Simulation Techniques and Prosthetic Approach Towards Biologically Efficient Artificial Sense Organs- An Overview
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paper_title: Effect on prosthetic vision visual acuity by filtering schemes, filter cut-off frequency and phosphene matrix: a virtual reality simulation

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Visual acuity of prosthetic vision was examined under virtual reality simulation. Prosthetic vision was simulated by first filtering an image using circular mean filters or Gaussian smoothing filters of different cut-off frequencies. Pixel values at 100 fixed sites of the filtered image were taken, sampling either with a regular rectangular or hexagonal matrix. Each pixel value was transformed into a Gaussian intensity profile centered at the corresponding position at which the sample was taken to simulate the evoked visual effect of an electric stimulation. Visual acuity scores of three subjects, each completing two sets of results, were recorded across different filtering schemes, cut-off frequencies and sampling matrices. The best mean score recorded was 1.55 logMAR, with the worst being 1.70 logMAR. The difference was mostly attributed to filter cut-off frequency. Differences between filtering schemes were insignificant. Results also showed emerging trends demonstrating differences between rectangular and hexagonal sampling matrices.
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paper_title: Facial recognition using simulated prosthetic pixelized vision

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PURPOSE. To evaluate a model of simulated pixelized prosthetic vision using noncontiguous circular phosphenes, to test the effects of phosphene and grid parameters on facial recognition. METHODS. A video headset was used to view a reference set of four faces, followed by a partially averted image of one of those faces viewed through a square pixelizing grid that contained 10 × 10 to 32 X 32 dots separated by gaps. The grid size, dot size, gap width, dot dropout rate, and gray-scale resolution were varied separately about a standard test condition, for a total of 16 conditions. All tests were first performed at 99% contrast and then repeated at 12.5% contrast. RESULTS. Discrimination speed and performance were influenced by all stimulus parameters. The subjects achieved highly significant facial recognition accuracy for all high-contrast tests except for grids with 70% random dot dropout and two gray levels. In low-contrast tests, significant facial recognition accuracy was achieved for all but the most adverse grid parameters: total grid area less than 17% of the target image, 70% dropout. four or fewer gray levels, and a gap of 40.5 arcmin. For difficult test conditions, a pronounced learning effect was noticed during high-contrast trials, and a more subtle practice effect on timing was evident during subsequent low-contrast trials. CONCLUSIONS. These findings suggest that reliable face recognition with crude pixelized grids can be learned and may be possible, even with a crude visual prosthesis.
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paper_title: Perceptual learning: learning to see

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Abstract Perceptual learning in vision has been found to be highly specific for simple stimulus attributes, implying highly specific modifications in the nervous system. The type of specificity found (location, orientation, eye) implied plasticity at very early stages of visual processing, where processing modules were believed to be hard-wired and task independent. Recent studies show, however, that learning is task dependent. Studies examining the time course of learning indicate that at least two different learning processes are involved in perceptual learning, reflecting different levels of processing. Perceptual learning appears to be governed by associative rules and to be constrained by system architecture.
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paper_title: Early ‘visual’ cortex activation correlates with superior verbal memory performance in the blind

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The visual cortex may be more modifiable than previously considered. Using functional magnetic resonance imaging (fMRI) in ten congenitally blind human participants, we found robust occipital activation during a verbal-memory task (in the absence of any sensory input), as well as during verb generation and Braille reading. We also found evidence for reorganization and specialization of the occipital cortex, along the anterior‐posterior axis. Whereas anterior regions showed preference for Braille, posterior regions (including V1) showed preference for verbal-memory and verb generation (which both require memory of verbal material). No such occipital activation was found in sighted subjects. This difference between the groups was mirrored by superior performance of the blind in various verbal-memory tasks. Moreover, the magnitude of V1 activation during the verbalmemory condition was highly correlated with the blind individual’s abilities in a variety of verbal-memory tests, suggesting that the additional occipital activation may have a functional role.
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paper_title: Visual form detection in 3-dimensional space

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Abstract : This monograph presents the results of a program of research dealing with the detection of dotted stimulus forms embedded in dotted visual noise. Nineteen experiments are described concerning the detection of single flashing dots, dotted lines, and both random and regularly dotted planes. A mathematical model based upon the autocorrelational transform is also tested for some of the experiments. Among the most important findings are a remarkable insensitivity of the perceptual system to temporal and spatial irregularities and a qualitative difference in the way observers deal with planes formed from random dot arrays and dotted outlines respectively. The autocorrelation model is in general agreement with the psychophysical results against which it is tested. The main conclusion arising from this research may be summarized as the rule of linear periodicity. Observers ar sensitive to forms to the extent that they contain dotted, straight lines with equal interdot spacing. This sensitivity appears to be a primitive of visual perception in a manner that is analogous to the sensitivity exhibited by the autocorrelation to periodic forms. Historical and lexicographic matters pertaining to the problem of form perception are also discussed in this monograph. (Author)
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paper_title: Reading speed with a pixelized vision system

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A visual prosthesis based on electrical stimulation of the visual cortex with an array of penetrating electrodes is expected to produce pixelized visual images consisting of punctate spots of light (phosphenes). We measured reading speed in subjects viewing text with optically simulated phosphene fields in order to obtain estimates of the following design parameters for such an electrode array: pixel number, pixel spacing, and visual-field size. Comparisons were made between scanning the text with eye movements and scanning the text with head movements. The results indicate that a 25 × 25 array of pixels representing four letters of text projected on a visual field of 1.7° is sufficient to provide reading rates near 170 words/min with scrolled text and near foveal 100 words/min with fixed text.
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paper_title: Visual acuity measurement of prosthetic vision: a virtual-reality simulation study

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A virtual-reality simulation tested prosthetic visual acuity for both rectangular and hexagonal phosphene grids. Thirteen normally sighted, untrained subjects were required to identify the Landolt C optotype over ten sessions. Overall performance, performance by filter setting (image analysis), and performance by size and orientation of the Landolt C optotype are reported. The results indicated that the hexagonal grid had a slight (4.1%) but statistically significant (p < 0.0001) performance advantage over the rectangular grid for correct identification of the testing symbol. It was also observed that both the phosphene grids had distinct performance profiles relating to their respective spatial orientation. Over the course of the ten sessions, learning afforded subjects an averaged improved performance of 10%.
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paper_title: Pattern Recognition with the Optic Nerve Visual Prosthesis

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A volunteer with retinitis pigmentosa and no residual vision was chronically implanted with an optic nerve electrode connected to an implanted neurostimulator and antenna. An external controller with telemetry was used for electrical activation of the nerve which resulted in phosphene perception. Open-loop stimulation allowed the collection of phosphene attributes and the ability to elicit perception of simple geometrical patterns. Low perception thresholds allowed for large current intensity range within safety limits. In a closed-loop paradigm, the volunteer was using a head-worn video camera to explore a projection screen. The volunteer underwent performance evaluation during the course of a training program with 45 simple patterns. After learning, the volunteer reached a recognition score of 63% with a processing time of 60 s. Mean performance in orientation discrimination reached 100% with a processing time of 8 s.
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paper_title: Mobility performance with a pixelized vision system

