The Oscillatory Network of Simple Bimanual Repetitive Movements

A characteristic of bimanual coordination is the strong and spontaneous tendency to favor spatially and temporally symmetric movements. This observation gave rise to the assumption that timing mechanisms controlling each hand independently might be integrated during bimanual temporal coordination. Although a specific role of the cerebellum for this integration process has been suggested, its neural foundations are still poorly understood. Since there is growing evidence that synchronization of oscillatory neural activity might be a fundamental mechanism of information coding in the brain, the aim of the present study was to determine the oscillatory network underlying a simple auditorily paced bimanual synchronization task and to characterize the interplay between underlying brain structures. Seven right-handed subjects synchronized left and right index finger-taps to a regular auditory pacing signal. We recorded continuous neuromagnetic activity using a 122-channel whole-head neuromagnetometer and surface EMGs of the first dorsal interosseus (FDI) of both hands. Data demonstrate that an oscillatory network coupling at 8–12Hz subserves task execution. The constituents are bilateral primary sensorimotor and premotor areas, posterior-parietal and primary auditory cortex, thalamus and lateral portions of the cerebellum. Coupling occurred within and on different cortical and subcortical levels between both hemispheres. Coupling between primary sensorimotor and premotor areas was observed directly and indirectly via the thalamus. Coupling directions suggest that information was integrated within the left premotor cortex corroborating a specific role of the left PMC for motor control in right-handers. Most importantly, our data indicate strong coupling between both cerebellar hemispheres substantiating the hypothesis that cerebellar signals might be integrated during temporal bimanual coordination.