Amassian V E, Cracco R Q, Maccabee P J, Cracco J B
Department of Physiology, SUNY, Health Science Center, Brooklyn 11203.
Electroencephalogr Clin Neurophysiol. 1992 Aug;85(4):265-72. doi: 10.1016/0168-5597(92)90115-r.
Focal stimulation over human cerebellum with a figure 8 magnetic coil (MC) results in an evoked wave recorded from bipolar scalp electrodes on the interaural line and more anteriorly. In 3 subjects, the wave responses along the interaural line had latencies of 8.8-13.8 msec, lasted 17.4-29.0 msec and had a maximum amplitude of 14.4-26.8 microV. The responses were recorded more anteriorly from leads midway between the interaural line and frontal leads; responses recorded from frontal leads were up to 3.5 msec later. The evoked wave was preceded by a diphasic EMG response with a latency of 1.2-2.0 msec. Analysis of the averaged responses recorded by adjoining bipolar leads indicated that the response was predominantly surface positive and crossed. Control experiments eliminated eye movement and somatosensory input as explanations of the evoked response, thereby identifying it as a cortical response. The surface positive wave in humans was compared with the responses recorded in cat and monkey to cerebellar stimulation. The responses in humans could reflect dysfacilitation through MC activation of Purkinje cells, or feed-forward facilitation through transsynaptic or antidromic activation of dentate neurons. The latency of the surface positive wave exceeds that of cerebellar inhibition of MC elicited hand muscle responses, but the discrepancy is at least partly accounted for by the extra delay required to set up the indirect cortico-spinal component required for motoneuron discharge. Estimates made of the cerebello-frontal cortical and peripheral feedback loop times suggest that the central has less than one quarter the delay of the peripheral loop, which would be especially advantageous during fast skilled movements of the fingers.
用8字形磁线圈（MC）对人类小脑进行局灶性刺激，会在双耳线上及更靠前位置的双极头皮电极记录到诱发波。在3名受试者中，沿双耳线的波反应潜伏期为8.8 - 13.8毫秒，持续时间为17.4 - 29.0毫秒，最大振幅为14.4 - 26.8微伏。在双耳线与额部导联中间位置的导联上，在更靠前位置记录到反应；从额部导联记录的反应延迟达3.5毫秒。诱发波之前有潜伏期为1.2 - 2.0毫秒的双相肌电图反应。对相邻双极导联记录的平均反应分析表明，该反应主要为表面阳性且呈交叉状。对照实验排除了眼动和体感输入作为诱发反应的解释，从而将其确定为皮质反应。将人类的表面阳性波与猫和猴小脑刺激记录的反应进行比较。人类的反应可能反映了通过MC激活浦肯野细胞导致的去易化，或通过齿状神经元的突触前或逆向激活产生的前馈易化。表面阳性波的潜伏期超过了小脑抑制MC诱发手部肌肉反应的潜伏期，但这种差异至少部分是由于建立运动神经元放电所需的间接皮质脊髓成分所需的额外延迟所致。对小脑 - 额叶皮质和外周反馈回路时间的估计表明，中枢回路的延迟不到外周回路的四分之一，这在手指快速熟练运动期间将特别有利。
