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Results for “Pattern Recognition, Physiological”

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PubMed2004

Neural correlates of sensory and decision processes in auditory object identification.

Physiological studies of auditory perception have not yet clearly distinguished sensory from decision processes. In this experiment, human participants identified speech sounds masked by varying levels of noise while blood oxygenation signals in the brain were recorded with functional magnetic resonance imaging (fMRI). Accuracy and response time were used to characterize the behavior of sensory and decision components of this perceptual system. Oxygenation signals in a cortical subregion just anterior and lateral to primary auditory cortex predicted accuracy of sound identification, whereas signals in an inferior frontal region predicted response time. Our findings provide neurophysiological evidence for a functional distinction between sensory and decision mechanisms underlying auditory object identification. The present results also indicate a link between inferior frontal lobe activation and response-selection processes during auditory perception tasks.

Acoustic Stimulation↗

PubMed1987

Physiological responses of type A and type B men during cognitive performance.

Twenty male medical students classified as Type A or Type B solved a Concept Identification (CI) problem while measurements were taken on cardiovascular and somatic activity. The As produced significantly more overall electromyogram (EMG) activity and greater vasomotor activity than the Bs at baseline and during the task. Both Type As and Bs showed significantly higher levels of Heart Rate (HR), systolic and diastolic blood pressures, skin conductance, frontal EMG, and lower levels of vasomotor activity during work on the problem than during pre- and post-problem baselines. Type As showed significant negative correlations between total errors during CI and level of vasomotor activity, and between postsolution response latency and skin conductance. Type Bs showed a strong positive association between presolution response time and heart rate that did not hold for the As. The As appear to have shown sympathetic activation associated with quality of problem-solving performance, while the B's showed a relationship that suggested an impaired efficiency of performance associated with cardiac activation.

Adult↗

PubMed2006

MR imaging and osteoporosis: fractal lacunarity analysis of trabecular bone.

We develop a method of magnetic resonance (MR) image analysis able to provide parameter(s) sensitive to bone microarchitecture changes in aging, and to osteoporosis onset and progression. The method has been built taking into account fractal properties of many anatomic and physiologic structures. Fractal lacunarity analysis has been used to determine relevant parameter(s) to differentiate among three types of trabecular bone structure (healthy young, healthy perimenopausal, and osteoporotic patients) from lumbar vertebra MR images. In particular, we propose to approximate the lacunarity function by a hyperbola model function that depends on three coefficients, alpha, beta, and gamma, and to compute these coefficients as the solution of a least squares problem. This triplet of coefficients provides a model function that better represents the variation of mass density of pixels in the image considered. Clinical application of this preliminary version of our method suggests that one of the three coefficients, beta, may represent a standard for the evaluation of trabecular bone architecture and a potentially useful parametric index for the early diagnosis of osteoporosis.

Adult↗

PubMed2001

Investigations into biochemical changes due to diurnal variation and estrus cycle in female rats using high-resolution (1)H NMR spectroscopy of urine and pattern recognition.

Metabonomic methods utilizing (1)H NMR spectroscopy and pattern recognition analysis (NMR-PR) have been applied to investigate biochemical variation in a control population of female rats over time in relation to diurnal and estrus cycle fluctuations. Urine samples were collected twice daily (6 AM-6 PM and 6 PM-6 AM) from female rats (n = 10) for a period of 10 days. (1)H NMR spectroscopic analysis and PR were performed on each sample. Subtle differences in the endogenous metabolite excretion profiles of urine samples at the various stages of the estrus cycle were observed. The main inherent metabolic clustering in the principal components analysis (PCA) maps was related to interrat variation and was observed in the first two principal components (PCs), accounting for 66% of the variance in these data. Separation of urinary data according to time of sampling (day and night) was achieved in the lower PCs. Some of the differences in the urinary profiles of day and night samples causing this separation were attributed to the increase in metabolic activity of the rat during the night. Individual rat data were also mapped as a function of time, using PCA, to produce a metabolic trajectory, which in a number of cases facilitated separation of one or more stages of the estrus cycle. Several of the fluctuations observed between urine samples collected during the different stages of the estrus cycle may be related to hormone levels. Although variation in metabolite profiles relating to both diurnal and hormonal variation could be detected these perturbations were minor compared with the effects observed due to interrat variation. This is the first time that a hormonal cycle has been described for individuals based on NMR spectroscopic and multivariate analysis of metabolic data and shows the value of metabonomic methods in the investigation of physiological variation and rhythms.

