Capturing with EEG the neural entrainment and coupling underlying sensorimotor synchronization to the beat

Synchronizing movements with rhythmic inputs requires tight coupling of sensory and motor neural processes. Here, using a novel approach based on the recording of steady-state evoked potentials (SS-EPs), we examine how distant brain areas supporting these processes coordinate their dynamics. The EEG was recorded while subjects listened to an auditory beat and tapped their hand on every second beat. We found that rhythmic sensorimotor synchronization was supported by a beat-related entrainment frequency-locked to the beat whose topography indicated activity originating from auditory areas, and a movement-related entrainment frequency-locked to the movement whose topography indicated activity originating from motor and/or somatosensory areas contralateral to the tapping hand. Most importantly, we found evidence for an interaction between sensory- and motor-related activities in the form of (1) a cross-modulation SS-EP appearing at the sum of beat- and movement-frequencies, indicating a non-linear process of sensorimotor integration, (2) a phase coupling of beat- and movement-related responses and (3) a selective enhancement of beat-related activities over the hemisphere contralateral to the tapping hand, suggesting a top-down effect of movement-related activities on auditory beat processing. Taken together, our results indicate that rhythmic sensorimotor synchronization is supported by a dynamic coupling of sensory and motor related activities