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Abstract A visual prosthesis, based on electrical stimulation of the visual cortex, has been suggested as a means for partially restoring functional vision in the blind. The prosthesis would create a pixelized visual sense consisting of punctate spots of light (phosphenes). The present study investigated the feasibility of achieving visually-guided mobility with such a visual sense. Psychophysical experiments were conducted on normally sighted human subjects, who were required to walk through a maze which included a series of obstacles, while their visual input was restricted to information from a pixelized vision simulator. Walking speed and number of body contacts with obstacles and walls were measured as a function of pixel number, pixel spacing, object minification, and field of view. The results indicate that a 25 × 25 array of pixels distributed within the foveal visual area could provide useful visually guided mobility in environments not requiring a high degree of pattern recognition.
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paper_title: Auditory cortical plasticity under operation: reorganization of auditory cortex induced by electric cochlear stimulation reveals adaptation to altered sensory input statistics

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We introduce a framework based on plastic-adaptational processes for an interpretation of electrical cochlear implant (CI) stimulation. Cochlear prostheses are used to restore sound perception in adults and children with profound deafness. After providing a review of cortical plasticity, we summarize our findings using optical imaging of intrinsic signals to map cat auditory cortex (AI) activated by CI stimulation. In adult AI of neonatally deafened animals, the acoustic deprivation caused a severe distortion of cochleotopic maps. A three-month period of CI-stimulation using the continuous interleaved sampling strategy did not re-install the status typically found in normal adults, but resulted in the emergence of a new topographical organization characterized by large, joint representations of all stimulated electrode sites. We suggest that the effectiveness of CI-stimulation relies primarily on a re-learning of input pattern arising from "artificial" sensory inputs via electrical stimulation, thereby supporting the importance of learning and training for the interpretation and understanding of the effects of CI stimulation. We suggest that the ability for gaining/ re-gaining speech understanding mediated by CI-stimulation is accomplished by new strategies of cortical processing due to enhanced cooperativity among large populations of neurons that serve higher processing stages to interpret new patterns arriving from the periphery. These strategies are thought to emerge from adaptational capacities in response to the constraints imposed by the properties of the new input statistics that in turn result from the stimulation strategy employed.
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paper_title: Festina Lente : Evidences for Fast and Slow Learning Processes and a Role for Sleep in Human Motor Skill Learning

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In our everyday life, a wide range of motor, perceptual, and cognitive abilities are gradually and implicitly acquired through our continuous interaction with the environment, a process referred to as skill learning. Converging data indicate that skill learning is a multiple step process that cannot be reduced to the acquisition episode only. In the initial step, while the subject is practicing the task, the performance asymptotically improves with continued practice. This corresponds to a process coined as fast learning by Karni and coworkers (Karni and Sagi 1993; Karni et al. 1995). Remarkably, however, the initially formed memory trace apparently continues to be reprocessed after the training has ended. Consequently, when tested at a later date, up to several days to weeks later, the performance to the task is markedly improved even without any intervening training sessions. This so-called slow component of learning has been observed in humans for both perceptual and motor skill learning (Karni and Sagi 1993; Karni et al. 1995), and seems to depend critically on sleep rather than simply on time or initial practice (Maquet 2001; Peigneux et al. 2001). In this issue, Walker and colleagues investigate the interplay between the fast and slow components of learning. In the domain of motor skill learning, the finger tapping task (FTT), or its variant the finger opposition task, has been a useful model to characterize the fast and slow components of the learning process as well as the respective effects of time, practice, and sleep on the latter. In this task, the subjects are asked to repeat a five-element sequence of finger movements with the nondominant hand, as fast and as accurately as possible (Fig. 1C). The performance measure consists of the number of correctly repeated sequences in a given time (usually 30 sec). Whereas a moderate, albeit significant, increase in performance is reported during the training session and between training episodes on the same day, a much larger gain in performance is systematically observed overnight (Fischer et al. 2002; Walker et al. 2002; Walker et al. 2003; Fig.1A,B). This suggests that sleep is a major factor underlying the overnight gain in performance. Accordingly, it was shown that slow learning is significantly enhanced when participants are allowed to sleep between the training and the retest sessions (Fischer et al. 2002). The large improvement in performance is observed both after night time and day time sleep, ruling out a potential circadian influence on slow learning (Fischer et al. 2002). The exact influence of sleep on the slow component of skill learning is still unclear. For some tasks, (FTT: Fischer et al. 2002; pursuit task: Maquet et al. 2003), a small gain in performance persists despite a total sleep deprivation during the first posttraining night. For other tasks (visual texture discrimination task; Stickgold et al. 2000a), sleep seems a prerequisite for any significant performance improvement. Likewise, the respective role of the various sleep stages in skill learning is still unclear. Early results suggested that perceptual (visual) learning was sensitive to rapid eye movement (REM) sleep deprivation (Karni et al. 1994). Subsequent work emphasized that a maximal improvement in performance was observed after the succession of a large amount of SWS early in the night and REM sleep late in the night, raising the possibility of a double-step process in memory consolidation (Gais et al. 2000; Stickgold et al. 2000a,b). For motor skill learning, data are still too fragmentary to reach any definite conclusion. The improvement in performance has been reported to be related linearly to the time spent in REM sleep (Fischer et al. 2002) or in stage-2 non-REM sleep late in the night (Walker et al. 2002). Future research should sort out this issue. In any case, the gain in performance after motor-skill learning is robust and long lasting. It is still there after two nights of sleep (Fischer et al. 2002) and as shown byWalker and colleagues in this issue, might still slightly increase after the third post training night. The combined effect of daily motor practice and regular sleep might eventually lead to dramatic improvement in performance that plateaus after 2–3 wk (Karni et al. 1995; Fig. 1C). In this issue, Walker and colleagues now focus on the relationships between the fast (within session) and the slow (between session, overnight) components of learning (Fig. 1A,B). Do these components evolve independently or not? No correlation between the within-session improvement and the overnight gain in performance was observed, suggesting statistical independence. This might indicate that fast and slow-learning phases rely on independent cellular mechanisms. Furthermore, they observe a nearly identical overnight improvement, irrespective of the amount of practice prior to sleep. Although subjects extensively trained reached a higher level of performance during practice than subjects with a limited amount of practice, the overnight gain was nearly identical (Fig.1B). This suggests that sleep-dependent slow learning is independent of the evolution of the fast component during prior practice. Still, this does not diminish the importance of the fast component of learning in order to initiate sleep-dependent slow learning processes, as suggested by Hauptmann and Karni (2002) in the case of a priming task. In this latter task, the fast (within-session) learning component has to be exhausted before any slow (between-day) learning can reliably be detected. As Walker and colleagues (this issue) used a pretty intensive training (4 12 30-sec blocks in group 1; 2 12 30-sec blocks in group 3), the fast learning component might have been exhausted on the first experimental day. Therefore, no significant within-session improvement occurs during subsequent sessions (on day 2), and the gain in performance is mainly accounted for by the slow sleep-dependent overnight component. Accordingly, at the systems level, it is known that there is a 1Corresponding author. E-MAIL Maquet@pet.crc.ulg.ac.be; FAX 32-4366-2946. Article and publication are at http://www.learnmem.org/cgi/doi/10.1101/ lm.64303.
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paper_title: Contour integration and cortical processing

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Abstract Our understanding of visual processing in general, and contour integration in particular, has undergone great change over the last 10 years. There is now an accumulation of psychophysical and neurophysiological evidence that the outputs of cells with conjoint orientation preference and spatial position are integrated in the process of explication of rudimentary contours. Recent neuroanatomical and neurophysiological results suggest that this process takes place at the cortical level V1. The code for contour integration may be a temporal one in that it may only manifest itself in the latter part of the spike train as a result of feedback and lateral interactions. Here we review some of the properties of contour integration from a psychophysical perspective and we speculate on their underlying neurophysiological substrate.
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paper_title: Artificial vision for the blind by connecting a television camera to the visual cortex.

