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Biomedical subjects

N N Verderevskaia

Publications and source records attributed to N N Verderevskaia.

8 recordsLinked to original sources
PubMed1983

[Differences in the dynamics of the visual receptive field and its summation zones in the cat].

In acute computer-controlled experiments on immobilized unanasthetized cats, dynamic reorganization of the recorded receptive field and its summation zone were compared for lateral geniculate body and cortical neurons. Counterphasic development of these processes was observed and investigated in detail, i.e. enlargement and then narrowing of the recorded receptive field as compared with narrowing and then enlargement of the summation zone. Differences of physiological mechanisms of these two processes and their possible functional role are discussed.

Animals↗
PubMed1982

[Dynamics of the receptive fields of visual cortex and lateral geniculate body neurons in the cat].

The dynamics of receptive fields of the visual cortex and lateral geniculate neurons were investigated in acute experiments on unanesthetized immobilized cats. For this purpose a computer presented small local flashes in a random order to 100 points of the receptive field and changes in three-dimensional relief of activity within the field were evaluated every 20 ms. Regular dynamic reorganizations of registered receptive fields of all investigated neurons were observed both after switching on and off the light stimulus. After the latency a small region of weak responses appeared in the centre of field. Later on the recorded field enlarged gradually, reaching maximal size at 60-100 ms, and after that began to narrow and disappeared or fell to pieces. The central inhibitory zone of the field had the same dynamics. If the neuron responded to stimulation by generating two bursts of spikes, during the second one the receptive field changed in the same way. The effect was revealed under various conditions of light stimulation. Functional significance of these effects for orientational information coding by visual cortex neurons is discussed.

Adaptation, Physiological↗
PubMedDate not supplied

[Relationship between level of vigilance and changes in the receptive fields of the cat visual cortex].

The activity of 118 neurones of the primary visual cortex (17th field) was studied in unanesthetized cats, immobilized with d-tubocurarine, in a state of calm wakefulness and in strained attention, alarm. The strained attention was elicited by an air-puff directed to the corner of the closed eye, not used for the photic stimulation. Considerable rearrangments of the receptive field of neurones (94%) were observed in the state of strained attention. In the majority of the studied cortical cells (75%) during 10-30 minutes the excitatory centres of their receptive fields became narrower while their inhibitory periphery widened; in the cells with the inhibitory centres of the receptive fields they were larger in 80% of the cases. It is shown that with dark, mesopic and scotopic adaptation the major characteristics of the changes in the receptive fields remain unaltered. It is assumed that these effects have a behavioural value for the organism, because the created rise in the level of alertness is accompanied by a sharpening of the receptive fields, i.e. by a greater ability to a fine analysis and recognition of visual images.

Adaptation, Physiological↗
PubMedDate not supplied

[Formation and functional significance of the dark receptive fields of the cat visual cortex].

Receptive fields (RFs) of single units in the 17th field of the visual cortex of immobilized cat were investigated under dark adaptation. The mean RF size was equal to 67 degrees and varied from 3 degrees up to 120 degrees. The RFs with centres located near gaze were from 3 degrees up to 120 degrees in dia, but with growth of excentricity the number of small RFs decreased, and in the region of 70 to 100 degrees from gaze only RFs with diameters equal to 100 degrees were found. The shape of "dark" RFs was either ellipsoidal (in most cases) or round. Detector properties (orientational, directional, size and velocity selectivity) of the "dark" RFs were significantly less manifest or absent. Under photopic light adaptation the same units reorganized their RFs to well known sizes and configuration. The hypothesis is discussed of the formation of local detector RF in the visual cortex in light adaptation by selective cortical inhibition which is activated in darkness only slightly. This view is an alternative to the commonly-accepted scheme of local cortical RF formation by the hierarchical and selective excitatory convergence.

Animals↗
PubMedDate not supplied

[Reorganization of changes in the receptive fields of cat visual cortex neurons during light anesthesia].

The activity of 127 neurones of the primary visual cortex (17th field) was recorded in unanaesthetized cats immobilized with d-tubocurarine, during calm alertness and during short sleep caused by intravenous administration of 5% water solution of sombrevine in a dose of 1.5 mg/kg. In all of the studied cells, considerable rearrangements in sizes and in form of the receptive fields (RF) were recorded. The studied neurones with excitatory RF centres formed two main groups. The first one comprised 52% of cells; the central excitatory zone of their RF became considerably wider due to administration of sombrevine. In the second group (48%), the drug produced a significant reduction of RF. Neurones with an inhibitory RF centre exhibited a different relation of RF changes: the RFs became larger in 68% and narrower in 32% of the studied cells. Cortical and reticular mechanisms are discussed of the observed rearrangements in the RFs of visual cortical neurones under the action of sombrevine--a general anaesthetic, provoking a short-term decrease in the brain functional state.

Anesthesia, General↗