Journal
JOURNAL OF NEUROPHYSIOLOGY
Volume 106, Issue 3, Pages 1379-1388Publisher
AMER PHYSIOLOGICAL SOC
DOI: 10.1152/jn.00193.2011
Keywords
electroencephalogram; electromyogram; EEG-EMG coherence; beta-band oscillation
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Funding
- Ministry of Education, Culture, Sports, Science, and Technology (MEXT), Japan
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Ushiyama J, Suzuki T, Masakado Y, Hase K, Kimura A, Liu M, Ushiba J. Between-subject variance in the magnitude of corticomuscular coherence during tonic isometric contraction of the tibialis anterior muscle in healthy young adults. J Neurophysiol 106: 1379-1388, 2011. First published June 8, 2011; doi:10.1152/jn.00193.2011.-Oscillatory activity of the sensorimotor cortex has been reported to show coherence with muscle activity in the 15- to 35-Hz frequency band (beta-band) during weak to moderate intensity of isometric contraction. The present study examined the variance of the magnitude of the corticomuscular coherence across a large number of subjects. We quantified the coherence between EEG over the sensorimotor cortex and rectified electromyogram (EMG) from the tibialis anterior muscle during tonic isometric contraction at 30% of maximal effort in 100 healthy young individuals. We estimated the maximal peak of EEG-EMG coherence (Cohmax) and the ratio of the sum of the autopower spectral density function within the beta-band to that of all frequency ranges for both EEG (EEG beta-PSD) and EMG (EMG beta-PSD) signals. The frequency histogram of Cohmax across all subjects showed a broad bell-shaped continuous distribution (range, 0.048-0.816). When the coherence was thresholded at the estimated significance level of P < 0.05 (0.114), 46 out of 100 subjects showed significant EEG-EMG coherence. Cohmax occurred within the beta-band in the majority of subjects who showed significant EEG-EMG coherence (n = 43). Furthermore, Cohmax showed significant positive correlations with both EEG beta-PSD (r = 0.575, P < 0.001) and EMG beta-PSD (r = 0.606, P < 0.001). These data suggest that even during simple tonic isometric contraction, the strength of oscillatory coupling between the sensorimotor cortex and spinal motoneurons varies among individuals and is a contributory factor determining muscle activation patterns such as the degree of grouped discharge in muscle activity within the beta-band for each subject.
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