Cantello R, Gianelli M, Civardi C, Mutani R
Department of Neurology, University School of Medicine, Novara, Italy.
Neurology. 1992 Oct;42(10):1951-9. doi: 10.1212/wnl.42.10.1951.
In 25 normal subjects, we studied the EMG silent period following the magnetic motor evoked potential (MEP) when the target muscle was tonically contracted (post-EMP silent period [PMSP]). In the first dorsal interosseous muscle (FDI), PMSP duration increased in linear proportion to stimulus intensity, but not to the size of the preceding MEP. The PMSP was longer in hand and forearm muscles than in upper arm muscles. In the FDI, PMSP was longer than the peripheral silent period (PSP) even when multiple peripheral stimuli were used to get M responses whose twitch force was equivalent to that of MEPs. Weak magnetic stimuli evoked silent periods preceded by no MEP in several subjects. Spinal alpha-motoneurons (alpha-MNs) were partially inhibited during the first PMSP portion, but later this effect recovered. MEPs due to weak electrical stimuli to motor cortex were only slightly inhibited during the late PMSP. Segmental inhibitory loops evoked by the muscle twitch and inhibitory projections descending to alpha-MNs from the cortex predominantly underlie earlier PMSP portions, but recurrent intracortical inhibition may also contribute. Later portions are predominantly due to other stimulus-related cerebral inhibitory or suppressing phenomena.
在25名正常受试者中，我们研究了目标肌肉进行强直性收缩时磁运动诱发电位（MEP）后的肌电图静息期（EMP后静息期[PMSP]）。在第一骨间背侧肌（FDI）中，PMSP持续时间与刺激强度呈线性比例增加，但与先前MEP的大小无关。手部和前臂肌肉的PMSP比上臂肌肉更长。在FDI中，即使使用多个外周刺激来获得与MEP抽搐力相当的M反应时，PMSP也比外周静息期（PSP）更长。在几名受试者中，弱磁刺激诱发的静息期之前没有MEP。在第一个PMSP部分期间，脊髓α运动神经元（α-MNs）受到部分抑制，但随后这种效应恢复。在PMSP后期，由对运动皮层的弱电刺激引起的MEP仅受到轻微抑制。由肌肉抽搐诱发的节段性抑制环路以及从皮层下行至α-MNs的抑制性投射主要构成早期PMSP部分的基础，但皮层内反复抑制也可能起作用。后期部分主要归因于其他与刺激相关的大脑抑制或抑制现象。
