PubMed Health⌕ Search

Biomedical subjects

N F Podvigin

Publications and source records attributed to N F Podvigin.

At least 19 recordsLinked to original sources
PubMed2000

[Sensitivity of the cat lateral geniculate body neurons to orientation of the brightness gradient vector].

A new property of visual neurons: their sensitivity to orientation and the vector brightness gradient, was revealed and described. Receptive fields of the lateral geniculate body neurons in the cat have preferred orientation maximum reaction (average mean of orientation sensitivity coefficient--0.55 +/- 0.20). The preferred orientation mainly has a radial or tangential trend in the visual field. Temporal characteristics of the neuronal responses were analysed. A role of inhibition processes in the orientation sensitivity is discussed.

Animals↗
PubMed1995

[A quantitative assessment of the process of the reflection of the spatial-brightness properties of a stimulus by the neuronal structures in the lateral geniculate body of the cat].

Correlation between spatial brightness distribution in the test image and the spatial response distribution was estimated for the cat LGB. The correlation was found to be quite high. The data obtained corroborate the hypothesis by Podvigin and Kuperman of the topological correspondence of isophote structure family to the pattern of activity reflecting the test image.

Animals↗
PubMed1987

[Role of the visual cortex in organizing eye movements induced by local electric stimulation of the lateral geniculate body of the cat].

Eye movements evoked by local electrical stimulation of the dorsal nucleus of the lateral geniculate body were analyzed in cats with extirpated visual cortex and in intact cats. The experiments were performed in alert cats. There were no differences between the obtained spatial characteristics of eye movements evoked by electrical stimulation in experimental and intact cats. These results suggest that visual cortical areas are not the main and necessary links in the chain for signal transmission (evoked by electrical stimulation of lateral geniculate body) from subcortical parts of the direct visual pathway to acting links of the oculomotor system. The possible pathways for transmission of information from the dorsal nucleus of the lateral geniculate body to structures of the oculomotor system are discussed.

Animals↗
PubMed1987

[Types of eye movement patterns induced by electric stimulation of the lateral geniculate body of the cat].

Three types of eye movement patterns evoked by electrical stimulation of the lateral geniculate nucleus were distinguished in cats. The first type is characterized by parallel eye movements. The second type is formed by goal-direction eye movements, while the third one--by centering saccades. Obtained results are compared with data received by electrical stimulation of superior colliculus and their possible physiological significance is discussed.

Animals↗
PubMed1985

[Relation between the spatial characteristics of the receptive fields of the superior colliculi of the cat and the rate of movement of a photic stimulus].

The receptive fields of visual cells in superficial and intermediate layers of the cat superior colliculus were investigated: their boundaries, size, shape, dependence on the velocity of stimulus. The size of the excitatory zone decreased whereas the firing rate of the cells increased when the velocity 3 +/- 180 degrees.S-1 was changed. That was typical of both directionally and non-directionally selective cells. The mechanism of directional selectivity is discussed.

Animals↗
PubMed1984

[Directional selectivity of the neurons of the superior colliculi in the cat: the effect of the rate of movement of a stimulus].

Responses to stimuli moving with velocities of 3-180 degrees X sec-1 were studied in each of four axes (eight directions) separated by 45 degrees in neurons of the cat superior colliculus. 69% of units were directionally selective. In 55% of all the neurons the directional selectivity depended on stimulus velocity and was the largest for high velocities (over 10-30 degrees X sec-1). The preferred direction for some neurons was reversed with velocity increasing. The directional selectivity-velocity relationships were compared for the cat superior colliculus and visual cortex and discussed in regard to probable role of this phenomenon in the oculomotor system.

Animals↗
PubMed1983

Multiunit activity of the cat lateral geniculate neurons evoked by moving light pattern of variable intensity.

The activity of groups of 2-5 cells with overlapping receptive fields (RFs) was recorded by one single electrode from the lateral geniculate nucleus. The histograms of responses to a moving complex stripe- pattern were qualitatively compared with the stimulus intensity change measured within the center of the RFs. We suggest that the intensity of the stimulus is matched by the integrated activity of several functionally related units.

Animals↗
PubMed1983

[Responses of neurons of the lateral geniculate body in the cat to moving photic stimuli of graded intensity].

The stimuli consisted of 8 steps-stripes with stepwise changing intensity (I). The magnitude of one step (delta I) was 0.5 lg un. under the condition: delta I/I = Const. The value of neuronal responses to stripes of stepwise increasing intensity moving across the neurons' receptive fields did not change within a wide range of intensities provided the speed of moving was slow (up to 15-20 degrees/sec), but it augmented with an increasing intensity if the speed was 20-60 degrees/sec. In further increase of the speed the responses occurred in some cells within a narrow range of I values. These characteristics of the responses were also regarded in changes of the total light intensity of a stimulus within the range 3 lg un. Both on-responses of on-central neurons and off-responses of off-central neurons were analysed. The data obtained revealed that neuronal responses to moving stimuli with stepwise changing intensity depended qualitatively on the light intensity as much as the responses to stationary stimuli of different brightness, i.e. the value of responses to changes of the light intensity of a moving stimulus followed the Weber-Fechner law.

Animals↗
PubMed1981

[Transmission of information concerning image brightness by neurons of the lateral geniculate body in the cat].

The response of the LGB neurons to moving stimuli consisting of 8 bars with stepwise increasing luminousness (by 0.47 lg units) revealed threshold intensities varying from neuron to neuron by 1.5--2.0 lg units. Frequency of the on- and off-central neurons activity depended on stimuli luminousness. Both on- and off-neurons increased their firing rate on increase of the stimuli luminousness. The probable mechanism of information transmission of the luminousness change (with constant contrast) and its place in the hypothesis of the point-to-point image description at the subcortical level of the visual system, are discussed.

Adaptation, Physiological↗