Modified corticomuscular coherence measurement and computation under static force output of human-machine interaction

Beta-rage electroencephalogram (EEG)-EMG coupling has been extensively investigated under different force output tasks of human-machine interaction over the past decades. By applying corticomuscular coherence (CMC), beta-range (15-30hz) coherence has been well investigated during static force condition as well as dynamic force condition. However, the traditional CMC method limits the two different signals within a same frequency band, thus, a large portion of useful frequency information may be lost. The present study addresses this problem by applying the modified CMC. The experimental results of 4 static force outputs with 8 subjects showed that by using the traditional CMC, as the force output increased, the dominant peak of EEG-EMG coherence spread from alpha and beta bands to gamma (30-45Hz) band, while by using the modified method, the highest EEG-EMG coherence value focused in beta band and a notable increasing tendency of coherence was achieved in gamma band as with the force value increased. By applying the modified method, more information under static force conditions instead of modulated force output have been obtained, there may be a promising application of this method in the neurophysiology study of motor control during human-machine interaction.