Intermuscular Coherence Reflects Functional Coordination

Coherence analysis has the ability to identify the presence of common descending drive shared by motor unit pools, and reveals its spectral properties. However, the link between spectral properties of shared neural drive and functional interactions among muscles remains unclear. We assessed shared neural drive between muscles of the thumb and index finger while participants executed two mechanically distinct precision pinch tasks, each requiring distinct functional coordination among muscles. We found that shared neural drive was systematically reduced or enhanced at specific frequencies of interest (~10 and ~40 Hz). While amplitude correlations between surface EMG signals also exhibited changes across tasks, only their coherence has strong physiological underpinnings indicative of neural binding. Our results support the use of intermuscular coherence as a tool to detect when co-activated muscles are members of a functional group or synergy of neural origin. Further, our results demonstrate the advantages of considering neural binding at 10, ~20, and >30 Hz, as indicators of task dependent neural coordination strategies.

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