagery is preferentially used during measurement of the same. Only a few voxels, falling in the left posterior cingulate and inferior parietal lobe, are more active in the 3 s condition. Overall, this study shows that although many brain regions are used for the measurement of both sub- and supra-second temporal durations, there are also differences in activation patterns, suggesting that distinct components are used for the two durations.
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paper_title: Interval timing as an emergent learning property

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Interval timing in operant conditioning is the learned covariation of a temporal dependent measure such as wait time with a temporal independent variable such as fixed-interval duration. The dominant theories of interval timing all incorporate an explicit internal clock, or pacemaker, despite its lack of independent evidence. The authors propose an alternative, pacemaker-free view that demonstrates that temporal discrimination can be explained by using only 2 assumptions: (a) variation and selection of responses through competition between reinforced behavior and all other, elicited, behaviors and (b) modulation of the strength of response competition by the memory for recent reinforcement. The model departs radically from existing timing models: It shows that temporal learning can emerge from a simple dynamic process that lacks a periodic time reference such as a pacemaker.
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paper_title: Cortico-striatal representation of time in animals and humans

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Interval timing in the seconds-to-minutes range is crucial to learning, memory, and decision-making. Recent findings argue for the involvement of cortico-striatal circuits that are optimized by the dopaminergic modulation of oscillatory activity and lateral connectivity at the level of cortico-striatal inputs. Striatal medium spiny neurons are proposed to detect the coincident activity of specific beat patterns of cortical oscillations, thereby permitting the discrimination of supra-second durations based upon the reoccurring patterns of subsecond neural firing. This proposal for the cortico-striatal representation of time is consistent with the observed psychophysical properties of interval timing (e.g. linear time scale and scalar variance) as well as much of the available pharmacological, lesion, patient, electrophysiological, and neuroimaging data from animals and humans (e.g. dopamine-related timing deficits in Huntington's and Parkinson's disease as well as related animal models). The conclusion is that although the striatum serves as a ‘core timer’, it is part of a distributed timing system involving the coordination of large-scale oscillatory networks.
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paper_title: The reproduction of temporal intervals.

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An electronic power varying controller device adapted for a dimmer, etc. and having substantially no mechanically sliding portions, comprising a thyristor connected with a load such as a lamp, a firing phase controller circuit for the thyristor, a field effect transistor for controlling the firing phase controller circuit, a capacitor connected in parallel with the gate circuit of the field effect transistor, a highly insulating switch connected in series to the gate of the field effect transistor, and a switch to be connected with the highly insulating switch for selecting a positive or negative potential.
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paper_title: A Model of Interval Timing by Neural Integration

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We show that simple assumptions about neural processing lead to a model of interval timing as a temporal integration process, in which a noisy firing-rate representation of time rises linearly on average toward a response threshold over the course of an interval. Our assumptions include: that neural spike trains are approximately independent Poisson processes, that correlations among them can be largely cancelled by balancing excitation and inhibition, that neural populations can act as integrators, and that the objective of timed behavior is maximal accuracy and minimal variance. The model accounts for a variety of physiological and behavioral findings in rodents, monkeys, and humans, including ramping firing rates between the onset of reward-predicting cues and the receipt of delayed rewards, and universally scale-invariant response time distributions in interval timing tasks. It furthermore makes specific, well-supported predictions about the skewness of these distributions, a feature of timing data that is usually ignored. The model also incorporates a rapid (potentially one-shot) duration-learning procedure. Human behavioral data support the learning rule's predictions regarding learning speed in sequences of timed responses. These results suggest that simple, integration-based models should play as prominent a role in interval timing theory as they do in theories of perceptual decision making, and that a common neural mechanism may underlie both types of behavior.
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paper_title: Cortico-striatal circuits and interval timing: coincidence detection of oscillatory processes

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Abstract Humans and other animals demonstrate the ability to perceive and respond to temporally relevant information with characteristic behavioral properties. For example, the response time distributions in peak-interval timing tasks are well described by Gaussian functions, and superimpose when scaled by the criterion duration. This superimposition has been referred to as the scalar property and results from the fact that the standard deviation of a temporal estimate is proportional to the duration being timed. Various psychological models have been proposed to account for such responding. These models vary in their success in predicting the temporal control of behavior as well as in the neurobiological feasibility of the mechanisms they postulate. A review of the major interval timing models reveals that no current model is successful on both counts. The neurobiological properties of the basal ganglia, an area known to be necessary for interval timing and motor control, suggests that this set of structures act as a coincidence detector of cortical and thalamic input. The hypothesized functioning of the basal ganglia is similar to the mechanisms proposed in the beat frequency timing model [R.C. Miall, Neural Computation 1 (1989) 359–371], leading to a reevaluation of its capabilities in terms of behavioral prediction. By implementing a probabilistic firing rule, a dynamic response threshold, and adding variance to a number of its components, simulations of the striatal beat frequency model were able to produce output that is functionally equivalent to the expected behavioral response form of peak-interval timing procedures.
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paper_title: The Sensory Representation of Time

