Chen R, Corwell B, Yaseen Z, Hallett M, Cohen L G
Human Cortical Physiology Unit, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland 20892-1430, USA.
J Neurosci. 1998 May 1;18(9):3443-50. doi: 10.1523/JNEUROSCI.18-09-03443.1998.
The human motor system undergoes reorganization after amputation, but the site of motor reorganization and the mechanisms involved are unknown. We studied the site and mechanisms of motor reorganization in 16 subjects with traumatic lower-limb amputation. Stimulation at different levels in the CNS was used to determine the site of reorganization. The mechanisms involved were evaluated by measuring the thresholds for transcranial magnetic stimulation (TMS) and by testing intracortical inhibition and facilitation. With TMS, the threshold for muscle activation on the amputated side was lower than that of the intact side, but with transcranial electrical stimulation there was no difference in motor threshold between the two sides. TMS at the maximal output of the stimulator activated a higher percentage of the motor neuron pool (%MNP) on the amputated side than on the intact side. The %MNP activated by spinal electrical stimulation was similar on the two sides. Paired TMS study showed significantly less intracortical inhibition on the amputated side. Our findings suggest that motor reorganization after lower-limb amputation occurs predominately at the cortical level. The mechanisms involved are likely to include reduction of GABAergic inhibition.
截肢后人体运动系统会发生重组，但运动重组的部位及相关机制尚不清楚。我们对16名创伤性下肢截肢患者的运动重组部位及机制进行了研究。通过在中枢神经系统的不同水平进行刺激来确定重组部位。通过测量经颅磁刺激（TMS）的阈值以及测试皮质内抑制和易化来评估相关机制。使用TMS时，截肢侧肌肉激活的阈值低于健侧，但经颅电刺激时两侧运动阈值无差异。在刺激器最大输出强度下进行TMS时，截肢侧激活的运动神经元池百分比（%MNP）高于健侧。脊髓电刺激激活的%MNP在两侧相似。配对TMS研究显示截肢侧皮质内抑制明显减少。我们的研究结果表明，下肢截肢后的运动重组主要发生在皮质水平。其相关机制可能包括γ-氨基丁酸能抑制的减少。