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Blindness is more feared by the public than any ailment with the exception of cancer and AIDS. We report the development of the first visual prosthesis providing useful "artificial vision" to a blind volunteer by connecting a digital video camera, computer, and associated electronics to the visual cortex of his brain. This device has been the objective of a development effort begun by our group in 1968 and represents realization of the prediction of an artificial vision system made by Benjamin Franklin in his report on the "kite and key" experiment, with which he discovered electricity in 1751.
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paper_title: Visually Guided Performance of Simple Tasks Using Simulated Prosthetic Vision

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: Loss of photoreceptor cells is one of the major causes of blindness. Several groups are exploring the functional replacement of photoreceptors by a retinal prosthesis. The goal of this study was to simulate the vision levels that recipients of retinal prostheses with 4 × 4, 6 × 10, and 16 × 16 electrode arrays may experience, and to test the functionality of this vision. A PC video camera captured images that were converted in real time into dots (“pixels”). The PC monitor and a head-mounted display worn by test subjects displayed the pixelized images. To assess performance of normally sighted individuals with each array, we designed a set of tasks including: four-choice orientation discrimination of a Sloan letter E, object recognition and discrimination, a cutting task, a pouring task, symbol recognition, and two reading tasks. In the letter E task, subjects were found to have visual acuities of 20/1,810, 20/1,330, and 20/420 with the 4 × 4, 6 × 10, and 16 × 16 arrays, respectively. Most subjects were able to read fonts as small as 36 point with the 16 × 16 array, corresponding with a visual acuity of 20/600 in our system. The test subjects partially overcame the visual limitation of the system by scanning the video camera over the letters allowing spatial and temporal integration of visual information. In all categories, subjects performed best with the 16 × 16 array and least well with the 4 × 4 array. Even with the lowest resolution array, however, some subjects could recognize simple objects and symbols.
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paper_title: Visual sensations produced by optic nerve stimulation using an implanted self-sizing spiral cuff electrode

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A blind volunteer with retinitis pigmentosa was chronically implanted with a self-sizing spiral cuff electrode around an optic nerve. Electrical stimuli applied to the nerve produced localized visual sensations that were broadly distributed throughout the visual field and could be varied by changing the stimulating conditions. These results demonstrate the potential for constructing a visual prosthesis, based on electrical stimulation of the optic nerve, for blind subjects who have intact retinal ganglion cells.
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paper_title: Simulated prosthetic visual fixation, saccade, and smooth pursuit

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A visual tracking task was administered to 20 subjects afforded simulated prosthetic vision (a phosphene array); a total of 3 h data was taken from each subject over the course of 10 visits. The experiment assessed prosthetic visual fixation, saccade and smooth pursuit and the effect of practice. Further, we demonstrated an image analysis technique that assisted fixation and pursuit (but not saccade) accuracy, and required less vigorous movement of the phosphene array in pursuing the target. As measured by mean deviation from the target, fixation and pursuit accuracies were improved by 8.3 and 3.3 min of visual arc, respectively (35.8% and 6.8%), for inter-phosphene spacing of 1.9°. The analysis technique, involving overlapping Gaussian kernels, was an heuristic design; this is the first step of an iterative, experimental approach to devising effective image analysis to be contained in an electronic vision prosthesis. The approach should ultimately afford implanted patients improved prosthetic visual function.
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paper_title: Visual Perception Elicited by Electrical Stimulation of Retina in Blind Humans

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Objective: To evaluate the feasibility of bypassing damaged photoreceptors and electrically stimulating the remaining viable retinal layers to provide limited visual input to patients who are blind because of severe photoreceptor degeneration. Methods: In the operating room with the patient under local anesthesia, focal electrical stimulation of the retinal surface with brief biphasic pulses was performed using small probes inserted through the sclera. The procedure was performed in five subjects who had little or no light perception. Three subjects had retinitis pigmentosa, one had age-related macular degeneration, and one had unspecified retinal degeneration from birth. Results: Stimulation elicited visual perception of a spot of light (phosphene). Subjects who previously had useful vision accurately localized the phosphenes according to the retinal area stimulated. Two subjects could track the movement of the stimulating electrode by reporting movement of the elicited phosphene, and could perceive two simultaneous phosphenes on independent stimulation with two electrodes. In a resolution test, one of the subjects wih no light perception in his left eye resolved phosphenes at 1.75° center-to-center distance (ie, 4/200 OS visual acuity). Conclusions: Local electrical stimulation of the retinal surface in patients blind from outer retinal disease results in focal light perception that seems to arise from the stimulated area. Such findings in an acute experiment warrant further research into the possibility of prolonged retinal stimulation, improved resolution, and ultimately, an intraocular visual prosthesis.
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paper_title: Contour integration by the human visual system: Evidence for a local “association field”

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Abstract The Gestalt law of “good continuation” has been used to describe a variety of phenomena demonstrating the importance of continuity in human perception. In this study, we consider how continuity may be represented by a visual system that filters spatial data using arrays of cells selective for orientation and spatial frequency. Many structures (e.g. fractal contours) show a form of redundancy which is well represented by the continuity of features as they vary across space and frequency. We suggest that it is possible to take advantage of the redundancy in continuous, but non-aligned features by associating the outputs of filters with similar tuning. Five experiments were performed, to determine the rules that govern the perception of continuity. Observers were presented with arrays of oriented, band-pass elements (Gabor patches) in which a subset of the elements was aligned along a “jagged” path. Using a forced-choice procedure, observers were found to be capable of identifying the path within a field of randomly-oriented elements even when the spacing between the elements was considerably larger than the size of any of the individual elements. Furthermore, when the elements were oriented at angles up to ± 60 deg relative to one another, the path was reliably identified. Alignment of the elements along the path was found to play a large role in the ability to detect the path. Small variations in the alignment or aligning the elements orthogonally (i.e. “side-to-side” as opposed to “end-to-end”) significantly reduced the observer's ability to detect the presence of a path. The results are discussed in terms of an “association field” which integrates information across neighboring filters tuned to similar orientations. We suggest that some of the processes involved in texture segregation may have a similar explanation.
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paper_title: Position, size and luminosity of phosphenes generated by direct optic nerve stimulation

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Pulses of low intensity current, delivered through a cuff electrode chronically implanted around the optic nerve of a blind retinitis pigmentosa patient generate visual sensations. These phosphenes are obtained at lower thresholds for a train of stimuli than for single pulses, which suggests the existence of a spatial and temporal integrating mechanism. The perceptions are much smaller than those predicted from model simulations. A set of equations are derived which show the effect of pulse current, duration, number and frequency on the position, size and, to some extent, luminosity of the resulting phosphenes.
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paper_title: Imaging Plasticity in Cochlear Implant Patients

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Auditory re-afferentation by cochlear implants (CI) offers a unique opportunity to study directly from within the auditory modality plastic changes taking place at organisational levels up to the supr
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paper_title: The effects of chronic intracochlear electrical stimulation on inferior colliculus spatial representation in adult deafened cats

