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A Bertulis

Publications and source records attributed to A Bertulis.

5 recordsLinked to original sources
PubMed1984

Colour-spatial vision.

A critical survey is made of neurophysiological and psychophysiological investigations of colour vision. A neuronal model of colour-spatial vision is suggested. The model allows a unified explanation of the whole range of psychophysiological phenomena: the mixing of colours of high-frequency image components, the McCollough type colour after-effects, the simultaneous and successive colour contrast, the hue constancy perception, the appearance of non-spectral colours by mixing of monochromatic lights. A suggestion is made as to the existence of two main mechanisms of colour vision. The first of these, by means of Fourier transforms, gives a set of coefficients which describes the spatial distribution of light (quantity of energy) and hue (quality of energy) in the visual field. The second mechanism establishes colour names in each chromatically homogenous area of the field described by the first mechanism. Both mechanisms cooperate on the basis of their common spatial organization.

Color Perception↗
PubMed1977

Spectral and orientation specificity of single cells in foveal striate cortex of the vervet monkey, Cercopithecus aethiops.

1. The spectral sensitivity, orientation specificity and inhibitory surround of seventy-three cells were studied in the vervet monkey. The eye was in the dark or illuminated with steady white or spectral light. The cells were in the striate cortex corresponding to the foveal representation. Nearly all the cells gave on- or on/off-responses.2. More than a third of the cells (41%) responded over a narrow spectral band, in the blue, green, yellow or red section. Three quarters of them were orientation specific with flanking inhibitory surround and half of these were of the ;stopped-end' variety as well. The effect of the wave-length of the background indicated that only a half were activated by such excitatory-inhibitory colour pairs as have been described in the geniculate nucleus.3. A third of the cells (36%) responded to most colours but with the greatest response to green, yellow or red. Less than half were orientation specific. Unlike the narrowband cells, the response decreased with the intensity of the light. Two thirds were activated by the excitatory-inhibitory colour pairs that have been described in the geniculate nucleus.4. In both groups of cells the wave-length of the spectral peak could be different when the stimuli were weak compared with when they were strong.5. One quarter of the cells (23%) gave on/off-responses to all spectral flashes; half were not orientation specific. The difference in orientation specificity between narrow- and broadband cells is significant (P < 0.01).

Action Potentials↗