PubMed Health⌕ Search

SEARCH · PubMed Health

Results for “Visual Perception”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 37 records · Page 2Linked to original sources
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↗
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↗
PubMed1978

Computer-based testing system for experiments in visual perception.

This paper discusses the increasing scope for the application of computing systems to the investigation of problems in the field of visual perception. A simple language for the generation of various perceptual testing schemes is described and some examples of possible applications are given.

Diagnosis, Computer-Assisted↗
PubMed1977

Impact of oculomotor retraining on the visual perception of curvature.

Observers viewed a computer-generated display consisting of horizontally oriented, concave-up curved lines. The position of these curves was contingent on the horizontal position of the eye so that, in order to change fixation errorlessly, from one point to another on the curve, the eye would have to execute a purely horizontal movement. In Condition H this was achieved by moving the curves horizontally, so that the minimum point was always at the horizontal eye position location, thus simulating the effect of viewing a line through a wedge prism on a contact lens. In Condition V it was achieved by moving the curves vertically so that the point fixated always had the same vertical location. In both conditions eye movements were reprogrammed rapidly to eliminate the vertical components of the saccades that were present at the start. While a small, but significant, amount of perceptual adaptation was obtained in Condition H, none at all was obtained in Condition V. The results are interpreted as not in support of such theories of perceptual adaptation to curvature distortion as require a close relationship between motor learning and perceptual change.

Adaptation, Ocular↗
PubMed1977

Studies on visual perception of locomotion.

The problem about visual discrimination between seeing objects in motion and perception of motion of the perceiver (locomotion) was taken up. A flow of vertical motion was presented to limited areas of the far periphery (45 degrees-90 degrees) of the retina simultaneously with optical information about a stationary room over the rest of the retina. The result was that most subjects perceived themselves as sitting in an elevator continuously moving upward or downward. Thus, peripheral motion stimulation over a few percent of the retinal area determines locomotion perception in apparent competition with information about a static state over the rest of the retina. The same type of stimulus presented to the central part of the retina always brought about perception of object motion and a static perceiver. Effects of size and localization of the area stimulated with the motion flow was studied. Theoretical consequences and problems for further experimental analyses are discussed.

Discrimination, Psychological↗
PubMed1978

Young children's knowledge about visual perception: hiding objects from others.

Children of ages 2 1/2, 3, and 3 1/2 years were tested for their understanding of object hiding, believed to reflect an early developmental level of knowledge about visual perception. Even the youngest subjects could nonegocentrically hide an object by placing it on the opposite side of a screen from another person, even though placing it there necessarily left it unhidden from themselves. In contrast, there was a significant increase with age in the ability to achieve the same physical end state by placing the screen between the other person and the object. Most subjects at each age level correctly indicated that the other person could see the object when the experimenter interposed the screen between the child and the object but that the other person could not see the object when she placed the screen between the other person and the object. These and other recent findings indicate that children of this age can be both nonegocentric and skillful at estimating what other people do and do not see under various viewing conditions.

Age Factors↗
PubMed1991

Selective impairment of memory and visual perception in splenial tumours.

The neuropsychological abnormalities found in 9 patients with tumours involving the splenium of the corpus callosum are described. The outstanding features of their cognitive deficits were a severe memory deficit and visual perception impairment in the presence of relatively intact intellect. It is argued that (1) the amnesia is due to damage to the fornix where that structure is closely applied to the splenium and that it is the result of a disconnection between the frontal and temporal lobes, although the possibility that damage to more than one structure, for example, retrosplenial cortex and fornix, cannot be excluded; (2) there is a dual pathway for visual object recognition, one of which passes directly to the dominant hemisphere for semantic analysis and the other via the nondominant hemisphere for prior perceptual analysis. Further, it is postulated that there is a subcortical as well as a callosal route between the hemispheres that is important for visual object recognition.

Aged↗
PubMed1975

[Social behavior, musicality and visual perception in monogloid children (author's transl)].

