Phase-shift gradients of dominant cortical potentials in rabbits

Abstract

Phase shifts of cortical potentials were studied in rabbits before and during photic stimulation and their importance for irradiation of excitation from the visual to the motor area was examined. Both before and during stimulation variations in phase relationships of various kinds were observed. In most cases, however, with an increase in distance between the electrodes, the phase shift of the theta-waves gradually increased. Most motor responses of the rabbits took place in the presence of a marked phase shift gradient. It is suggested that the state of the brain in which a spatial phase shift gradient of the theta-waves is recorded in the EEG is the optimal condition for realization of the motor response. Photic stimulation increases the number of in-phase waves in the EEG recorded from closely situated points and it reduces scatter of the phase shift values between components of the sensomotor and visual cortical EEG, i.e., it leads to an increase in coherence. Motor responses of the rabbits to stimulation take place in the presence of theta-waves with the most constant phase shift in the EEG of the sensomotor and visual cortex.