Animals↗

PubMed2005

Characterizing vascular connectivity from microCT images.

X-ray microCT (computed tomography) has become a valuable tool in the analysis of vascular architecture in small animals. Because of its high resolution, a detailed assessment of blood vessel physiology and pathology is possible. Vascular measurement from noninvasive imaging is important for the study and quantification of vessel disease and can aid in diagnosis, as well as measure disease progression and response to therapy. The analysis of tracked vessel trajectories enables the derivation of vessel connectivity information, lengths between vessel junctions as well as level of ramification, contributing to a quantitative analysis of vessel architecture. In this paper, we introduce a new vessel tracking methodology based on wave propagation in oriented domains. Vessel orientation and vessel likelihood are estimated based on an eigenanalysis of gray-level Hessian matrices computed at multiple scales. An anisotropic wavefront then propagates through this vector field with a speed modulated by the maximum vesselness response at each location. Putative vessel trajectories can be found by tracing the characteristics of the propagation solution between different points. We present preliminary results from both synthetic and mouse microCT image data.

Algorithms↗

PubMed1984

[Threshold-adjusted supraliminal pattern perimetry with the Goldmann perimeter].

This paper describes a method of supraliminal pattern perimetry for use with a Goldmann perimeter. In this method, the stimuli are adjusted in stages in accordance with the normal physiological sensitivity gradient. The threshold is determined on four meridians located 10 degrees and 30 degrees from the center. These threshold values are used to define three different levels of brightness which exceed the threshold by approximately the same amounts in three sectors of the field of vision extending from 2 degrees to 10 degrees, 10 degrees to 20 degrees and 20 degrees to 30 degrees. The points arranged in a rectangular pattern at intervals of 3 1/3 degrees are used to check for relative and absolute defects in the patient's field of vision. Supraliminal pattern perimetry can be performed manually on the Goldmann perimeter in a manner similar to automatic supraliminal perimetry to detect small defects in the field of vision. Manual perimetry, though, allows the physician to use his clinical experience directly and also makes it possible to combine screening and detection into a single procedure, since it is then possible to alter pattern density and to switch from supraliminal pattern perimetry to kinetic and free static threshold determination during the actual course of the examination. The flexibility of the manual method may well save both physician and patient time and effort, especially in difficult cases. With automatic perimetry, however, such flexibility is hampered by the fact that programs must be run through in succession (with the exception of the Octopus Program 4).

Computers↗

PubMed1992

Letter memory loads change more than visual-field advantage: interhemispheric coupling effects.

A derivation from Denenberg's (Denenberg, 1980. American Journal of Physiology, 238, R3-R13) model of brain organization is that significant correlations between left-hemisphere (LH) and right-hemisphere (RH) measures indicate that the hemispheres are coupled together in a general system. Two formally similar visual-field (VF) reaction-time (RT) tasks, one a LH-right (R) VF and the other a RH-left (L) VF advantage task, were performed by 30 female and 30 male right-handers under single-task (zero load) and dual task (three or six consonants in memory) conditions. Expected letter load effects upon VF performances were obtained. Particularly for RT variability, correlations of measures lateralized to different hemispheres (i.e., LVF-RVF, LH and RH tasks) increased linearly as load increased, while correlations of measures lateralized to the same hemisphere (i.e., two LH tasks) did not. Bihemispheric cortical activation may play a role in this general system coupling caused by complexity or load. Females demonstrated greater interhemispheric coupling.

Adult↗

PubMed1996

Processing visual evoked potentials based on matched filtering of single trial responses.

