Temporal control of muscle synergies is linked with alpha‐band neural drive

Abstract

It is theorized that the nervous system controls groups of muscles together as functional units, or ‘synergies’, resulting in correlated electromyographic (EMG) signals among muscles. However, such correlation does not necessarily imply group‐level neural control. Oscillatory synchronization (coherence) among EMG signals implies neural coupling, but it is not clear how this relates to control of muscle synergies. EMG was recorded from seven arm muscles of 10 adult participants rotating an upper limb ergometer, and EMG–EMG coherence, EMG amplitude correlations and their relationship with each other were characterized. A novel method to derive multi‐muscle synergies from EMG–EMG coherence is presented and these are compared with classically defined synergies. Coherent alpha‐band (8–16 Hz) drive was strongest among muscles whose gross activity levels are well correlated within a given task. The cross‐muscle distribution and temporal modulation of coherent alpha‐band drive suggests a possible role in the neural coordination/monitoring of synergies.