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PubMed1984

Color perception under contralateral and binocularly fused chromatic adaption.

Observers viewed a thin (1.0-1.5 degree) annular mixture of 450 plus 660 nm light with the left eye, and a 4.8 degrees circular 660 nm adapting field with the right eye. The annular test was centered upon the adapting field in the fused percept. The contralateral field, which bleached negligible photopigment, caused the test to appear more reddish; however quantitative results reject the hypothesis that a given contralateral 660 nm light simply adds redness to the test. Additional experiments with a separate 660 nm adapting light presented to each eye reveal that fused chromatic adapting fields affect a complex central mechanism. For example, a dim background presented to the same eye as the annular test can reduce the effect of an opposite-eye field, even when the dim test-eye background has no measurable influence in a purely monocular experiment.

Adaptation, Ocular↗
PubMedDate not supplied

[The spherical theory of color perception: its verification by the methods of psychophysics and neurophysiology].

In the paper data of experimental verification of "spherical theory of perception" (E. N. Sokolov) are summed on the material of colour perception study. The results of psychophysical experiments with subjects having different forms of colour perception (normal trichromats, colour anomalies) and neurophysiological experiments on animals (carp) are considered within single psychophysiological system--spherical model of colour discrimination. Neuron-like elements of the model reflect the activity of light-sensitive cells of the visual system and at the same time reproduce some rules of subjective colours discrimination at the psychophysical level. Advantages of spherical model are considered allowing to analyze human individual colour functions in norm and pathology and giving the opportunity of strictly quantitative approach to description of neuronal mechanisms of colour vision. From the position of spherical model of colour discrimination neuronal structure of colour analyzer is discussed, which includes layers of photoreceptors, ++predetectors (colour-opponent and achromatic cells) and colour-selective detectors.

Animals↗
PubMed1992

The dermo-optical perception of color as an information source for blind travelers.

Dermo-optical color perception refers to a person's ability to distinguish color surfaces through "skin perception" without the use of sight. The aims of this study were (1) to assess prior research findings which apparently demonstrated the existence of dermo-optical color perception and (2) to explore the possibilities of using color to indicate reference points for blind travellers. Three experiments were conducted with 20 congenitally blind subjects and a sighted blindfolded control group matched on age, sex, and education. In Exp. 1 on a discrimination task subjects were asked if two boards were of the same color and on a pairing task were asked to match a colored board with one among a set of three boards having the same color. In Exp. 2 the discrimination task was identical to that in Exp. 1, but instead of using boards perceived through haptic exploration, we used colored cubicles in which the whole body would be exposed to the color. In Exp. 3 subjects were asked to walk along the corridor of a labyrinthine set-up and to identify any changes of color they could perceive. The experiments were designed to provide measures of reliability of subjects' responses. Analysis showed little or no support for the ability to perceive color by dermo-optical means. The comparisons of the blind and the sighted control groups were nonsignificant. On the basis of our findings, the use of color to help blind travellers has to be rejected. The paper concludes with a discussion suggesting reasons for the contradictory results emerging from studies on dermo-optical color perception.

Adolescent↗
PubMed1989

Influence of achromatic surrounds on categorical perception of surface colors.

Color samples selected from the OSA Uniform Color Scales set were seen isolated in a dark field, illuminated by hidden projectors. These appeared as self-luminous aperture colors when thus isolated. We employed a categorical color-naming procedure to assess color appearance. Achromatic surrounds of 33 min width, if adjacent to samples subtending about 2.2 deg, were sufficient to render normal categorical surface-color perception. As the size of surrounds decreased, color naming shifted from that normally observed in the surface-color mode to that appropriate to the aperture-color mode. For isolated samples, brown was almost never seen, being most often replaced by orange; a white border less than one-sixtieth the width of the color samples was sufficient to restore its perception in an otherwise dark field. The reflectance of the surround and the gap between test and surround stimuli were also examined and found to be important factors in surface color perception, whereas the overall luminance level was not.

Adult↗
PubMedDate not supplied

[Perception of color and volumetric shape of objects].

The problem of recognition of coloration of volume objects, illuminated simultaneously with bright point ans weak diffuse sources (having arbirary and previously unknown spectra) is considered. A mathematical model, in which a process of recognition of coloration is accompanied by determining orientations of surface elements relatively the point source is described. The information on orientation allows in many cases to calculate the volume shape of objects of the external world form their monocular ""retinal"" image.

Color Perception↗
PubMed1992

Cortical area V4 and its role in the perception of color.

