Chen R, Corwell B, Hallett M
Human Motor Control Section, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD, USA.
Exp Brain Res. 1999 Nov;129(1):77-86. doi: 10.1007/s002210050938.
We investigated the time course of changes in motor cortex excitability after median nerve and digit stimulation. Although previous studies showed periods of increased and decreased corticospinal excitability following nerve stimulation, changes in cortical excitability beyond 200 ms after peripheral nerve stimulation have not been reported. Magnetoencephalographic studies have shown an increase in the 20-Hz rolandic rhythm from 200 to 1000 ms after median nerve stimulation. We tested the hypothesis that this increase is associated with reduced motor cortex excitability. The right or left median nerve was stimulated and transcranial magnetic stimulation (TMS) was applied to left motor cortex at different conditioning-test (C-T) intervals. Motor-evoked potentials (MEPs) were recorded from the right abductor pollicis brevis (APB), first dorsal interosseous (FDI), and extensor carpi radialis (ECR) muscles. Right median nerve stimulation reduced test MEP amplitude at C-T intervals from 400 to 1000 ms for APB, at C-T intervals from 200 to 1000 ms for FDI, and at C-T intervals of 200 and 600 ms for ECR, but had no effect on FDI F-wave amplitude at a C-T interval of 200 ms. Left median nerve (ipsilateral to TMS) stimulation resulted in less inhibition than right median nerve stimulation, but test MEP amplitude was significantly reduced at a C-T interval of 200 ms for all three muscles. Digit stimulation also reduced test MEP amplitude at C-T intervals of 200-600 ms. The time course for decreased motor cortex excitability following median nerve stimulation corresponds well to rebound of the 20-Hz cortical rhythm and supports the hypothesis that this increased power represents cortical deactivation.
我们研究了正中神经和手指刺激后运动皮层兴奋性的变化时间过程。尽管先前的研究表明神经刺激后皮质脊髓兴奋性有升高和降低的时期，但外周神经刺激后200毫秒以上的皮质兴奋性变化尚未见报道。脑磁图研究显示，正中神经刺激后200至1000毫秒，20赫兹的罗兰节律增强。我们检验了这样一个假设，即这种增强与运动皮层兴奋性降低有关。刺激右侧或左侧正中神经，并在不同的条件-测试（C-T）间隔对左侧运动皮层施加经颅磁刺激（TMS）。从右侧拇短展肌（APB）、第一背侧骨间肌（FDI）和桡侧腕伸肌（ECR）记录运动诱发电位（MEP）。右侧正中神经刺激在APB的C-T间隔为400至1000毫秒时、FDI的C-T间隔为200至1000毫秒时以及ECR的C-T间隔为200和600毫秒时降低测试MEP的幅度，但在C-T间隔为200毫秒时对FDI的F波幅度没有影响。左侧正中神经（与TMS同侧）刺激产生的抑制作用小于右侧正中神经刺激，但在C-T间隔为200毫秒时，所有三块肌肉的测试MEP幅度均显著降低。手指刺激在C-T间隔为200 - 600毫秒时也降低测试MEP幅度。正中神经刺激后运动皮层兴奋性降低的时间过程与20赫兹皮质节律的反弹非常吻合，并支持了这种功率增加代表皮质失活的假设。
