The significance of coherency between EEG and EMG in motor control

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We investigated the manner of MU discharge in both subjects who showed significant cortico-muscular coherence and subjects who showed non-significant coherence. We compared the two types of subjects about cortico-muscular coherence and coherence between cortical drive and MU activity. It has been shown that, even if MUs did not construct temporally ensemble such as grouped discharge, single MU was coherent with cortical drive. We evaluated dependency of MU on phase of cortical drive quantitatively by calculating circular variance of instantaneous phase distribution of cortical drive on MU firing timing. We found that MU was gradually being entrapped by the rhythm of the cortical drive as the level of force increased. Furthermore, by ISIH using phase of cortical drive, intermittent MU discharge has also demonstrated. We have shown the evidence of phase-locked activity and intermittent discharge of MU, and revealed the causal relationship between net neuromuscular activity and individual motor unit firing.