Reduction of cortico-spinal excitability by transcranial magnetic stimulation at predictable timing
Reduction of cortico-spinal excitability by transcranial magnetic stimulation at predictable timing
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DOI：
10.2170/jjphysiol.r2075
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发表时间：
2005-04-01
期刊：
影响因子：
--
通讯作者：
Naito, E
中科院分区：
文献类型：
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作者：
Takei, T;Hashimoto, T;Naito, E
电生理学研究表明，在反应时（RT）范式中，运动准备期皮质脊髓兴奋性增加。然而，有一系列相互矛盾的证据表明，经颅磁刺激（TMS）的兴奋性在准备期间降低。在这些研究中，受试者可以预测TMS的时间。因此，我们研究了TMS时间的可预测性如何影响皮质脊髓兴奋性。一个单脉冲TMS被传递到左运动皮层的手部，而七个右撇子的受试者放松他们的手在弯曲的位置。我们准备了三个条件：（i）在半可预测条件下，以500 ms的间隔呈现两个视觉刺激，并且在第一刺激后0、125、250、375或500 ms递送TMS;（ii）在可预测条件下，仅在第一刺激后500 ms提供TMS;（iii）在不可预测条件下，在TMS之前没有视觉提示。我们记录运动诱发电位（MEP）从腕屈肌和伸肌。我们发现在可预测和半可预测的条件下，屈肌MEP振幅均显著降低，但在不可预测的条件下则没有。这些结果表明，TMS本身的可预测性，没有运动输出的准备，可以降低皮质脊髓兴奋性。
Electrophysiological studies have shown that cortico-spinal excitability increases during the motor preparation period in reaction time (RT) paradigms. However, there is a line of contradictory evidence with transcranial magnetic stimulation (TMS) showing that its excitability is reduced during the preparation period. In these studies, the subjects can predict the TMS timings. Thus we investigated how the predictability of TMS timing affects cortico-spinal excitability. A single-pulse TMS was delivered to the hand section of the left motor cortex while seven right-handed subjects relaxed their hands in a flexed position. We prepared three conditions: (i) in the semi-PREDICTABLE condition, two visual stimuli at 500 ms interval were presented and the TMS was delivered either 0, 125, 250, 375, or 500 ms after the first stimulus; (ii) in the PREDICTABLE condition, the TMS was provided only at 500 ms after the first stimulus; (iii) in the UNPREDICTABLE condition, no visual cue preceded the TMS. We recorded motor evoked potentials (MEPs) from the wrist flexor and extensor muscles. We found a significant reduction of MEP amplitude in the flexor muscles in both the PREDICTABLE and semi-PREDICTABLE conditions, but not in the UNPREDICTABLE condition. These results showed that the predictability of TMS per se, without the preparation of motor outputs, can reduce cortico-spinal excitability.