The Nick Davey Laboratory, Division of Surgery, Department of Surgery and Cancer, Faculty of Medicine, Imperial College London, UK.
J Physiol. 2018 Apr 1;596(7):1295-1306. doi: 10.1113/JP275312. Epub 2018 Feb 25.
Increases in activity of trunk muscles that occur prior to, or concurrent with, a voluntary limb movement are termed anticipatory postural adjustments (APAs). APAs are important for maintaining postural stability in response to perturbations but the neural mechanisms underlying APAs remain unclear. Our results showed that corticospinal excitability of erector spinae (ES) muscle increased at 40 ms prior to rapid shoulder flexion, with a reduction in intracortical inhibition and no change in spinal excitability. Changes in corticospinal excitability were observed in ES, with similar excitability profiles between standing and lying positions, but were not observed in rectus abdominis. We suggest that the neural control of postural adjustments involves changes at a cortical level, which in part are due to reduced inhibition.
Voluntary limb movements are associated with increases in trunk muscle activity, some of which occur within a time window considered too fast to be induced by sensory feedback; these increases are termed anticipatory postural adjustments (APAs). Although it is known that the function of APAs is to maintain postural stability in response to perturbations, excitability of the corticospinal projections to the trunk muscles during the APAs remains unclear. Thirty-four healthy subjects performed rapid shoulder flexion in response to a visual cue in standing and lying positions. Transcranial magnetic stimulation (TMS) was delivered over the trunk motor cortex to examine motor evoked potentials (MEPs) in erector spinae (ES) and in rectus abdominis (RA) muscles at several time points prior to the rise in electromyographic activity (EMG) of anterior deltoid (AD) muscle. TMS was also used to assess short-interval intracortical inhibition (SICI) and cervicomedullary MEPs (CMEPs) in ES in the standing position. MEPs in ES were larger at time points closer to the rise in AD EMG in both standing and lying positions, whereas MEPs in RA did not differ over the time course examined. Notably, SICI was reduced at time points closer to the rise in AD EMG, with no change in CMEPs. Our results demonstrate that increasing excitability of corticospinal projections to the trunk muscles prior to a voluntary limb movement is likely to be cortical in origin and is muscle specific.
在自愿肢体运动之前或同时发生的躯干肌肉活动增加被称为预期姿势调整（APAs）。APAs 对于响应扰动维持姿势稳定性很重要，但 APAs 的神经机制仍不清楚。我们的结果表明，竖脊肌（ES）的皮质脊髓兴奋性在快速肩部前屈前 40 毫秒增加，皮质内抑制减少，脊髓兴奋性没有变化。在 ES 中观察到皮质脊髓兴奋性的变化，在站立和卧位之间具有相似的兴奋性曲线，但在腹直肌中未观察到。我们认为，姿势调整的神经控制涉及皮质水平的变化，其中部分原因是抑制作用降低。
自愿肢体运动与躯干肌肉活动增加有关，其中一些发生在被认为太快而不能由感觉反馈引起的时间窗口内；这些增加被称为预期姿势调整（APAs）。虽然已知 APAs 的功能是响应扰动维持姿势稳定性，但在 APAs 期间对躯干肌肉的皮质脊髓投射兴奋性仍不清楚。34 名健康受试者在站立和卧位下响应视觉提示进行快速肩部前屈。在几个时间点，在三角肌前束（AD）肌电图升高之前，经颅磁刺激（TMS）施加于躯干运动皮层，以检查竖脊肌（ES）和腹直肌（RA）肌肉的运动诱发电位（MEPs）。TMS 还用于评估站立位 ES 中的短程皮质内抑制（SICI）和颈髓 MEPs（CMEPs）。在站立和卧位下，ES 中的 MEPs 在更接近 AD 肌电图升高的时间点更大，而 RA 中的 MEPs 在整个时间过程中没有差异。值得注意的是，SICI 在更接近 AD 肌电图升高的时间点降低，而 CMEPs 没有变化。我们的结果表明，在自愿肢体运动之前增加对躯干肌肉的皮质脊髓投射兴奋性可能起源于皮质，并且是肌肉特异性的。
