Cue-Dependent Modulation of Synchrony in Primates’ Medial Motor Areas

Although β oscillations are the representative brain activity in sensorimotor areas and the basal ganglia, how they coordinate activities of multiple structures in the brain is poorly understood. To examine the coordination of the activities of the pre-supplementary motor area (pre-SMA) and the SMA through β oscillations, we recorded local field potentials simultaneously in these areas while monkeys performed a motor task. Examination of inter-area phase difference revealed that the pre-SMA became phase-advanced in β oscillations relative to the SMA when a visual cue signaled initiation of a trial. The strength of phase synchrony decreased markedly while the monkeys were visually instructed about the movement to be performed and was strengthened when the monkeys repeated the movements they had performed in the previous trial. These results suggest that visual input initializes the dynamic state of the pre-SMA and SMA when a trial starts. Additionally, sensory signals seem to be acquired and motor plans formed via modulation of the strength of inter-area synchrony of β oscillations.