Non-focal beta oscillation suppression along the sensorimotor cortex revealed by corticomuscular coherence

An Event-Related Desynchronization (ERD) of the 13-30 Hz sensorimotor (SM1) beta oscillations is commonly observed during movement preparation and execution. Human electrophysiological measurements suggest that such a beta ERD has a wide topographical distribution along the SM1, however, no accessible means of quantifying the degree of its focality exist. Therefore, we investigated how the movement-induced beta ERD in one somatotopic SM1 area affects beta oscillations in a neighbouring SM1 area. Thirty-six participants performed right brachium movements while holding a submaximal isometric contraction with their right first dorsal interosseous (FDI) muscle. Beta ERD in the left SM1 brachium area was assessed with electroencephalography (EEG). The effect of that ERD on beta activity in the neighbouring SM1 FDI area was assessed through the corticomuscular coherence (CMC) between SM1 EEG signals and the electromyographic and force signals recorded from the contracted right FDI muscle. Our results showed that the strong movement-induced beta ERD in the SM1 brachium area spreads to the neighbouring SM1 FDI area and suppresses beta oscillations therein, as evidenced by significantly attenuated CMC with both FDI signals. These findings confirm that beta ERD is not a strictly focal phenomenon as it spreads to a neighbouring SM1 area. Importantly, we introduced a novel approach that combines a dual motor task paradigm with CMC to assess beta propagatory effects. This approach could allow for investigating the topographical properties of beta oscillations and their role for motor control in healthy and clinical populations.