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PubMed1999

Separating visual perception and non-verbal intelligence in children with early brain injury.

The relationship between impairments of visual perception and of non-verbal intelligence was studied in 28 children who, due to the nature of their neurological pathology, were at risk for visual perceptual impairments (high-risk), and 18 mentally disabled children without such risk (low-risk). Their age range was 3-14 years. A child was considered specifically visual-perceptually impaired (VPI) if performance on the De Vos task, a visual object recognition task, was weaker than expected from the baseline performance level obtained on non-verbal intelligence subtests. Accordingly, 22 high-risk children (79%) were classified VPI, against only four low-risk children (22%). Comparing intelligence data of children with and without VPI revealed a WPPSI non-verbal to verbal intelligence impairment in the former. At the subtest level, comparing five verbal and five non-verbal WPPSI subtests, and five subtests from the Snijders-Oomen non-verbal intelligence scale, revealed a difference only on Animal House. The absence of any systematic effects of specific visual perceptual impairment on intelligence subtest performance leads us to conclude that in these children VPI and selective non-verbal intelligence impairment coexist as two separate and irreducible deficits.

Brain Injuries↗
PubMed1975

Auditory-visual perception of speech.

Hearing-impaired persons usually perceive speech by watching the face of the talker while listening through a hearing aid. Normal-hearing persons also tend to rely on visual cues, especially when they communicate in noisy or reverberant environments. Numerous clinical and laboratory studies on the auditory-visual performance of normal-hearing and hearing-impaired children and adults demonstrate that combined auditory-visual perception is superior to perception through either audition or vision alone. This paper reviews these studies and provides a rationale for routine evaluation of auditory-visual speech perception in audiology clinics.

Auditory Perception↗
PubMed1980

Unilateral auditory stimulation and the visual perception of verticality: one more time.

The effects of varying conditions of unilateral auditory stimulation on the visual perception of verticality were examined in two experiments using 18 and 42 subjects, respectively. Significant effects of auditory stimulation and hand used to make the verticality adjustments were not found. With only one exception in Exp. 2, the starting position of the rod also had no influence on the ability of the subjects to adjust a rod to its vertical position. The literature pertaining to sensory-tonic field theory of perception was critically reviewed.

Acoustic Stimulation↗
PubMed1999

Children's and parents' visual perception of physicians.

The purpose of this study is to evaluate the child's and parents' visual perception of physicians. To do this, 50 children and their parents were asked which physician they preferred, when shown eight pairs of photographs. Four characteristics were tested twice, white coat versus no white coat, smile versus stern face, cartoon posters versus no posters, and standing versus stooping. We found that both children and parents preferred the smiling physician and the physician with cartoon posters on the wall. Surprisingly 54% of children preferred the physician in the white coat, whereas only 35% of parents preferred the white coat. Sixty-eight percent of children also preferred the standing physician compared with only 41% of parents. There was little correlation between the parent's and child's answers. The results did not differ significantly with age, gender, or number of hospitalizations. In conclusion our study did not confirm the popular belief that children are afraid of physicians in white coats, although children did strongly prefer physicians who smiled and those with cartoon posters on the wall.

Adult↗
PubMed1997

The influence of established and new antiepileptic drugs on visual perception. 1. A placebo-controlled, double-blind, single-dose study in healthy volunteers.