Forty-nine mongoloid and 48 non-mongol test persons of equivalent age and intelligence were selected and studied with respect to social behavior, speech disorders (observation of behavior), musicality and visual perception. There were significant differences in favor of the mongols with respect to social adaption. Speech disorders of all kinds occurred significantly more frequently in mongol children; stuttering was significantly more frequent in the boys. The mongol group did significantly better in the musicality test; the difference in the rhythmical part was highly significant. The average differences in the capacity for visual discrimination of colors, geometrical forms and the spatial relationship of geometrical forms were not significant.

Adolescent↗
PubMed1992

[An instrument for projecting visual perception by monofocal and bifocal intraocular lenses].

With the aid of a simple optical system similar to an astronomical telescope, images of spectacle lenses, contact lenses and intraocular lenses can be projected in front of, onto or into the eye. These optical images function like real lenses and enable their performance to be evaluated. In the case of intraocular lenses, visual perception through monofocal or bifocal lenses and teledioptric systems can be reproduced.

Equipment Design↗
PubMed1991

Visual perception of texture in aggressive behavior of Betta splendens.

In order to elucidate the role of texture in fish vision, the agonistic behavior of male Siamese fighting fish (Betta splendens) was tested in a response to models composed by means of image processing techniques. Using the models with the contour shape of a side view of Betta splendens in an aggressive state, the responses were vigorous when there was a fine distribution of brightness and naturalistic color, producing textures like a scale pattern. Reactions became weaker as the brightness and color distribution reverted to more homogeneous levels and the scale pattern disappeared. When the artificial models with the circular contour shape were used, models with the scale pattern evoked more aggressive behaviors than those without it, while the existence of spherical gradation affected the behavior slightly. These results suggest that texture plays an important role in fish visual perception.

Aggression↗
PubMed1977

Effect of gradually increasing carboxyhaemoglobin saturation on visual perception and psychomotor performance of smoking and nonsmoking subjects.

The effect of gradually increasing COHb saturation on human visuoperceptual and psychomotor performance was studied in 22 nonsmokers and 22 smokers. Each subject performed two sessions in randomized order, one during air breathing and the other during CO breathing on two separate days. Testing and COHb saturation measurement were repeated six times during each session. Gas breathing was between the test periods. The increase of COHb saturation up to 12--13 per cent units had no effect (p greater than 0,05) on perceptual speed and accuracy as measured by the Bourdon--Wiersma test. Finger tapping speed was also unaffected. Visual perception measured with critical flicker frequency (CFF) was sensitive to CO. The gradual increase in COHb saturation caused a linear decrease in CFF in the both groups. An increase of one per cent unit in COHb saturation caused significant decrease in CFF (p less than 0.001), when intraindividual changes were taken into account. During acute exposure to CO there was no difference in any test performance between the groups. During air preathing there was no difference in performance although there was a significant difference (p less than 0,001) in the COHb saturation levels. This negative finding might be due to adaptation of smokers to chronic exposure of CO because of smoking.

Adult↗
PubMed1979

Auditory-visual perception of speech with reduced optical clarity.

Optical cues for visual and auditory-visual (A-V) perception of speech were varied by placing a sheet of rough-surfaced Plexiglas between talker and lipreader and systematically changing the distance between Plexiglas and talker. This distorts the optical environment in a way that is analogous to masking or filtering in the acoustic domain. In studies with normal-hearing adults and with hearing-impaired children, speech (words, sentences) was presented live under different degrees of optical distortion, and observers attempted to identify the stimuli. Visual-along (lipreading) scores dropped abruptly to the chance level as Plexiglas distance (blurring) was increased. A-V scores were relatively high for clear conditions but diminished gradually as Plexiglas distance (blurring) was increased. Under extremely poor optical conditions, A-V scores reached a plateau. This represents essentially auditory perception without meaningful optical cues for speech. Results parallel those of previous acoustic studies that compared auditory with A-V perception of speech as a function of S/N ratio or sensation level, demonstrating a reciprocal aspect of optical and acoustic cues for speech perception. Optical distortion seems to have potential as an auditory training technique to shift attention of hearing-impaired observers to non-dominant acoustic cues during A-V perception of speech.

Adolescent↗