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Time is embedded in many aspects of our sensory experience; sensory events unfold in time and often acquire particular meaning because of their specific temporal structure. The speed of a moving object, the words pronounced by a speaker and the tactile exploration of a texture, are all examples of temporally structured sensory experiences. Despite the ubiquitousness of the temporal dimension of our sensory experience, the understanding of the neural mechanisms underlying the temporal representation of sensory events, that is the capacity to estimate duration in milliseconds/seconds range, remains a controversial and complex issue. The controversy relates to the effective involvement of sensory-specific brain regions in the processing of temporal information. The complexity arises from the neurophysiological mechanisms underlying the representation of time in these areas and the functional interplay between sensory-specific and amodal temporal mechanisms (Harrington et al., 2011). ::: ::: The idea that we time sensory signals via a single “centralized” and “amodal” clock dominated the field of temporal cognition over the last 30 years. More recently the universality of timing mechanisms has been challenged by new theoretical positions and a growing body of empirical data (Buhusi and Meck, 2005). From a theoretical perspective the challenge comes from “distributed” timing models. This is a broad class of models, which – although different regarding the neurophysiological mechanisms proposed for time processing – collectively share the idea that we have multiple timing mechanisms “distributed” across brain areas or circuits; and that the engagement of each single mechanism depends on the psychophysical task, sensory modality, and lengths of temporal intervals (Ivry and Richardson, 2002; Durstewitz, 2003; Matell and Meck, 2004; Buonomano and Maass, 2009). The idea that sensory-specific timing mechanisms exist is supported by studies showing that the ability to discriminate temporal information depends on the modality of the signals. For example, temporal discrimination thresholds are lower for auditory compared to visual signal durations (Grondin, 1993; Grondin et al., 2005; Merchant et al., 2008); and the capacity to keep in memory multiple intervals improves if the temporal signals belong to different modalities and therefore rely on different memory resources (Gamache and Grondin, 2010). The existence of independent sensory-specific clocks is also suggested by the observation that the perceived duration of a sensory event can be distorted by modality-specific properties of the stimuli such as visual adaptation (Johnston et al., 2006; Ayhan et al., 2009), spatial, and temporal frequency (Kanai et al., 2006; Kaneko and Murakami, 2009); or by the observation that such distortions are limited to a single sensory domain, like in case of saccadic eye movements causing compression of the perceived duration of visual but not of auditory stimuli (Morrone et al., 2005; Burr et al., 2011). From the neurophysiological point of view, electrophysiological recordings in animals as well as neuroimaging and magnetic stimulation studies in humans suggest that both modality-specific and supramodal mechanisms underlie the estimation of temporal intervals (Ghose and Maunsell, 2002; Shuler and Bear, 2006; Bosco et al., 2008; Bueti et al., 2008b; Sadeghi et al., 2011). For example, it has been demonstrated that the extrastriate visual area MT/V5 is necessary for temporal discrimination of visual, but not of auditory durations (Bueti et al., 2008a) and that duration estimation to predict expected visual and auditory events involves secondary as well as primary visual and auditory cortices (Ghose and Maunsell, 2002; Shuler and Bear, 2006; Bueti and Macaluso, 2010; Bueti et al., 2010). ::: ::: Taken together these behavioral and neurophysiological data highlight the functional contribution of sensory-specific cortices and support the existence of modality-specific timing mechanisms. However, how temporal information is actually represented in these cortices and what is the neurophysiological mechanism behind it, remain unclear. A few interesting theoretical hypotheses have been advanced. “Intrinsic” timing models for example, describe time as a general and inherent property of neural dynamics. A consequence of this assumption is that any area of the brain is in principle able to encode time. Temporal computations according to these models rely on inherent temporal properties of neural networks like short-term synaptic plasticity [i.e., state-dependent networks (SDNs) model; Buonomano and Maass, 2009] or arise either from the overall magnitude of neural activity (Eagleman, 2008) or from the linear ramping of neuronal firing rate (Durstewitz, 2003; Reutimann et al., 2004). “Intrinsic models” of temporal coding are particularly suitable to describe the functional organization of sensory timing mechanisms because they assume that time is encoded by the same circuits encoding other stimulus properties such as color or motion in the visual modality. However the explanatory power of some of these models, like for example the SDNs model, is constrained to durations of a few hundred milliseconds (i.e., <500 ms; Buonomano et al., 2009; Spencer et al., 2009); this is indeed a strong limitation, given that most of the neurophysiological evidence in favor of modality-specific timing mechanisms deal with durations from hundreds of milliseconds to a few seconds. An alternative possibility is that temporal computations in sensory cortices engage wider and specialized temporal circuit (s), where time signals from sensory cortex are sent to “dedicated” timing areas where these signals are integrated and used to guide action for example (Coull et al., 2011). In this latter case the relationship between sensory-specific and sensory independent timing areas need to be elucidated. Many cortical (parietal, premotor, prefrontal, and insular cortices) and subcortical (basal ganglia and cerebellum) brain structures have indeed been implicated in the processing of temporal information independently from the sensory modality of the stimuli (see Spencer et al., 2003; Coull et al., 2004; Koch et al., 2008; Wiener et al., 2010 for a review; Wittmann et al., 2010). Although there is only a partial agreement regarding the relevance of all these structures to time processing, the challenge is now to explore whether these areas have dissociable or interchangeable/overlapping functional roles and therefore whether these areas support the same or different temporal mechanisms compared to sensory-specific areas. A very special case of multimodal timing area is represented by the auditory cortex, a sensory-specific area. It has been recently demonstrated indeed that the auditory cortex is important for temporal discrimination not only of auditory but also of somatosensory and visual stimuli (Bolognini et al., 2009; Kanai et al., 2011). The supramodal involvement of auditory areas in temporal tasks has been associated with a strategic use of auditory-based mental representations for time estimation (Franssen et al., 2006). An interesting hypothesis, suggested by Kanai and colleagues, is that given the dominance of the auditory system over vision in temporal tasks (Walker and Scott, 1981; Burr et al., 2009), visual information is converted into an auditory code for temporal computation(Kanai et al., 2011). This hypothesis is interesting because offers new insight into the relationship between visual and auditory timing systems and highlights a possible link between modality independent and modality-specific temporal mechanisms. ::: ::: It is therefore clear that the study of the functional architecture of sensory timing mechanisms poses a few more theoretical and experimental challenges. A few important questions are still open. It is, for example, unclear whether the organizational principles that apply to space also apply to time and whether the temporal dimension of visual stimuli is processed by the same or distinct networks compared to those for space. Is time coding in visual cortex retinotopic specific? Do we encode all possible temporal intervals at each retinotopic position? In which context do sensory-specific temporal mechanisms work? Is temporal information encoded in sensory cortices automatically or does it require explicit attention? Are sensory areas engaged only during duration encoding or are also active during working memory maintenance? ::: ::: The already complex scenario of the neural representation of time is getting even more intricate. From the idea of a single “amodal” mechanism we moved into the idea of multiple “modality-specific” and “modality independent” temporal mechanisms (Wiener et al., 2011). The challenge is now to find out the functional architecture of these mechanisms as well as the interaction between them. As a concluding remark, I would like to emphasize that the focus of the majority of studies exploring the neural correlates of temporal processing has been so far to identifying the key components of internal timing networks (i.e., the “where” of timing mechanisms). The result of this approach has been, for example, an exponential increase of the number of neuroimaging studies on this topic that has lead to a substantial disagreement regarding the structures that are relevant to time processing (Wiener et al., 2010 for a review). It is time to adopt new experimental approaches that pose more mechanistically oriented questions about the underlying timing mechanisms while at the same time attempting to link computational models and neurophysiology (Portugal et al., 2011).
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paper_title: Time And Memory: Towards A Pacemaker-Free Theory Of Interval Timing

