The effect of white and filtered noise on contrast detection thresholds

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 periods distribution, which corresponded to the frequencies 40-60, 70-100, and 100-200 Hz. These oscillation frequencies were also revealed after the HFMS in neural interactions of the cells, which were active before the HFMS; the frequency 40-60 Hz, which dominated before the HFMS, became even more pronounced. The same three groups of oscillation frequencies were found in the activity of cells which became active after the HFMS. The expression of oscillations, the number of oscillatory interactions, as well as the number of neuronal pairs with additional synchronization decreased after the HFMS, which suggests a decrease in synchronization. Taking into account the results of simulation experiments that the frequency of gamma-oscillations is determined by the strength of inhibitory and excitatory input, we suggest that the long-term posttetanic modifications in the efficacy of synaptic inputs of the neurons of both hemispheres underlie the observed posttetanic changes.