Sugawara Kenichi, Furubayashi Toshiaki, Takahashi Makoto, Ni Zhen, Ugawa Yoshikazu, Kasai Tatsuya
School of Rehabilitation, Faculty of Health and Social Work, Kanagawa University of Human Services, 1-10-1 Heisei-cho, Yokosuka, Kanagawa, Japan.
Neurosci Lett. 2005 Mar 22;377(1):25-30. doi: 10.1016/j.neulet.2004.11.059. Epub 2005 Jan 6.
The aim of the present study was to investigate effects of voluntary teeth clenching (VTC) on motor evoked potentials (MEPs) from the first dorsal interosseous (FDI) muscle to transcranial magnetic stimulation (TMS) by different oriented currents (anterior-medially (AM), posterior-laterally (PL)) of the human motor cortex. In active FDI, VTC enhanced MEP responses induced by AM directed current but reduced these responses induced by PL. In relaxed FDI, VTC enhanced MEP responses by AM but had no significant effects on those by PL. Thus, the results suggest that any components produced by AM directed current were enhanced, whereas those by PL directed currents were not affected or reduced. The present evidence indicates that I-waves recorded at the same latency were not completely the same between those produced by AM and PL directed currents. Because VTC had no influence on responses to brainstem electrical stimulation (BES) or F-waves just after the onset of teeth clenching [T. Furubayashi, K. Sugawara, T. Kasai, A. Hayashi, R. Hanajima, Y. Shiio, N.K. Iwara, Y. Ugawa, Remote effects of self-paced teeth clenching on the excitability of hand motor area, Exp. Brain Res., 148 (2003) 261-265], these modulatory effects on MEPs to both AM and PL directed currents must be due to changes of the motor cortical excitability. Thus, we conclude that VTC affects the motor cortical circuits activated by PL and AM directed currents differentially; it facilitates the one and inhibits the other. This is the first demonstration of opposite effects of the same maneuver on MEP responses elicited by AM and PL directed currents.
本研究的目的是通过人类运动皮层不同方向电流（前内侧（AM）、后外侧（PL））的经颅磁刺激（TMS），研究自愿紧咬牙（VTC）对第一背侧骨间肌（FDI）运动诱发电位（MEP）的影响。在活动的FDI中，VTC增强了由AM方向电流诱发的MEP反应，但降低了由PL方向电流诱发的这些反应。在放松的FDI中，VTC增强了由AM方向电流诱发的MEP反应，但对由PL方向电流诱发的反应没有显著影响。因此，结果表明，由AM方向电流产生的任何成分都增强了，而由PL方向电流产生的成分则不受影响或减少。目前的证据表明，在相同潜伏期记录的I波在由AM和PL方向电流产生的I波之间并不完全相同。因为VTC在紧咬牙开始后对脑干电刺激（BES）或F波的反应没有影响[T. Furubayashi, K. Sugawara, T. Kasai, A. Hayashi, R. Hanajima, Y. Shiio, N.K. Iwara, Y. Ugawa, 自定节奏紧咬牙对手部运动区兴奋性的远程影响，《实验脑研究》，148 (2003) 261 - 265]，对AM和PL方向电流诱发的MEP的这些调节作用一定是由于运动皮层兴奋性的变化。因此，我们得出结论，VTC对由PL和AM方向电流激活的运动皮层回路有不同的影响；它促进一种而抑制另一种。这是首次证明相同操作对由AM和PL方向电流诱发的MEP反应有相反的影响。
