Cortico-motoneuronal output to intrinsic hand muscles is differentially influenced by static changes in shoulder positions
Cortico-motoneuronal output to intrinsic hand muscles is differentially influenced by static changes in shoulder positions
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DOI：
10.1007/s00221-005-2270-5
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发表时间：
2005-08-01
影响因子：
2
通讯作者：
Rossi, A
中科院分区：
文献类型：
--
作者：
Dominici, F;Popa, T;Rossi, A
我们研究了肩位是否影响外展指小肌（ADM）和第一背骨间肌（FDI）的收缩特性。研究了7名健康志愿者在肩关节内收30度和外展30度两种不同静态体位(手臂被动支撑于肩关节水平（水平面90度），肘关节固定于90度时，经颅磁刺激（TMS）对ADM和FDI运动诱发电位（MEPs）的响应。在(1)以2 Hz的频率在两个不同的肩部位置外展手指时（EMG（ADM）和EMG（FDI）是回溯平均时间锁定到手指外展结束时）和(2)小指和食指最大自主外展时，也检查了ADM和FDI的自愿活动。分析两种肩位的最大肌电功率和力。两名被试也获得了ADM和FDI的h反射。经颅磁刺激的ADM刺激反应曲线显示，当肩部外展30度时，斜坡和平台水平显著降低。相反，FDI对TMS的刺激反应曲线不受肩部位置的影响。背平均肌电图（ADM）显示，在30度外展时，肌电图（FDI）的峰值幅度和面积明显减少，而在相同条件下，肌电图（FDI）没有变化。同样，当肩外展30度时，最大肌电图（ADM）和小指用力明显减少，而FDI没有观察到这种影响。肩关节外展时，ADM h反射下降，FDI不明显。这些结果表明，当肩关节外展30度时，经颅磁刺激（TMS）和自主指挥的皮质脊髓通路难以到达ADM。相比之下，无论是通过经颅磁刺激还是通过意志，FDI的激活都不受肩部位置的影响。这一发现表明，ADM和FDI的皮质脊髓神经支配存在差异，可能是由于这些肌肉在手部功能中的作用不同。
We investigated whether shoulder position influenced the recruitment properties of the abductor digiti minimi muscle (ADM) and first dorsal interosseous muscle (FDI). ADM and FDI motor evoked potentials (MEPs) in response to transcranial magnetic stimulation (TMS) were obtained in seven healthy volunteers at two different static positions of the shoulder joint (30 degrees adduction vs 30 degrees abduction) while the arm was passively supported at shoulder level (90 degrees in the horizontal plane) and the elbow joint was fixed at 90 degrees. ADM and FDI voluntary activity was also examined during (1) externally paced finger abductions at 2 Hz in the two different shoulder positions (EMG(ADM) and EMG(FDI) was back-averaged time-locked to the end of finger abduction) and (2) maximal voluntary abduction of the little finger and the index finger. Maximal EMG power and force were analysed in the two shoulder positions. H-reflexes from ADM and FDI were also obtained in two subjects. The ADM stimulus-response curve to TMS showed that the slope and plateau level were significantly reduced with the shoulder at 30 degrees abduction. In contrast, the FDI stimulus-response curve to TMS was not influenced by shoulder position. The back-averaged EMG(ADM) showed a significant decrease in peak amplitude and area with the shoulder at 30 degrees abduction, while no change in EMG(FDI) was observed under the same condition. Similarly, maximal EMG(ADM) and force exertion by the little finger were significantly reduced with the shoulder at 30 degrees abduction, while no such effect was observed for FDI. ADM H-reflex, but not FDI, was also decreased with shoulder abduction. These results indicate that the corticospinal pathway to ADM is less accessible to TMS and to voluntary command when the shoulder is placed at 30 degrees abduction. In contrast, activation of FDI, whether by TMS or by volition, is not influenced by shoulder position. This finding suggests that there are differences in the corticospinal innervation to ADM and FDI, possibly due to the different role of these muscles in hand function.