Physiological signals recorded after presentation of a stimulus can be considered as the sum of an evoked sensory response and uncorrelated noise corresponding to the spontaneous neural background activity. In case of low signal-to-noise ratio, the sensory signal is estimated by averaging a large number of single trial records sampled under the same experimental conditions. The averaging technique, however, is inappropriate for displaying trial-to-trial variations that may occur during a recording session. A method based on matched filtering was developed for processing single visual evoked potentials (VEPs). To illustrate the performance of this method, a set of VEPs for grating patches of 8 different contrasts (including 0) was evaluated. The VEPs were subjected to signal detection analysis by computing for each contrast similarity indices between the single trial records and the averaged response used as a template. The signals were analysed in terms of probability density distributions, expressing the goodness of fit between template and each single waveform.

Cluster Analysis↗

PubMed1976

Decreased resistance to intravenous tumour-cell challenge during reticuloendothelial depression following surgery.

The influence of surgical stress on resistance to i.v. challenge with Walker 256 tumour cells was investigated in rats, with respect to the functional state of the reticuloendothelial system (RES). Phagocytic activity of the RES was evaluated by colloid (gelatinized [131I] "RE test lipid emulsion") clearance, and opsonin levels were determined by bioassay. Reticuloendothelial clearance capacity was significantly (P less than 0-05) depressed 60 min following surgery (coeliotomy plus jejunal enterotomy) as quantified by both humoral and cellular parameters of RE function. Phagocytic depression was primarily due to impaired hepatic Kupffer cell function and related to a deficiency in the phagocytic supporting capacity of plasma, also referred to as opsonic or recognition factor (RF) capacity. During the postoperative period of RES colloid clearance depression, pulmonary localization of the blood-borne test particulate matter increased. Rats challenged with 51Cr-labelled viable tumour cells at a dose of 1-0 X 106 i.v., either prior to or during the postoperative period of RE depression, manifested a significant (P less than 0-05) increment in pulmonary localization of the viable tumour cells, and a decrease (P less than 0-05) in hepatic clearance. Evaluation of survival patterns demonstrated a significant (P less than 0-01) decrease in host resistance to i.v. tumour cell challenge (2 X 103 cells) during the postoperative period of RE depression and hypo-opsonaemia. Sham-anaesthetized control animals survived 17-9 +/- 0-8 days, while animals challenged during the period of RE depression survived 7-9 +/- 0-4 days. An increased incidence of respiratory distress and nasal discharge was observed in the animals with impaired survival. Thus, surgical manipulation may transiently compromise RES systemic host defence and may be reflected in an increment in the pulmonary localization of blood-borne tumour cells. The relationship of this altered pattern of tumour cell distribution to the impaired survival remains to be determined, and warrants investigations.

Animals↗

PubMed2006

Physiological responses of 5-month-old infants to smiling and blank faces.

Physiological responses (i.e., EEG, heart period, respiratory sinus arrhythmia (RSA)) were monitored in 5-month-old infants during the replacement of an adult's smiling (SF) with a blank face (BF) in a face-to-face setting. Affect, while the infant looked at and away from the adult's face during both conditions, was analyzed. Infants displayed neutral and some positive affect while looking at both SF and BF. RSA was quantified continuously during both conditions. RSA increased during BF relative to SF. EEG was quantified only while the infants were looking at the adult's face during both conditions. An increase in theta over multiple scalp areas (AF3,4; F7,8; FC3; T6) was observed during BF relative to SF. The data suggest that infant attention to BF and SF reflect different psychophysiological processes that can be indexed by RSA and scalp-recorded theta.

Affect↗

PubMed2004

Skin cancer detection by spectroscopic oblique-incidence reflectometry: classification and physiological origins.

Data obtained from 102 skin lesions in vivo by spectroscopic oblique-incidence reflectometry were analyzed. The participating physicians initially divided the skin lesions into two visually distinguishable groups based on the lesions' melanocytic conditions. Group 1 consisted of the following two cancerous and benign subgroups: (1) basal cell carcinomas and squamous cell carcinomas and (2) benign actinic keratoses, seborrheic keratoses, and warts. Group 2 consisted of (1) dysplastic nevi and (2) benign common nevi. For each group, a bootstrap-based Bayes classifier was designed to separate the benign from the dysplastic or cancerous tissues. A genetic algorithm was then used to obtain the most effective combination of spatiospectral features for each classifier. The classifiers, tested with prospective blind studies, reached statistical accuracies of 100% and 95% for groups 1 and 2, respectively. Properties that related to cell-nuclear size, to the concentration of oxyhemoglobin, and to the concentration of deoxyhemoglobin as well as the derived concentration of total hemoglobin and oxygen saturation were defined to explain the origins of the classification outcomes.