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Abstract Previous studies have shown that chronic electrical stimulation through a cochlear implant causes significant alterations in the central auditory system of neonatally deafened cats. The goal of this study was to investigate the effects of chronic stimulation in the mature auditory system. Normal hearing adult animals were deafened by ototoxic drugs and received daily electrical stimulation over periods of 4–6 months. In terminal physiology experiments, response thresholds to pulsatile and sinusoidal signals were recorded within the inferior colliculus (IC). Using previously established methods, spatial tuning curves (STCs; threshold vs. IC depth functions) were constructed, and their widths measured to infer spatial selectivity. The IC spatial representations were similar for pulsatile and sinusoidal stimulation when phase duration was taken into consideration. However, sinusoidal signals consistently elicited much lower thresholds than pulsatile signals, a difference not solely attributable to differences in charge/phase. The average STC width was significantly broader in the adult deafened/stimulated animals than in controls (adult deafened/unstimulated cats), suggesting that electrical stimulation can induce spatial expansion of the IC representation of the chronically stimulated cochlear sector. Further, results in these adult animals were not significantly different from results in neonatally deafened, early stimulated animals, suggesting that a similar degree of plasticity was induced within the auditory midbrains of mature animals.
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paper_title: Simulation of a phosphene-based visual field: Visual acuity in a pixelized vision system

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A visual prosthesis for the blind using electrical stimulation of the visual cortex will require the development of an array of electrodes. Passage of current through these electrodes is expected to create a visual image made up of a matrix of discrete phosphenes. The quality of the visual sense thus provided will be a function of many parameters, particularly the number of electrodes and their spacing. We are conducting a series of psychophysical experiments with a portable "phosphene" simulator to obtain estimates of suitable values for electrode number and spacing. The simulator consists of a small video camera and monitor worn by a normally sighted human subject. To simulate a discrete phosphene field, the monitor is masked by an opaque perforated film. The visual angle subtended by images from the masked monitor is 1.7 degrees or less, depending on the mask, and falls within the fovea of the subject. In the study presented here, we measured visual acuity as a function of the number of pixels and their spacing in the mask. Visual acuity was inversely proportional to pixel density, and trained subjects could achieve about 20/26 visual acuity with a 1024 pixel image. We conclude that 625 electrodes implanted in a 1 cm by 1 cm area near the foveal representation of the visual cortex should produce a phosphene image with a visual acuity of approximately 20/30. Such an acuity could provide useful restoration of functional vision for the profoundly blind.
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paper_title: What spatial frequency do we use to detect the orientation of a Landolt C?

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Abstract We calculated the two-dimensional Fourier spectrum of a Landolt C. For Landolt Cs of orthogonal orientation, the main differences in the amplitude spectrum were found at a low frequency such that 1.3 periods were equal to the size of the Landolt C, rather than at the high frequency corresponding to the size of the gap, i.e., such that 2.5 periods were equal to the size of the Landolt C. We compared visual acuity assessments obtained with Landolt C optotypes and the cut-off of the contrast sensitivity function measured with sinusoidal gratings. We found that the frequency corresponding to the size of the gap is twice the latter frequency. We suggest that, in fact, this lower frequency can be used to determine the position of the gap.
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paper_title: Visual perception in a blind subject with a chronic microelectronic retinal prosthesis

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Abstract A retinal prosthesis was permanently implanted in the eye of a completely blind test subject. This report details the results from the first 10 weeks of testing with the implant subject. The implanted device included an extraocular case to hold electronics, an intraocular electrode array (platinum disks, 4 × 4 arrangement) designed to interface with the retina, and a cable to connect the electronics case to the electrode array. The subject was able to see perceptions of light (spots) on all 16 electrodes of the array. In addition, the subject was able to use a camera to detect the presence or absence of ambient light, to detect motion, and to recognize simple shapes.
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paper_title: Learning prosthetic vision: a virtual-reality study

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Acceptance of prosthetic vision will be heavily dependent on the ability of recipients to form useful information from such vision. Training strategies to accelerate learning and maximize visual comprehension would need to be designed in the light of the factors affecting human learning under prosthetic vision. Some of these potential factors were examined in a visual acuity study using the Landolt C optotype under virtual-reality simulation of prosthetic vision. Fifteen normally sighted subjects were tested for 10-20 sessions. Potential learning factors were tested at p<0.05 with regression models. Learning was most evident across-sessions, though 17% of sessions did express significant within-session trends. Learning was highly concentrated toward a critical range of optotype sizes, and subjects were less capable in identifying the closed optotype (a Landolt C with no gap, forming a closed annulus). Training for implant recipients should target these critical sizes and the closed optotype to extend the limit of visual comprehension. Although there was no evidence that image processing affected overall learning, subjects showed varying personal preferences.
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paper_title: How do cochlear prostheses work?

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The past two decades have witnessed a revolution in the treatment of sensorineural hearing loss. Cochlear prostheses have evolved from laboratory experiment to a commercial technology that has benefited over 20,000 people. Paralleling this phenomenal development has been a substantial increase in our understanding of the biophysical, physiological and psychophysical mechanisms underlying the function of these devices.
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paper_title: The human-based multi-sensor fusion method for artificial nose and tongue sensor data

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Presently, an increased interest is apparent for the development of integrated human-like smell and taste sensing capabilities, e.g. for chemical, paper pulp, food, and medicine applications. This paper will present an original sensor fusion method based on human expert opinions about smell and taste and measurement data from artificial nose and taste sensors. The "electronic nose" consists of an array of gas sensors with different selectivity patterns, signal handling, and a sensor signal pattern recognition and decision strategy. The "electronic tongue", which was developed for the taste analysis of liquids is based on pulse voltammetry. Measurement data from the artificial smell and taste sensors are used to produce sensor-specific opinions about these two human-like sensing modalities. This is achieved by a team of artificial neural networks and conventional signal handling which approximates a Bayesian decision strategy for classifying the sensor information. Further, a fusion algorithm based on the maximum likelihood principle provides a combination of the smell and, respectively, taste opinions, into an overall integrated opinion similar to human beings. The proposed integrated smell- and taste-sensing method is then illustrated by an application of real world measurements in the food industry.
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paper_title: Odor discrimination using insect electroantennogram responses from an insect antennal array.

