Origin of facilitation of motor-evoked potentials after paired magnetic stimulation: Direct recording of epidural activity in conscious humans
Origin of facilitation of motor-evoked potentials after paired magnetic stimulation: Direct recording of epidural activity in conscious humans
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DOI：
10.1152/jn.00360.2006
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发表时间：
2006-10-01
影响因子：
2.5
通讯作者：
Rothwell, J. C.
中科院分区：
文献类型：
--
作者：
Di Lazzaro, V.;Pilato, F.;Rothwell, J. C.
以低于运动诱发电位(MEPs)活动阈值的强度在运动皮质上施加磁条件刺激，可促进10-25ms后给予阈值以上磁刺激所引起的手部肌肉静止时的肌电反应。这被称为皮层内促进(ICF)。我们记录了6名清醒患者通过植入用于止痛的高颈硬膜外电极，通过单对和成对磁运动皮质刺激产生的下行抽动。在10ms和15ms的刺激间期(ISIS)，虽然MEP被促进，但下降抽动的幅度和数目没有变化。在25ms ISI时，有时可观察到额外的I波。在一个受试者中，我们还评估了反转大脑感应电流方向的效果。在10ms ISI时，MEP的易化作用消失，取而代之的是轻微的抑制；在2ms ISI时，硬膜外抽射明显易化。随后在健康受试者身上的实验表明，能够产生MEP ICF的条件性刺激对经乳突电刺激皮质脊髓束诱发的EMG反应没有影响。我们得出结论，ICF的发生是因为1)条件性刺激对脊髓的兴奋性有一个(到目前为止还没有检测到的)效应，增加了它对相同幅度测试截击的反应，或者2)它可以改变测试刺激设置的下行截击的成分(但不是幅度)，使得更大比例的活动被指定给目标肌肉。
A magnetic transcranial conditioning stimulus given over the motor cortex at intensities below active threshold for obtaining motor-evoked potentials (MEPs) facilitates EMG responses evoked at rest in hand muscles by a suprathreshold magnetic stimulus given 10-25 ms later. This is known as intracortical facilitation (ICF). We recorded descending volleys produced by single and paired magnetic motor cortex stimulation through high cervical epidural electrodes implanted for pain relief in six conscious patients. At interstimulus intervals (ISIs) of 10 and 15 ms, although MEP was facilitated, there was no change in the amplitude or number of descending volleys. An additional I wave sometimes was observed at 25 ms ISI. In one subject, we also evaluated the effects of reversing the direction of the induced current in the brain. At 10 ms ISI, the facilitation of the MEPs disappeared and was replaced by slight suppression; at 2 ms ISI, there was a pronounced facilitation of epidural volleys. Subsequent experiments on healthy subjects showed that a conditioning stimulus capable of producing ICF of MEPs had no effect on the EMG response evoked by transmastoidal electrical stimulation of corticospinal tract. We conclude that ICF occurs because either 1) the conditioning stimulus has a (thus far undetected) effect on spinal cord excitability that increases its response to the same amplitude test volley or 2) that it can alter the composition (but not the amplitude) of the descending volleys set up by the test stimulus such that a larger proportion of the activity is destined for the target muscle.