Algorithms↗

PubMed1980

Parametric and feature extraction analyses of the receptive fields of visual neurones. Two streams of thought in the study of a sensory pathway.

Two major conceptual approaches to the study of visual receptive field physiology can be identified; one, here termed the 'parametric' approach, which considers all the properties of a cell to be potentially related to that cell's functional role, and a second, here termed the 'feature extraction' approach, which regards a particular receptive field property as defining a cell's role in the visual system. The parametric approach seems most compatible with network theories of visual information processing, while the feature extraction approach suggests a localized single-cell form of visual representation. In this paper we trace the growth and development of these two approaches, from 1938 to the present, by dividing this period into four segments: 1938--1953, during which the foundations of both approaches were laid; 1953--1966, the major period of growth for feature-extraction analyses; 1966--1975, the major period of growth for parametric analyses; and 1975 to the present, during which the parametric approach has been expanded by the incorporation of principles of systematics and population biology to enable groups of neurones to be studied from a biological perspective.

Animals↗

PubMedDate not supplied

Contrast adaptation in retinal and cortical evoked potentials: no adaptation to low spatial frequencies.

Contrast adaptation occurs in both the retina and the cortex. Defining its spatial dependence is crucial for understanding its potential roles. We thus asked to what degree contrast adaptation depends on spatial frequency, including cross-adaptation. Measuring the pattern electroretinogram (PERG) and the visual evoked potential (VEP) allowed separating retinal and cortical contributions. In ten subjects we recorded simultaneous PERGs and VEPs. Test stimuli were sinusoidal gratings of 98% contrast with spatial frequencies of 0.5 or 5.0 cpd, phase reversing at 17 reversals/s. Adaptation was controlled by prolonged presentation of these test stimuli or homogenous gray fields of the same luminance. When adaptation and test frequency were identical, we observed significant contrast adaptation only at 5 cpd: an amplitude reduction in the PERG (-22%) and VEP (-58%), and an effective reduction of latency in the PERG (-0.95 ms). When adapting at 5 cpd and testing at 0.5 cpd, the opposite effect was observed: enhancement of VEP amplitude by +26% and increase in effective PERG latency by + 1.35 ms. When adapting at 0.5 cpd and testing at 5 cpd, there was no significant amplitude change in PERG and VEP, but a small effective PERG latency increase of +0.65 ms. The 0.5-cpd channel was not adapted by spatial frequencies of 0.5 cpd. The adaptability of the 5-cpd channel may mediate improved detail recognition after prolonged blur. The existence of both adaptable and nonadaptable mechanisms in the retina allows for the possibility that by comparing the adaptational state of spatial-frequency channels the retina can discern between overall low contrast and defocus in emmetropization control.

Adaptation, Physiological↗

PubMed1998

Texture segregation, surface representation and figure-ground separation.

A widespread view is that most texture segregation can be accounted for by differences in the spatial frequency content of texture regions. Evidence from both psychophysical and physiological studies indicate, however, that beyond these early filtering stages, there are stages of 3-D boundary segmentation and surface representation that are used to segregate textures. Chromatic segregation of element-arrangement patterns--as studied by Beck and colleagues--cannot be completely explained by the filtering mechanisms previously employed to account for achromatic segregation. An element arrangement pattern is composed of two types of elements that are arranged differently in different image regions (e.g. vertically on top and diagonally on the bottom). FACADE theory mechanisms that have previously been used to explain data about 3-D vision and figure-ground separation are here used to simulate chromatic texture segregation data, including data with equiluminant elements on dark or light homogeneous backgrounds, or backgrounds composed of vertical and horizontal dark or light stripes, or horizontal notched stripes. These data include the fact that segregation of patterns composed of red and blue squares decreases with increasing luminance of the interspaces. Asymmetric segregation properties under 3-D viewing conditions with the equiluminant elements close or far are also simulated. Two key model properties are a spatial impenetrability property that inhibits boundary grouping across regions with non-collinear texture elements and a boundary-surface consistency property that uses feedback between boundary and surface representations to eliminate spurious boundary groupings and separate figures from their backgrounds.

