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Results for “Pattern Recognition, Physiological”

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PubMed1976

Dynamic decision models for clinical diagnosis.

A unified approach to clinical decision-making is presented. This combines partially observable Markovian decision processes (Markov or semi-Markov) with cause-effect models as a probabilistic representation of the diagnostic process. Pattern recognition techniques are used in a first stage of system state identification. This new class of dynamic models has a direct application to medical diagnosis and treatment and specific physiological examples are emphasised. The methodology is given for combining the patient state of health, the clinician's state of knowledge of the cause-effect representation from the observation space (measurements), feature selection using pattern recognition techniques and, finally, the treatment decisions with which to restore the patient to a more desirable state of health. A cost functional for the decision process has then to be optimised according to some pre-assigned objective function (social return from the patient state of health or treatment cost for the patient), when the process has an infinite time horizon.

Computers↗
PubMed2005

Lee-Associator-a chaotic auto-associative network for progressive memory recalling.

In the past few decades, neural networks have been extensively adopted in various applications ranging from simple synaptic memory coding to sophisticated pattern recognition problems such as scene analysis and robot vision. Moreover, current studies on neuroscience and physiology have reported that in a typical scene segmentation problem our major senses of perception (e.g. vision, olfaction, etc.) are highly chaotic and involved non-linear neural dynamics and oscillations. In this paper, the author proposes an innovative chaotic neural oscillator-namely the Lee-oscillator (Lee's Chaotic Neural Oscillator) to provide a chaotic neural coding and information processing scheme. To illustrate the capability of Lee-oscillators upon pattern association, a chaotic auto-associative network, namely Lee-Associator (Lee's Chaotic Auto-associator) is constructed. Different from classical auto-associators such as the celebrated Hopfield network, which provides time-independent and static pattern association scheme, the Lee-Associator provides a remarkable progressive memory association scheme (what the author called 'Progressive Memory Recalling Scheme, PMRS') during the chaotic memory association. This is exactly consistent with the latest research in psychiatry and perception psychology on dynamic memory recalling schemes, as well as the implications and analogues to human perception as illustrated by the remarkable Rubin-vase experiment on visual psychology.

Artificial Intelligence↗
PubMed2004

Informatics platform for global proteomic profiling and biomarker discovery using liquid chromatography-tandem mass spectrometry.

We have developed an integrated suite of algorithms, statistical methods, and computer applications to support large-scale LC-MS-based gel-free shotgun profiling of complex protein mixtures using basic experimental procedures. The programs automatically detect and quantify large numbers of peptide peaks in feature-rich ion mass chromatograms, compensate for spurious fluctuations in peptide signal intensities and retention times, and reliably match related peaks across many different datasets. Application of this toolkit markedly facilitates pattern recognition and biomarker discovery in global comparative proteomic studies, simplifying mechanistic investigation of physiological responses and the detection of proteomic signatures of disease.

Algorithms↗
PubMed1998

Understanding sleep ontogeny to assess brain dysfunction in neonates and infants.

The ontogenetic framework onto which a child's sleep is constructed undergoes significant developmental alterations during early life. Sleep state behaviors, in large part, reflect continuities from fetal through neonatal time periods. Major changes in sleep organization subsequently occur throughout infancy. Maturational expressions of sleep behaviors must be understood by the pediatric neurologist before specific physiologic phenomena can be assessed as transient sleep disturbances or clinically relevant sleep disorders. The first part of this two-part review article focuses on the major aspects of developmental sleep physiology in the first few months of life. Recognition of age-specific electroencephalographic/polysomnographic patterns will facilitate the child neurologist's evaluation of the newborn with suspected seizures and interictal encephalopathies, as well as the prediction of neurologic sequelae.

Child Development↗
PubMed1998

Evolution of adaptive neural networks: the role of voltage-dependent K+ channels.

The vestibular pathway of the mollusk Hermissenda crassicornis mediates a reflexive, unconditioned response to disorientation, clinging, that has been conserved during evolution even to the emergence of our own species. This response becomes associated with a visual stimulus (mediated by a precisely ordered visual-vestibular synaptic network) according to principles of Pavlovian conditioning that are also followed in human learning. It is not entirely surprising therefore that molecular and biophysical cascades responsible for this associative learning appear to function in both mollusks and mammals. In brief, combinational elevation of (Ca2+)i, diacylglycerol, and arachidonic acid activates protein kinase C to phosphorylate the Ca2+ and guanosine triphosphate-binding protein, cp20 (now called calexcitin (Nelson T, et al. Proc Natl Acad Sci USA 1996;93:13808-13)), which potently inactivates postsynaptic voltage-dependent K+ currents and thereby increases synaptic weight. Longer term changes included rearrangement of synaptic terminals and modified protein synthesis. This cascade has also been implicated in other associative-learning paradigms (e.g., spatial maze, olfactory discrimination) and as a pathophysiologic target in early Alzheimer's disease. Recent molecular biologic experiments also demonstrate the dependence of associative memory (but not long-term potentiation) on voltage-dependent K+ currents. Theoretic learning models based on these findings focus on dendritic spine clusters and yield computer implementations with powerful pattern-recognition capabilities.

