Time Course of Corticospinal Excitability and Intracortical Inhibition Just before Muscle Relaxation.
Time Course of Corticospinal Excitability and Intracortical Inhibition Just before Muscle Relaxation.
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DOI：
10.3389/fnhum.2016.00001
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发表时间：
2016
影响因子：
2.9
通讯作者：
Higashi T
中科院分区：
文献类型：
--
作者：
Suzuki T;Sugawara K;Ogahara K;Higashi T
通过经颅磁刺激(TMS)，我们研究了短时间间隔皮质内抑制(SICI)与运动皮质(M1)兴奋性变化的关系，这些变化发生在肌肉收缩到肌肉松弛的转变之前。10名健康的参与者同时进行了同侧手指和脚的放松任务，在GO信号发出后，放松了他们最大自愿收缩(MVC)力的10%。在简单反应时(RT)范式中，在GO信号后随机发出单个或成对的TMS脉冲，并记录右侧第一背侧骨间(FDi)肌的运动诱发电位(MEP)。我们分析了在估计的松弛反应时间(RRT)之前的时间进程，这里的RRT定义为自愿松弛的开始。在单脉冲试验中，SICI在RRT前80-100ms降低，MEP在RRT前60-80ms的波幅明显大于其他间期。TMS脉冲不能有效增加RRT。这些结果表明，在肌肉松弛之前的早期阶段，大脑皮层兴奋性在肌肉松弛控制中起着重要作用。在松弛反应期间或之后，SICI回路可以在减少和增加的激活之间变化，以持续保持肌肉放松。关于M1兴奋性的动力学，我们认为SICI在肌肉松弛过程中也是动态变化的。
Using transcranial magnetic stimulation (TMS), we investigated how short-interval intracortical inhibition (SICI) was involved with transient motor cortex (M1) excitability changes observed just before the transition from muscle contraction to muscle relaxation. Ten healthy participants performed a simultaneous relaxation task of the ipsilateral finger and foot, relaxing from 10% of their maximal voluntary contraction (MVC) force after the go signal. In the simple reaction time (RT) paradigm, single or paired TMS pulses were randomly delivered after the go signal, and motor evoked potentials (MEPs) were recorded from the right first dorsal interosseous (FDI) muscle. We analyzed the time course prior to the estimated relaxation reaction time (RRT), defined here as the onset of voluntary relaxation. SICI decreased in the 80–100 ms before RRT, and MEPs were significantly greater in amplitude in the 60–80 ms period before RRT than in the other intervals in single-pulse trials. TMS pulses did not effectively increase RRT. These results show that cortical excitability in the early stage, before muscle relaxation, plays an important role in muscle relaxation control. SICI circuits may vary between decreased and increased activation to continuously maintain muscle relaxation during or after a relaxation response. With regard to M1 excitability dynamics, we suggest that SICI also dynamically changes throughout the muscle relaxation process.