Evidence suggesting that a transcortical reflex pathway contributes to cutaneous reflexes in the tibialis anterior muscle during walking in man
Evidence suggesting that a transcortical reflex pathway contributes to cutaneous reflexes in the tibialis anterior muscle during walking in man
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DOI：
10.1007/s002210050600
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发表时间：
1999-01-01
影响因子：
2
通讯作者：
Nielsen, J
中科院分区：
文献类型：
--
作者：
Christensen, LOD;Morita, H;Nielsen, J
研究表明，在人类行走的早期和中期摆动阶段，刺激皮肤足部传入神经可以在70-95 ms的潜伏期内促进胫骨前肌（TA）肌电活动。本研究调查了这种促进的潜在机制。在坐位强直性背屈时可能诱发反射的受试者中（17名受试者中有6名），经腓肠神经刺激（3次电击，间隔3毫秒，2.0-2.5倍感知阈值）诱发的TA肌电图中的促进作用在步行的摆动阶段具有相同的潜伏期。在强直性背屈过程中观察到的促进作用被认为是-至少部分-由一个跨皮层通路介导的。为了研究行走过程中是否存在类似的促进机制，我们对17名受试者进行了不同时间间隔的运动皮层磁刺激（1.2倍运动阈值），并与皮肤刺激相比较。在13例受试者中，先前腓肠神经刺激（调节-测试间隔为50 ~ 80 ms）诱发的运动电位比单独诱发的对照MEP和肌电图中皮肤促进电位的代数和诱发的运动电位更容易。在这些受试者中，有4人在行走时也能诱发胫骨前肌ii反射。在所有受试者中，ii反射都没有出现与MEP观察到的相似的增加。在4个被试的5个实验中，比较了脑皮层磁刺激和电刺激诱发的mep。在其中的四个实验中，只有磁诱导的mep是通过事先刺激腓肠神经而促进的。我们认为，在行走过程中，经皮质通路也可能导致晚期皮肤反射。
Stimulation of cutaneous foot afferents has been shown to evoke a facilitation of the tibialis anterior (TA) EMG-activity at a latency of 70-95 ms in the early and middle swing phase of human walking. The present study investigated the underlying mechanism for this facilitation. In those subjects in whom it was possible to elicit a reflex during tonic dorsiflexion while seated (6 out of 17 tested), the facilitation in the TA EMG evoked by stimulation of the sural nerve (3 shocks, 3-ms interval, 2.0-2.5x perception threshold) was found to have the same latency in the swing phase of walking. The facilitation observed during tonic dorsiflexion has been suggested to be - at least partly - mediated by a trans cortical pathway. To investigate whether a similar mechanism contributes to the facilitation observed during walking, magnetic stimulation of the motor cortex (1.2x motor threshold) was applied in the early swing phase at different intervals in relation to the cutaneous stimulation in 17 subjects. In 13 of the subjects, the motor potentials evoked by the magnetic stimulation (MEPs) were more facilitated by prior sural-nerve stimulation (conditioning-test intervals of 50-80 ms) than the algebraic sum of the control MEP and the cutaneous facilitation in the EMG when evoked separately. In four of these subjects, a tibialis anterior II-reflex could also be evoked during walking. In none of the subjects was an increase of the II-reflex similar to that for the MEP observed. In five experiments on four subjects, MEPs evoked by magnetic and electrical cortical stimulation were compared. In four of these experiments, only the magnetically induced MEPs were facilitated by prior stimulation of the sural nerve. We suggest that a transcortical pathway may also contribute to late cutaneous reflexes during walking.