Adaptation, Physiological↗
PubMed2004

Do pattern recognition skills transfer across sports? A preliminary analysis.

The ability to recognize patterns of play is fundamental to performance in team sports. While typically assumed to be domain-specific, pattern recognition skills may transfer from one sport to another if similarities exist in the perceptual features and their relations and/or the strategies used to encode and retrieve relevant information. A transfer paradigm was employed to compare skilled and less skilled soccer, field hockey and volleyball players' pattern recognition skills. Participants viewed structured and unstructured action sequences from each sport, half of which were randomly represented with clips not previously seen. The task was to identify previously viewed action sequences quickly and accurately. Transfer of pattern recognition skill was dependent on the participant's skill, sport practised, nature of the task and degree of structure. The skilled soccer and hockey players were quicker than the skilled volleyball players at recognizing structured soccer and hockey action sequences. Performance differences were not observed on the structured volleyball trials between the skilled soccer, field hockey and volleyball players. The skilled field hockey and soccer players were able to transfer perceptual information or strategies between their respective sports. The less skilled participants' results were less clear. Implications for domain-specific expertise, transfer and diversity across domains are discussed.

Adaptation, Physiological↗
PubMed2005

Object-selective cortex exhibits performance-independent repetition suppression.

Object-selective cortical regions exhibit a decreased response when an object stimulus is repeated [repetition suppression (RS)]. RS is often associated with priming: reduced response times and increased accuracy for repeated stimuli. It is unknown whether RS reflects stimulus-specific repetition, the associated changes in response time, or the combination of the two. To address this question, we performed a rapid event-related functional MRI (fMRI) study in which we measured BOLD signal in object-selective cortex, as well as object recognition performance, while we manipulated stimulus repetition. Our design allowed us to examine separately the roles of response time and repetition in explaining RS. We found that repetition played a robust role in explaining RS: repeated trials produced weaker BOLD responses than nonrepeated trials, even when comparing trials with matched response times. In contrast, response time played a weak role in explaining RS when repetition was controlled for: it explained BOLD responses only for one region of interest (ROI) and one experimental condition. Thus repetition suppression seems to be mostly driven by repetition rather than performance changes. We further examined whether RS reflects processes occurring at the same time as recognition or after recognition by manipulating stimulus presentation duration. In one experiment, durations were longer than required for recognition (2 s), whereas in a second experiment, durations were close to the minimum time required for recognition (85-101 ms). We found significant RS for brief presentations (albeit with a reduced magnitude), which again persisted when controlling for performance. This suggests a substantial amount of RS occurs during recognition.

Adaptation, Physiological↗
PubMed1978

Associative memory and pattern recognition.

This tutorial review presents a model of neural associative memory along with a set of computer demonstrations showing the relevance of this memory mechanism in visual information processing. The model is based upon the hypothesis that adaptive changes in neural networks are intermediated by changes in synaptic efficacies. The signal patterns are stored by gradual changes of the network and they may be recalled later using a part of the original signal pattern as a key. The ability of this type of memory mechanism to process sensory information is emphasized.

Adaptation, Physiological↗
PubMed2001

Automated detection of tracé alternant during sleep in healthy full-term neonates using discrete wavelet transform.

OBJECTIVE: To develop an automated procedure for scoring neonatal sleep states using signal processing which are based on visual pattern recognition techniques. METHODS: We are developing an automated computer system to study relationships among multiple non-cerebral physiologic measures and brain activity in newborn infants, and are evaluating the usefulness of a number of different time-frequency domain transforms as potential diagnostic tools. RESULTS: Wavelet transforms yield excellent results in the detection of all twenty tracé alternant quiet sleep segments for 6 full-term healthy infants. CONCLUSIONS: We suggest that this method will be useful for the automated detection of neonatal sleep states, and may help delineate when sleep cycle disturbances occur on either an environmental or disease basis. More accurate physiologic descriptions of neonatal state may improve the clinician's ability to assess functional brain organization for a given post-conceptional age as well as document functional brain maturation at progressively older corrected ages.

