National Rehabilitation Hospital, Georgetown University, Washington, DC, USA.
Neurorehabil Neural Repair. 2011 Jun;25(5):398-411. doi: 10.1177/1545968310395600. Epub 2011 Feb 22.
The neurophysiological mechanisms underlying improved upper-extremity motor skills have been partially investigated in patients with good motor recovery but are poorly understood in more impaired individuals, the majority of stroke survivors.
The authors studied changes in primary motor cortex (M1) excitability (motor evoked potentials [MEPs], contralateral and ipsilateral silent periods [CSPs and ISPs] using transcranial magnetic stimulation [TMS]) associated with training-induced reaching improvement in stroke patients with severe arm paresis (n = 11; Upper-Extremity Fugl-Meyer score (F-M) = 27 ± 6).
All patients underwent a single session of reaching training focused on moving the affected hand from a resting site to a target placed at 80% of maximum forward reaching amplitude in response to a visual "GO" cue. Triceps contribute primarily as agonist and biceps primarily as antagonist to the trained forward reaching movement. Response times were recorded for each reaching movement.
Preceding training (baseline), greater interhemispheric inhibition (measured by ISP) in the affected triceps muscle, reflecting inhibition from the nonlesioned to the lesioned M1, was observed in patients with lower F-M scores (more severe motor impairment). Training-induced improvements in reaching were greater in patients with slower response times at baseline. Increased MEP amplitudes and decreased ISPs and CSPs were observed in the affected triceps but not in the biceps muscle after training.
These results indicate that along with training-induced motor improvements, training-specific modulation of intrahemispheric and interhemispheric mechanisms occurs after reaching practice in chronic stroke patients with substantial arm impairment.
在运动功能恢复良好的患者中，已经部分研究了改善上肢运动技能的神经生理机制，但在运动功能受损更严重的患者（大多数为脑卒中幸存者）中，其机制仍知之甚少。
作者研究了脑卒中后上肢运动严重瘫痪患者（上肢 Fugl-Meyer 评分（F-M）=27±6）经训练后，与运动改善相关的初级运动皮层（M1）兴奋性（经颅磁刺激[TMS]记录的运动诱发电位[MEPs]、对侧和同侧静息期[CSP 和 ISP]）的变化。
所有患者均接受单次上肢训练，其任务为在视觉“GO”提示下，将患手从休息位置移动至目标位置，目标位置为最大向前伸展幅度的 80%。三头肌主要作为主动肌，二头肌主要作为拮抗肌参与训练的向前伸展运动。为每次伸展运动记录反应时间。
在训练前（基线），根据 ISP （反映非病变半球对病变 M1 的抑制作用）的测量，F-M 评分较低（运动功能损伤更严重）的患者，其患侧三头肌的抑制作用更强。在基线时反应时间较慢的患者，其伸展运动的改善程度更大。在训练后，患侧三头肌的 MEP 振幅增加，ISP 和 CSP 减少，但肱二头肌无此变化。
这些结果表明，在慢性脑卒中且上肢运动功能严重受损的患者中，经过上肢伸展训练后，除了运动功能的改善，还会出现针对特定训练的同侧和对侧半球机制的调节。