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A popular view of interval timing in animals is that it is driven by a discrete pacemaker-accumulator mechanism that yields a linear scale for encoded time. But these mechanisms are fundamentally at odds with the Weber law property of interval timing, and experiments that support linear encoded time can be interpreted in other ways. We argue that the dominant pacemaker-accumulator theory, scalar expectancy theory (SET), fails to explain some basic properties of operant behavior on interval-timing procedures and can only accommodate a number of discrepancies by modifications and elaborations that raise questions about the entire theory. We propose an alternative that is based on principles of memory dynamics derived from the multiple-time-scale (MTS) model of habituation. The MTS timing model can account for data from a wide variety of time-related experiments: proportional and Weber law temporal discrimination, transient as well as persistent effects of reinforcement omission and reinforcement magnitude, bisection, the discrimination of relative as well as absolute duration, and the choose-short effect and its analogue in number-discrimination experiments. Resemblances between timing and counting are an automatic consequence of the model. We also argue that the transient and persistent effects of drugs on time estimates can be interpreted as well within MTS theory as in SET. Recent real-time physiological data conform in surprising detail to the assumptions of the MTS habituation model. Comparisons between the two views suggest a number of novel experiments.
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paper_title: Scalar Timing in Memory

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A recent report of ours’ proposed an information-processing account of temporal generalization. The account posited a clock process, which was the basic time measurement device, and working and reference memory for storing the output of the clock either temporarily or relatively permanently. Records of time intervals in working and reference memory were then compared using a binary decision process, which dictated responding or not responding. The analysis concentrated on a relativistic Weber’s law property of the data from temporal generalization, and the constraints this property imposed on sources of variance in the information-processing stages. Our purpose here is to summarize that work and generalize the model in two ways: First we consider several sources of variance operating simultaneously. The original analysis demonstrated that if only one source of variance is present, it must be a scalar source, that is, it must result in a variable memory for which variance increases with the square of the mean.’ In the generalized account proposed here, we will develop the conclusion that scalar sources dominate in some time ranges, while other sources may dominate in others. These ideas are then applied to two additional timing tasks with different characteristics.
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paper_title: A Unified Model of Time Perception Accounts for Duration-Based and Beat-Based Timing Mechanisms