Color Perception↗

PubMed1998

Spatial frequency discrimination and detection characteristics for gratings defined by orientation texture.

We describe evidence consistent with the proposal that the visual system contains a parallel array of size-tuned mechanisms sensitive to orientation texture-defined (OTD) form, and propose that the relative activity of these mechanisms determines spatial frequency discrimination threshold for OTD gratings. Using a pattern of short lines we measured spatial frequency discrimination thresholds for OTD gratings and luminance-defined (LD) gratings. For OTD gratings, the orientation of texture lines varied sinusoidally across the bars of the gratings, but line luminance was constant. For LD gratings, line orientation was constant, but line luminance varied sinusoidally across the bars of the grating. When the number of texture lines (i.e. spatial samples) per grating cycle was below about six, spatial sampling strongly affected both the spatial frequency discrimination and grating detection thresholds for OTD and LD gratings. However, when the number of spatial samples per grating cycle exceeded about six, plots of both discrimination threshold and detection threshold were different for OTD and LD gratings. For an OTD grating of any given spatial frequency, spatial frequency discrimination threshold fell as the number of samples per grating cycle was increased while holding texture line length constant: the lower limit was reached at six to ten samples per cycle. When we progressively increased the viewing distance (keeping the cycles per degree (cpd) constant), spatial frequency discrimination threshold reached a lower limit and increased thereafter. We propose that this minimum threshold represents a balance between opposing effects of the number of samples per grating cycle and the length of texture lines, and approaches the absolute physiological lower limit for OTD gratings. Spatial frequency discrimination was possible up to at least 7 cpd. Grating acuity for an OTD grating was considerably lower than the physiological limit for LD gratings, presumably because detectors of OTD form include a spatial integration stage following the processing of individual lines. For an LD grating, discrimination threshold fell as the number of samples per grating cycle was increased and asymptoted at six to ten samples per cycle. Spatial frequency discrimination thresholds for OTD and LD gratings were similar at low spatial frequencies (up to 3-4 cpd), but increased more steeply for OTD gratings at high spatial frequencies. For both OTD and LD gratings, discrimination threshold fell steeply as the number of grating cycles was increased from 0.5 to ca. 2.5 cycles, and thereafter decreased more slowly or not at all suggesting that, for both OTD and LD gratings, spatial frequency discrimination can be regarded as a special case of line interval or bar width discrimination. As orientation contrast was progressively increased, discrimination threshold for an OTD grating fell steeply up to about four to five times grating detection threshold, then saturated. This parallels the effect of luminance contrast on discrimination threshold for an LD grating.

Adult↗

PubMed1989

Effects of physical exercise on peripheral vision and learning in children with spina bifida manifesta.

The purpose of this research was to investigate the effects of active exercise of the arms on various physiological, perceptual, and cognitive parameters of children with spina bifida manifesta who were aged 9 to 12 yr. Following a 5-min. rest interval, subjects were either not exercised (control days) for a 6-min. period or were exercised (experimental days) for a 6-min. period. Cardiac measures, respiratory function, peripheral vision, and figural learning trials were recorded after exercise. Wilcoxon matched-pairs signed rank tests were computed on the means of the exercise and no-exercise conditions for each measure. Six minutes of active exercise resulted in significant increases in peripheral vision, respiratory and cardiac measures and significant decreases in figural learning trials for these children. A floor effect was noted for the figural learning test. It was concluded that exercise increased blood flow through the lungs allowing for greater oxygen diffusion in the brain and other facilitatory effects resulting in more effective cerebral activity. Curriculum revisions for such children seem to indicate the importance of activity in facilitating subsequent learning.