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Insects have a highly developed olfactory sensory system, mainly based in their antennae, for the detection and discrimination of volatile compounds in the environment. Electroantennogram (EAG) response profiles of five different insect species, Drosophila melanogaster, Heliothis virescens, Helicoverpa zea, Ostrinia nubilalis and Microplitis croceipes, showed different, species-specific EAG response spectra to 20 volatile compounds tested. The EAG response profiles were then reconstructed for each compound across the five insect species. Most of the compounds could be distinguished by comparing the response spectra. We then used a four-antenna array, called a Quadro-probe EAG, to see if we could discriminate among odorants based on the relative EAG amplitudes evoked when the probe was placed in plumes in a wind tunnel and in a field. Stable EAG responses could be simultaneously and independently recorded with four different insect antennae mounted on the Quadro-probe, and different volatile compounds could be distinguished in real time by comparing relative EAG responses with a combination of differently tuned insect antennae. Regardless of insect species or EAG amplitudes, antennae on the Quadro-probe maintained their responsiveness with higher than 1 peak/s of time resolution.
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paper_title: Odor discrimination using a hybrid-device olfactory biosensor

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Current trends in artificial nose research are strongly motivated by knowledge of biological olfactory systems, but are primarily confined to improving pattern recognition strategies for data derived from a relatively simple sensor array. Biological olfactory systems are able to discriminate weak, transient, broad-band signals ranging over a poorly-defined parameter space, and therefore outperform current artificial nose systems in several respects. A biological olfactory sense organ, the insect antenna, has been exploited in a hybrid-device biosensor. An algorithm was developed to analyze the electrophysiological responses recorded from a sensor array comprised of antennae from different species of insects. A training period during which the array was exposed to known target odors established response signatures for those odors. Subsequent odor stimuli were then classified using a forced-choice nearest neighbor technique. As odorants arrived in discrete packets in the turbulent air stream, individual sensor response events lasted less than one second, and could be classified with accuracy dependant on the differential tuning of the sensor array to the compounds being classified.
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paper_title: Odor-Driven Attractor Dynamics in the Antennal Lobe Allow for Simple and Rapid Olfactory Pattern Classification

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The antennal lobe plays a central role for odor processing in insects, as demonstrated by electrophysiological and imaging experiments. Here we analyze the detailed temporal evolution of glomerular activity patterns in the antennal lobe of honeybees. We represent these spatiotemporal patterns as trajectories in a multidimensional space, where each dimension accounts for the activity of one glomerulus. Our data show that the trajectories reach odor-specific steady states (attractors) that correspond to stable activity patterns at about 1 second after stimulus onset. As revealed by a detailed mathematical investigation, the trajectories are characterized by different phases: response onset, steady-state plateau, response offset, and periods of spontaneous activity. An analysis based on support-vector machines quantifies the odor specificity of the attractors and the optimal time needed for odor discrimination. The results support the hypothesis of a spatial olfactory code in the antennal lobe and suggest a perceptron-like readout mechanism that is biologically implemented in a downstream network, such as the mushroom body.
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paper_title: Wavelet filter for noise reduction and signal compression in an artificial nose

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This work presents results of using a wavelet filter for noise reduction and data compression of signals generated by artificial nose sensors. To verify the performance of wavelet analysis in the treatment of odor patterns, we compare the use of two widely used artificial nose classifiers, Multi-Layer Perceptron (MLP) neural network and Time Delay Neural Network (TDNN), in the analysis of signals generated by eight conducting polymer sensors exposed to gases derived from the petroliferous industry.
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paper_title: Pattern recognition of gases of petroleum based on RBF model

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In the case of aerial accident spreading out dangerous gases into the atmosphere, an instrument called electronic nose can warn about the beginning of petroleum derived leaks. In this paper we present the architecture of the neural network for pattern recognition of gases of petroleum based on an RBF model. With this model we analyzed the pattern recognition of five gases: ethane, methane, propane, butane and carbon monoxide, separated in three classes of problems.
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paper_title: Taste sensor with global selectivity

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Abstract A recently developed multichannel taste sensor with global selectivity is being reviewed. This sensor is composed of several kinds of lipid/ polymer membranes for transforming information of taste substances into electric signals, which are analysed by a computer. The sensor output shows different patterns for chemical substances which have different taste qualities such as saltiness and sourness, while it shows similar patterns for chemicals with similar tastes. The sensor responds to taste in itself, as can be understood from the fact that taste interactions such as the suppression effect, which appears between sweet and bitter substances, can be well reproduced. Amino acids can be classified into several groups according to their own tastes with sensor outputs. The taste of foodstuffs such as beer, coffee, mineral water and vegetables can be discussed quantitatively using the taste sensor, which provides the objective scale for the human sensory expression. The taste sensor will open the door to a new stage of food culture.
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paper_title: Global optimization methods for designing and training neural networks

paper_content:

This paper shows results of two approaches for the optimization of neural networks: one uses simulated annealing for optimizing both architectures and weights combined with backpropagation for fine tuning, while the other uses tabu search for the same purpose. Both approaches generate networks with good generalization performance (mean classification error of 1.68% for simulated annealing and 0.64% for tabu search) and low complexity (mean number of connections of 11.15 out of 36 for simulated annealing and 11.62 out of 36 for tabu search) for an odor recognition task in an artificial nose.
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paper_title: A review of digital data acquisition hardware and software for a portable electronic nose

paper_content:

This paper discusses the digital hardware and software that is required for data acquisition in a portable electronic nose (e‐nose) system. A review of current e‐nose systems is presented highlighting the methods employed by these systems to acquire the data from the sensor head.
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paper_title: An artificial nose based on m-porphyrin (M = Mg, Zn) thin film and optical spectroscopy

paper_content:

Artificial nose has recently become an emerging instrument for quality assurance in the food industry. These paper presents the optical gas sensors based on Magnesium - 5,10,15,20 - tetra phenyl - porphyrin (MgTPP) and Zinc - 5,10,15,20 - tetra phenyl - porphyrin (ZnTPP) thin films and their application as an artificial nose. Based on the measurement of optical absorbance response using a general UV-Vis spectroscopy, this artificial noses was tested to discriminate various volatile organic compounds (VOCs) and Thai beverages. Atomic force microscopy (AFM) and X-rays diffraction were used to confirm the polycrystalline structure of the sensing materials. Density functional theory (DFT) calculations reveal that MgTPP interacts more strongly with the VOCs than ZnTPP, especially with water and methanol. The classification results of VOCs and Thai beverage vapors using the principle component analysis indicate that both MgTPP and ZnTPP-based artificial noses can be an efficient tool for quality assurance of alcoholic beverages.
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paper_title: Bioelectronic Artificial Nose Using Four-Channel Moth Antenna Biopotential Recordings

paper_content:

The use of insect antennae as an odor sensor array was evaluated as a means to advance the current capabilities of " artificial nose" technology. A given species is highly sensitive to odors of survival interest (e.g. species-specific pheromones), but also to a broad range of other natural and anthropogenic compounds. The sensitivity of the antennae to some odors extends to the parts per billion range. In contrast, the best current artificial nose technology is able to detect compounds in the parts per million range. Here, a system designed to utilize four antenna biopotential signals suitable for field use and a computational analysis strategy which allows discrimination between specific odors, and between odor and background or unknown compounds, with high fidelity and in real time, is described. The automated analysis measures three parameters per odor response. Following a training period, a K nearest-neighbor (KNN) approach is used to classify an unknown odor, assuming equal prior probabilities. The algorithm can also declare an odor as "unknown". System responses to single filaments in an odor plume can be analyzed and classified in less than one second
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paper_title: On the road to the artificial nose

paper_content:

We conduct active research on the creation of a so-called "Electronic nose". The principle of an operation of the gas sensor is based on the ability of SnO/sub 2/ films to change conductivity in the presence of oxidizing and restoring gases. With the purpose of researching the opportunity of increasing the films' stability and increasing their selective sensitivity to different gases, the influence of doping of the films by various additives was investigated.
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paper_title: Evolving fuzzy neural networks applied to odor recognition in an artificial nose

paper_content:

A pattern recognition system using evolving fuzzy neural networks for an artificial nose is presented. The artificial nose is composed of an adaptive and on-line learning method. For the classification of gases derived from the petroliferous industry, the method presented achieves better results (mean classification error of 0.88%) than those obtained by time delay neural networks (10.54%).
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paper_title: Tasting of beverages using an electronic tongue

paper_content:

