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首页> 外文期刊>Journal of Neurophysiology >Origin of facilitation of motor-evoked potentials after paired magnetic stimulation: direct recording of epidural activity in conscious humans.
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Origin of facilitation of motor-evoked potentials after paired magnetic stimulation: direct recording of epidural activity in conscious humans.

机译：配对磁刺激后促进电机诱发电位的起源：在有意识的人类中直接记录硬膜外活动。

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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.
机译：以低于活动阈值的强度在运动皮层上施加的经颅磁调节刺激以获得运动诱发电位（MEP），通过在10-25毫秒后给予超阈值磁刺激，促进手部肌肉在静止时诱发的EMG反应。这被称为皮质内促进（ICF）。我们记录了由六只意识清醒的患者植入的高颈硬膜外硬膜外电极通过单次和配对的磁运动皮层刺激产生的下降齐射。在刺激间隔（ISI）为10和15 ms时，尽管促进了MEP，但降落的幅度或数量没有变化。在25 ms ISI时有时会观察到另外的I波。在一个主题中，我们还评估了反转大脑中感应电流方向的效果。 ISI 10毫秒时，对MEP的促进消失了，取而代之的是轻微的抑制;在ISI 2毫秒时，明显改善了硬膜外截击。随后在健康受试者上进行的实验表明，能够产生MEP的ICF的条件刺激对经脊髓上皮电刺激皮质脊髓束引起的EMG反应没有影响。我们得出结论认为，ICF的发生是由于以下两种情况：1）条件刺激对脊髓兴奋性具有（至今尚未发现）效应，从而增加了其对相同幅度测试截击的响应，或者2）可以改变神经刺激的成分（但幅度没有改变）。测试刺激引起的下降抽射，使得较大比例的活动指定给目标肌肉。

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