title: Excitability changes in the left primary motor cortex innervating the hand muscles induced during speech about hand or leg movements.
abstract: In the present study, we used transcranial magnetic stimulation (TMS) to investigate the changes in the excitability of the left primary motor cortex (M1) innervating the hand muscles and in short-interval intracortical inhibition (SICI) during speech describing hand or leg movements. In experiment 1, we investigated the effects of the contents of speech on the amplitude of the motor evoked potentials (MEPs) induced during reading aloud and silent reading. In experiment 2, we repeated experiment 1 with an additional condition, the non-vocal oral movement (No-Voc OM) condition, and investigated the change in SICI induced in each condition using the paired TMS paradigm. The MEP observed in the reading aloud and No-Voc OM conditions exhibited significantly greater amplitudes than those seen in the silent reading conditions, irrespective of the content of the sentences spoken by the subjects or the timing of the TMS. There were no significant differences in SICI between the experimental conditions. Our findings suggest that the increased excitability of the left M1 hand area detected during speech was mainly caused by speech-related oral movements and the activation of language processing-related brain functions. The increased left M1 excitability was probably also mediated by neural mechanisms other than reduced SICI; i.e., disinhibition.
authors: Human Motor Control Laboratory, Graduate School of Integrated Arts and Sciences, Hiroshima University, 1-7-1 Kagamiyama, Higashi-Hiroshima 739-8521, Japan.
authors: Yusuke
authors: Y
authors: Onmyoji
authors: Human Motor Control Laboratory, Graduate School of Integrated Arts and Sciences, Hiroshima University, 1-7-1 Kagamiyama, Higashi-Hiroshima 739-8521, Japan; Research Fellow of the Japan Society for the Promotion of Science, Japan.
authors: Shinji
authors: S
authors: Kubota
authors: Human Motor Control Laboratory, Graduate School of Integrated Arts and Sciences, Hiroshima University, 1-7-1 Kagamiyama, Higashi-Hiroshima 739-8521, Japan.
authors: Masato
authors: M
authors: Hirano
authors: Human Motor Control Laboratory, Graduate School of Integrated Arts and Sciences, Hiroshima University, 1-7-1 Kagamiyama, Higashi-Hiroshima 739-8521, Japan.
authors: Megumi
authors: M
authors: Tanaka
authors: Human Motor Control Laboratory, Graduate School of Integrated Arts and Sciences, Hiroshima University, 1-7-1 Kagamiyama, Higashi-Hiroshima 739-8521, Japan; Research Fellow of the Japan Society for the Promotion of Science, Japan.
authors: Takuya
authors: T
authors: Morishita
authors: Human Motor Control Laboratory, Graduate School of Integrated Arts and Sciences, Hiroshima University, 1-7-1 Kagamiyama, Higashi-Hiroshima 739-8521, Japan; Research Fellow of the Japan Society for the Promotion of Science, Japan.
authors: Kazumasa
authors: K
authors: Uehara
authors: Human Motor Control Laboratory, Graduate School of Integrated Arts and Sciences, Hiroshima University, 1-7-1 Kagamiyama, Higashi-Hiroshima 739-8521, Japan. Electronic address: funase@hiroshima-u.ac.jp.
authors: Kozo
authors: K
authors: Funase
mesh_terms: D000328:Adult; D019054:Evoked Potentials, Motor; D005260:Female; D007839:Functional Laterality; D006225:Hand / Q000294:innervation / Q000502:physiology*; D006801:Humans; D007866:Leg / Q000502:physiology*; D008297:Male; D009044:Motor Cortex / Q000502:physiology*; D009068:Movement; D018482:Muscle, Skeletal / Q000294:innervation*; D009433:Neural Inhibition; D011597:Psychomotor Performance; D011932:Reading; D013060:Speech; D013067:Speech Perception / Q000502:physiology*; D050781:Transcranial Magnetic Stimulation; D055815:Young Adult
keywords: Motor cortex excitability; Sentence; Speech; Transcranial magnetic stimulation