An electronic tongue based on the sensor array of non-specific solution sensors together with pattern recognition tools has been applied to qualitative analysis of different beverages. It has been found that it is capable both to discriminate reliably between various sorts of the same type of beverages (tea, coffee, beer, soft drinks, juice, etc.) and to monitor the process of aging of juice. Correlations have been found between integral parameters produced by electronic tongue and quality of juice. Some conceptions and backgrounds used for electronic tongue development have been put forward and discussed.
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paper_title: An electronic tongue based on voltammetry

paper_content:

Abstract Presently, great interest is shown in the concept of an electronic nose. It consists of an array of gas sensors with different selectivity patterns, a signal collecting unit and pattern recognition software applied to a computer. Similar concepts, but for analysis in liquids have also been described, and since they are related to the tasting sense, the term `electronic tongue' or `taste sensor' was coined. This paper describes how various voltammetric techniques such as large and small amplitude pulse voltammetry can generate information when combined with a multivariate analysis method. A prototype of an electronic tongue was designed, based on the combination of voltammetry, using a double working electrode of gold and platinum, and principal component analysis. It is demonstrated how this electronic tongue is able to classify various samples such as fruit juices, still drinks and milk. It was also possible to follow aging processes of milk and orange juice when stored at room temperature.
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paper_title: [Taste sensor].

paper_content:

A multichannel taste sensor, namely an electronic tongue, with global selectivity is composed of several kinds of lipid/polymer membranes for transforming information about substances producing taste into electrical signals, which are input to a computer. The sensor output exhibits different patterns for chemical substances which have different taste qualities such as saltiness, sourness and bitterness, whereas it exhibits similar patterns for chemical substances with similar tastes. The sensor responds to the taste itself, as can be understood from the fact that taste interactions such as the suppression effect, which appears for mixtures of sweet and bitter substances, can be reproduced well. The suppression of the bitterness of quinine and a drug substance by sucrose can be quantified. Amino acids can be classified into several groups according to their own tastes on the basis of sensor outputs. The tastes of foodstuffs such as beer, coffee, mineral water, milk, sake, rice, soybean paste and vegetables can be discussed quantitatively using the taste sensor, which provides the objective scale for the human sensory expression. The flavour of a wine is also discriminated using the taste-odour sensory fusion conducted by combining the taste sensor and an odour-sensor array using conducting polymer elements. The taste sensor can also be applied to measurements of water pollution. Miniaturization of the taste sensor using FET produces the same characteristics as those of the above taste sensor by measuring the gate-source voltage. Use of the taste sensor will lead to a new era of food and environmental sciences.
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paper_title: Design, manufacturing, and characterization of high-frequency thickness-shear mode resonators

paper_content:

AT-cut quartz crystals vibrating in the thickness-shear mode are well known as mass sensitive devices. After deposition of a sensitive layer on one or both surfaces of the quartz discs these resonators are suitable for the application as chemical sensors for analysis in gaseous and liquid media, which are known as quartz crystal microbalances (QCM). Up to now the resonant frequencies of these resonators are 5 to 30 MHz. The application of combined photolithographic and etching processes offers new promising approaches for the manufacturing of quartz resonators with higher resonant frequencies, up to 75 MHz, and smaller diameters. Resonators were fabricated and subsequently characterized optically and mechanically by means of light microscopy, SEM, and surface profiling and electrically by means of impedance analysis. The etched surfaces are very smooth and parallel, leading to high Q-factors up to 5/spl middot/10/sup 4/, which is excellent for high frequency resonators. A high mechanical stability due to the 128 /spl mu/m thick quartz frame was proofed. The influences of surface roughness and etch channels on the resonators' performance were examined. The behaviour under acoustic load was investigated experimentally. The results showed that 50 MHz resonators operated in water reach zero phase of impedance. In liquid media, changes in the viscosity (/spl eta//sub L/) and density (/spl rho//sub L/) lead to a decrease of the resonant frequency (/spl Delta/f) of the QCM. A linear relationship between (/spl eta//sub L//spl rho//sub L/)/sup 1/2/ and /spl Delta/f was observed, in agreement with theory, while the frequency shifts are much higher than reported before.
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paper_title: Electronic sensing of the taste of beer and other foodstuffs

paper_content:

A recently developed electronic sensing system with global selectivity is composed of several kinds of lipid/polymer membranes for transforming information of taste substances into an electric signal. The sensor output shows different patterns for chemical substances which have different taste qualities such as saltiness and sourness. Amino acids can be classified into several groups according to their own tastes with sensor outputs. The taste of foodstuffs such as beer, coffee, mineral water and vegetables can be discussed quantitatively using the taste sensor, which provides the objective scale for the human sensory expression.
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paper_title: Application of novel sensor electronics for quartz resonators in artificial tongue

paper_content:

Many applications in environmental analysis, chemical or food industry require special sensors for qualitative and/or quantitative detection of substances in gaseous atmosphere or liquids. Sometimes the measuring task is a distinction of different typical odours or flavours of a complex medium. For that an electronic nose or tongue emulating the human sense organs could be useful in future. The performance of such devices is determined by sensor characteristics such as sensitivity, selectivity or long term stability and a powerful data acquisition and evaluation. An electronic tongue consisting of quartz crystal microbalance sensors is presented in this paper. The newly developed sensor electronics determine additional sensor parameters in comparison to the normally used resonance frequency. These parameters help to distinguish between gravimetric and non-gravimetric effects. Furthermore the additional information content gives better results of pattern recognition using sensor arrays for analyte detection.
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paper_title: Artificial electronic tongue in comparison to the electronic nose. State of the art and trends

paper_content:

Many researchers aim for the development of sensors or sensor systems which are similar or comparable to the human sensory system. Of all the human sensory systems, olfaction is the least understood in terms of the primary receptor mechanism and biological transduction. It is difficult to describe a set of reference odours that describe the olfactory input. A high degree of signal processing takes place in the olfactory system so that compounds of similar chemical structure can give completely different olfactory responses. That is the reason why the understanding of the olfactory system is relatively poor. The situation is comparable in the case of gustation. Nevertheless, there are many practical applications that require a quantitative or qualitative objective recording of odours or taste. In the following the development in the field of electronic tongue is described. It is a relatively new field. The state-of-the-art in understanding of electronic noses and tongues is discussed. They are illustrated describing their working principles, the types of sensors, circuit architectures and features. The applied sensor types are considered more in detail. Future perspectives of electronic tongue systems and their applications are illustrated. Problems which had to be solved yet are discussed.
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paper_title: Taste sensor with global selectivity

paper_content:

Abstract A recently developed multichannel taste sensor with global selectivity is being reviewed. This sensor is composed of several kinds of lipid/ polymer membranes for transforming information of taste substances into electric signals, which are analysed by a computer. The sensor output shows different patterns for chemical substances which have different taste qualities such as saltiness and sourness, while it shows similar patterns for chemicals with similar tastes. The sensor responds to taste in itself, as can be understood from the fact that taste interactions such as the suppression effect, which appears between sweet and bitter substances, can be well reproduced. Amino acids can be classified into several groups according to their own tastes with sensor outputs. The taste of foodstuffs such as beer, coffee, mineral water and vegetables can be discussed quantitatively using the taste sensor, which provides the objective scale for the human sensory expression. The taste sensor will open the door to a new stage of food culture.
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paper_title: Taste reception in a synthetic lipid membrane.

