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

Abstract

Corticomuscular coherence (CMC) is an oscillatory synchronization of 15–35 Hz (β-band) between electroencephalogram (EEG) of the sensorimotor cortex and electromyogram of contracting muscles. Although we reported that the magnitude of CMC varies among individuals, the physiological mechanisms underlying this variation are still unclear. Here, we aimed to investigate the associations between CMC and intracortical inhibition (ICI) in the primary motor cortex (M1)/recurrent inhibition (RI) in the spinal cord, which probably affect oscillatory neural activities. Firstly, we quantified ICI from changes in motor-evoked potentials induced by paired-pulse transcranial magnetic stimulation in M1 during tonic isometric voluntary contraction of the first dorsal interosseous. ICI showed a significant, negative correlation with the strength of EEG β-oscillation, but not with the magnitude of CMC across individuals. Next, we quantified RI from changes in H-reflexes induced by paired-pulse electrical nerve stimulation to the posterior tibial nerve during isometric contraction of the soleus muscle. We observed a significant, positive correlation between RI and peak CMC across individuals. These results suggest that the local inhibitory interneuron networks in cortical and spinal levels are associated with the oscillatory activity in corticospinal loop.

Increased central common drive to ankle plantar flexor and dorsiflexor muscles during visually guided gait

“…This is not surprising given the dynamic and rhythmic nature of gait, which will elicit rhythmic oscillations in all sensori-motor networks that contribute to the activation of the muscles. Brain imaging studies also confirm that sensory feedback mechanisms are responsible for a very significant part of the activation of cortical motor areas during locomotion (Christensen et al 2000;Promjunyakul et al 2015) and local inhibitory interneurons have been shown to modulate EEG-EMG coherence in a sustained isometric contraction (Matsuya et al 2017).…”

“…) and local inhibitory interneurons have been shown to modulate EEG‐EMG coherence in a sustained isometric contraction (Matsuya et al. ).…”

Using Corticomuscular and Intermuscular Coherence to Assess Cortical Contribution to Ankle Plantar Flexor Activity During Gait

“…They thus reported a positive correlation between the amount of corticospinal coherence between Cz EEG and SOL and the level of recurrent inhibition indicating that spinal mechanisms indeed modulate the corticomuscular coherence. In the present study, the source of the oscillatory activity cannot be isolated and both cortical and spinal mechanisms most likely contribute and modulate the observed coherence (Matsuya et al 2017).…”

Classification of grasping tasks based on EEG-EMG coherence

“…CMC is a well-known concept in the neurorehabilitation field, defined as the coherence function between an electroencephalographic (EEG) and an electromyographic (EMG) signal, well characterized in boh healthy subjects [1] and those affected by different kinds of motor-related diseases.…”