Adaptive regulation of the nonlinear dynamics of electrical activity of the brain.

A programmable system was used to provide contingent reinforcement of EEG cycles corresponding to a selected criterion in a dynamic regime. Use of automated reinforcing stimulation of emotionally positive zones of the hypothalamus led to a significant increase in the number of cycles with the characteristics specified by the dynamic regime within the dominant EEG frequency bands. This effect lasted for some time after withdrawal of reinforcing stimulation, and then died down gradually. These changes in the EEG activity structure did not occur in conditions of nonassociated hypothalamic stimulation. Pseudoreinforced background EEG cycles showed complex nonlinear dynamics with competitive interactions between processes in which the large dimensionality of the attractor was difficult to interpret because of indeterminacy in the trends of the dominant process. In contingent hypothalamic stimulation, the form of the correlation integral changed towards a predominance of a single nonlinear process determining all the activity recorded. In fact, a single dominant nonlinear process was formed, which became responsible for the entire dynamics of the system with concordance of its internal structure.

[The adaptive regulation of the nonlinear dynamics of brain electrical activity]. / Adaptivnaia reguliatsiia nelineinoi dinamiki élektricheskoi aktivnosti golovnogo mozga.

The reinforcing automated stimulation of the emotional positive hypothalamic areas which was contingent upon the multiperiodical events in the EEG structure increased the number of episodes with non-linear dynamics. It resulted in an increase in the frequency of the intracranial self-stimulation. Under conditions of controlled experiment a possibility was shown of the intentional experimental formation of the EEG episodes with different types of non-linear dynamics. At the stages preceding the associative learning, the application of fractal analysis enabled revealing a complex character of non-linearity in the bands of the EEG dominant frequencies with a slight tendency to a dominant process. The associative learning produced one dominant non-linear process which determined the dynamics of the whole system. The neurophysiological characteristics of the given adaptive process were determined as well as the difference between this process and the response to control stimulation.