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Biomedical subjects

A B Kogan

Publications and source records attributed to A B Kogan.

At least 73 records · Page 4Linked to original sources
PubMedDate not supplied

Spread of excitation along neuron chains of the frog tectum opticum in response to various visual stimuli.

The construction of "chains of excitation" based on latent periods of responses of silent neurons of the frog tectum opticum to repetitive visual stimuli revealed significant differences in the course of excitation of the neuronal structures during the action of simple (flashes) and complex (movement of a visual object) stimuli. Movement of excitation over tectal neurons is shown to be very complex in character, for whereas the excitation wave develops comparatively quickly in response to simple stimuli and narrowing of the pathway of excitation soon arises, in response to a stimulus of definite shape it lasts longer and the pathway of excitation remains comparatively constant in width for much longer.

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PubMedDate not supplied

Role of inhibition in the formation of a dynamic mosaic of neuronal ensembles in the cerebral cortex.

The spatial-temporal organization of neuronal responses in the rat visual cortex was investigated during the action on the retina of light stimuli of various size. It was shown that a leading role in the formation of a dynamic mosaic of neuronal ensembles belongs to inhibition. Two systems of inhibition are distinguished, involved in differing degree in the organization of the operating mechanisms of the brain during the action of various stimuli.

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PubMedDate not supplied

Some mechanisms of central inhibition.

Central inhibition is viewed as the result of the interaction of processes at the level of the neuron, nerve center, and intercentral relationships. At all levels this involves activity for the reorganization of a functional structure that realizes a state of excitation under one organization and a state of inhibition under another. The results are presented of an investigation of subcellular reorganizations during the inhibition of a neuron, the reorganization of neuronal activity during the inhibition of nervous centers, and the subordination of the centers of an equivalent level during the inhibition of acts in systemic activity.

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PubMedDate not supplied

Intercellular relationships in elementary neuronal ensembles.

The mechanisms of combination of cortical neurons into discrete modules or elementary ensembles, serving as functional units and forming a mosaic of activity in which incoming information is coded, have been investigated. Neurons activated primarily by terminals of specific afferents respond stably with a minimal latent period and become the centers of ensembles, whose periphery is formed by secondarily activated neurons, responding variably with a longer latent period. The stochastic participation of these neurons in the structure of the ensembles lies at the basis of plasticity of cortical mechanisms. Neurons inhibited intracortically, and possibly, via ascending inhibitory pathways, are concentrated at the periphery and near the output cells of the ensemble.

Action Potentials↗
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[Autooscillatory processes in the thalamocortical nonspecific system].

Dynamic properties of the thalamo-cortical system, regarded as a self-oscillating system, have been studied in experiments with chronically prepared rabbits. Different types of dynamic behaviour of the system have been revealed in response to stimulation with sine-type amplitude modulation. It is shown that self-oscillation process which develops in the thalamo-cortical non-specific system, is of relaxation type.

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PubMedDate not supplied

[Informational characteristics of the impulse activity of cat sensomotor cortex neurons during elaboration of a defensive conditioned reflex].

Manifestations of the dynamics of defensive conditioning were studied in the cat sensorimotor cortical units. It has been shown that the process of learning is linked to the dynamics of the amount of total and useful information present in the evoked spike responses to a conditioned stimulus. As the pairings continue, the amount of useful information increases in reactions to conditioned or unconditioned stimuli and in the period preceding the conditioned stimulation.

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PubMedDate not supplied

[The neuronal organization of a focus of conditioned excitation in the cat sensory-motor cortex].

The activity of single units in the focus of conditioned excitation was studied during defensive conditioning to direct electrical stimulation of the cat sensorimotor cortex. Reorganizations of spike activity set in during the period of reflex elaboration, were manifest in the increased number of excited neurones and those which respond both to the conditioned and unconditioned stimuli. In the course of elaboration, the inhibitory phase of unit responses to direct electrical stimulation of the sensorimotor cortex was reduced, while the frequency of background unit spike activity was enhanced. Acute extinction of the reflex restored the initial duration of the inhibitory phase and reduced the frequency of the background activity.

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