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Accurate timing is an integral aspect of sensory and motor processes such as the perception of speech and music and the execution of skilled movement. Neuropsychological studies of time perception in patient groups and functional neuroimaging studies of timing in normal participants suggest common neural substrates for perceptual and motor timing. A timing system is implicated in core regions of the motor network such as the cerebellum, inferior olive, basal ganglia, pre-supplementary, and supplementary motor area, pre-motor cortex as well as higher-level areas such as the prefrontal cortex. In this article, we assess how distinct parts of the timing system subserve different aspects of perceptual timing. We previously established brain bases for absolute, duration-based timing and relative, beat-based timing in the olivocerebellar and striato-thalamo-cortical circuits respectively (Teki et al., 2011). However, neurophysiological and neuroanatomical studies provide a basis to suggest that timing functions of these circuits may not be independent. Here, we propose a unified model of time perception based on coordinated activity in the core striatal and olivocerebellar networks that are interconnected with each other and the cerebral cortex through multiple synaptic pathways. Timing in this unified model is proposed to involve serial beat-based striatal activation followed by absolute olivocerebellar timing mechanisms.
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paper_title: The Storage of Time Intervals Using Oscillating Neurons

paper_content:

A mechanism to store and recall time intervals ranging from hundreds of milliseconds to tens of seconds is described. The principle is based on beat frequencies between oscillating elements; any small group of oscillators codes specifically for an interval equal to the lowest common multiple of their oscillation periods. This mechanism could be realized in the nervous system by an output neuron, excited by a group of pacemaker neurons, and able to select via a Hebbian rule a subgroup of pacemaker cells to encode any given interval, or small number of intervals (for example, a pattern of pulses). Recall could be achieved by resetting the pacemaker cells and setting a threshold for activation of the output unit. A simulation is described and the main features of such an encoding scheme are discussed.
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paper_title: Sensory modality and time perception in children and adults

paper_content:

This experiment investigated the effect of signal modality on time perception in 5- and 8-year-old children as well as young adults using a duration bisection task in which auditory and visual signals were presented in the same test session and shared common anchor durations. Durations were judged shorter for visual than for auditory signals by all age groups. However, the magnitude of this modality difference was larger in the children than in the adults. Sensitivity to time was also observed to increase with age for both modalities. Taken together, these two observations suggest that the greater modality effect on duration judgments for the children, for whom attentional abilities are considered limited, is the result of visual signals requiring more attentional resources than are needed for the processing of auditory signals. Within the framework of the information-processing model of Scalar Timing Theory, these effects are consistent with a developmental difference in the operation of the "attentional switch" used to transfer pulses from the pacemaker into the accumulator. Specifically, although timing is more automatic for auditory than visual signals in both children and young adults, children have greater difficulty in keeping the switch in the closed state during the timing of visual signals. Language: en
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paper_title: Timing in the Absence of Clocks: Encoding Time in Neural Network States

paper_content:

Summary Decisions based on the timing of sensory events are fundamental to sensory processing. However, the mechanisms by which the brain measures time over ranges of milliseconds to seconds remain unclear. The dominant model of temporal processing proposes that an oscillator emits events that are integrated to provide a linear metric of time. We examine an alternate model in which cortical networks are inherently able to tell time as a result of time-dependent changes in network state. Using computer simulations we show that within this framework, there is no linear metric of time, and that a given interval is encoded in the context of preceding events. Human psychophysical studies were used to examine the predictions of the model. Our results provide theoretical and experimental evidence that, for short intervals, there is no linear metric of time, and that time may be encoded in the high-dimensional state of local neural networks.
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paper_title: The dual klepsydra model of internal time representation and time reproduction

paper_content:

Abstract We present a model of the internal representation and reproduction of temporal durations, the ‘dual klepsydra’ model ( DKM ). Unlike most contemporary models operating on a ‘pacemaker-counter’ scheme, the DKM does not assume an oscillatory process as the internal time-base. It is based on irreversible, dissipative processes in inflow/outflow systems (leaky klepsydrae), whose states are continuously compared; if their states are equal, durations are subjectively perceived as equal. Model-based predictions fit experimental time reproduction data with good accuracy, and show qualitative features not accounted for by other models. The deterministic model is characterized by two parameters, κ (outflow rate coefficient) and η (ratio of inflow rates). A stochastic version of the model ( SDKM ) assumes randomly fluctuating inflows, involves two more parameters, and accounts for intra-individual variance of reproduced durations. Analysis of the SDKM leads to non-trivial problems in the stochastic theory, briefly sketched here. Methods of parameter estimation for both deterministic and stochastic versions are given. Applying the DKM to the subjective experience of time passage, we show how subjective measure of elapsed time is constituted. Finally, essential features of the model and its possible neurophysiological interpretation are discussed.
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paper_title: Learning the temporal dynamics of behavior.

paper_content:

This study presents a dynamic model of how animals learn to regulate their behavior under timebased reinforcement schedules. The model assumes a serial activation of behavioral states during the interreinfbrcement interval, an associative process linking the states with the operant response, and a rule mapping the activation of the states and their associative strength onto response rate or probability. The model fits data sets from fixed-interval schedules, the peak procedure, mixed fixedinterval schedules, and the bisection of temporal intervals. The major difficulties of the model came from experiments that suggest that under some conditions animals may time 2 intervals independently and simultaneously. :
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paper_title: Simulating autonomous coupling in discrimination of light frequencies

paper_content:

To study the interfacial complexity between an agent and its environment such as the adaptive selection aspects of sensory inputs, we propose a new coupling mechanism, called autonomous coupling, where an agent can spontaneously switch on or off its interaction with the environment. An oscillatory neural system with autonomous coupling sums the sensory inputs and initiates action selection via a sensorimotor coupling. An example task we designed to show dynamical categorization is the classification of light frequencies. An evolved agent selects specified light frequencies by approaching them and avoiding light of other frequencies. Dynamical categorization and active coupling are the key concepts for the understanding of situated and embodied cognitive functions.
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paper_title: Explorations on Artificial Time Perception

paper_content:

