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Biomedical subjects

E V Polkoshnikov

Publications and source records attributed to E V Polkoshnikov.

At least 19 recordsLinked to original sources
PubMed1988

[Functional characteristics of the orientation-selective neurons in the frontal visual field of the striate cortex in the baronduki].

The extracellular activity of 150 neurons (field 17) from binocular region of the visual cortex in the Siberian chipmunk was investigated. 65% of neurons proved to be selective to orientation and selective (but differently) to the direction of movements of the contrast boundaries and light. 18% of neurons were nonselective to the orientation and direction of the stimulus movement. 17% of neurons were activated only with the total illumination of the receptive field. Out of 39 orientation-selective neurons investigated by the moving and stationary stimuli 16 neurons reacted only to the moving stimuli: 13 neurons responded to exposure to stationary bars with prolonged tonic activation, 7 neurons showed a short phasic response and 3 neurons--a phasically-tonic response. All the phasic neurons were a maximally activated at higher movement velocities compared with the tonic neurons. The possible analogy between fast-phasic and slow-tonic neurons and Y- and X-systems is discussed.

Animals↗
PubMed1988

[The chromatic characteristics of neuronal receptor fields in the visual cortex of the baronduki].

39 orientation-selective neurons and 25 neurons responding to total illumination of the receptive field were investigated by exposing to achromatic and chromatic stimuli. Switching on and off of the bar stationary stimuli has revealed that orientation-selective neurons were not chromatically opponent. But when they were tested by moving chromatic bars, pronounced maximum responses were found either to green (520-540 nm) or to blue (449-458 nm) colours. 7 neurons of 39 were either not activated by exposure to achromatic stimuli of any brightness or were slightly activated. Among 25 neurons responding to total illumination of receptive field, 5 neurons were chromatically opponent. They responded by prolonged tonic activation to the switching on of the green and switching off of the blue stimuli.

Animals↗
PubMed1985

[Color properties of the receptive fields of visual cortex neurons in the squirrel].

The colour-sensitive properties of the visual cortex neurons were studied in the squirrel. All the neurons responded to achromatic, green and blue visual stimuli; responses to red stimuli were slight or absent. According to responses to patterned visual stimuli the neurons were classified as non-selective, directionally-selective and orientation-selective (simple and complex). No colour-opponent properties were revealed in any of these neuronal groups: neuronal responses were qualitatively the same to achromatic, green and blue stimuli, and the receptive fields organization was independent of the stimulus colour. These data are discussed with respect to the fact of presence of colour-opponent cells in the retina and lateral geniculate nucleus of squirrel.

Animals↗
PubMed1984

[Detector neurons of the visual cortex of the chipmunk].

Three functional classes of neurons are described in the Siberian chipmunk visual cortex: neurons nonselective to movement direction, movement-direction-selective neurons and orientation-selective neurons. Nonselective and direction-selective neurons showed maximum adaptiveness at high speeds of movement: 100-500 degrees/s and more. Most of orientation-selective neurons were maximally activated at speeds 10-50 degrees/s. For all neuronal classes a clear-cut correlation between selectivity and movement speed as well as pattern of responses to stationary stimuli in the receptive field were found. The data obtained allowed a division of the neurons into two groups: phasically-fast and tonically-slow with predominance of the first group.

Animals↗
PubMed1981

[Functional characteristics of visual cortex neurons in the squirrel].

The main functional classes of neurons in the squirrel visual cortex are described. The following classes were revealed on the basis of the receptive field organization and the pattern of response to visual stimuli: direction-non-selective neurons (14%), direction-selective neurons (30%), orientation-selective neurons (49%); 7% of neurons were unclassified. Direction-selective neurons and some non-selective ones were specifically sensitive to high speed of the stimulus movement (hundreds deg/s). Orientation-selective neurons differed in the degree of on- and off-zones overlapping; they may include analogues of simple and complex neurons.

Animals↗
PubMed1979

[Squirrel visual cortex neurons selective for contour orientation].

The receptive field organization of orientation-selective neurons was studied in the squirrel visual cortex. Neurons with mutual inhibiting on- and off-areas of the receptive field, partially and completely overlapping excitatory and inhibitory mechanisms were observed. Neurons of the second group are the most typical. They reveal orientation selectivity if the stimuli are in the excitatory area of the receptive field, the inhibitory areas outside the excitatory area sharpen the selectivity. It is supposed that no obvious differentiation between simple and complex neurons exist in the squirrel visual cortex.

Animals↗
PubMed1975

Light-sound interaction in the neurons of the rabbit's visual cortex.

One hundred cells of the visual cortex were studied using flashes, clicks and light-sound combinations with different delays. Forty nine neurons changed the total number of spikes to click stimulation. Twenty eight cells responded to clicks with specific response pattern. In 23 cells the initial discharge occurred at 60-70 ms after the onset of clicks. In 39 cells the responses to light-sound combinations differed from the responses to flashes. While 16 cells decreased their responses, the addition of sound increased firing in 23 cells. The specific modification of the light-evoked responses under acoustic stimulation were classified into three main categories: 22 cells generated new response patterns, 18 cells showed a re-distribution of peaks in the PTS histogram and three cells demonstrated a desynchronization of the spike discharge. The study of the heteromodal recovery cycle revealed that the majority of the cells increased their firing during 0-100 ms and decreased firing during 200-300 ms of the response time scale. The critical delays between light and sound, resulting in the modification of the response for the majority of the cells, were within 100 ms in both directions.

Acoustic Stimulation↗
PubMedDate not supplied

[Responses of nervous elements of the visual cortex of the chipmunk Eutamias sibiricus to moving and stationary stimuli].

The receptive field organization of cortical units has been studied in experiments with testing by moving and stationary light spots. The size of the receptive fields varied from 3 degrees to 10 degrees. Receptive fields which were tested by a stationary light spot exhibited various types of organization. Some of the neurons produced extensive excitatory on- and off-responses to stimulation by a light spot. Neuronal excitation evoked by light decreased if the stimulus was near the field boundary. Some of the neurons produced either on- or off-responses in any point of the receptive field. A small part of neurons had receptive fields with on- and off-reactions in the center, and either on- or off-responses at the peripheral zones. Most of the neurons exhibited specialization with respect to high-speed motion.

Animals↗