Department of Neurosurgery, Keio University School of Medicine, Tokyo, Japan.
Neurosci Lett. 2012 Dec 7;531(2):86-90. doi: 10.1016/j.neulet.2012.10.027. Epub 2012 Nov 2.
This study aimed to determine the effects of speech and mastication on interhemispheric inhibition between the right and left primary motor areas (M1s) by using transcranial magnetic stimulation (TMS). Motor-evoked potentials (MEPs) were recorded from the first dorsal interossei (FDIs) of each hand of 10 healthy right-handed subjects under 3 conditions: at rest (control), during mastication (non-verbal oral movement), and during speech (reading aloud). Test TMS was delivered following conditioning TMS of the contralateral M1 at various interstimulus intervals. Under all conditions, the MEPs in the left FDIs were significantly inhibited after conditioning of the left M1 (i.e. inhibition of the right M1 by TMS of the left hemisphere). In contrast, the left M1 was significantly inhibited by the right hemisphere only during the control and mastication tasks, but not speech task. These results suggest that speech may facilitate the activity of the dominant M1 via functional connectivity between the speech area and the left M1, or may modify the balance of interhemispheric interactions, by suppressing inhibition of the dominant hemisphere by the non-dominant hemisphere. Our findings show a novel aspect of interhemispheric dominance and may improve therapeutic strategies for recovery from stroke.
本研究旨在通过经颅磁刺激（TMS）来确定言语和咀嚼运动对大脑左右初级运动区（M1）之间的抑制作用。 10 名健康右利手的受试者在 3 种条件下记录了来自双手第一背侧骨间肌（FDIs）的运动诱发电位（MEPs）：休息时（对照）、咀嚼时（非言语性口腔运动）和说话时（大声朗读）。在各种刺激间隔下，在对侧 M1 进行条件性 TMS 后，进行测试性 TMS。在所有条件下，左侧 M1 的条件刺激后，左侧 FDIs 的 MEPs 均受到明显抑制（即左侧半球 TMS 对右侧 M1 的抑制）。相反，仅在对照和咀嚼任务期间，而不是在言语任务期间，左侧 M1 才受到右侧半球的明显抑制。这些结果表明，言语可能通过言语区与左侧 M1 之间的功能连接来促进优势 M1 的活动，或者通过抑制非优势半球对优势半球的抑制来改变半球间相互作用的平衡。我们的发现展示了半球间优势的一个新方面，并可能改善中风康复的治疗策略。