The influence of single oral dosages of carbamazepine (CBZ), valproic acid, vigabatrin (VGB), lamotrigine (LTG), gabapentin (GBP), and losigamone (LSG) on visual perception was investigated in ten healthy volunteers according to a double-blind, placebo-controlled, cross-over study design. The test battery comprised visual acuity, the Lanthony-D-15-désaturé colour perception test, increment, postadaptation and transient tritanopia threshold measurements, perception threshold assessment for monochromatic and chromatic gaussian dots, monochromatic gratings and gratings of differing spatial frequency, and critical flicker fusion tests with various stimuli. The only consistent and partly significant effects were seen after VGB and GBP. After VGB, increment, postadaptation and transient tritanopia thresholds and the critical flicker fusion increased, whereas GBP led to a somewhat converse profile. The other tests were not influenced consistently by any antiepileptic drug (AED). We conclude that: (i) gamma-amino-butyric acid-(GABA)-related properties as under the prototype drug VGB result in specific alterations of the transient tritanopia phenomenon which is consistent with the physiological hypothesis for this retinal paradigm based on extracellular recordings in primates. The possible mechanisms why VGB improved critical flicker fusion as the only AED in this trial are discussed. The profile of GBP indicates a unique mechanism of action. We have not observed specific influences on visual perception under AEDs which act mainly via alterations of ion membrane conductance. The transient tritanopia and flicker fusion paradigms we used appear to be promising to investigate antiepileptic drugs with hitherto unknown modes of actions in human noninvasively.

Adaptation, Ocular↗
PubMed1975

Applying concepts of visual perception to formats of hospital menus.

Standardized printed menu formats for all diets utilizing concepts of visual perception were evaluated in a machine-paced hospital tray-assembly process. Formats of existing menus differed among the various diets. On the redesigned menus, all menu items were arranged in basic groups which were assigned specific positions; groups were accentuated by white strips across the various color-coded selective menus; and accessory items were placed in specific, standard positions on all menus. Criteria for evaluating the effect of using the redesigned menu in tray assembly operations were: overall productivity, individual productivity, and error rate per tray. Data were charted (a) during a control period when the existing menu formats were used to provide baseline data and (b) during an experimental period when the redesigned menu formats were used. Overall productivity was measured by man-minutes per tray. Video tapes of five station operators servicing selected trays were made to study individual productivity. Station operator and checker accuracy were measured in terms of ratio of error-free trays, errors per tray, and errors to possibility of errors per tray. Man-minutes per tray decreased significantly in the experimental period from 2.44 to 2.17--a productivity increase of 11.1 per cent. The individual productivity analysis revealed no significant changes from control to experimental periods. Accuracy of the tray assembly station operators improved significantly. Decreases in ratio of mean number of errors to possibility of errors per tray were recorded in the experimental period. The error rate per tray decreased 44.9 per cent from 0.48 to 0.26, and the ratio of errors to possibility of errors per tray decreased from 6.3 to 3.5 per cent. The percentage of error-free trays rose from 69.9 to 80.9 per cent. Checkers' errors per tray did not change significantly from control to experimental period when data for the two periods were compared. This study provides a practical means of increasing productivity and improving accuracy of the machine-paced tray assembly process.

Audiovisual Aids↗
PubMed1979

Hemispheric dysfunction in schizophrenia: assessment by visual perception tasks.

Before and after a double-blind trial of haloperidol vs. mesoridazine, 24 hospitalized schizophrenics performed visual perception tasks designed to assess function of the cerebral hemispheres. Tasks involved identifying as "same" or "different" two images (either letters, digits, or unfamiliar shapes) projected tachistoscopically to the right or left visual field or to both together. Multivariate analysis of variance related response latency and accuracy to task type, hemisphere stimulated, and pre- vs. posttreatment testing. Both before and after treatment, subjects responded most slowly and least accurately to letter-matching. Bilateral presentation of stimuli resulted in faster and more accurate responses, except on shape-matching. Neuroleptic treatment improved speed and accuracy overall, though not under certain task conditions. Results accorded more with an impairment in verbal processing and interhemispheric coordination than with a specific left-hemispheric deficit in schizophrenia.

Acute Disease↗
PubMed1999

Mu rhythm modulation during changes of visual percepts.

