Spatiotemporal reorganization of electrical activity in the human brain associated with a timing transition in rhythmic auditory-motor coordination

We used a 61-channel electrode array to investigate the spatiotemporal dyna mics of electroencephalographic (EEG) activity related to behavioral transi tions in rhythmic sensorimotor coordination. Subjects were instructed to ma intain a 1:1 relationship between repeated right index finger flexion and a series of periodically delivered tones (metronome) in a syncopated (anti-p hase) fashion. Systematic increases in stimulus presentation rate are known to induce a spontaneous switch in behavior from syncopation to synchroniza tion (in-phase coordination). We show that this transition is accompanied b y a large-scale reorganization of cortical activity manifested in the spati al distributions of EEG power at the coordination frequency. Significant de creases in power were observed at electrode locations over left central and anterior parietal areas, most likely reflecting reduced activation of left primary sensorimotor cortex. A second condition in which subjects were ins tructed to synchronize with the metronome controlled for the effects of mov ement frequency, since synchronization is known to remain stable across a w ide range of frequencies. Different, smaller spatial differences were obser ved between topographic patterns associated with synchronization at low ver sus high stimulus rates. Our results demonstrate qualitative changes in the spatial dynamics of human brain electrical activity associated with a tran sition in the timing of sensorimotor coordination and suggest that maintena nce of a more difficult anti-phase timing relation is associated with great er activation of primary sensorimotor areas.