Cerebrospinal Fluid Shunts↗

PubMed1999

The visual physiology of the wild type mouse determined with pattern VEPs.

Genetically manipulated mice are important tools for studies on plasticity and degeneration/regeneration in the visual system. However, a description of the basic properties of the visual performance of the wild type mouse is still lacking. To characterize the visual physiology of the wild type (C57BL/6J) mouse we recorded Visual Evoked Potentials (VEPs) from the primary visual cortex. As compared to behavioral methods, VEPs may have the advantage that different aspects of vision can be screened readily and simultaneously in the same animals, including those with poor visual behavior due to motor or learning deficits. Local VEP responses to patterned visual stimuli have been recorded from the binocular visual cortex of anesthetized mice. Spatial (visual acuity, contrast threshold) and temporal (temporal function, response latency, motion sensitivity) aspects of VEPs were evaluated. The mouse VEP acuity was 0.6 c/deg, which is comparable to the behavioral visual acuity. The VEP peak contrast threshold was 5% (no behavioral data are available). Cortical representation of visual coordinates and cortical magnification factor corresponded to those previously reported using single cell recordings. Laminar analysis of VEPs indicated a dipole source in the supragranular layers of the visual cortex as a major response generator. VEPs showed contribution from both eyes, although biased strongly towards the eye contralateral to the recorded cortex. Results provide a comprehensive framework for characterizing visual phenotypes of a variety of transgenic mice.

Animals↗

PubMedDate not supplied

Anatomy of the auditory cortex.

Cortical auditory areas located in the superior temporal region (STR) in monkey and human. The primary auditory area (AI) occupies the cortex of the supratemporal plane (STP) and is surrounded by auditory association areas in circular sulcus and superior temporal gyrus (STG). Architectonic studies have parcellated auditory areas into a number of subregions. Beginning from the temporal polar proisocortex up to the parietal cortex, these areas shows progressive laminar differentiation, and are arranged into three parallel lines. The most medial line occupies the cortex of the circular sulcus. The regions of this line maintains limbic features and is termed as root line. Another line is located in STG. The regions of this line show progressive emphasis in the third and fourth layer neurons and is termed as belt line. Interposed between root and belt line is a core line located in STP. In this line there is greater accumulation of fourth layer neurons. Recent physiological studies have outlined several auditory representations surrounding AI. These auditory representations correspond to above mentioned architectonic subregions of STR. The subregions within each line have bidirectional connectional laminar specificity. The feedforward connections originate from the supragranular layer III and terminate in the around layer IV of the rostrally adjacent region. Feedback projections in contrast stem from the infragranular layers and terminate in layer I. The long association connections of auditory areas are with the prefrontal cortex (PFC), the multimodal areas and the limbic regions, and are derived from belt and root line areas of STR. These projections follow the rostro-caudal architectonic differentiation of STR. Thus the rostral STG areas are mainly connected with orbital and medial PFC areas whereas the caudal STG areas are connected with caudal PFC. The intermediate STG areas are preferentially related to the lateral PFC regions. It seems that STG-PFC connections are between the areas with similar level of architectonic differentiation. The thalamic connections of the subregions of STR also follow the architectonic organizations. The core line areas are preferentially related to ventral nucleus (MGv) of medial geniculate nucleus (MGN) whereas the root and belt line areas are connected respectively to magnocellular (MGmc) and dorsal (MGd) subdivisions of MGN. The root and belt areas share some connections and are also related to pulvinar, suprageniculate, dorsomedial and intralaminar nuclei. It seems therefore that progressive laminar and tripartrate organization of auditory regions of STR is reflected in intrinsic, association and thalamic connections. The feedforward connections may be engaged in analysis of external environmental cues whereas feedback connections may have a role in matching learned or stored information with incoming auditory signals. The preferential core line connectivity with MGv may be involved in spectral analysis of sound whereas the connections of the belt and root areas with MGmc, MGd, and pulvinar may have role in sound pattern recognition, auditory memory, the localization of sound in space as well as matching auditory information with other modalities.

Animals↗