Department of Sport Science, University of Freiburg, Freiburg, 79117, Germany.
Bernstein Center Freiburg, University of Freiburg, Freiburg, 79104, Germany.
J Physiol. 2020 Aug;598(16):3485-3500. doi: 10.1113/JP279879. Epub 2020 Jun 8.
The primary motor cortex (M1) is fundamentally important for the acquisition of skilled motor behaviours. We tested the excitability changes of distinct M1 circuits at movement onset with TMS H-reflex conditioning. Human subjects trained a discrete spatiotemporal motor skill. Practice was associated with reduced kinematic variability and improved motor performance. Performance improvements were paralleled by task-specific excitability increases of the fastest corticospinal connections at infragranular layer 5b of M1. No task-related changes in excitability were observed at supragranular layers. Excitability changes in the fastest corticospinal connections were not directly related to changes in motor performance.
The primary motor cortex (M1) is fundamentally important for the acquisition of skilled motor behaviours. Recent advances in imaging and electrophysiological techniques have improved our understanding of M1 neural circuit modulation in rodents and non-human primates during motor learning. However, little remains known about the learning-related changes of distinct elements in the human brain. In this study, we tested excitability changes of different neural circuits (infragranular and supragranular layers) in the M1 of human subjects who underwent training in a discrete spatiotemporal motor skill. Excitability modulations were assessed by recording H-reflex facilitation from transcranial magnetic stimulation at movement onset. Motor practice improved the consistency of movements and was accompanied by an excitability increase of the fastest corticospinal connections during the initial stages of motor practice. No such excitability changes were observed for training in a simple motor skill and circuits at supragranular layers of M1. Notably, changes in excitability were not associated with changes in motor performance. Our findings could reflect learning-related increases in the recruitment and/or reorganisation of the fastest corticospinal connections.
初级运动皮层（M1）对于获得熟练的运动行为至关重要。我们使用 TMS H 反射的条件反射测试了运动开始时不同 M1 回路的兴奋性变化。人类受试者接受了离散时空运动技能的训练。练习与运动的运动学变异性降低和运动表现提高有关。运动表现的提高与 M1 内颗粒层 5b 中最快皮质脊髓连接的特定任务兴奋性增加相平行。在颗粒层以上没有观察到与任务相关的兴奋性变化。最快皮质脊髓连接的兴奋性变化与运动表现的变化没有直接关系。
初级运动皮层（M1）对于获得熟练的运动行为至关重要。成像和电生理技术的最新进展提高了我们对啮齿动物和非人类灵长类动物在运动学习过程中 M1 神经回路调制的理解。然而，对于人类大脑中不同元素的学习相关变化知之甚少。在这项研究中，我们测试了在进行离散时空运动技能训练的人类受试者的 M1 中不同神经回路（内颗粒层和外颗粒层）的兴奋性变化。通过在运动开始时记录经颅磁刺激的 H 反射易化来评估兴奋性调制。运动练习提高了运动的一致性，并伴随着运动练习初始阶段最快皮质脊髓连接的兴奋性增加。在简单运动技能和 M1 外颗粒层的训练中没有观察到这种兴奋性变化。值得注意的是，兴奋性的变化与运动表现的变化无关。我们的发现可能反映了与学习相关的最快皮质脊髓连接的募集和/或重组的增加。
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