Lin Chien-Ho Janice, Winstein Carolee J, Fisher Beth E, Wu Allan D
Division of Biokinesiology and Physical Therapy, School of Dentistry, University of Southern California, Los Angeles, CA, USA.
J Mot Behav. 2010 Jul-Aug;42(4):223-32. doi: 10.1080/00222895.2010.492720.
The authors applied transcranial magnetic stimulation (TMS) to investigate the causal role of the primary motor cortex (M1) for the contextual-interference effect in motor learning. Previous work using a nonfocal TMS coil suggested a casual role for M1 during high-interference practice conditions, but this hypothesis has not yet been proven. In the 1st experiment, participants practiced 3 rapid elbow flexion-extension tasks in either a blocked or random order, with learning assessed by a delayed retention test. TMS was delivered immediately after feedback during practice using a circular coil, centered over the contralateral M1. Each participant practiced with 1 of 3 TMS conditions: no TMS, real TMS, or sham TMS. Although no significant differences were observed between groups during acquisition, retention of the random group was better than the blocked group. The learning benefits of random practice were attenuated in the real-TMS condition, but not in the sham-TMS or no-TMS conditions. In the second experiment, the authors studied the effects of suprathreshold TMS and subthreshold TMS over M1, lateral premotor cortex, and peripheral arm stimulation using a focal figure-8 coil on motor learning under random practice conditions. The authors found that only suprathreshold TMS on M1 produced significant disruption of retention compared to the other stimulation conditions. Results suggest that a high-threshold neuronal population within M1 is causally important for enhanced retention following random, but not block, practice. Results also support the early intertrial interval as a critical period of M1 activity during practice. Overall, these results suggest neural circuits within M1 contribute to motor learning processing that depends on learners' training experience. Results contribute to knowledge of the critical and specific role that M1 plays in generating a learning advantage following high-interference practice conditions.
作者应用经颅磁刺激（TMS）来研究初级运动皮层（M1）在运动学习中对情境干扰效应的因果作用。以往使用非聚焦TMS线圈的研究表明，在高干扰练习条件下M1起到了因果作用，但这一假设尚未得到证实。在第一个实验中，参与者以组块或随机顺序练习3项快速肘部屈伸任务，并通过延迟保持测试来评估学习情况。在练习过程中，每次反馈后立即使用圆形线圈在对侧M1中心施加TMS。每位参与者在3种TMS条件之一进行练习：无TMS、真TMS或假TMS。虽然在习得过程中各实验组之间未观察到显著差异，但随机组的保持情况优于组块组。随机练习的学习优势在真TMS条件下被削弱，但在假TMS或无TMS条件下未被削弱。在第二个实验中，作者使用聚焦的“8”字形线圈研究了阈上TMS和阈下TMS对M1、外侧运动前皮层以及外周手臂刺激在随机练习条件下对运动学习的影响。作者发现，与其他刺激条件相比，仅M1上的阈上TMS对保持产生了显著干扰。结果表明，M1内的高阈值神经元群对于随机练习（而非组块练习）后增强的保持具有因果重要性。结果还支持练习过程中的早期试间间隔是M1活动的关键时期。总体而言，这些结果表明M1内的神经回路有助于依赖学习者训练经验的运动学习过程。这些结果有助于了解M1在高干扰练习条件后产生学习优势中所起的关键和特定作用。
