Todd Gabrielle, Flavel Stanley C, Ridding Michael C
Discipline of Physiology, School of Molecular and Biomedical Science, University of Adelaide, SA, Australia.
Exp Brain Res. 2009 May;195(2):307-15. doi: 10.1007/s00221-009-1791-8. Epub 2009 Apr 11.
Repetitive transcranial magnetic stimulation (rTMS) can be used to study metaplasticity in human motor cortex. The term metaplasticity describes a phenomenon where the prior synaptic history of a pathway can affect the subsequent induction of long-term potentiation or depression. In the current study, we investigated metaplasticity in human motor cortex with the use of inhibitory continuous theta-burst stimulation (cTBS). cTBS involves short bursts of high frequency (50 Hz) rTMS applied every 200 ms for 40 s. In the first series of experiments, cTBS was primed with 10 min of intermittent 2 or 6 Hz rTMS. Subjects (n = 20) received priming stimulation at 70% of active motor threshold or 90% of resting motor threshold. In another series of experiments, cTBS was primed with excitatory intermittent theta-burst stimulation (iTBS). iTBS involves a 2 s train of theta-burst stimulation delivered every 10 s for 190 s. Stimuli were delivered over the first dorsal interosseus motor area.. The effect of cTBS alone and primed cTBS on motor cortical excitability was investigated by recording motor-evoked potentials (MEP) in the first dorsal interosseus following single-pulse TMS. MEP area in the cTBS alone condition was not significantly different from cTBS primed with 2 or 6 Hz rTMS. However, priming cTBS with iTBS suppressed MEP area to a greater extent than in cTBS alone. Our results provide further evidence of metaplasticity in human motor cortex when appropriate priming protocols are employed.
重复经颅磁刺激（rTMS）可用于研究人类运动皮层的元可塑性。元可塑性一词描述了一种现象，即一条通路先前的突触历史可以影响随后长时程增强或抑制的诱导。在当前的研究中，我们使用抑制性连续theta爆发刺激（cTBS）来研究人类运动皮层的元可塑性。cTBS包括以200毫秒的间隔施加高频（50赫兹）rTMS的短脉冲串，持续40秒。在第一组实验中，cTBS先用10分钟的2赫兹或6赫兹间歇性rTMS进行预处理。受试者（n = 20）在主动运动阈值的70%或静息运动阈值的90%接受预处理刺激。在另一组实验中，cTBS先用兴奋性间歇性theta爆发刺激（iTBS）进行预处理。iTBS包括每隔10秒给予一次持续2秒的theta爆发刺激，共持续190秒。刺激施加于第一背侧骨间肌运动区。通过记录单脉冲TMS后第一背侧骨间肌的运动诱发电位（MEP），研究了单独的cTBS和预处理后的cTBS对运动皮层兴奋性的影响。单独cTBS条件下的MEP面积与用2赫兹或6赫兹rTMS预处理的cTBS无显著差异。然而，用iTBS预处理的cTBS比单独的cTBS更能抑制MEP面积。我们的结果为采用适当的预处理方案时人类运动皮层的元可塑性提供了进一步的证据。