paper_content:

The effect of taste stimulants on a DOPH (dioleyl phosphate) Millipore membrane was investigated as a model system of taste reception. Quinine, HCl, NaCl and sucrose were chosen as bitter, sour, salty and sweet substances, respectively. From the measurements of membrane potential and membrane resistance, it is conceivable that quinine, HCl and NaCl affect a phase boundary potential while sucrose affects a diffusion potential. Dynamic profiles of membrane potential also suggested that HCl and NaCl acted at the surface of membrane, but quinine and sucrose penetrated into the membrane. The intensity of their action on an electric potential was associated qualitatively with the threshold values of taste reception in man. Most of the results found in this model membrane may be realized for a living system. On the difference of taste quality between sour and salty substances, some discussions were added.
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paper_title: Transport pathways in rat lingual epithelium

paper_content:

Measurements of ion transport across isolated lingual epithelium of rat were correlated with electrophysiological recordings from tastenerves. At hyperosmotic concentrations of NaCl, sodium ions enter the mucosal membrane of the isolated epithelium partially through an amiloride-inhibitable pathway and exit the serosal membrane through a Na+-K+-ATPase. At hyposmotic concentrations of KCl, potassium ions enter the mucosal membrane through a K+ pathway that is inhibited by 4-aminopyridine and exit at the serosal membrane through a K+ pathway that is inhibited by BaCl2. The inhibition of sodium transport by amiloride and potassium transport by 4-aminopyridine is consistent with previously published electrophysiological recordings from the chorda tympani nerve bundle (CT) and recordings from nucleus of the solitary tract (NST) obtained here. The responses to NaCl are greater than the responses to KCl at equimolar concentrations over the entire concentration range both in epithelial and neural measurements. At hyposmotic concentrations of NaCl the epithelial responses include inward sodium and outward chloride components. Isolated rat tongue is only slightly stimulated by D-glucose or sucrose as are the CT and NTS responses. These data suggest that events in taste transduction can be understood, in part, by measuring the epithelial responses of isolated rat tongue.
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paper_title: Sensors : principles and applications

paper_content:

Definition of the word "sensor" techniques for manufacturing of sensors Si-sensors thin film sensor techniques fibre optic sensors chemical sensors sensors on the basis of "classical" transducers new sensor materials resonance sensors new trends.
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paper_title: Salt and acid studies on canine lingual epithelium

paper_content:

A section of dog tongue just anterior to the circumvallate papillae was placed in an Ussing chamber and characterized with respect to monovalent cation transport pathways, response to HCl, and the interaction between salt and acid for the purposes of determining whether ion transport through the tongue is related to the transduction process. The primary findings of this work follow. The stimulation of the short-circuit current (Isc) with decreasing pH on the dorsal surface results from a net Cl- efflux through an amiloride- and ouabain-insensitive pathway that changed its selectivity from cationic at neutral pH to anionic at lower pH values. The stimulation is abolished at isotonic NaCl concentrations. This behavior would not be predicted from the proton-binding model to a "sour receptor" as suggested by Beidler (Handbook of Sensory Physiology; Berlin: Springer-Verlag, 1971). In symmetrical solutions of Krebs-Henseleit buffer, Isc is inhibited 30% by 10(-4) M amiloride on the mucosal side and 100% by 10(-3) M ouabain on the serosal side. These results coupled with net Cl- and Na+ flux measurements show that Isc is due to a net Cl- efflux. With 1.0 M NaCl on the dorsal side, 10(-4) M amiloride inhibits Isc 84%. In contrast, when the mucosal surface is bathed in KCl (1.0 M), CsCl (1.0 M), or HCl (10(-3) M), Isc is insensitive to both 10(-4) M amiloride and/or 10(-3) M ouabain. These data suggest that K+, Cs+, and H+ traverse the tongue through different pathways from Na+ and are not energized by a Na+ gradient.
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paper_title: Using MLP networks to classify red wines and water readings of an electronic tongue

paper_content:

Feasible efforts have been made to mimic the human gustatory system through an "artificial tongue". This device comprises an array of sensing units that is able to differentiate tastes with a higher sensitivity than the biological system. Experimental results indicate that when the data generated by such sensing units are handled by artificial neural networks, this "artificial tongue" can successfully discriminate wines of different winemakers, vintage and grapes, as well as different brands of mineral water, distilled water and Milli-Q water. The accuracy achieved by the experiments suggests that the sensing units may be used to detect abnormal chemical substances in a production line or even set a new approach to control quality standards in food industry.
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paper_title: A digital speech processor with lateral inhibition for artificial hearing

paper_content:

An 8-channel, real-time vibrotactile digital vocoder for artificial hearing is developed. The device is based on a TMS320C25 digital signal processor chip and uses the FFT spectral analysis technique. To improve tactile recognition, a lateral inhibition filter is implemented. Live and taped speech are used to evaluate the performance of the device. Preliminary results indicate that important speech features, such as formants and gaps, are transmitted efficiently by the system. >
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paper_title: Audio Environment Classication for Hearing Aids using Artificial Neural Networks with Windowed Input

paper_content:

Excessive background noise is one of the most common complaints from hearing aid users. Background noise classification systems can be used in hearing aids to adjust the response based on the noise environment. This paper examines and compares two promising classification techniques, non-windowed artificial neural networks (ANN) and hidden Markov models (HMM), with an artificial neural network using windowed input. Results obtained show that an ANN with a windowed input gives an accuracy of up to 97.9%, which is more accurate than both the non-windowed ANN and the HMM. Overall, a windowed ANN is able to give excellent accuracy and reliability and is considered to be a good model for background noise classification in hearing aids
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paper_title: Algorithms for feature selection: An evaluation

paper_content:

A large number of algorithms have been proposed for doing feature subset selection. The goal of this paper is to evaluate the quality of feature subsets generated by the various algorithms, and also compare their computational requirements. Our results show that the sequential forward floating selection (SFFS) algorithm, proposed by Pudil et al. (1994), dominates the other algorithms tested. This paper also illustrates the dangers of using feature selection in small sample size situations. It gives the results of applying feature selection to land use classification of SAR satellite images using four different texture models. Pooling features derived from different texture models, followed by a feature selection results in a substantial improvement in the classification accuracy. Application of feature selection to classification of handprinted characters illustrates the value of feature selection in reducing the number of features needed for classifier design.
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paper_title: Auditory handicap of hearing impairment and the limited benefit of hearing aids.

paper_content:

The aim of this article is to promote a better understanding of hearing impairment as a communicative handicap, primarily in noisy environments, and to explain by means of a quantitative model the essentially limited applicability of hearing aids. After data on the prevalence of hearing impairment and of auditory handicap have been reviewed, it is explained that every hearing loss for speech can be interpreted as the sum of a loss class A (attenuation), characterized by a reduction of the levels of both speech signal and noise, and a loss D (distortion), comparable with a decrease in speech-to-noise ratio. On the average, the hearing loss of class D (hearing loss in noise) appears to be about one-third (in decibels) of the total hearing loss (A + D, hearing loss in quiet). A hearing aid can compensate for class-A-hearing losses, giving difficulties primarily in quiet, but not for class-D hearing losses, giving difficulties primarily in noise. The latter class represents the first stage of auditory handicap, beginning at an average hearing loss of about 24 dB.
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paper_title: An efficient robust sound classification algorithm for hearing aids

paper_content:

An efficient robust sound classification algorithm based on hidden Markov models is presented. The system would enable a hearing aid to automatically change its behavior for differing listening env ...
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paper_title: Multimodal speaker detection using error feedback dynamic Bayesian networks

paper_content:

Design and development of novel human-computer interfaces poses a challenging problem: actions and intentions of users have to be inferred from sequences of noisy and ambiguous multi-sensory data such as video and sound. Temporal fusion of multiple sensors has been efficiently formulated using dynamic Bayesian networks (DBNs) which allows the power of statistical inference and learning to be combined with contextual knowledge of the problem. Unfortunately simple learning methods can cause such appealing models to fail when the data exhibits complex behavior. We formulate a learning framework for DBNs based on error-feedback and statistical boosting theory. We apply this framework to the problem of audio/visual speaker detection in an interactive kiosk environment using "off-the-shelf" visual and audio sensors (face, skin, texture, mouth motion, and silence detectors). Detection results obtained in this setup demonstrate superiority of our learning framework over that of the classical ML learning in DBNs.
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paper_title: Intelligent and active system for human-robot interaction based on sound source localization

paper_content:

Today, we can see many kinds of robots anywhere. Robots are inseparable from human-beings. In result, human-robot interaction is getting more important. This paper describes a system for human-robot interaction which is one of the biggest issues recently. We approach the interaction from a localization point of view. The aim of the system for human-robot interaction is that the robot finds a person speaking in an area and goes to the speaker while the robot avoids static obstacles using mapping data obtained before. As well as this, the system acts like human especially when turning its head after someone calls.
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paper_title: A tutorial on hidden Markov models and selected applications in speech recognition

paper_content:

This tutorial provides an overview of the basic theory of hidden Markov models (HMMs) as originated by L.E. Baum and T. Petrie (1966) and gives practical details on methods of implementation of the theory along with a description of selected applications of the theory to distinct problems in speech recognition. Results from a number of original sources are combined to provide a single source of acquiring the background required to pursue further this area of research. The author first reviews the theory of discrete Markov chains and shows how the concept of hidden states, where the observation is a probabilistic function of the state, can be used effectively. The theory is illustrated with two simple examples, namely coin-tossing, and the classic balls-in-urns system. Three fundamental problems of HMMs are noted and several practical techniques for solving these problems are given. The various types of HMMs that have been studied, including ergodic as well as left-right models, are described. >
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paper_title: Automatic classification of speech and music using neural networks

paper_content:

The importance of automatic discrimination between speech signals and music signals has evolved as a research topic over recent years. The need to classify audio into categories such as speech or music is an important aspect of many multimedia document retrieval systems. Several approaches have been previously used to discriminate between speech and music data. In this paper, we propose the use of the mean and variance of the discrete wavelet transform in addition to other features that have been used previously for audio classification. We have used Multi-Layer Perceptron (MLP) Neural Networks as a classifier. Our initial tests have shown encouraging results that indicate the viability of our approach.
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paper_title: Sound Classification in Hearing Aids Inspired by Auditory Scene Analysis

paper_content:

A sound classification system for the automatic recognition of the acoustic environment in a hearing aid is discussed. The system distinguishes the four sound classes "clean speech," "speech in noise," "noise," and "music." A number of features that are inspired by auditory scene analysis are extracted from the sound signal. These features describe amplitude modulations, spectral profile, harmonicity, amplitude onsets, and rhythm. They are evaluated together with different pattern classifiers. Simple classifiers, such as rule-based and minimum-distance classifiers, are compared with more complex approaches, such as Bayes classifier, neural network, and hidden Markov model. Sounds from a large database are employed for both training and testing of the system. The achieved recognition rates are very high except for the class "speech in noise." Problems arise in the classification of compressed pop music, strongly reverberated speech, and tonal or fluctuating noises.
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paper_title: Estimating friction using incipient slip sensing during a manipulation task

paper_content:

A scheme is presented by which a manipulator can use dynamic tactile sensing to detect when it is about to lose hold of a grasped object. By detecting localized slips on the gripping surface which precede gross slip, the controller can modify the grasp force to prevent the object from slipping. Also, by monitoring normal and tangential forces at the contact when these incipient slip signals occur, the controller obtains an accurate estimate of the friction coefficient which can then be used during the manipulation task. Accurate knowledge of the friction coefficient is essential when grasping fragile objects or manipulating with sliding. >
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paper_title: Slip phase isolating: impulsive signal generating vibrotactile sensor and its application to real-time object regrip control

paper_content:

This paper mainly concerns a vibrotactile sensor capable of generating impulsive high-frequency signals for exclusively distinguishing a slip phase from various other contact phases. We describe the structure of the vibrotactile sensor with surface ridges and, after analyzing the slip signals, conclude that the output signal originates in the free vibration of the ridge. By using a two-fingered robot hand with the sensor attached to its compliant endtips, we verify that the vibrotactile sensor has a slip phase isolating function and demonstrate object regrip control in real time.
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paper_title: Detection of incipient object slippage by skin-like sensing and neural network processing

paper_content:

Detection of incipient slippage is of great importance in robotics for the control of grasping and manipulation tasks. Together with fine-form reconstruction and primitive recognition, it has to be the main feature of an artificial tactile system. The system presented here is based on a neural network used to detect incipient slippage and on a skin-like sensor sensible to normal and shear stresses. Normal and shear stresses components inside the sensor are the input data of the neural net. An important feature of the system is that the a priori knowledge of the friction coefficient between the sensor and the object being manipulated is not needed. To validate the method we worked on both simulated and experimental data. In the first case, the finite element method is used to solve the direct problem of elastic contact in its full nonlinearity by resorting to the lowest number of approximations regarding the real problem. Simulation has shown that the network learns and is robust to noise. Then an experimental test was carried out. Experimental results show that, in a simple case, the method is able to detect the insipiency of slippage between an object and the sensor.
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Title: Simulation Techniques and Prosthetic Approach Towards Biologically Efficient Artificial Sense Organs- An Overview
Section 1: Introduction
Description 1: This section introduces the topic of prosthetic sense organs, highlighting their significance and the goal of the paper.

Section 2: Visual Acuity and Virtual-Reality Replication
Description 2: This section discusses the principles and methods of simulating prosthetic vision, including studies and trials conducted using virtual reality.

Section 3: Fuzzy Neural Network in Bio-electric Prosthetic Nose
Description 3: This section covers the development and techniques used for artificial noses, including sensor systems, pattern recognition, and neural networks.

Section 4: Neural Network and Electronic Artificial Tongue
Description 4: This section delves into the creation of electronic tongues, their structure and functionality, and the role of neural networks in enhancing their performance.

Section 5: Sound Source Localization with Artificial Neural Network
Description 5: This section outlines the advancements in prosthetic ears, focusing on sound localization and the use of neural networks and hidden Markov models.

Section 6: Vibrotactile Sensing Elements for Artificial Skin
Description 6: This section examines the development of artificial skin, particularly vibrotactile sensing elements that simulate human tactile perception.

Section 7: Conclusion
Description 7: This section provides a summary of the paper’s findings and discusses the future direction of research in prosthetic sense organs.