Lewko J P, Stokić D S, Tarkka I M
Baylor College of Medicine, Division of Restorative Neurology and Human Neurobiology, Houston, Texas, USA.
Brain Topogr. 1996 Summer;8(4):397-405. doi: 10.1007/BF01186915.
Noninvasive transcranial magnetic stimulation (TMS) of the brain using a focal eight-shaped coil with 100% stimulation output was performed in eleven healthy subjects to find out if excitatory and inhibitory responses in the small hand muscles could be dissociated. Motor evoked potentials (MEP) as well as silent periods (SP) were recorded from the right abductor pollicis brevis (APB), and first dorsal interosseus (FDI) muscles at rest and during weak voluntary contraction. Mapping of the cortical representation area was performed over different scalp locations on the left hemisphere. The cortical representation maps for ABP and FDI recorded during contraction covered much larger area and were more elongated in the anterior-posterior than in the medial-lateral direction compared to maps obtained during relaxation. The distribution maps for SPs covered larger scalp areas compared to the maps of MEPs obtained during voluntary contraction. Also during voluntary contraction the locations for evoking the longest SPs were not identical to locations for evoking the peak MEP amplitudes; the longest SPs were observed during stimulation of more medial and frontal locations compared to peak MEPs. Interestingly, stimulation of some locations resulted in the appearance of an isolated MEP without the following SP and in other locations an isolated SP was recorded. The areas for evoking isolated MEPs were in the center, whereas the areas for isolated SPs were located in the periphery of the map. Features such as exclusive locations for MEPs and SPs, and different locations for peak MEP amplitudes and longest SPs, suggest dissociation of the excitatory and inhibitory cortical processes evoked by transcranial magnetic stimulation during voluntary contraction.
在11名健康受试者中，使用具有100%刺激输出的聚焦八字形线圈对大脑进行无创经颅磁刺激（TMS），以探究能否分离手部小肌肉中的兴奋性和抑制性反应。在静息状态和轻度自主收缩期间，从右侧拇短展肌（APB）和第一背侧骨间肌（FDI）记录运动诱发电位（MEP）以及静息期（SP）。在左半球的不同头皮位置进行皮质代表区映射。与放松期间获得的图谱相比，收缩期间记录的APB和FDI的皮质代表图谱覆盖的面积更大，并且在前后方向上比内外侧方向上更长。与自主收缩期间获得的MEP图谱相比，SP的分布图覆盖的头皮面积更大。同样在自主收缩期间，诱发最长SP的位置与诱发MEP峰值幅度的位置并不相同；与MEP峰值相比，在刺激更内侧和额叶位置时观察到最长的SP。有趣的是，刺激某些位置会导致出现孤立的MEP而没有随后的SP，而在其他位置则记录到孤立的SP。诱发孤立MEP的区域在中心，而孤立SP的区域位于图谱的周边。MEP和SP的专属位置、MEP峰值幅度和最长SP的不同位置等特征表明，在自主收缩期间经颅磁刺激诱发的兴奋性和抑制性皮质过程是分离的。
