Burke-Cornell Medical Research Institute, White Plains, NY, USA.
J Neuroeng Rehabil. 2011 Aug 24;8:46. doi: 10.1186/1743-0003-8-46.
A single session of isolated repetitive movements of the thumb can alter the response to transcranial magnetic stimulation (TMS), such that the related muscle twitch measured post-training occurs in the trained direction. This response is attributed to transient excitability changes in primary motor cortex (M1) that form the early part of learning. We investigated; (1) whether this phenomenon might occur for movements at the wrist, and (2) how specific TMS activation patterns of opposing muscles underlie the practice-induced change in direction.
We used single-pulse suprathreshold TMS over the M1 forearm area, to evoke wrist movements in 20 healthy subjects. We measured the preferential direction of the TMS-induced twitch in both the sagittal and coronal plane using an optical goniometer fixed to the dorsum of the wrist, and recorded electromyographic (EMG) activity from the flexor carpi radialis (FCR) and extensor carpi radialis (ECR) muscles. Subjects performed gentle voluntary movements, in the direction opposite to the initial twitch for 5 minutes at 0.2 Hz. We collected motor evoked potentials (MEPs) elicited by TMS at baseline and for 10 minutes after training.
Repetitive motor training was sufficient for TMS to evoke movements in the practiced direction opposite to the original twitch. For most subjects the effect of the newly-acquired direction was retained for at least 10 minutes before reverting to the original. Importantly, the direction change of the movement was associated with a significant decrease in MEP amplitude of the antagonist to the trained muscle, rather than an increase in MEP amplitude of the trained muscle.
These results demonstrate for the first time that a TMS-twitch direction change following a simple practice paradigm may result from reduced corticospinal drive to muscles antagonizing the trained direction. Such findings may have implications for training paradigms in neurorehabilitation.
单次孤立的拇指重复运动可以改变经颅磁刺激（TMS）的反应，使得训练后测量的相关肌肉抽搐发生在训练方向。这种反应归因于初级运动皮层（M1）的短暂兴奋性变化，这是学习的早期部分。我们研究了：（1）这种现象是否可能发生在手腕运动中，以及（2）拮抗肌的特定 TMS 激活模式如何构成方向训练变化的基础。
我们使用单脉冲超阈值 TMS 刺激 M1 前臂区域，以诱发 20 名健康受试者的手腕运动。我们使用固定在手腕背侧的光学测角器测量矢状面和冠状面中 TMS 诱导的抽搐的优先方向，并记录来自屈肌腕桡侧（FCR）和伸肌腕桡侧（ECR）肌肉的肌电图（EMG）活动。受试者以 0.2 Hz 的频率进行 5 分钟的柔和自愿运动，方向与初始抽搐相反。我们在基线和训练后 10 分钟收集 TMS 诱发的运动诱发电位（MEP）。
重复运动训练足以使 TMS 诱发与原始抽搐相反的训练方向的运动。对于大多数受试者，新获得的方向效果至少保持 10 分钟，然后恢复到原始方向。重要的是，运动方向的变化与拮抗肌的 MEP 振幅显著降低相关，而不是训练肌的 MEP 振幅增加。
这些结果首次表明，简单的训练范式后 TMS-抽搐方向的变化可能是由于对拮抗于训练方向的肌肉的皮质脊髓驱动减少所致。这些发现可能对神经康复中的训练范式具有启示意义。
