Corticomuscular Coherence Reflects Interindividual Differences in the State of the Corticomuscular Network During Low-Level Static and Dynamic Forces

In the investigation of corticomuscular coherence (CMC), it remained unclear why some subjects do not present significant CMC. We predicted that such subjects will develop CMC as a result of learning as indexed by improved performance during a visuomotor task. We investigated CMC, cortical motor spectral power (SP), and performance in 14 subjects during isometric compensation of a static force or dynamic force (DF) with their right index finger. We compared data from the beginning of the experiment (Time-Period 1) and after learning (Time-Period 2). Eight subjects (Group CMC++) presented CMC during Period 1 which increased during Period 2. Six subjects (Group CMC-+) presented CMC only during Period 2. Group CMC-+ was "more desynchronized" (lower SP, and stronger task-related desynchronization) than Group CMC++. The performance was better in Group CMC++ than in Group CMC-+. Learning was associated with higher SP, higher CMC, and better performance in both groups. However, in the more complicated DF condition, Group CMC++ learned better than Group CMC-+. The present study demonstrates the presence of CMC in all subjects tested and evidence that this is due to the fact that individuals may fall into 2 different groups in terms of oscillatory motor control: Group CMC-+ presents CMC only after learning.