Cooperation between vision and somatomotor behavior, such as manual exploration of objects, suggests close functional coupling between the visual and sensorimotor systems. We observed this type of interaction in human volunteers during binocular rivalry while following the level of sensorimotor mu rhythm with a whole-scalp neuromagnetometer. The observers viewed a weak vertical grating in the lower visual field of one eye and a strong horizontal grating in the same spatial window of the other eye. When stationary, the weak grating was permanently invisible because of its low contrast and spatial frequency. A sudden brief drifting movement of the weak grating wiped out the dominant grating, and the weak grating became visible for less than the 3-s interval between the movements. The postcentral 8- to 15-Hz mu rhythm was found in six of nine observers, and its level increased transiently by 10-15%, starting about 450 ms after the beginning of the movement. The mu level was also enhanced by the actual disappearance of the stronger stimulus, when it occurred in random order with the rivalry stimuli. Identical visual motion, when not accompanied by a perceptual dominance change, produced only minor effects on the mu rhythm. Our results show that a change in visual percept, even with no real or imagined motor response, is associated with modified activity of the postcentral gyrus. This modification may reflect visuohaptic interactions and/or activity of the distributed cortical network implementing visually guided movements.

Adult↗
PubMed1994

Visual readaptation after flash exposure under scotopic conditions. A study using optokinetic nystagmus as an indicator of visual perception.

The purpose of the present study was to establish a method for objective measurements of visual readaptation after flash exposures and to define a model for measurements. Influences of target direction, luminance and velocity on optokinetic nystagmus (OKN) were investigated under scotopic conditions. Visual readaptation was measured using OKN as an indicator of visual perception after exposure to a flash. The interval between the triggering of the flash and the reoccurrence of OKN was defined as the visual readaptation time (RAT). A Goldmann perimeter hemisphere was used for flash stimulation. A horizontally moving vertical grating projected inside the hemisphere was used as the OKN stimulus. Eye movements were recorded by DC electrooculography (EOG). The dependence of RAT on the dose of the flash, the wavelength of the flash and the luminance of the OKN target were investigated. The precision of the measurement method was studied. This includes the analysis of the variance due to the experimental occasions, the repeated exposures, the sexes of the subjects, the methods for recognition of OKN and the ways of visual adaptation before measurements. The contributions of retinal receptor and the neural activity to RAT were investigated by electroretinography (ERG). The influences of target direction and luminance on binocular motion perception and OKN as well as monocular OKN were examined at various target velocities. The dependence of the frequency and amplitude of eye jerks during monocular OKN on target luminance and velocity were also examined. It was found that RAT increases with increasing doses of the flash or decreasing luminance of the grating. RAT is most extended after flashes near 520 nm. RAT does not differ between experimental occasions, between a manual and a semi-automatic method for recognition of OKN, between the sexes and between goggle adaptation and ordinary dark adaptation. There is a reduction of RAT due to repeated flash exposures. The data collected indicate that a well-defined model is crucial for measurements of RAT. The measurement of ERG showed that RAT is mediated by both retinal receptor and the neural activities. The receptor component depends on the wavelength of the flash while the neural component is wavelength-independent. Moreover, it was found that motion perception and OKN gain does not differ between right and left target directions. For a given target velocity, motion perception and OKN gain under both binocular and monocular viewing conditions increase with increasing luminance of the target with an exponential decay. The maximum OKN gain decreases as target velocity increases.(ABSTRACT TRUNCATED AT 400 WORDS)

Adaptation, Ocular↗
PubMed2003

Textural properties corresponding to visual perception based on the correlation mechanism in the visual system.

We present a set of texture parameters that correspond to perceptual properties of visual texture. For machine vision or a computer interface, it is important that the computational measurements of texture correspond well to the perceptual properties. To understand the mechanism of our visual system, it is important to know how we extract or characterize information for texture perception. In this study, we show that the autocorrelation function (ACF) analysis provides useful measures for representing three salient perceptual properties of texture: contrast, coarseness, and regularity. The validity of the ACF analysis was examined by comparing the calculated factors to the subjective scores collected for various kinds of natural textures. The effectiveness of the analysis depends on the structure of the estimated ACF. When a texture has a harmonic structure, the estimated ACF has periodical peaks corresponding to the periods of the texture. Both perceived coarseness and regularity are strongly related to these peaks in the ACF. However, the estimated ACF does not have a periodical structure when the texture is random. In this case, the texture coarseness and regularity are represented by the decay rate of the ACF.

