Inter- and intra-individual differences in temporal modulation patterns of the β-band sensorimotor rhythm and its relationship to corticomuscular coherence during intermittent voluntary contraction

The {beta}-band sensorimotor rhythm (SMR), recorded using electroencephalography, generally desynchronizes from motor preparation and subsequently synchronizes with electromyogram signals during voluntary contraction, thus forming corticomuscular coherence (CMC). However, it remains unclear how the temporal modulation of {beta}-band SMR varies among individuals, potentially leading to individual differences in CMC. It is also unclear how the nervous system modulates {beta}-band SMR to meet varying task demands within individuals. Here, we explored how temporal modulation patterns of {beta}-band SMR affect CMC from two perspectives: inter-individual differences (Experiment 1), and intra-individual variability depending on task demands (Experiment 2). In Experiment 1, participants repeated a steady-force maintenance task. The degree of {beta}-band SMR modulation (i.e., rebound from desynchronization to synchronization) during contractions varied greatly among individuals and was positively correlated with CMC magnitude. This suggests that even under steady-force maintenance, the motor control strategy used while regulating {beta}-band SMR varies greatly among individuals. In Experiment 2, participants who showed significant CMC in Experiment 1 performed four tasks with varying target trajectories. Even within individuals, the degree of {beta}-band SMR modulation was reduced in parallel with the CMC magnitude as more difficult force adjustment was required. This finding suggests that, when confronted with more challenging task demands, our nervous system reduces the oscillation of SMR and desynchronizes its coupling with muscles. Overall, the way in which our nervous system regulates {beta}-band SMR is assumed to represent a strategy for flexible adaptation to diverse motor environments. Significance StatementAlthough the {beta}-band sensorimotor rhythm (SMR) undergoes a dynamic transition from desynchronization to synchronization when generating voluntary movements, it remains unclear how such {beta}-band SMR modulation relates to the emergence of corticomuscular coherence (CMC). The present study is the first to systematically investigate the temporal association between SMR and CMC from both inter-individual (i.e., identical tasks) and intra-individual (i.e., different tasks) perspectives. We found that: 1) the degree of {beta}-band SMR modulation was tightly related to the CMC magnitude across individuals; and 2) the {beta}-band SMR and CMC decreased in parallel as task demands increased. These findings offer novel insights into the sensorimotor processes in which regulating {beta}-band SMR serves as a neural basis of flexible motor control.