Di Lazzaro V, Oliviero A, Profice P, Insola A, Mazzone P, Tonali P, Rothwell J C
Istituto di Neurologia, Università Cattolica, Rome, Italy.
Exp Brain Res. 1999 Feb;124(4):520-4. doi: 10.1007/s002210050648.
Electromyographic (EMG) responses evoked in hand muscles by a magnetic test stimulus over the motor cortex can be suppressed if a conditioning stimulus is applied to the opposite hemisphere 6-30 ms earlier. In order to define the mechanism and the site of action of this inhibitory phenomenon, we recorded descending volleys produced by the test stimulus through high cervical, epidural electrodes implanted for pain relief in three conscious subjects. These could be compared with simultaneously recorded EMG responses in hand muscles. When the test stimulus was given on its own it evoked three waves of activity (I-waves) in the spinal cord, and a small EMG response in the hand. A prior conditioning stimulus to the other hemisphere suppressed the size of both the descending spinal cord volleys and the EMG responses evoked by the test stimulus when the interstimulus interval was greater than 6 ms. In the spinal recordings, the effect was most marked for the last I-wave (I3), whereas the second I2-wave was only slightly inhibited, and the first I-wave (I1) was not inhibited at all. We conclude that transcranial stimulation over the lateral part of the motor cortex of one hemisphere can suppress the excitability of the contralateral motor cortex.
如果在运动皮层上施加磁测试刺激之前6 - 30毫秒，在对侧半球施加一个条件刺激，那么手部肌肉中由该磁测试刺激诱发的肌电图（EMG）反应就会被抑制。为了确定这种抑制现象的机制和作用部位，我们通过为三名清醒受试者植入的用于缓解疼痛的高颈段硬膜外电极，记录了测试刺激产生的下行冲动。这些下行冲动可以与同时记录的手部肌肉的EMG反应进行比较。当单独给予测试刺激时，它在脊髓中诱发了三波活动（I波），并在手部诱发了一个小的EMG反应。当刺激间隔大于6毫秒时，对另一半球的先前条件刺激会抑制测试刺激诱发的下行脊髓冲动的大小以及EMG反应。在脊髓记录中，这种效应在最后一波I波（I3）上最为明显，而第二波I2波仅略有抑制，第一波I波（I1）则完全没有受到抑制。我们得出结论，对一个半球运动皮层外侧部分的经颅刺激可以抑制对侧运动皮层的兴奋性。
