[Spatial-phase relations of dominant fluctuations of brain potentials in the rabbit]

Phase shifts of cortical electrical activity and their role in excitation irradiation from the visual zone to the motor one were studied in rabbits before and during light stimulation. Different variations of the phase relations were observed both in the background activity and during stimulation. In most cases, however, a gradual increase in the theta-waves phase shift was observed parallel with an increase in the distance between the recording electrodes. The most motor reactions were carried out by the animal, if a phase shift gradient was expressed. Therefore the brain status characterized by spatial phase gradient of the theta-waves was supposed to be optimal for realization of the motor reaction. Light stimulation increased the quantity of synphasic oscillations between EEG processes in the points situated not far from each other and decreased the variability of the phase shift value between the sensorimotor and visual cortex, i.e. stabilized the phase gradient. This stabilization was expressed in the increase of wave coherence. Motor reactions of the rabbit in response to stimulation were realized when the most stable phase shift between the theta-waves in the sensorimotor and visual cortex was recorded.