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.

Piracetam-induced changes in the functional activity of neurons as a possible mechanism for the effects of nootropic agents.

Studies were carried out on the effects of piracetam (4-20 mM) on the electrical activity of identified neurons in the isolated central nervous system of the pond snail in conditions of single-electrode intracellular stimulation and recording. Piracetam-induced changes were seen in 60-70% of the neurons studied. Different parameters showed different sensitivities to piracetam: the most frequent changes were in the action potential generation threshold, the slope and shape of the steady-state voltage-current characteristics of neuron membranes, and the appearance of piracetam-induced transmembrane ion currents. Nifedipine and cadmium ions, both of which are calcium channel blockers, generally reversed or weakened the effects of piracetam on the changes seen in test cells. This indicates that the effects of piracetam result from its action on calcium channels; selective changes in calcium channels may determine which piracetam-induced effects appear at the cellular level. It is hypothesized that the piracetam-sensitive cellular plasticity mechanisms may make a significant contribution to its nootropic action at the behavioral level.

[Changes in the indices of neuronal functional activity under the action of piracetam as a possible basis for realizing the effects of nootropic agents]. / Izmenenie pokazatelei funktsional'noi aktivnosti neironov pod deistviem piratsetama kak vozmozhnaia osnova realizatsii éffektov nootropov.

Effects of piracetam (PA, 4-20 mM) on some electric characteristics of neuron activity were studied in vitro in identified neurons of Lymnaea stagnalis. Stimulation, single-electrode voltage clamping and recording of activity of the neuron were realized via the same intracellular microelectrode. PA-induced alterations of the characteristics under study were observed in 60-70% of recorded neurons. Modifications of action potential generation threshold, of the slope and shape of steady-state membrane current-voltage characteristics and appearance of PA-induced transmembrane ion currents occurred more frequently than changes in other parameters. Typically, Ca channel blockers (nifedipine and Cd ions) reversed or reduced the influence of PA on the studied characteristics of tested cell activity, i. e., acted as PA antagonists. This suggests that realization of observed PA effects is due to its action on Ca channel functioning. Selective modification of the latter can determine development of various PA effects at the cellular level. An assumption is discussed that piracetam, being a highly efficient cellular adaptogen and modifying specifically Ca channels of cells, is capable of moving them to a new level of functioning which is necessary for ensuring complex forms of nervous activity.