In the field of biologically inspired cognitive systems, time perception, a fundamental aspect of natural cognition is not sufficiently explored. The majority of existing works ignore the importance of experiencing the flow of time, and the implemented agents are rarely furnished with time processing capacities. The current work aims at shedding light on this largely unexplored issue, focusing on the perception of temporal duration. Specifically, we investigate a rule switching task that consists of repeating trials with dynamic temporal lengths. An evolutionary process is employed to search for neuronal mechanisms that accomplish the underlying task and self-organize time-processing dynamics. Our repeated simulation experiments showed that the capacity of perceiving duration biases the functionality of neural mechanisms with other cognitive responsibilities and additionally that time perception and ordinary cognitive processes may share the same neural resources in the cognitive system. The obtained results are related with previous brain imaging studies on time perception, and they are used to formulate suggestions for the cortical representation of time in biological agents.
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paper_title: Are We There Yet? Grounding Temporal Concepts in Shared Journeys

paper_content:

An understanding of time and temporal concepts is critical for interacting with the world and with other agents in the world. What does a robot need to know to refer to the temporal aspects of events-could a robot gain a grounded understanding of “a long journey,” or “soon?” Cognitive maps constructed by individual agents from their own journey experiences have been used for grounding spatial concepts in robot languages. In this paper, we test whether a similar methodology can be applied to learning temporal concepts and an associated lexicon to answer the question “how long” did it take to complete a journey. Using evolutionary language games for specific and generic journeys, successful communication was established for concepts based on representations of time, distance, and amount of change. The studies demonstrate that a lexicon for journey duration can be grounded using a variety of concepts. Spatial and temporal terms are not identical, but the studies show that both can be learned using similar language evolution methods, and that time, distance, and change can serve as proxies for each other under noisy conditions. Effective concepts and names for duration provide a first step towards a grounded lexicon for temporal interval logic.
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paper_title: Learning to perceive time: A connectionist, memory-decay model of the development of interval timing in infants.

paper_content:

We present the first developmental model of interval timing. It is a memory-based connectionist model of how infants learn to perceive time. It has two novel features that are not found in other models. First, it uses the uncertainty of a memory for an event as an index of how long ago that event happened. Secondly, embodiment – specifically, infant motor activity – is crucial to the calibration of time-perception both within and across sensory modalities. We describe the model and present three simulations which show (1) how it uses sensory memory uncertainty and bodily representaions to index time, (2) that the scalar property of interval timing (Gibbon, 1977) emerges naturally from this network and (3) that motor activity can synchronize independent timing mechanisms across different sensory modalities.
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paper_title: An integrated theory of prospective time interval estimation: The role of cognition, attention and learning

paper_content:

A theory of prospective time perception is introduced and incorporated as a module in an integrated theory of cognition, thereby extending existing theories and allowing predictions about attention and learning. First, a time perception module is established by fitting existing datasets (interval estimation and bisection and impact of secondary tasks on attention). The authors subsequently used the module as a part of the adaptive control of thought-rational (ACT-R) architecture to model a new experiment that combines attention, learning, dual tasking, and time perception. Finally, the model predicts time estimation, learning, and attention in a new experiment. The model predictions and fits demonstrate that the proposed integrated theory of prospective time interval estimation explains detailed effects of attention and learning during time interval estimation.
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paper_title: A model of episodic memory: Mental time travel along encoded trajectories using grid cells

paper_content:

The definition of episodic memory includes the concept of mental time travel: the ability to re-experience a previously experienced trajectory through continuous dimensions of space and time, and to recall specific events or stimuli along this trajectory. Lesions of the hippocampus and entorhinal cortex impair human episodic memory function and impair rat performance in tasks that could be solved by retrieval of trajectories. Recent physiological data suggests a novel model for encoding and retrieval of trajectories, and for associating specific stimuli with specific positions along the trajectory. During encoding in the model, external input drives the activity of head direction cells. Entorhinal grid cells integrate the head direction input to update an internal representation of location, and drive hippocampal place cells. Trajectories are encoded by Hebbian modification of excitatory synaptic connections between hippocampal place cells and head direction cells driven by external action. Associations are also formed between hippocampal cells and sensory stimuli. During retrieval, a sensory input cue activates hippocampal cells that drive head direction activity via previously modified synapses. Persistent spiking of head direction cells maintains the direction and speed of the action, updating the activity of entorhinal grid cells that thereby further update place cell activity. Additional cells, termed arc length cells, provide coding of trajectory segments based on the one-dimensional arc length from the context of prior actions or states, overcoming ambiguity where the overlap of trajectory segments causes multiple head directions to be associated with one place. These mechanisms allow retrieval of complex, self-crossing trajectories as continuous curves through space and time.
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paper_title: Mathematical learning theory through time

paper_content:

Abstract Stimulus sampling theory (SST: Estes, 1950 , Estes, 1955a , Estes, 1955b , Estes, 1959 ) was the first rigorous mathematical model of learning that posited a central role for an abstract cognitive representation distinct from the stimulus or the response. SST posited that (a) conditioning takes place not on the nominal stimulus presented to the learner, but on a cognitive representation caused by the nominal stimulus, and (b) the cognitive representation caused by a nominal stimulus changes gradually across presentations of that stimulus. Retrieved temporal context models assume that (a) a distributed representation of temporal context changes gradually over time in response to the studied stimuli, and (b) repeating a stimulus can recover a prior state of temporal context. We trace the evolution of these ideas from the early work on SST, and argue that recent neuroscientific evidence provides a physical basis for the abstract models that Estes envisioned more than a half-century ago.
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paper_title: Modeling working memory: a computational implementation of the Time-Based Resource-Sharing theory

paper_content:

Working memory is a core concept in cognition, predicting about 50% of the variance in IQ and reasoning tasks. A popular test of working memory is the complex span task, in which encoding of memoranda alternates with processing of distractors. A recent model of complex span performance, the Time-Based-Resource-Sharing (TBRS) model of Barrouillet and colleagues, has seemingly accounted for several crucial findings, in particular the intricate trade-off between deterioration and restoration of memory in the complex span task. According to the TBRS, memory traces decay during processing of the distractors, and they are restored by attentional refreshing during brief pauses in between processing steps. However, to date, the theory has been formulated only at a verbal level, which renders it difficult to test and to be certain of its intuited predictions. We present a computational instantiation of the TBRS and show that it can handle most of the findings on which the verbal model was based. We also show that there are potential challenges to the model that await future resolution. This instantiated model, TBRS*, is the first comprehensive computational model of performance in the complex span paradigm. The Matlab model code is available as a supplementary material of this article.
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paper_title: Human memory reconsolidation can be explained using the temporal context model

paper_content:

Recent work by Hupbach, Gomez, Hardt, and Nadel (Learning & Memory, 14, 47–53, 2007) and Hupbach, Gomez, and Nadel (Memory, 17, 502–510, 2009) suggests that episodic memory for a previously studied list can be updated to include new items, if participants are reminded of the earlier list just prior to learning a new list. The key finding from the Hupbach studies was an asymmetric pattern of intrusions, whereby participants intruded numerous items from the second list when trying to recall the first list, but not viceversa. Hupbach et al. (2007; 2009) explained this pattern in terms of a cellular reconsolidation process, whereby first-list memory is rendered labile by the reminder and the labile memory is then updated to include items from the second list. Here, we show that the temporal context model of memory, which lacks a cellular reconsolidation process, can account for the asymmetric intrusion effect, using well-established principles of contextual reinstatement and item–context binding.
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paper_title: Mathematical learning theory through time

paper_content:

Abstract Stimulus sampling theory (SST: Estes, 1950 , Estes, 1955a , Estes, 1955b , Estes, 1959 ) was the first rigorous mathematical model of learning that posited a central role for an abstract cognitive representation distinct from the stimulus or the response. SST posited that (a) conditioning takes place not on the nominal stimulus presented to the learner, but on a cognitive representation caused by the nominal stimulus, and (b) the cognitive representation caused by a nominal stimulus changes gradually across presentations of that stimulus. Retrieved temporal context models assume that (a) a distributed representation of temporal context changes gradually over time in response to the studied stimuli, and (b) repeating a stimulus can recover a prior state of temporal context. We trace the evolution of these ideas from the early work on SST, and argue that recent neuroscientific evidence provides a physical basis for the abstract models that Estes envisioned more than a half-century ago.
---
paper_title: Modeling working memory: a computational implementation of the Time-Based Resource-Sharing theory

paper_content:

Working memory is a core concept in cognition, predicting about 50% of the variance in IQ and reasoning tasks. A popular test of working memory is the complex span task, in which encoding of memoranda alternates with processing of distractors. A recent model of complex span performance, the Time-Based-Resource-Sharing (TBRS) model of Barrouillet and colleagues, has seemingly accounted for several crucial findings, in particular the intricate trade-off between deterioration and restoration of memory in the complex span task. According to the TBRS, memory traces decay during processing of the distractors, and they are restored by attentional refreshing during brief pauses in between processing steps. However, to date, the theory has been formulated only at a verbal level, which renders it difficult to test and to be certain of its intuited predictions. We present a computational instantiation of the TBRS and show that it can handle most of the findings on which the verbal model was based. We also show that there are potential challenges to the model that await future resolution. This instantiated model, TBRS*, is the first comprehensive computational model of performance in the complex span paradigm. The Matlab model code is available as a supplementary material of this article.
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paper_title: Temporal Cognition: A Key Ingredient of Intelligent Systems

paper_content:

Experiencing the flow of time is an important capacity of biological systems that is involved in many ways in the daily activities of humans and animals. However, in the field of robotics, the key role of time in cognition is not adequately considered in contemporary research, with artificial agents focusing mainly on the spatial extent of sensory information, almost always neglecting its temporal dimension. This fact significantly obstructs the development of high level robotic cognitive skills, as well as the autonomous and seamless operation of artificial agents in human environments. Taking inspiration from biological cognition, the present work puts forward time perception as a vital capacity of artificial intelligent systems and contemplates the research path for incorporating temporal cognition in the repertoire of robotic skills.
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paper_title: Space , Time and Number Space , time , and number : a Kantian research program

paper_content:

The 24th Attention & Performance meeting on ‘Space, Time, and Number: Cerebral Foundations of Mathematical Intuitions’ was sponsored by Commissariat a l’Energie Atomique et aux Energies Alternatives (CEA), Ecole des Neurosciences de Paris (ENP), European Society for Cognitive Psychology (ESCOP), the Bettencourt-Schueller Foundation, the Fondation de France, the Hugot Foundation of the College de France, the IPSEN Foundation, Institut National de la Sante et de la Recherche Medicale (INSERM), the James D. McDonnell Foundation, National Institute of Child Health & Human Development (NICHD R13HD065378), the National Science Foundation (NSF), and Ministere de l’Enseignement Superieur et de la Recherche. We thank Susana Franck, Laurence Labruna and Giovanna Santoro for their help in organizing the meeting.
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paper_title: Moving Through Time

paper_content:

/ FREE Full Text 8. 1. Riley M.A., 2. Balasubramaniam R., 3. Mitra S., 4. Turvey M.T. (1998). Visual influences on centre of pressure dynamics in upright posture. Ecological Psychology, 10, 65–91. CrossRef Web of Science
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paper_title: Sensory modality and time perception in children and adults

paper_content:

This experiment investigated the effect of signal modality on time perception in 5- and 8-year-old children as well as young adults using a duration bisection task in which auditory and visual signals were presented in the same test session and shared common anchor durations. Durations were judged shorter for visual than for auditory signals by all age groups. However, the magnitude of this modality difference was larger in the children than in the adults. Sensitivity to time was also observed to increase with age for both modalities. Taken together, these two observations suggest that the greater modality effect on duration judgments for the children, for whom attentional abilities are considered limited, is the result of visual signals requiring more attentional resources than are needed for the processing of auditory signals. Within the framework of the information-processing model of Scalar Timing Theory, these effects are consistent with a developmental difference in the operation of the "attentional switch" used to transfer pulses from the pacemaker into the accumulator. Specifically, although timing is more automatic for auditory than visual signals in both children and young adults, children have greater difficulty in keeping the switch in the closed state during the timing of visual signals. Language: en
---
paper_title: Putting Time in Perspective: A Valid, Reliable Individual-Differences Metric

paper_content:

Time perspective (TP), a fundamental dimension in the construction of psychological time, emerges from cognitive processes partitioning human experience into past, present, and future temporal frames. The authors’ research program proposes that TP is a pervasive and powerful yet largely unrecognized influence on much human behavior. Although TP variations are learned and modified by a variety of personal, social, and institutional influences, TP also functions as an individual-differences variable. Reported is a new measure assessing personal variations in TP profiles and specific TP biases. The five factors of the Zimbardo Time Perspective Inventory were established through exploratory and confirmatory factor analyses and demonstrate acceptable internal and test–retest reliability. Convergent, divergent, discriminant, and predictive validity are shown by correlational and experimental research supplemented by case studies.
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paper_title: Threaded cognition: An integrated theory of concurrent multitasking

paper_content:

The authors propose the idea of threaded cognition, an integrated theory of concurrent multitasking-that is, performing 2 or more tasks at once. Threaded cognition posits that streams of thought can be represented as threads of processing coordinated by a serial procedural resource and executed across other available resources (e.g., perceptual and motor resources). The theory specifies a parsimonious mechanism that allows for concurrent execution, resource acquisition, and resolution of resource conflicts, without the need for specialized executive processes. By instantiating this mechanism as a computational model, threaded cognition provides explicit predictions of how multitasking behavior can result in interference, or lack thereof, for a given set of tasks. The authors illustrate the theory in model simulations of several representative domains ranging from simple laboratory tasks such as dual-choice tasks to complex real-world domains such as driving and driver distraction.
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paper_title: Habituation revisited: An updated and revised description of the behavioral characteristics of habituation

paper_content:

In the 20th century, great progress was made in understanding the behavioral characteristics of habituation. A landmark paper published by Thompson and Spencer in 1966 clarified the definition of habituation, synthesized the research to date and presented a list of nine behavioral characteristics of habituation that appeared to be common in all organisms studied The history of habituation and the historical context of Thompson & Spencer's (1966) distillation are reviewed more fully in an article by Thompson (2009) that is included in this issue. This list was repeated and expanded upon by Groves and Thompson in 1970. These two papers are now citation classics and are considered to be the authorities on the characteristics of habituation. In August 2007, a group of 15 researchers (the authors of this review) who study habituation in a wide range of species and paradigms met to revisit these characteristics and refine them based on the 40 years of research since Thompson and Spencer 1966. The descriptions and characteristics from 1966 have held up remarkably well, and the revisions we have made to them were often for clarity rather than content. We made substantial changes to only a few of the characteristics, usually to add new information and expand upon the description rather than to substantially alter the original point. We restricted ourselves to an analysis of habituation; there was insufficient time for detailed discussions of the other form of non-associative learning “sensitization.” Thus this review is restricted to our discussions of habituation and dishabituation (as it relates directly to habituation). ::: ::: Many people will be surprised to learn that, although habituation is termed ”the simplest form of learning” and is well studied behaviorally, remarkably little is known about the neural mechanisms underlying habituation. Researchers who work on this form of learning believe that because habituation allows animals to filter out irrelevant stimuli and focus selectively on important stimuli, it is a prerequisite for other forms of learning. Therefore, to fully understand the mechanisms of more complex forms of learning and cognition it is important to understand the basic building blocks of habituation. The objectives of this special issue are to re-ignite interest in studying the mechanisms of habituation and thereby to stimulate efforts to further our understanding of the neural basis of habituation. ::: ::: In this review, we will first define habituation, then review and revise the nine characteristics of habituation that were originally determined by Thompson and Spencer in 1966 and that have been seen across all species studied. In addition, we describe a tenth characteristic that was added at the workshop. Finally we present several issues that were discussed extensively at the meeting and highlight how the view of habituation that arose from our discussions differs from the original characterization by Thompson and Spencer.
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paper_title: Environmental, seasonal, and social modulations of basal activity in a weakly electric fish

