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首页> 外文期刊>BMC Neuroscience >Changes in corticospinal excitability and the direction of evoked movements during motor preparation: A TMS study
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Changes in corticospinal excitability and the direction of evoked movements during motor preparation: A TMS study

机译：运动准备过程中皮质脊髓兴奋性的变化和诱发运动的方向：TMS研究

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Background Preparation of the direction of a forthcoming movement has a particularly strong influence on both reaction times and neuronal activity in the primate motor cortex. Here, we aimed to find direct neurophysiologic evidence for the preparation of movement direction in humans. We used single-pulse transcranial magnetic stimulation (TMS) to evoke isolated thumb-movements, of which the direction can be modulated experimentally, for example by training or by motor tasks. Sixteen healthy subjects performed brisk concentric voluntary thumb movements during a reaction time task in which the required movement direction was precued. We assessed whether preparation for the thumb movement lead to changes in the direction of TMS-evoked movements and to changes in amplitudes of motor-evoked potentials (MEPs) from the hand muscles. Results When the required movement direction was precued early in the preparatory interval, reaction times were 50 ms faster than when precued at the end of the preparatory interval. Over time, the direction of the TMS-evoked thumb movements became increasingly variable, but it did not turn towards the precued direction. MEPs from the thumb muscle (agonist) were differentially modulated by the direction of the precue, but only in the late phase of the preparatory interval and thereafter. MEPs from the index finger muscle did not depend on the precued direction and progressively decreased during the preparatory interval. Conclusion Our data show that the human corticospinal movement representation undergoes progressive changes during motor preparation. These changes are accompanied by inhibitory changes in corticospinal excitability, which are muscle specific and depend on the prepared movement direction. This inhibition might indicate a corticospinal braking mechanism that counteracts any preparatory motor activation.
机译：背景技术即将运动的方向的准备对灵长类运动皮层中的反应时间和神经元活动都具有特别强烈的影响。在这里，我们旨在寻找直接的神经生理证据，为人类运动方向的准备。我们使用单脉冲经颅磁刺激（TMS）引起孤立的拇指运动，其方向可以通过实验来调节，例如通过训练或运动任务。 16名健康受试者在反应时间任务中执行了快速的同心自愿拇指运动，其中确定了所需的运动方向。我们评估了拇指运动的准备是否会导致TMS诱发的运动方向的改变以及手部肌肉的马达诱发电位（MEP）幅度的变化。结果当在准备间隔中提前确定所需的运动方向时，反应时间比在准备间隔结束时提前50 ms。随着时间的流逝，TMS引起的拇指运动的方向变得越来越多，但并没有朝着预定的方向转变。拇指肌肉（激动剂）的MEP受先兆方向的调节，但仅在预备间隔的后期和之后。食指肌肉的MEP并不取决于预先设定的方向，在准备间隔期间会逐渐降低。结论我们的数据表明，在运动准备过程中，人类皮质脊髓运动的表现经历了逐渐的变化。这些变化伴随着皮质脊髓兴奋性的抑制性变化，这是肌肉特异性的，并取决于所准备的运动方向。这种抑制作用可能表明皮质脊髓制动机制会抵消任何预备性的电动机激活。

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