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At least 19 recordsLinked to original sources
PubMed1978

Analysis of the Development Test of Visual Perception and the Motor-Free Visual Perception Test.

To identify children with learning problems and to compare test results, 28 kindergarten children were tested with the Developmental Test of Visual Perception and the Motor-free Visual Perception Test. The tests identified some children already noted by the teacher to exhibit characteristics of learning difficulty, failed to confirm the teacher's judment in others, and identified some children with previously undetected difficulties. Basic differences in the two tests are reported.

Child↗
PubMed1976

Delayed visual perception and delayed visual evoked potentials in the spinal form of multiple sclerosis and in retrobulbar neuritis.

(1) We have used both subjective and evoked potential tests to study cases of multiple sclerosis with no history of retrobulbar neuritis (spinal patients) and compared them with patients with multiple sclerosis who had experienced an attack of retrobulbar neuritis (RBN). We measured the delay of steady-state evoked potentials (EPs) elicited by flicker in the medium-frequency (13-25 c/s) range, by flicker in the high-frequency (30-60 c/s) range, and by pattern-reversal. We also measured the delay in seeing (perceiving) both an increase of light intensity and a decrease of light intensity. (2) The difference between perceptual delays for the left and right eyes (D s) was abnormal when retrobulbar neuritis affected only one eye (22/22 patients) even when acuity and discs were normal. It might be supposed that this perceptual test would be ineffective when both eyes were affected by retrobulbar neuritis. However, the value of D was abnormal in cases of bilateral retrobulbar neuritis (5/5 patients). Probably the principal reason is that demyelination was patchy in the patients studied. For this same reason the difference between perceptual delays for two sites in the visual field (T s) may also be abnormal. In principle the perceptual delay test can be effective even when both eyes are similarly delayed: abnormal values of T were recorded in 5 spinal patients for whom D was normal. (3) Perceptual delays were measured for an extended group of 19 patients suffering from spinal multiple sclerosis. Taking both D and T into account, the perceptual delay test alone picked out 12/19 spinal patients. The perceptual delay test has the advantage over EP tests that it can detect islands of demyelination as small as 3 degrees diameter, and the apparatus is cheap and straightforward to use. (4) Thirteen patients with spinal multiple sclerosis, including 6 with no ocular signs or symptoms, were examined with a battery of two evoked potential and one perceptual test. Ten patients had clearly abnormal visual delays. Results for the remaining 3 were equivocal. Delay tests can reveal visual damage in most patients who have not experienced an attack of RBN as well as in practically all patients who have experienced an attack. (5) Correlations between the results of the various tests were different in spinal patients and in multiple sclerosis patients who had experienced an attack of retrobulbar neuritis. Flicker EPs, pattern EPs and visual perception were all delayed in every RBN patient, whereas for spinal patients different tests could pick up different patients. Flicker EPs picked up 5/13 spinal patients, pattern EPs 6/13, perceptual delay (D) picked up 4/13 and perceptual delay T picked up 7/13. (6) Delay tests divided spinal multiple sclerosis patients into two fairly distinct groups. In one group pattern EPs and perception were delayed; in the other group flicker EPs were delayed. This grouping corresponded to a clinical distinction between long-standing patients with visual signs and recent patients without visual signs...

Adult↗
PubMed1976

Physiological aspects of visual perception. I. Functional aspects of visual cortex.

The first part of the Bennett Lecture for 1975 is a description of the dissociation of visual perception in the macaque monkey by ablation of area 17 on the one hand, and of areas 18 and 19 on the other. Bilateral removal of area 17, with careful preservation of a great part of areas 18 and 19, and of the inferior pulvinar, resulted in loss of binocular fixation, loss of visual recognition of still objects, and loss of visuosocial behavior such as grimacing and vocalization. There remained excellent visuospatial orientation and reaching for moving peripheral visual targets. Removal of areas 18 and 19, with isolation of area 17 from the remainder of cortex, was accomplished in two animals and left intact the ability to distinguish and sort out still objects by vision, with intact fixation, and visuosocial behavior. Spatial orientation was then easily confused by movement.

Animals↗
PubMed1976

Physiological aspects of visual perception. II. The subcortical visual direction of behavior.

The second part of the Bennett Lecture for 1975 by Denny-Brown examined the subcortical representation of the dissociation of function described by Denny-Brown and Chambers. Complete removal in the macaque monkey of the corticomesencephalic fibers where they pass from pulvinar to colliculus, and of the colliculus, resulted in the same loss of visual object identification, binocular fixation, and visuosocial behavior that followed removal of area 17. Vision for peripheral movement and spatial orientation ("panoramic vision") remained excellent, with release of catatonia. Conversely, unilateral electrolytic lesions of the mesencephalic tegmentum produced visuospatial distortion, asymmetry of optic righting, and directional difficulties in eye movement (Parinaud syndrome and skew deviation). When bilateral, tegmental lesions produced great constriction of visual field with release of convergence and fixation spasm. Suppression of peripheral attention resulted from perceptual rivalry.

Animals↗
PubMed1977

Lateral asymmetries in visual perception: a review of tachistoscopic visual half-field studies.

