title: Effect of muscle contraction strength on gating of somatosensory magnetic fields.
abstract: Afferent somatosensory information is modulated before the afferent input arrives at the primary somatosensory cortex during voluntary movement. The aim of the present study was to clarify the effect of muscular contraction strength on somatosensory evoked fields (SEFs) during voluntary movement. In addition, we examined the differences in gating between innervated and non-innervated muscle during contraction. We investigated the changes in gating effect by muscular contraction strength and innervated and non-innervated muscles in human using 306-channel magnetoencephalography. SEFs were recorded following the right median nerve stimulation in a resting condition and during isometric muscular contractions from 10 % electromyographic activity (EMG), 20 and 30 % EMG of the right extensor indicis muscle and abductor pollicis brevis muscle. Our results showed that the equivalent current dipole (ECD) strength for P35m decreased with increasing strength of muscular contraction of the right abductor pollicis brevis muscle. However, changes were observed only at 30 % EMG contraction level of the right extensor indicis muscle, which was not innervated by the median nerve. There were no significant changes in the peak latencies and ECD locations of each component in all conditions. The ECD strength did not differ significantly for N20m and P60m regardless of the strength of muscular contraction and innervation. Therefore, we suggest that the gating of SEF waveforms following peripheral nerve stimulation was affected by the strength of muscular contraction and innervation of the contracting muscle.
authors.affiliation: Department of Rehabilitation, Faculty of Health Sciences, Tohoku Fukushi University, 1-8-1 Kunimi, Aoba-ku, Sendai City, Miyagi, 981-8522, Japan. k-sugawara@tfu-mail.tfu.ac.jp.
authors.forename: Kazuhiro
authors.initials: K
authors.lastname: Sugawara
authors.affiliation: Institute for Human Movement and Medical Sciences, Niigata University of Health and Welfare, 1398 Shimami-cho, Kita-ku, Niigata City, 9503198, Japan.
authors.forename: Hideaki
authors.initials: H
authors.lastname: Onishi
authors.affiliation: Institute for Human Movement and Medical Sciences, Niigata University of Health and Welfare, 1398 Shimami-cho, Kita-ku, Niigata City, 9503198, Japan.
authors.forename: Koya
authors.initials: K
authors.lastname: Yamashiro
authors.affiliation: Department of Rehabilitation, Tohoku University Hospital, Sendai, Japan.
authors.forename: Shinichi
authors.initials: S
authors.lastname: Kotan
authors.affiliation: Institute for Human Movement and Medical Sciences, Niigata University of Health and Welfare, 1398 Shimami-cho, Kita-ku, Niigata City, 9503198, Japan.
authors.forename: Sho
authors.initials: S
authors.lastname: Kojima
authors.affiliation: Institute for Human Movement and Medical Sciences, Niigata University of Health and Welfare, 1398 Shimami-cho, Kita-ku, Niigata City, 9503198, Japan.
authors.forename: Shota
authors.initials: S
authors.lastname: Miyaguchi
authors.affiliation: Institute for Human Movement and Medical Sciences, Niigata University of Health and Welfare, 1398 Shimami-cho, Kita-ku, Niigata City, 9503198, Japan.
authors.forename: Atsuhiro
authors.initials: A
authors.lastname: Tsubaki
authors.affiliation: Institute for Human Movement and Medical Sciences, Niigata University of Health and Welfare, 1398 Shimami-cho, Kita-ku, Niigata City, 9503198, Japan.
authors.forename: Hikari
authors.initials: H
authors.lastname: Kirimoto
authors.affiliation: Institute for Human Movement and Medical Sciences, Niigata University of Health and Welfare, 1398 Shimami-cho, Kita-ku, Niigata City, 9503198, Japan.
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Tamaki
authors.affiliation: Department of Neurosurgery, Nishi-Niigata Chuo National Hospital, 14-1-1 Masago, Nishi-ku, Niigata, 950-2085, Japan.
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Shirozu
authors.affiliation: Department of Neurosurgery, Nishi-Niigata Chuo National Hospital, 14-1-1 Masago, Nishi-ku, Niigata, 950-2085, Japan.
authors.forename: Shigeki
authors.initials: S
authors.lastname: Kameyama
mesh_terms: D000328:Adult; D000704:Analysis of Variance; D004558:Electric Stimulation; D005073:Evoked Potentials, Somatosensory / Q000502:physiology*; D005260:Female; D006801:Humans; D015225:Magnetoencephalography; D008297:Male; D008475:Median Nerve / Q000502:physiology; D009119:Muscle Contraction / Q000502:physiology*; D053580:Muscle Strength / Q000502:physiology*; D011930:Reaction Time / Q000502:physiology; D055139:Sensory Gating / Q000502:physiology*; D013003:Somatosensory Cortex / Q000502:physiology*; D014953:Wrist / Q000294:innervation; D055815:Young Adult
keywords: Gating effect; Magnetoencephalography; Median nerve stimulation; Somatosensory evoked magnetic fields; Strength of muscular contraction