Biomedical subjects

V I Sbitnev

Publications and source records attributed to V I Sbitnev.

5 recordsLinked to original sources

PubMed1976

[Spike tranfer in statistical neuron assemblies. II. Neuron--nonlinear spike source].

The mathematical model of the neuron function is known to rely on space summing of excitement. The spikes contribute to the inner state of the neuron the farther from cell soma the synapses are located. The difference between excitatory and inhibitory effect results in spike firing if only neural firing threshold is achieved. The values of spike flux have been estimated on the basis of the model of CA3 sector of the Hippocampus and were found to be 15 divided by 35 imp/s.

Hippocampus↗

PubMedDate not supplied

[Propagation of spikes in statistical neuron ensembles. I. Concept of phase transitions].

A system of two coupled integro-differential equations for the propagation of sipkes is presented. A qualitative consideration of the system shows possibility of concentrational phase transition in the neuron ensemble from the state of spontaneous firing to the strong periodic oscilltation activity. Naer the point of the phase transition the neuron ensemble becomes labile, which maintains appropriate conditons for the existence of mosaic structures in the neuron network.

Models, Neurological↗

PubMedDate not supplied

[Spike transmission in statistical neuronal ensembles. IVa. Stating the problem in a diffusion approximation].

An area of tissue in the field CA3 of the Hippocampus has been selected controled by a basket cell. The functioning of the basket cell has been described by a point approximation method forthe transport equation, and that of the ensemble of pyramidal cells by a diffusion approximation one. Furthermore, the area of tissue is broken up into N2 of "cells" wherein a transition is effected from the diffusion equation of the N2 of the point equations involved. If the sizes of "cells" are commeasurable to the diffusional length of the pyramidal cell collaterals each "cells" being relatively independent generator of activity. In the latter case the fundamental interaction type is the mutual negative influence of the "cells" through the basket cell. Should the area be broken up into further, the mutual influence of the "cells" becomes noticeable and cannot be neglected. The behaviour of spatially homogenous diffusion approximation model is equivalent of the point approximation model.

Action Potentials↗

PubMedDate not supplied

[Spike transmission in statistical neuronal ensembles. Induced epileptic focus in a model of hippocampal field CA3].

In a spatially heterogeneous model the transition to supercritical phase was investigated as to the parameter characterizing the activation level of the pyramidal cells related to one another assuming the nonuniformity radius to be R0 = const. This is a transition from spontaneous activity to epileptoid bursts. Before the onset of epileptoid bursts the region of stochastic nonequilibrium of solutions is developed likely to produce pathologic dynamic patterns. With further increase of the activation parameter the system comes to epileptoid state. This synchronized firing of pyramidal cells is accompanied with phases of inhibition. A decrease in the nonuniformity radius leads to the formation of an epileptic focus. It is a dissipative structure. The evolution of it is not further followed, since the transport equations do not include its dynamics.

Hippocampus↗

PubMedDate not supplied

[Spike transmission in statistical neuron ensembles. III. Phase transition in a model of hippocampal field CA3].

The model consists of two types of neurons i. e. excitatory pyramidal cells and inhibitory basket ones. (the problem was formulated by Drs. O. S. Vinogradova and A. G. Bragin). The analysis of neuron activity has been carried out on the basis of "point approximation" of spikes transport equations. The graphs were obtained by computer. These graphs of the postsynaptic potentials averaged over ensemble are in good agreement with experimental data. The model observed demonstrates the phase transition over parameter characterizing the conduction of excitation between pyramidal cells. For weak pyramidal cells link there takes place the spontaneous activity regime. For strong link there were observed the epileptoid firing of neurons at 3 divided by 5 hertz and 140 divided by 240 msec phases of inhibition between bursts.

Hippocampus↗