Inhibitory influence of the ipsilateral motor cortex on responses to stimulation of the human cortex and pyramidal tract
Inhibitory influence of the ipsilateral motor cortex on responses to stimulation of the human cortex and pyramidal tract
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DOI：
10.1111/j.1469-7793.1998.249bz.x
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发表时间：
1998-07-01
影响因子：
5.5
通讯作者：
Hallett, M
中科院分区：
文献类型：
--
作者：
Gerloff, C;Cohen, LG;Hallett, M
1.初级运动皮层（M1）调节同侧手部肌肉运动反应的能力似乎对正常的运动控制很重要，也可能对脑损伤后的恢复很重要。目前尚不清楚哪些途径介导这种同侧调制。已经提出了经胼胝体的连接，但已知在灵长类动物的皮质手部运动表征之间是稀疏的。本研究的目的是确定下行同侧运动反应调制是否也可能在人类皮层水平以下介导。使用成对脉冲协议，其中运动诱发电位（MEP）产生的皮质经颅磁刺激（cTMS）或电刺激的锥体束水平的锥体交叉（pdTES），在预激活和放松的手肌肉。配对刺激施加在各种刺激间隔（ISI）之间的2和100毫秒。条件刺激（CS）总是磁性的，并提供给M1同侧的目标手，之前的测试刺激（TX）。将磁性TS输送到靶手对侧的M1;通过双侧乳突上方的电极施加电TX。进一步的实验包括皮层电刺激和H反射。分别对每个ISI和对照条件（无CX）的MEP幅度进行平均，并表示为非条件反应的百分比。条件刺激的同侧M1导致磁诱发的MEP的显着抑制，也产生的PDTES的MEP。抑制发生在6和50毫秒之间的ISI，并观察到在预激活和放松的肌肉。更高的CX强度引起cTMS和pdTES诱发的MEP的更大抑制。虽然对磁诱发肌肉反应的条件作用可以通过经胼胝体机制来解释，但对pdTEX诱发的MEP的作用不能，因为它们是在皮质下引起的，因此不容易受到在皮质-皮质水平传递的抑制机制的影响。总之，本研究结果提供了新的证据，人类MJ的抑制作用。对同侧手部肌肉的影响在很大程度上是在皮质水平下介导的，而不仅仅是通过皮质-皮质经胼胝体连接。他们指出了两个初级运动皮质之间抑制性相互作用的概念，这种抑制性相互作用沿着神经轴在多个水平沿着传递，因此可能提供了一个结构冗余的系统，在病变的情况下可能变得重要。
1. The ability of the primary motor cortex (M1) to modulate motor responses in ipsilateral hand muscles seems to be important for normal motor control and potentially also for recovery after brain lesions. It is not clear which pathways mediate this ipsilateral modulation. Transcallosal connections have been proposed, but are known to be sparse between cortical hand motor representations in primates. The present study was performed to determine whether descending ipsilateral modulation of motor responses might also be mediated below the cortical level in humans.2. A paired-pulse protocol was used, in which motor-evoked potentials (MEPs) were produced by cortical transcranial magnetic stimulation (cTMS) or by electrical stimulation of the pyramidal tract at the level of the pyramidal decussation (pdTES), in both preactivated and relaxed hand muscles. Paired stimuli were applied at various interstimulus intervals (ISIs) between 2 and 100 ms. The conditioning stimulus (CS) was always magnetic, and delivered to the M1 ipsilateral to the target hand, prior to the test stimulus (TX). The magnetic TS was delivered to the M1 contralateral to the target hand; the electrical TX was applied through electrodes placed over the mastoid process bilaterally. Further experiments included cortical electrical stimulation and H-reflexes. The MEP amplitudes were averaged separately for each ISI and the control condition (no CX), and expressed as a percentage of the unconditioned response.3. Conditioning stimulation of the ipsilateral M1 resulted in significant inhibition of magnetically evoked MEPs, and also of MEPs produced by pdTES. Inhibition occurred at ISIs between 6 and 50 ms, and was observed in preactivated and relaxed muscles. Higher CX intensities caused greater inhibition of both cTMS- and pdTES-evoked MEPs.4. While the conditioning effects on magnetically evoked muscle responses could be explained by a transcallosal mechanism, the effects on pdTEX-evoked MEPs cannot, because they are elicited subcortically and are therefore not susceptible to inhibitory mechanisms transmitted at the cortico-cortical level.5. In conclusion, the present results provide novel evidence that the inhibitory influence of the human MJ. on ipsilateral hand muscles is to a significant extent mediated below the cortical level, and not only through cortico-cortical transcallosal connections. They point to a concept of inhibitory interaction between the two primary motor cortices that is relayed at multiple levels along the neuroaxis, thus perhaps providing a structurally redundant system which may become important in case of lesions.