Between-subject variance in the magnitude of corticomuscular coherence during tonic isometric contraction of the tibialis anterior muscle in healthy young adults

Abstract

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 (␤-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 ␤-band to that of all frequency ranges for both EEG (EEG␤-PSD) and EMG (EMG␤-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 Ͻ 0.05 (0.114), 46 out of 100 subjects showed significant EEG-EMG coherence. Cohmax occurred within the ␤-band in the majority of subjects who showed significant EEG-EMG coherence (n ϭ 43). Furthermore, Cohmax showed significant positive correlations with both EEG␤-PSD (r ϭ 0.575, P Ͻ 0.001) and EMG␤-PSD (r ϭ 0.606, P Ͻ 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 ␤-band for each subject.electroencephalogram; electromyogram; EEG-EMG coherence; ␤-band oscillation IT IS WELL-ESTABLISHED THAT oscillatory neural activity of the sensorimotor cortex shows coherence with electromyographic activity in contralateral limb muscles within the 15-to 35-Hz frequency band (␤-band) during weak-to-moderate intensity tonic isometric contraction in both animals (Baker et al. 1997; Witham et al.

Poor motor function is associated with reduced sensory processing after stroke

“…Finally, a large downside for the potential clinical application of CMC is that it cannot be detected in all cases: even healthy subjects, with normal voluntary motor control, do not all present CMC (Ushiyama et al. 2011; Mendez-Balbuena et al. 2011; Campfens et al.…”

“…The inter-individual difference in the presence of CMC reflects physiological inter-individual differences in the strength of the oscillatory corticomuscular coupling and is not the result of technical aspects such as the (mis-) placement of EEG electrodes (Ushiyama et al. 2011). …”

Inhibitory interneuron circuits at cortical and spinal levels are associated with individual differences in corticomuscular coherence during isometric voluntary contraction

“…Corticomuscular coherence (CMC) has been considered to reflect the mutual interaction between the sensorimotor cortex and contracting muscles via descending motor pathways and ascending somatosensory pathways34567. Recently, we have reported that the magnitude of CMC varies among individuals even in healthy young adults8910. However, the physiological mechanisms underlying the inter-individual differences in CMC are still unclear.…”

“…However, the physiological mechanisms underlying the inter-individual differences in CMC are still unclear. Although the inter-individual differences include some technical limitations for EEG/EMG, we believe that it is valuable to examine the physiological mechanisms behind inter-individual differences in CMC, since CMC is associated with insensible personal behaviour such as force steadiness10 and reaction time11.…”

Functional recovery from chronic writer’s cramp by brain-computer interface rehabilitation: a case report

“…Tecchio et al reported patients’ exaggerated and bilaterally coupled cortico-muscular coherence in the beta band (mean frequency 21.5 Hz) during isometric contraction [16], which is not seen in healthy participants (e.g. [17]). These studies suggest the existence of different mechanisms of cortico-muscular coupling from healthy individuals in dystonia patients.…”