PHASE-RELATIONS BETWEEN RHYTHMIC ACTIVITY OF RABBITS CORTICAL STRUCTURES AT DIFFERENT FREQUENCIES OF STIMULATION OF THE MIDBRAIN RETICULAR-FORMATION

Phase shifts between the rhythmical activity of the hippocampus (CA1), somatosensory, motor and visual areas of the neocortex in the delta-, theta- and alpha-bands were studied during electrostimulation of the mesencephalic reticular formation with different frequencies. It was f ound that increasing stimulation frequency resulted in nonlinear decre ase of the phase shifts in the theta-band between recordings which inc luded the visual cortical area, and increase of the phase shifts betwe en the theta-rhythm, recorded in the hippocampus, somatosensory and mo tor cortical areas. In the delta-band increase of the phase shifts was observed only in the pairs of recordings from the last-mentioned grou p of structures at stimulation frequencies more than 200 1/sec. Phase shifts in the alpha-rhythm between the cortical recordings varied at d ifferent stimulation frequencies. Reliable changes of the alpha-rhythm phase shifts were observed during stimulation with the frequency 60-2 00 1/sec between recordings from the hippocampus, motor and somatosens ory areas, and at 500-700 1/sec - in the pairs of recordings which inc luded the visual cortical area.