paper_content:

The electric organ discharge (EOD) of weakly electric fish encodes information about species, sex, behavioral, and physiological states throughout the lifetime. Its central command is crucial for sensory-motor coordination, and is therefore the target of plastic mechanisms that adapt fish to environmental and social challenges. The EOD waveform of Brachyhypopomus pinnicaudatus is modulated by environmental factors and the neuroendocrine system. In this study we investigate the effects of water temperature and day-night cycle upon EOD rate in this species during the breeding and non-breeding seasons. During the non-breeding season, EOD rate is a linear function of water temperature and exhibits counterclockwise hysteresis. During breeding, a thermal resistance strategy prevents the decrease of EOD rate to cooling. A nocturnal increase of EOD basal rate independent of water temperature and locomotor activity was demonstrated in isolated non-breeding adults and in male-female dyads all year round. An additional increase of nocturnal EOD rate, probably acting as a social courtship signal, was found in breeding dyads. This additional increase of nocturnal EOD rate could not be fully explained by gonadal maturation and was modulated by social stimuli. This study provides novel data on the complex interactions between environment, reproductive cycle, social behavior, and electromotor output in an advantageous model of the vertebrate central nervous system.
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paper_title: The inner sense of time: how the brain creates a representation of duration

paper_content:

A large number of competing models exist for how the brain creates a representation of time. However, several human and animal studies point to 'climbing neural activation' as a potential neural mechanism for the representation of duration. Neurophysiological recordings in animals have revealed how climbing neural activation that peaks at the end of a timed interval underlies the processing of duration, and, in humans, climbing neural activity in the insular cortex, which is associated with feeling states of the body and emotions, may be related to the cumulative representation of time.
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Title: Time models and cognitive processes: a review
Section 1: INTRODUCTION
Description 1: Write an overview of the importance of time perception in biological systems and its recent integration into cognitive and robotic models.

Section 2: TIME PROCESSING MECHANISMS IN THE BRAIN
Description 2: Discuss various brain areas implicated in time-keeping and their roles in processing temporal information.

Section 3: COMPUTATIONAL MODELS OF TIME PERCEPTION
Description 3: Review the different computational models explaining how time is processed in the brain, differentiating between the dedicated and intrinsic models.

Section 4: COGNITIVE MODELS EXPLOITING SENSE OF TIME
Description 4: Outline existing computational models that integrate time perception with other cognitive functions.

Section 5: TIME IN DECISION MAKING
Description 5: Explore models where robotic agents use time perception for decision-making processes.

Section 6: A GROUNDED TEMPORAL LEXICON
Description 6: Discuss how robots learn terms for space and time and develop a temporal lexicon.

Section 7: INTERVAL TIMING GROUNDED IN MOTOR ACTIVITY
Description 7: Explain models where time perception is grounded in motor activities, particularly in the context of memory-trace decay.

Section 8: REPRESENTATION OF DURATION
Description 8: Investigate alternative representations of duration in cognitive systems through self-organized computational models.

Section 9: TIME PERCEPTION AS A SECONDARY TASK
Description 9: Describe how timing modules in architectures like ACT-R explore the interaction of timing mechanisms with other cognitive functions.

Section 10: PAST, FUTURE PERCEPTION
Description 10: Examine models that discuss the evolution and role of perceiving past and future in cognitive systems.

Section 11: MENTAL TIME TRAVEL
Description 11: Review computational models that explain the brain’s ability to recall past experiences and project future events.

Section 12: LEARNING THROUGH TIME
Description 12: Discuss the role of time in the learning process and contrast different mathematical models for learning over time.

Section 13: FORGETTING
Description 13: Explain computational models of forgetting, particularly how memory decays over time and how it is restored.

Section 14: MEMORY RECONSOLIDATION
Description 14: Review computational models explaining how memory reconsolidation works, including how retrieval changes memory representation over time.

Section 15: DISCUSSION
Description 15: Summarize the multimodal interaction between time perception and various cognitive functions, highlighting future research directions for improving artificial systems' temporal cognition.

Section 16: CONCLUSIONS
Description 16: Provide concluding remarks on the importance of integrating time perception in cognitive models and the future impact of such research on human-robot interaction.