Corticomuscular and intermuscular coherence are correlated after stroke: a simplified motor control?

Abstract

During movement, corticomuscular coherence is a measure of central-peripheral communication while intermuscular coherence is a measure of the amount of common central drive to the muscles. Although these two measures being modified in stroke subjects, no author has explored a correlation between them, neither in stroke subjects nor in healthy subjects. 24 chronic stroke subjects and 22 control healthy subjects were included in this cohort study and performed 20 active elbow extension movements. The electroencephalographic and electromyographic activity of elbow flexors and extensor were recorded. Corticomuscular and intermuscular coherence were calculated in the time-frequency domain for each limb of stroke and control subjects. Partial rank correlations were performed to study the link between these two variables. Our results showed a positive correlation between corticomuscular and intermuscular coherence only for stroke subjects, for their paretic and nonparetic limb (p < 0.022; Rho > 0.50). These results suggest, beyond the cortical and spinal hypothesis to explained them, that stroke subjects present a form of simplification of motor control. When central-peripheral communication increases, it is less modulated and more common to the muscles involved in the active movement. This motor control simplification suggests a new way of understanding the plasticity of the neuromuscular system after stroke.