Experiments using the visual half-field paradigm are reviewed with special reference to the three theories which purport to account for perceptual asymmetries: the left-to-right internal scanning mechanism theory, the direct anatomical access theory, and the attentional bias theory. Recent evidence has clearly shown that the direct anatomical access theory can account for virtually all lateral asymmetries in the perception of verbal and spatial stimuli. The results of the studies reviewed strongly support a model of brain function which suggests that the simultaneous processing of verbal and spatial stimuli does not constrict the attention of either hemisphere. The difficulty in separating the factors of hemispheric processing and stimulus characteristics is discussed. It is suggested that a reliable conclusion about the role of the cerebral hemispheres can only be made when a better description of the operating characteristics of the hemispheres is available.

Attention↗
PubMed1977

The development of knowledge about visual perception.

This chapter describes recent theory and research in one limited area of social-cognitive development, namely, the childhood acquisition of knowledge about visual perception. The author and his co-workers have hypothesized that there are two developmental levels of such knowledge. At earlier-developing Level 1, the child understands that others as well as the self see objects, and is also able to infer correctly what objects they do or do not currently see if provided with adequate cues. At later-developing Level 2, the child understands not only that people can see objects, but also that they can have differing visual experiences while seeing the same object; most notably, they can have different spatial perspectival views of it when looking at it from different positions. Arguments and evidence for the developmental distinction between Level 1 and Level 2 knowledge are briefly presented in Section I. A more detailed model of Level 1 knowledge is presented in Section II, together with an account of several studies of its development during the first four years of life. During these early years, children appear to learn a great deal about how to produce visual percepts in others (showing and pointing to things), how to deprive others of percepts (hide objects), and how to diagnose the percepts they currently have (follow others' direction of gaze and pointing gestures). Section III similarly reviews recent theory and research on the development of Level 2 perspective-taking knowledge in older children. This work is focused mainly on the acquisition and use of very general perspective-taking rules, such as the rule that two observers who look at an object array from the same spatial position must on that account necessarily have identical perspectival views of the array. Section IV described further developmental research that could be or is being done on Level 2 knowledge, Level 1 knowledge, and on the Level 1-Level 2 distinction.

Age Factors↗
PubMed1979

An examination of relationship between subliminal perception, visual information processing, levels of processing, and hemispheric asymmetries.

A sublimiinal letter was exposed to the left or right hemisphere for either 15 or 30 msec. Subjective guesses were more accurate for visuo-spatial positional recognition made to presentations in the right hemisphere whereas verbal recognition was more accurate to presentations in the left hemisphere. The 30-msec. exposure increased the accuracy of the guesses. These findings were discussed in terms of differential triggering mechanisms for levels of hemispheric processing.

Adult↗
PubMed1979

The effects of age upon the visual perception of speech.

A sample of 110 middle-aged and geriatric subjects (40 to 87 years) with normal hearing and vision was drawn from the general population in order to compare visual performance for consonant-vowel (CV) syllables and sentences. Results of this investigation revealed that, above 70, age was a factor affecting visual perception of syllables. Individuals above age 70 received the poorest speechreading scores and were inconsistent in viseme categorization. Results of a comparison of speechreading scores for sentences and syllables revealed a greater number of differences among sentences. Only individuals between 40 and 60 years of age received statistically similar mean scores when presented with common sentences. Finally, using a linear regression model, it was found that sentence speechreading performance could be accurately predicted from the CV syllable score within a range of accuracy of +/- 9.7%.

Adult↗
PubMedDate not supplied

Mechanism of visual perception of movement.

We here present a logical mathematical model for the visual perception of movement in man; it is based on the treatment of signals in the retina in relation to time and distance and on the statistical theory of the separation of signal from noise in the visual system. It shows good agreement with experimental results and has made it possible to determine the comparative level of internal noise of the visual system, the mean rate of spread of excitation from the photoreceptors along the surface of the retina, and many other characteristics.

Adaptation, Physiological↗
PubMed1992

Solving the "real" mysteries of visual perception: the world as an outside memory.

Visual science is currently a highly active domain, with much progress being made in fields such as colour vision, stereo vision, perception of brightness and contrast, visual illusions, etc. But the "real" mystery of visual perception remains comparatively unfathomed, or at least relegated to philosophical status: Why it is that we can see so well with what is apparently such a badly constructed visual apparatus? In this paper I will discuss several defects of vision and the classical theories of how they are overcome. I will criticize these theories and suggest an alternative approach, in which the outside world is considered as a kind of external memory store which can be accessed instantaneously by casting one's eyes (or one's attention) to some location. The feeling of the presence and extreme richness of the visual world is, under this view, a kind of illusion, created by the immediate availability of the information in this external store.

Attention↗
PubMed1978

[Piecewise Fourier analysis of images and the role of the occipital, temporal and parietal cortex in visual perception].

On the basis of previously published data, a neuronal scheme of organization of the visual perception in the cerebral cortex, is suggested. An idea of neuronal module is introduced: a cylinder of cortical neurons whose receptive fields are directed towards the same area of the visual field and respond to different spatial frequencies and orientations. A system of overlapping modules is able of piece--wise Fourier--description of portions of the image. The modules of the Clare--Bishop area are composed of receptive fields of different size. Owing to that each neuron of the module projects inhibitory influence upon other neurons, the module acts as a filter picking out the texture. Therefore, the modules of the Clare--Bishop area single out and supply Fourier--description of subimages, the latters being characterized by the same local spectrum within their own limits. The lower portiön of temporal cortex performs a rough identification of subimages and images with the aid of systems of learning neurons. The parietal cortex conforms the description from temporal cortex to the complete description in the modules of occipital cortex, thus performing the transition from an image to a concrete picture.

Animals↗
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↗