Priori A, Bertolasi L, Dressler D, Rothwell J C, Day B L, Thompson P D, Marsden C D
MRC Human Movement and Balance Unit, Institute of Neurology, London, UK.
Electroencephalogr Clin Neurophysiol. 1993 Apr;89(2):131-7. doi: 10.1016/0168-5597(93)90095-7.
We compared single motor unit and surface EMG responses in the active right tibialis anterior following anodal electrical or magnetic stimulation of the motor cortex over the vertex. Magnetic stimulation used a monophasic current pulse through a circular coil centred 3 cm anterior to the vertex. Lowest threshold magnetic stimulation occurred when the current in the coil flowed from the left to the right side at the posterior rim of the coil. Such stimulation produced single unit and surface EMG responses which had the same latency as those produced by anodal electric stimulation. If the direction of the magnetic stimulating current was reversed, response latencies became more variable from unit to unit, and on average they occurred 1.0 +/- 0.5 msec later. In single motor units anodal and magnetic post-stimulus time histogram (PSTH) peaks had the same duration. This was similar to the duration of the PSTH peaks produced by a single low intensity stimulus given to the common peroneal nerve. We conclude that magnetic stimulation can produce direct activation of corticospinal neurones to the tibialis anterior if the direction of induced current flow is optimal. This projection is likely to be either monosynaptic or oligosynaptic.
我们比较了在头顶对运动皮层进行阳极电刺激或磁刺激后，右侧主动胫骨前肌的单个运动单位和表面肌电图反应。磁刺激通过一个位于头顶前方3厘米处的圆形线圈施加单相电流脉冲。当线圈中的电流从线圈后缘的左侧流向右侧时，出现最低阈值磁刺激。这种刺激产生的单个单位和表面肌电图反应的潜伏期与阳极电刺激产生的反应相同。如果磁刺激电流的方向相反，单位之间的反应潜伏期变得更具变异性，平均延迟1.0 +/- 0.5毫秒。在单个运动单位中，阳极和磁刺激后的时间直方图（PSTH）峰值持续时间相同。这与对腓总神经给予单个低强度刺激产生的PSTH峰值持续时间相似。我们得出结论，如果感应电流的方向最佳，磁刺激可以直接激活皮质脊髓神经元至胫骨前肌。这种投射可能是单突触或寡突触的。
