title: 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.
authors.affiliation: Graduate School of Science and Technology, Keio University, Kanagawa, Japan.
authors.forename: Ryosuke
authors.initials: R
authors.lastname: Matsuya
authors.affiliation: Faculty of Environment and Information Studies, Keio University, Kanagawa, Japan.|Department of Rehabilitation Medicine, Keio University School of Medicine, Tokyo, Japan.
authors.forename: Junichi
authors.initials: J
authors.lastname: Ushiyama
authors.affiliation: Department of Rehabilitation Medicine, Keio University School of Medicine, Tokyo, Japan.|Department of Biosciences and Informatics, Faculty of Science and Technology, Keio University, Kanagawa, Japan.
authors.forename: Junichi
authors.initials: J
authors.lastname: Ushiba
mesh_terms: D000328:Adult; D004569:Electroencephalography; D004576:Electromyography; D019054:Evoked Potentials, Motor / Q000502:physiology; D005260:Female; D006801:Humans; D007395:Interneurons / Q000502:physiology*; D007537:Isometric Contraction / Q000502:physiology*; D008297:Male; D009044:Motor Cortex / Q000502:physiology*; D009119:Muscle Contraction / Q000502:physiology*; D018482:Muscle, Skeletal / Q000502:physiology; D066191:Sensorimotor Cortex / Q000502:physiology; D055815:Young Adult