Mouthon A, Ruffieux J, Wälchli M, Keller M, Taube W
Department of Medicine, Movement and Sport Science, University of Fribourg, Switzerland.
Department of Medicine, Movement and Sport Science, University of Fribourg, Switzerland.
Neuroscience. 2015 Sep 10;303:535-43. doi: 10.1016/j.neuroscience.2015.07.031. Epub 2015 Jul 17.
Non-physical balance training has demonstrated to be efficient to improve postural control in young people. However, little is known about the potential to increase corticospinal excitability by mental simulation in lower leg muscles. Mental simulation of isolated, voluntary contractions of limb muscles increase corticospinal excitability but more automated tasks like walking seem to have no or only minor effects on motor-evoked potentials (MEPs) evoked by transcranial magnetic stimulation (TMS). This may be related to the way of performing the mental simulation or the task itself. Therefore, the present study aimed to clarify how corticospinal excitability is modulated during AO+MI, MI and action observation (AO) of balance tasks. For this purpose, MEPs and H-reflexes were elicited during three different mental simulations (a) AO+MI, (b) MI and (c) passive AO. For each condition, two balance tasks were evaluated: (1) quiet upright stance (static) and (2) compensating a medio-lateral perturbation while standing on a free-swinging platform (dynamic). AO+MI resulted in the largest facilitation of MEPs followed by MI and passive AO. MEP facilitation was significantly larger in the dynamic perturbation than in the static standing task. Interestingly, passive observation resulted in hardly any facilitation independent of the task. H-reflex amplitudes were not modulated. The current results demonstrate that corticospinal excitability during mental simulation of balance tasks is influenced by both the type of mental simulation and the task difficulty. As H-reflexes and background EMG were not modulated, it may be argued that changes in excitability of the primary motor cortex were responsible for the MEP modulation. From a functional point of view, our findings suggest best training/rehabilitation effects when combining MI with AO during challenging postural tasks.
非身体平衡训练已被证明对改善年轻人的姿势控制有效。然而，关于通过对小腿肌肉进行心理模拟来增加皮质脊髓兴奋性的潜力，人们知之甚少。对肢体肌肉孤立、自主收缩的心理模拟会增加皮质脊髓兴奋性，但像行走这样更自动化的任务似乎对经颅磁刺激（TMS）诱发的运动诱发电位（MEP）没有影响或只有轻微影响。这可能与进行心理模拟的方式或任务本身有关。因此，本研究旨在阐明在平衡任务的动作观察加想象（AO+MI）、想象（MI）和动作观察（AO）过程中皮质脊髓兴奋性是如何被调节的。为此，在三种不同的心理模拟过程中引出MEP和H反射：（a）AO+MI，（b）MI和（c）被动AO。对于每种情况，评估两项平衡任务：（1）安静直立站立（静态）和（2）站在自由摆动平台上时补偿中外侧扰动（动态）。AO+MI导致MEP的促进作用最大，其次是MI和被动AO。动态扰动时MEP的促进作用明显大于静态站立任务。有趣的是，被动观察几乎没有产生任何促进作用，与任务无关。H反射幅度没有被调节。目前的结果表明，在平衡任务的心理模拟过程中，皮质脊髓兴奋性受心理模拟类型和任务难度的影响。由于H反射和背景肌电图没有被调节，可以认为初级运动皮层兴奋性的变化是MEP调节的原因。从功能的角度来看，我们的研究结果表明，在具有挑战性的姿势任务中，将MI与AO相结合时训练/康复效果最佳。
