POSTTETANIC MODIFICATION OF SPONTANEOUS G AMMA-OSCILLATIONS IN TRANSCALLOSAL INTERACTIONS

The influence of high-frequency microstimulation (HFMS) of one of the hemispheres on the parameters of spontaneous gamma-oscillations in the neural network containing callosal cells of the motor cortex of both hemispheres. There were three modes in the background oscillation peri ods distribution, which corresponded to the frequencies 40-60, 70-100, and 100-200 Hz. These oscillation frequencies were also revealed afte r the HFMS in neural interactions of the cells. which were active befo re the HFMS; the frequency 40-60 Hz, which dominated before the HFMS, became even more pronounced. The same three groups of oscillation freq uencies were found in the activity of cells which became active after the HFMS. The expression of oscillations, the number of oscillatory in teractions, as well as the number of neuronal pairs with additional sy nchronization decreased after the HFMS, which suggests a decrease in s ynchronization. Taking into account the results of simulation experime nts that the frequency of gamma-oscillations is determined by the stre ngth of inhibitory and excitatory input, we suggest that the long-term posttetanic modifications in the efficacy of synaptic inputs Of the n eurons of both hemispheres underlie the observed posttetanic changes.