The color and lightness vision of three monkeys with bilateral removal of cortical area V4 and three unoperated controls were tested by measuring their ability to discriminate between two rows of colored or gray stimuli. In one row, the stimuli were ordered in terms of either chromaticity or luminance, whereas in the other row they were disordered. Their ability to select the odd-one-out in an array of colors or grays and to select the colored patch from an array of achromatic grays was also assessed. Unlike an achromatopsic patient tested previously in an identical fashion, monkeys with V4 lesions performed indistinguishably from controls in the oddity test. The animals lacking V4 were slightly impaired at discriminating between ordered and disordered arrays of colors or grays, but the color impairment was no more severe than the impairment with grays. These deficits were readily accounted for in terms of the conspicuous deficits in pattern discrimination apparent in a nine-choice pattern oddity task. The results do not support the view that cortical area V4 in the monkey is the homolog of the cortical "color center" in humans, located in the lingual and fusiform gyri and damage to which leads to the clinical syndrome of cerebral achromatopsia, unless it is the additional damage to underlying white matter that leads to the severe color disorder in patients.

Animals↗
PubMed1990

Role of color in perception of attractiveness.

In this color study females reported a favorite color significantly more often than males. Males preferred bright colors significantly more than females, with a converse finding for preference for soft colors. The 276 subjects, when asked to evaluate the attractiveness of stimulus models in photographs, gave as the reason color significantly more often than style of clothing or facial expressions. Subjects significantly concurred with expert choices of recommended and nonrecommended colors in five of the six sets of photographs. This study lends credence that wearing recommended colors makes a difference in judgments of what looks best by subjects over the age of 12.

Adolescent↗
PubMed1985

A central spectrum model for the perception of coloration in filtered Gaussian noise.

In this paper we describe a monaural auditory signal-processing model for the perception of coloration. The model gives a central spectrum display of a stationary input signal. The central spectrum level for a nerve fiber tuned to a given frequency is computed as a combination of the average firing rate and the firing synchronized to the center frequency of the nerve. The model incorporates a critical-band filter bank, steady-state representations of the average and synchronized firing rates, and temporal integration. The central spectrum model, when used to process simulated data, accurately predicts the perception of coloration in filtered Gaussian noise.

Auditory Perception↗
PubMed1984

The effect of glaucoma on central visual function.

Glaucoma has traditionally been thought to affect peripheral visual function in its early stages and to spare central visual function until late in the disease process. The basis for this assumption has been the reliance on Goldmann-type perimetry, a rather sensitive method for assessing the peripheral visual function, and on Snellen-type visual acuity measurements, a rather insensitive method of assessing central visual function. This belief has persisted despite frequent complaints from patients with glaucoma that their central vision is disturbed. Over the past two decades, several investigations of central visual functions and their anatomic substrate have challenged this assumption. Histologic studies of the nerve fiber layer in eyes with glaucoma suggest that the number of ganglion cells subserving macular function is decreased even in early stages of the disease. In addition, afferent pupillary defects (a gross measurement of macular nerve fiber function) may also be present in eyes with early glaucoma. Several studies have demonstrated that color perception (largely mediated by the fovea) is defective in glaucoma. Furthermore, defects in color perception may even precede the development of visual field abnormalities. Seventy-eight percent of patients with early glaucomatous visual field defects were found to have a defect in color perception when tested with a desaturated D-15 color panel that tests only the central 1.5 degrees. In addition, both chromatic and achromatic foveal perception channels are defective in eyes with glaucoma and even in some eyes of those with suspected glaucoma. Contrast sensitivity has become recognized as an important component of visual function. Partial loss of contrast sensitivity may cause a degradation in the quality of perception even though the Snellen visual acuity remains normal. Although contrast sensitivity is not entirely a macular function, it has been shown that as little as 3 degrees of disturbance of the macula (eg, with macular degeneration or with an artificial central scotoma) will reduce the contrast sensitivity, suggesting that this modality is indeed mediated to a significant extent by this portion of the retina. Spatial contrast sensitivity appears to be reduced in patients with glaucoma. However, because of overlap and lack of a sharp cutoff measurement, present testing procedures fail to allow a clear distinction between the glaucomatous and normal populations. Although reduced temporal contrast sensitivity has been demonstrated in glaucomatous eyes by others, I undertook a systematic investigation of this function in a large group of patients with glaucoma and with suspected glaucoma.(ABSTRACT TRUNCATED AT 400 WORDS)

Adolescent↗