Onmyoji Yusuke, Kubota Shinji, Hirano Masato, Tanaka Megumi, Morishita Takuya, Uehara Kazumasa, Funase Kozo
Human Motor Control Laboratory, Graduate School of Integrated Arts and Sciences, Hiroshima University, 1-7-1 Kagamiyama, Higashi-Hiroshima 739-8521, Japan.
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.
Neurosci Lett. 2015 May 6;594:46-50. doi: 10.1016/j.neulet.2015.03.052. Epub 2015 Mar 26.
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.
在本研究中，我们使用经颅磁刺激（TMS）来探究在描述手部或腿部运动的言语过程中，支配手部肌肉的左侧初级运动皮层（M1）的兴奋性变化以及短间隔皮质内抑制（SICI）情况。在实验1中，我们研究了言语内容对大声朗读和默读过程中诱发的运动诱发电位（MEP）幅度的影响。在实验2中，我们在实验1的基础上增加了一个条件，即非发声性口腔运动（No-Voc OM）条件，并使用配对TMS范式研究了每种条件下诱发的SICI变化。无论受试者说出的句子内容或TMS的时机如何，在大声朗读和No-Voc OM条件下观察到的MEP幅度均显著大于默读条件下的MEP幅度。各实验条件之间的SICI没有显著差异。我们的研究结果表明，言语过程中检测到的左侧M1手部区域兴奋性增加主要是由与言语相关的口腔运动和语言处理相关脑功能的激活引起的。左侧M1兴奋性增加可能还由除SICI降低之外的其他神经机制介导；即去抑制。
