Brain ICT Laboratory, National Institute of Information and Communications Technology, Kyoto, Japan.
PLoS One. 2011;6(10):e25670. doi: 10.1371/journal.pone.0025670. Epub 2011 Oct 4.
Procedural motor learning includes a period when no substantial gain in performance improvement is obtained even with repeated, daily practice. Prompted by the potential benefit of high-frequency transcutaneous electrical stimulation, we examined if the stimulation to the hand reduces redundant motor activity that likely exists in an acquired hand motor skill, so as to further upgrade stable motor performance. Healthy participants were trained until their motor performance of continuously rotating two balls in the palm of their right hand became stable. In the series of experiments, they repeated a trial performing this cyclic rotation as many times as possible in 15 s. In trials where we applied the stimulation to the relaxed thumb before they initiated the task, most reported that their movements became smoother and they could perform the movements at a higher cycle compared to the control trials. This was not possible when the dorsal side of the wrist was stimulated. The performance improvement was associated with reduction of amplitude of finger displacement, which was consistently observed irrespective of the task demands. Importantly, this kinematic change occurred without being noticed by the participants, and their intentional changes of motor strategies (reducing amplitude of finger displacement) never improved the performance. Moreover, the performance never spontaneously improved during one-week training without stimulation, whereas the improvement in association with stimulation was consistently observed across days during training on another week combined with the stimulation. The improved effect obtained in stimulation trials on one day partially carried over to the next day, thereby promoting daily improvement of plateaued performance, which could not be unlocked by the first-week intensive training. This study demonstrated the possibility of effectively improving a plateaued motor skill, and pre-movement somatic stimulation driving this behavioral change.
程序性运动学习包括一个阶段，即使进行重复的日常练习，也无法获得实质性的表现提升。受到高频经皮电刺激潜在益处的启发，我们研究了手部刺激是否可以减少习得性手部运动技能中可能存在的冗余运动活动，从而进一步提升稳定的运动表现。健康参与者接受训练，直到他们用右手手掌连续旋转两个球的运动表现变得稳定为止。在一系列实验中，他们在 15 秒内重复尽可能多次地进行这种循环旋转的试验。在他们开始任务之前，我们对手部放松的拇指进行刺激的试验中，大多数参与者报告说他们的动作变得更加流畅，并且可以以更高的周期进行动作，与对照试验相比。当刺激手腕的背面时，这是不可能的。这种性能提升与手指位移幅度的减小有关，无论任务需求如何，这一变化都是一致观察到的。重要的是，这种运动学变化是参与者没有注意到的，并且他们对运动策略的有意改变（减小手指位移幅度）从未改善过性能。此外，在没有刺激的情况下，经过一周的训练，性能从未自发提高，而在另一周的训练中结合刺激进行训练时，每天都能观察到与刺激相关的性能提高。在一天的刺激试验中获得的改善效果部分转移到了第二天，从而促进了稳定表现的日常提高，而第一周的密集训练无法实现这一点。本研究表明，有可能有效地改善稳定的运动技能，并通过预先的躯体刺激推动这种行为改变。