Algorithms↗
PubMed2000

Structure and function of the bat superior olivary complex.

The superior olivary complex (SOC) is a mammalian auditory brainstem structure that contains several nuclei. Some of them are part of the ascending system projecting to higher auditory centers, others belong to the descending system projecting to the cochlear nuclei or the cochlea itself. The main nuclei of the ascending system, the lateral and medial superior olive (LSO, MSO), as well as the lateral and medial nuclei of the trapezoid body (LNTB, MNTB), have been traditionally associated with sound localization. Here we review the results of recent studies on the main SOC nuclei in echolocating bats. These studies suggest that some SOC structures and functions are highly conserved across mammals (e.g., the LSO, which is associated with interaural intensity difference processing), while others are phylogenetically highly variable in both form and function (e.g., the MSO, traditionally associated with interaural time difference processing). For the MSO, these variations indicate that we should broaden our view regarding what functions the MSO might participate in, since its function in echolocation seems to lie in the context of pattern recognition rather than sound localization. Furthermore, across bat species, variations in the form and physiology of the MSO can be linked to specific behavioral adaptations associated with different echolocation strategies. Finally, the comparative approach, including auditory specialists such as bats, helps us to reach a more comprehensive view of the functional anatomy of auditory structures that are still poorly understood, like the nucleus of the central acoustic tract (NCAT).

Animals↗
PubMed1977

Adaptation of evoked potentials by patterns of texture-contrast.

Visual evoked potentials (VEPs) to a briefly presented pattern in black-ahd-white are reduced by pre-exposure to the same pattern formed only by contrasting textures. When such texture-contrast patterns are used as stimuli, however, the VEP is different in latency and in its sensitivity to changes in pattern geometry.

Adaptation, Physiological↗
PubMed1995

Unequal amplitude saccades produced by aniseikonic patterns: effects of viewing distance.

This study describes differences in horizontal and vertical disconjugate saccades under far and close viewing conditions of two dichoptically presented aniseikonic random checkerboard patterns. At far viewing, disconjugacy of horizontal saccades requiring divergence was accomplished intrasaccadically after several minutes; for convergence the intrasaccadic disconjugacy was limited. Size differences partially persisted in open-loop trials. At close viewing intrasaccadic divergent changes in conjugacy were instantaneous, but motor storage during open-loop was absent. It is concluded that disconjugate saccades to targets at far distance lead to an adaptation process, whereas at close viewing distance horizontal disparity is a visual compensation process used directly to scale the relative amplitudes of both eyes, not leading to adaptation. The time-course of disconjugate vertical saccades was much slower, with mostly postsaccadic vergence. Nearby viewing enhanced the disconjugacy of vertical saccades.

Adaptation, Physiological↗
PubMedDate not supplied

Rat and human visual-evoked potentials recorded under comparable conditions: a preliminary analysis to address the issue of predicting human neurotoxic effects from rat data.

Pattern-onset visual-evoked potentials (VEPs) were recorded from rats and humans in order to perform cross-species comparison of neuronal functional properties reflected by the early VEP components. The spatial frequency of a sinusoidal test grating was varied in Experiment 1. For both species, amplitude of the first positive VEP component was larger at low spatial frequency and decreased as spatial frequency increased. The immediately succeeding negative component was small at low spatial frequency and was of maximal amplitude at moderate spatial frequency. The effects of stationary pattern adaptation on these components were investigated in Experiment 2. Subjects viewed either a blank field or the test grating prior to recording VEPs. For both species, adaptation had no effect on the positive component but strongly attenuated the negative component. Experiment 3, in which only humans were tested, indicated that the negative component was of cortical origin. Only cortical neurons are known to be orientation selective, and the effect of adaptation diminished as the orientation difference between the adaptation and test gratings increased. These results suggest that the early positive and negative components arise from parallel visual pathways, and that the rat components may reflect visual processes qualitatively similar to those of humans.

Adaptation, Physiological↗
PubMed2005

Adaptation to asymmetrically distorted faces and its lack of effect on mirror images.

Previous research showed that viewing symmetrically distorted faces for a few minutes causes undistorted faces to appear distorted in the opposite manner (face-distortion aftereffect, FDAE). Three experiments with 90 observers demonstrated that adaptation to an asymmetrically distorted face also causes FDAE, but does not affect perception of its mirror image. The results suggested the FDAE occurs at the level of visual processing where distinct neural populations respond to a non-frontal facial image and its mirror image. Unlike most aftereffects, this FDAE lasts at least 30 min. Spatial and temporal characteristics of the FDAE and its relevance to portrait drawing and painting are discussed.

