Service de Neurologie, Centre Hospitalier Universitaire de Toulouse, Pôle Neurosciences, CHU Purpan, Place du Dr Baylac, TSA40031, 31059 Toulouse Cedex 9, France.
Exp Brain Res. 2012 Sep;221(4):449-58. doi: 10.1007/s00221-012-3187-4. Epub 2012 Jul 24.
The interhemispheric interactions between homologous wrist extensor and flexor muscles representations in the right and left primary cortex (M1) were studied using a paired-pulse transcranial magnetic stimulation in healthy subjects. The magnitude of interhemispheric inhibition (IHI) was studied in 9 right-handed subjects at short (10 ms, SIHI) and long (40 ms, LIHI) interstimulus intervals between the magnetic conditioning (CS) and test stimulus in the motor dominant to non-dominant cortex and vice versa, while the right or left hand was at rest or performing a unimanual sustained tonic contraction (holding a pen with the hand contralateral to the CS). A bidirectional powerful interhemispheric inhibition could be elicited at the short and long IHI phases (SIHI and LIHI) in wrist extensor and flexor muscles in most of the subjects at rest. SIHI but not LIHI was significantly bidirectionally reduced during unimanual contraction of the hand contralateral to the CS stimulation in comparison with rest. The amount of IHI after the stimulation of the "non-dominant" right hemisphere was not reduced in comparison with IHI after stimulation of the "dominant" left hemisphere whatever the active or resting condition. IHI directed to the wrist muscles had a similar level than IHI directed to digit muscles (FDI) at rest. Our data indicate that contralateral wrist muscles activity evokes a global, bidirectional reduction in IHI which was more pronounced for SIHI. These results provide additional evidence that changes in interhemispheric interactions between the M1s are involved in the control of unimanual movements including suppression of unwanted motor activity in the opposite limb during unilateral movements.
本研究使用成对经颅磁刺激技术，在健康受试者中研究了双侧初级运动皮层（M1）中同源腕伸肌和屈肌代表区之间的半球间相互作用。在 9 名右利手受试者中，研究了短（10 ms，SIHI）和长（40 ms，LIHI）刺激间隔时，磁刺激（CS）与测试刺激之间的半球间抑制（IHI）程度，刺激对侧非优势侧 M1 和同侧 M1 时，右手或左手处于休息状态或进行单手持续紧张收缩（用与 CS 刺激对侧的手握住笔）。在大多数受试者休息时，腕伸肌和屈肌在短和长 IHI 阶段（SIHI 和 LIHI）均可引出双向强半球间抑制。与休息时相比，在 CS 刺激对侧手进行单手收缩时，SIHI 而非 LIHI 明显双向减少。与刺激优势侧左半球后的 IHI 相比，无论活动或休息状态如何，刺激“非优势”右半球后的 IHI 量均未减少。与休息时相比，对指向腕肌的 IHI 与指向 FDI 的 IHI 水平相似。本研究结果表明，对侧腕肌活动引起 IHI 的全局双向减少，而 SIHI 更为明显。这些结果进一步证明，M1 之间的半球间相互作用的变化参与了单侧运动的控制，包括在单侧运动期间抑制对侧肢体的不想要的运动活动。
