Electrophysiological Analysis of Gait and Posture Laboratory, Sensory Motor Performance Program, Rehabilitation Institute of Chicago, 345 East Superior Street, Chicago, IL 60611, USA.
Biomed Res Int. 2013;2013:516427. doi: 10.1155/2013/516427. Epub 2012 Dec 26.
Activity-dependent plasticity as a result of reorganization of neural circuits is a fundamental characteristic of the central nervous system that occurs simultaneously in multiple sites. In this study, we established the effects of subthreshold transcranial magnetic stimulation (TMS) over the primary motor cortex region on the tibialis anterior (TA) long-latency flexion reflex. Neurophysiological tests were conducted before and after robotic gait training in one person with a motor incomplete spinal cord injury (SCI) while at rest and during robotic-assisted stepping. The TA flexion reflex was evoked following nonnociceptive sural nerve stimulation and was conditioned by TMS at 0.9 TA motor evoked potential resting threshold at conditioning-test intervals that ranged from 70 to 130 ms. Subthreshold TMS induced a significant facilitation on the TA flexion reflex before training, which was reversed to depression after training with the subject seated at rest. During stepping, corticospinal facilitation of the flexion reflex at early and midstance phases before training was replaced with depression at early and midswing followed by facilitation at late swing after training. These results constitute the first neurophysiologic evidence that locomotor training reorganizes the cortical control of spinal interneuronal circuits that generate patterned motor activity, modifying spinal reflex function, in the chronic lesioned human spinal cord.
活动依赖性的可塑性是由于神经回路的重组，这是中枢神经系统的一个基本特征，它同时发生在多个部位。在这项研究中，我们确定了阈下经颅磁刺激（TMS）对初级运动皮层区域对胫骨前肌（TA）长潜伏期屈肌反射的影响。在一名运动不完全性脊髓损伤（SCI）患者进行机器人步态训练前后，在休息和机器人辅助踏步期间，对其进行了神经生理测试。在非伤害性的腓肠神经刺激后，诱发 TA 屈肌反射，并通过 TMS 在 0.9 TA 运动诱发电位静息阈值的条件 - 测试间隔（70 至 130ms）进行调节。阈下 TMS 在训练前对 TA 屈肌反射有明显的易化作用，而在训练后，当受试者在休息时坐着时，这种易化作用则变为抑制。在踏步期间，在训练前的早期和中期支撑阶段，屈肌反射的皮质脊髓易化作用被抑制所取代，随后在晚期摆动阶段再次出现易化作用。这些结果构成了第一个神经生理学证据，表明运动训练改变了脊髓反射功能，重组了产生模式化运动活动的脊髓中间神经元回路的皮质控制，在慢性损伤的人类脊髓中。
