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Biomedical subjects

S A Chebkasov

Publications and source records attributed to S A Chebkasov.

At least 19 recordsLinked to original sources
PubMed1984

[Arrangement and afferent connections of the neurons in the visual cortex differing in the size of the receptive fields].

In the area 17 of the cerebral cortex of guinea pigs cells with small and medial receptive fields (RF) are concentrated at the sites of separate groupings of neurons excited by flashes of diffusion light. There are also cells with large RF here. At such sites of the cortex when specific afferents are electrically stimulated many cells exhibit monosynaptic activation irrespective of their RF size. The main part of the neurons with large RF is situated in the areas of the cortex between the excited grouping and monosynaptical excitation is not inherent in such neurons. Most cells of these areas are not excited by specific afferents.

Afferent Pathways↗
PubMed1983

[Changes in the spatial distribution of the neuronal activity in the visual cortex after stimulation with flashes of diffuse light].

At different stages of development of the response to flash, grouping of excited neurons of the guinea pig 17th area occurs within the same cortical microzones separated by narrow inhibition zones common to the neighbouring excited ones. The ensembles of excited neurons have the form of columns narrowing into depth. The grouping of cells into a silent gap indicates the grouping of inhibiting neurons. Three subgroups are differentiated by the character of averaged dynamics of impulse activity in ensembles, the essential moment of their interrelationship being the reciprocity. The one subgroup in deep layers is characterized by stability of the focus at different stages of the response development and seems to express the grouping of corticofugal neurons. The ensembles are considered to be one of the forms of activity of the structured morphofunctional cortical units, i.e. the columns.

Animals↗
PubMed1977

[Spatial-temporal structure of the primary evoked activity of visual cortex neurons].

The unit activity displayed a mosiac position of the activated neuronal ensembles with asymmetrically inhibited adjacent areas development of primary response. The average distance between the centers of these ensembles, the latter's diameter being less than 240 mcm, was not more than 300 mcm. The centers displayed the most intensive activity of the neurons ranged in a column, with the shortest latency, the greatest synchronization, and the diffuse peripheral area which might be asymmetrical in respect to the center.

Animals↗
PubMedDate not supplied

Spatial distribution of activity of the neurons of the visual cortex during stimulation with a flash of diffused light.

At different stages in the development of the response to a flash of diffused light, groupings of excited neurons in field 17 of the guinea pig continue to occur within the same cortical microzones. These zones are separated from neighboring microzones by narrow inhibition zones. The ensembles of cells participating in excitation form columns tapering with depth. The groupings of excited cells noted during a silent break indicates a grouping of inhibitory neurons. Three subgroups are distinguished within the ensembles according to the average dynamics of their impulse activity; the groups are reciprocally interrelated. One of the subgroups is in the lower layers of the cortex. This subgroup is characterized by stably localized foci of maximal activity; their dynamics, apparently reflecting groupings of corticofugal neurons, are sharply distinguished from the subgroups of the middle layers. The ensembles under investigation are considered to be one of the forms of activity of the structural-morphological units in the cortex.

Animals↗
PubMedDate not supplied

Tangential segregation of simple and complex cells in the visual cortex and their connections. A universal neocortical module.

In the visual cortex of the guinea pig brain, the primary convergence zones for afferents correspond to basal modules--columns which are about 200 microm in diameter-and are separated by secondary convergence zones. The former are characterized by their concentrations of neurons with simple receptive fields and afferent inhibitory cells, and have a different organization of local interneuronal connections as compared with secondary convergence zones, which have an increased proportion of inhibitory influences, addressed excitatory inputs, and more selectivity in their cellular reactions. The basal modules have parameters similar to those of higher mammals; secondary convergence zones are smaller in rodents, and have simpler organization.

Animals↗
PubMedDate not supplied

[Discrete wave mechanism of integral activity in heterogenic neuron synapses].

On the basis of the conception of the discrete wave mechanism for the integration of heterogeneous neuron elements, a hypothesis was put forward that neuron excitation propagates as waves of changes in the conformational states of neuron membrane lipids. A mathematical model was constructed, which confirms the wave mode of excitation propagation. The model enables one to consider the integration of postsynaptic potentials as a process of wave interference. It was assumed that the training of neuron elements can be considered as a process of nonuniform distribution of lipids.

Excitatory Postsynaptic Potentials↗
PubMedDate not supplied

[Effect of nonspecific thalamic nuclei on individual ensemble-forming loci in the visual cortex].

Electric stimulation of guinea pigs' medial thalamic nuclei (MT) creates in the area 17 of the visual cortex functional groups of excited neurones, located within the same structural columns as ensembles of neurones excited by flashes of diffuse light. Together with analogous effects of the MBRF stimulation, such results indicate a convergence of different non-specific influences on separate columns of the visual cortex. MT exert their initial and mainly activating influences on the lower, efferent layers, while MBRF, according to literary data, activates afferent, middle layers of the cortex. This points to the existence in the visual cortex of separate non-specific regulation of the input on the part of the reticular formation and of the output on the part of MT.

Afferent Pathways↗
PubMedDate not supplied

[Spatial distribution of heterogeneous afferent influences in the visual cortex of the guinea pig].

In the 17-th area of guinea pig's visual cortex the electric stimulation of LGN, SC, and the cortex itself creates within the zones of the column-like ensembles of neurones excited by the light flash, local excited groups, with overlapping marginal zones. Together with analogous results of the MBRF stimulation this demonstrates that different functional neuronal ensembles achieve various forms of functioning of the same structural units of the cortex structure, i.e. columns. Thus, convergence of specific, unspecific and cortico-cortical afferent influences upon individual columns take place. This phenomenon suggests a realization of a higher, as compared with cellular, level of the nervous integration by neuronal ensembles.

Afferent Pathways↗