Adult↗
PubMed2005

Comparison of fMRI activation as measured with gradient- and spin-echo EPI during visual perception.

In this study, we compared fMRI activation measured with gradient- and spin-echo-based fMRI during visual perception of faces, which is mediated by neural activation within a distributed cortical network. With both fMRI techniques, bilateral activation was observed in multiple regions including the inferior occipital gyrus, fusiform gyrus, superior temporal sulcus, amygdala, inferior frontal gyrus, and orbitofrontal cortex. When compared with the gradient-echo sequence, activation measured with the spin-echo sequence was significantly reduced. This decrease was manifested by smaller cluster size, lower statistical significance, smaller amplitude of the fMRI signal, and smaller number of subjects who showed activation in all face-responsive regions. In orbitofrontal cortex, a region prone to susceptibility-related signal dephasing, the spin-echo acquisition considerably restored the signal, but did not reveal stronger activation when compared with the gradient-echo acquisition. Our data indicate that optimized GE sequences that reduce susceptibility artefacts are sufficient to detect activation in regions such as the orbitofrontal cortex.

Adult↗
PubMed2006

Microsaccades: A microcosm for research on oculomotor control, attention, and visual perception.

Miniature eye movements occur involuntarily during visual fixation. The most prominent contribution to these fixational eye movements is generated by microsaccades, which are rapid small-amplitude saccades with a rate of about one per second. Recent work demonstrates that microsaccades are optimized to counteract perceptual fading during perception of a stationary scene. Furthermore, microsaccades are modulated by visual attention and turned out to generate rich spatio-temporal dynamics. We conclude that the investigation of microsaccades will evolve into a new research field contributing to many facets of oculomotor control, visual perception, and the allocation of attention.

Animals↗
PubMedDate not supplied

[Evaluation of time parameters of visual perception in the diagnosis of retrobulbar neuritis].

The suggested complex of the perimetric and electrophysiologic methods for the assessment of the function of the visual analyzer has helped detect diffuse involvement of the ocular system in clinically unilateral retrobulbar neuritis and define the incidence rate of involvement of the contralateral normal optic nerve. Prolongation of the latency of visual perception appears to be characteristic of retrobulbar neuritis and indicates the demyelinization of the nerve visual fibers.

Adult↗
PubMed1989

How and what do autistic children see? Emotional, perceptive and social peculiarities reflected in more recent examinations of the visual perception and the process of observation in autistic children.

Autistic symptoms become apparent at the earliest during the 2nd-3rd month of life when the spontaneous registration of the meaning of specific-visual stimuli (eyes, configuration of the mother's face) do not occur and also learning experiences by reason of mimic and gestures repeatedly shown by the interaction partner can neither evoke a social smile nor stimulate anticipational behaviour. Even with increasing age an empathetic perception of feelings in the corresponding mimical gesticular formation is very difficult and they themselves are only insufficiently able to express their own feelings intelligibly to everyone. As mimic and gestures are, however, visually perceived, the autistic perceptive child's competence is of great importance. On the basis of the examinations of visual perception (retinal pathology, tunnel vision) perceptual processing (recognition of feelings, sex and age) and the disintegration of multimodal stimuli it can be presumed that social and emotional deficits are to be seen in connection with a deviant perceptive interpretation of the world and irregular processing on the basis of a neuro-biological handicap (the absence of a genetic determined reference-system for emotionally significant stimuli), which can have various causes (comp. Gillberg 1988) and also impede the adequate expression of feelings in mimic, gestures and voice. Autistic people see, experience and understand the world in a specific way in which and by which they differ from non-handicapped people.(ABSTRACT TRUNCATED AT 250 WORDS)

Affective Symptoms↗