Effect of background activity of a net of excitatory neuron-like elements on conduction of excitation.

Abstract

1. Investigations on a mathematical model have shown that the presence of an optimal system of parameters of neuron-like excitatory elements (EE) and of connections between them is essential for the undistorted conduction of excitation along a network composed of them. If these parameters deviate from their optimal values excitation will be transmitted along the net either with attenuation or with amplification, due to the presence of divergence and convergence of influences of EE of the preceding layer of the net on the succeeding layer. 2. Optimal values of the parameters of EE and of the connections between them for undistorted conduction of excitation are not strictly determined. Deviations of some parameters can be compensated by changes in others. 3. The presence of dispersion of thresholds of EE induces chaos in the working of the net, weakens the degree of synchronization in the activation of EE to an external agency, and impairs the detection of activity of input EE at the output of the net. 4. Background activity of the net, both tonic and periodic, above the threshold for impulse generation prevents the appearance of activation of input EE at the output of the net, whereas near-threshold tonic activity of the net facilitates the conduction of excitation along it. 5. Periodic below-threshold activity of the net facilitates the conduction of excitation along it only in the presence of optimal proportions of frequencies and phase shift of coherent rhythmic oscillations of excitability of EE, and also of the time required for excitation to be transmitted from the input of the net to its output. If those conditions are not present, the presence of below-threshold rhythmic oscillations of excitability (including high-frequency oscillations) in the net will limit the conduction of excitation along it by comparison with tonic below-threshold activation.