Influence of different intracellular electrostimulation regimes on the dynamics of the adaptational processes of neurons.

The influence of rhythmic, random, and associative intracellular electrostimulation under the conditions of a controllable experiment was investigated in individual identified and nonidentified neurons of the isolated central nervous system of the pond snail. Two phases distinguished by the markedness and stability of the observed adaptive changes of the initial spike activity, which were evaluated by means of various statistical tests, were discriminated during the adaptation of the neuron to the applied regimes of influences. In the first phase, which reflects the search for a strategy of optimization of the incoming external influences, an increase in a scatter of interimpulse intervals and in the disorderliness in the discharge pattern takes place. In the second phase, observed only in the case of associative influences, a true adaptation of the neuron develops, accompanied by stable changes in endogenous rhythmicity, which lead to the achievement of minimization or maximization of the associated stimulations. The changes accompanying the effective optimization of external influences are most marked at the end of the epoch of the corresponding associative stimulation, and are maintained for some time following its cessation. Possible endoneuronal mechanisms of the observed adaptive reorganizations of spike activity are discussed.