Ziemann U, Tergau F, Netz J, Hömberg V
Department of Clinical Neurophysiology, Georg-August-University of Gttingen, Germany.
Brain Res. 1997 Jan 2;744(1):32-40. doi: 10.1016/s0006-8993(96)01062-1.
It is known that the execution of the motor response in a simple reaction time (RT) task can be delayed by transcranial magnetic stimulation (TMS). This paper is aimed at determining the site of action where the delay in RT occurs. A delay in RT was obtained only at those TMS sites over the motor cortex contralateral to the responding hand, which produced also a muscle twitch in the responding hand. The delay in RT covaried with the TMS intensity and increased the closer the time of TMS approached the expected time of reaction onset. Visual and auditory go-signals yielded similar delays in RT, but only when TMS was applied about 40 ms later for the visual go-signal, corresponding to the modality specific difference in RT control values. TMS of the supplementary motor area (SMA) immediately prior to the expected time of reaction onset produced no delay in RT. Spinal excitability as tested by F waves showed a pre-movement facilitation in the control trials which continued seemingly undisturbed during the period of RT delay after TMS. It can be concluded that the delay in RT is not due to SMA stimulation or spinal inhibition but depends on effective stimulation of neural elements in the motor cortex which are active very late in the process of movement release from the final motor output stage.
众所周知，在简单反应时（RT）任务中，运动反应的执行可能会因经颅磁刺激（TMS）而延迟。本文旨在确定RT延迟发生的作用部位。仅在与反应手对侧的运动皮层上的那些TMS部位获得了RT延迟，这些部位也会在反应手中产生肌肉抽搐。RT延迟与TMS强度相关，并且在TMS时间越接近预期反应开始时间时增加。视觉和听觉启动信号在RT中产生了相似延迟，但仅当对视觉启动信号的TMS应用大约延迟40毫秒时，这与RT控制值中的模态特异性差异相对应。在预期反应开始时间之前立即对辅助运动区（SMA）进行TMS，在RT中未产生延迟。通过F波测试的脊髓兴奋性在对照试验中显示出运动前促进作用，在TMS后的RT延迟期间似乎持续不受干扰。可以得出结论，RT延迟不是由于SMA刺激或脊髓抑制，而是取决于对运动皮层中神经元的有效刺激，这些神经元在从最终运动输出阶段开始的运动释放过程中非常晚才活跃。
