Studies on the corticospinal control of human walking. I. Responses to focal transcranial magnetic stimulation of the motor cortex
Studies on the corticospinal control of human walking. I. Responses to focal transcranial magnetic stimulation of the motor cortex
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DOI：
10.1152/jn.1999.81.1.129
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发表时间：
1999-01-01
影响因子：
2.5
通讯作者：
Bonnard, M
中科院分区：
文献类型：
--
作者：
Capaday, C;Lavoie, BA;Bonnard, M
通过实验来确定在人类行走过程中，皮质脊髓束与控制踝关节屈肌和伸肌的节段运动回路的联系程度，并将其与需要注意运动活动水平的自愿运动任务进行比较。运动皮层通过经颅磁刺激线圈被激活。对于每个受试者，在规定的胫骨前肌（TA）或比目鱼肌强直性自愿收缩期间测量整个输入-输出（I-O）曲线[即运动诱发电位（MEP）与刺激强度的积分]。同样，I-O曲线是在摇摆阶段的早期测量的，或者在步行的站立阶段的早期测量的。I-O数据点采用玻尔兹曼s型函数拟合，占总数据方差的80%以上。在背景肌电图（EMG）活动水平相匹配的情况下，自愿踝关节背屈和步行摆动阶段测量的TA I-O曲线之间没有统计学上的显著差异。此外，变异系数与各任务测得的mep振幅之间的关系无显著差异。相比之下，在站立行走阶段，比目鱼肌mep的大小比自愿踝关节跖屈时平均减少了26%。此外，在站立时，相对于踝关节跖屈时，非活动TA的mep增大，并且6名受试者中有4名TA的mep大于比目鱼肌的mep。最后，在步进循环的不同阶段刺激运动皮层并没有重置循环。下一步的时间发生在预期的时刻，由相位重置曲线确定。对这一结果的一种解释是，运动皮层可能不是中枢神经系统的一部分，在步进周期中参与定时运动爆发。我们认为，在行走过程中，皮质脊髓束与控制屈肌（TA）的节段运动回路的联系比与控制伸肌（比目鱼肌）的联系更紧密。然而，在需要注意运动活动水平的自愿任务中，它同样与踝关节屈肌或伸肌的节段运动回路有关。
Experiments were done to determine the extent to which the corticospinal tract is linked with the segmental motor circuits controlling ankle flexors and extensors during human walking compared with voluntary motor tasks requiring attention to the level of motor activity. The motor cortex was activated transcranially using a focal magnetic stimulation coil. For each subject, the entire input-output (I-O) curve [i.e., the integral of the motor evoked-potential (MEP) versus stimulus strength] was measured during a prescribed tonic voluntary contraction of either the tibialis anterior (TA) or the soleus. Similarly, I-O curves were measured in the early part of the swing phase, or in the early part of the stance phase of walking. The I-O data points were fitted by the Boltzmann sigmoidal function, which accounted for greater than or equal to 80% of total data variance. There was no statistically significant difference between the I-O curves of the TA measured during voluntary ankle dorsiflexion or during the swing phase of walking, at matched levels of background electromyographic (EMG) activity. Additionally, there was no significant difference in the relation between the coefficient of variation and the amplitude of the MEPs measured in each task, respectively. In comparison, during the stance phase of walking the soleus MEPs were reduced on average by 26% compared with their size during voluntary ankle plantarflexion. Furthermore, during stance the MEPs in the inactive TA were enhanced relative to their size during voluntary ankle plantarflexion and in four of six subjects the TA MEPs were larger than those of the soleus. Finally, stimulation of the motor cortex at various phases of the step cycle did not reset the cycle. The time of the next step occurred at the expected moment, as determined from the phase-resetting curve. One interpretation of this result is that the motor cortex may not be part of the central neural system involved in timing the motor bursts during the step cycle. We suggest that during walking the corticospinal tract is more closely linked with the segmental motor circuits controlling the flexor, TA, than it is with those controlling the extensor, soleus. However, during voluntary tasks requiring attention to the level of motor activity, it is equally linked with the segmental motor circuits of ankle flexors or extensors.