Institute of Neuroscience, Université Catholique de Louvain, Brussels, Belgium.
Center for Neuroprosthetics and Brain Mind Institute, Swiss Federal Institute of Technology (EPFL), Campus Biotech, Geneva, Switzerland.
J Neurophysiol. 2020 Dec 1;124(6):1656-1666. doi: 10.1152/jn.00378.2020. Epub 2020 Sep 30.
Training can improve motor skills and modify neural activity at rest and during movement execution. Learning-related modulations may also concern motor preparation but the neural correlates and the potential behavioral relevance of such adjustments remain unclear. In humans, preparatory processes have been largely investigated using transcranial magnetic stimulation (TMS) with several studies reporting decreased corticospinal excitability (CSE) relative to a baseline measure at rest; a phenomenon called preparatory suppression. Here, we investigated the effect of motor training on such preparatory suppression, in relation to resting CSE, in humans. We trained participants to initiate quick movements in an instructed-delay reaction time (RT) task and used TMS to investigate changes in CSE over the practice blocks. Training on the task speeded up RTs, with no repercussion on error rates. Training also increased resting CSE. Most interestingly, we found that CSE during action preparation did not mirror the training-related increase observed at rest. Rather, compared with the rising baseline, the degree of preparatory suppression strengthened with practice. This training-related change in preparatory suppression (but not the changes in baseline CSE) predicted RT gains: the subjects showing a greater strengthening of preparatory suppression were also those exhibiting larger gains in RTs. Finally, such a relationship between RTs and preparatory suppression was also evident at the single-trial level, though only in the nonselected effector: RTs were generally faster in trials where preparatory suppression was deeper. These findings suggest that training induces changes in motor preparatory processes that are linked to an enhanced ability to initiate fast movements. Movement preparation involves a broad suppression in the excitability of the corticospinal pathway, a phenomenon called preparatory suppression. Here, we show that motor training strengthens preparatory suppression and that this strengthening is associated with faster reaction times. Our findings highlight a key role of preparatory suppression in training-driven behavioral improvements.
训练可以改善运动技能，并在休息和运动执行期间改变神经活动。与学习相关的调节也可能涉及运动准备，但这些调整的神经相关性和潜在的行为相关性尚不清楚。在人类中，准备过程主要使用经颅磁刺激 (TMS) 进行研究，多项研究报告称，与休息时的基线测量相比，皮质脊髓兴奋性 (CSE) 降低；这种现象称为预备性抑制。在这里，我们研究了运动训练对这种预备性抑制的影响，以及与休息时 CSE 的关系。我们训练参与者在指令延迟反应时间 (RT) 任务中快速启动运动，并使用 TMS 来研究 CSE 在练习块中的变化。任务训练加速了 RT，而不会对错误率产生影响。训练还增加了休息时的 CSE。最有趣的是，我们发现动作准备期间的 CSE 与休息时观察到的训练相关增加并不一致。相反，与上升基线相比，预备性抑制的程度随着练习而增强。预备性抑制的这种与训练相关的变化（而不是基线 CSE 的变化）预测了 RT 的提高：表现出预备性抑制增强的受试者也表现出 RT 更大的提高。最后，这种 RT 和预备性抑制之间的关系在单试次水平上也是明显的，尽管仅在非选择效应器中：在预备性抑制更深的试验中，RT 通常更快。这些发现表明，训练会引起运动预备过程的变化，这些变化与更快地启动运动的能力增强有关。运动准备涉及皮质脊髓通路兴奋性的广泛抑制，这种现象称为预备性抑制。在这里，我们表明运动训练增强了预备性抑制，并且这种增强与更快的反应时间有关。我们的发现强调了预备性抑制在训练驱动的行为改善中的关键作用。