Adaptation, Physiological↗
PubMed2006

Slant perception, and its voluntary control, do not govern the slant aftereffect: multiple slant signals adapt independently.

Although it is known that high-level spatial attention affects adaptation for a variety of stimulus features (including binocular disparity), the influence of voluntary attentional control-and the associated awareness-on adaptation has remained unexplored. We developed an ambiguous surface slant adaptation stimulus with conflicting monocular and binocular slant signals that instigated two mutually exclusive surface percepts with opposite slants. Using intermittent stimulus removal, subjects were able to voluntarily select one of the two rivaling slant percepts for extended adaptation periods, enabling us to dissociate slant adaptation due to awareness from stimulus-induced slant adaptation. We found that slant aftereffects (SAE) for monocular and binocular test patterns had opposite signs when measured simultaneously. There was no significant influence of voluntarily controlled perceptual state during adaptation on SAEs of monocular or binocular signals. In addition, the magnitude of the binocular SAE did not correlate with the magnitude of perceived slant. Using adaptation to one slant cue, and testing with the other cue, we demonstrated that multiple slant signals adapt independently. We conclude that slant adaptation occurs before the level of slant awareness. Our findings place the site of stereoscopic slant adaptation after disparity and eye posture are interpreted for slant [as demonstrated by Berends et al. (Berends, E. M., Liu, B., & Schor, C. M. (2005). Stereo-slant adaptation is high level and does not involve disparity coding. Journal of Vision 5 (1), 71-80), using that disparity scales with distance], but before other slant signals are integrated for the resulting awareness of the presented slant stimulus.

Adaptation, Physiological↗
PubMed2007

The role of familiarity in three-dimensional view-transferability of face identity adaptation.

Recent studies show that face adaptation effects partially transfer across three-dimensional viewpoint change. Here we investigated whether the degree of adaptation transfer is mediated by experience with a face. We manipulated face familiarity and measured identity aftereffects both within- and across-viewpoint. Familiarity enhanced the overall strength of identity adaptation as well as the degree to which adaptation transferred across-viewpoint change. These findings support the idea that transfer effects in adaptation vary as a function of experience with particular faces, and suggest the use of adaptation as a tool for tracking face representations as they develop.

Adaptation, Physiological↗
PubMed2002

Orthogonal adaptation and orientation discrimination.

The change in apparent orientation of lines and gratings induced by surrounding or preceding patterns of a different orientation (the tilt illusion and tilt after-effect) has been abundantly documented, but there is no unanimity about the effect of such inducing patterns on orientation discrimination thresholds. In particular, because inducing contours that are almost orthogonal cause the direction of the tilt illusion to reverse, evidence for an improvement of orientation discrimination with orthogonal adaptation has been welcomed on theoretical ground as supporting concepts of inversion of polarity of neural connection between cortical cells with oriented receptive fields for large orientation differences. In careful psychophysical experiments on human observers with several kinds of test and orthogonal adaptation patterns the average ratio of adapted/unadapted discrimination thresholds in paired sets of data was 1.027+/-0.13, which does not differ significantly from unity and hence constitutes evidence that orthogonal adaptation does not improve orientation discrimination.

Adaptation, Physiological↗
PubMed1997

Analysis of the effect of pattern adaptation on pattern pedestal effects: a two-process model.

Pattern contrast thresholds for vertical Gabor patterns were measured on pattern pedestals that were vertical or horizontal. Contrast of the pedestal was varied to measure the function relating target contrast threshold to pedestal contrast (TvC function). TvC functions were measured without an adaptor and after adaptation to vertical, horizontal and plaid patterns. For a pedestal with the same orientation as the target, the vertical and plaid adapters increased thresholds at low pedestal contrasts, but not high. For the pedestal orthogonal to the target, the same two adaptors increased thresholds over the whole range of pedestal contrasts. These asymmetric effects are described by a model of adaptation and masking derived from a model of masking (Foley, 1994a) by allowing two parameters to vary with the adapt state; one of them is an additive parameter in the denominator of the response function, which can be interpreted as adaptor-produced divisive inhibition that persists after adaptor offset; the other is the sensitivity to pedestal-produced divisive inhibition, which is changed by adaptation for the pedestal orthogonal to the target. Other models do not account for both effects.

Adaptation, Physiological↗