Sommer Martin, Alfaro Aránzazu, Rummel Milena, Speck Sascha, Lang Nicolas, Tings Tobias, Paulus Walter
Department of Clinical Neurophysiology, University of Göttingen, Robert-Koch-Street 40, 37075 Göttingen, Germany.
Clin Neurophysiol. 2006 Apr;117(4):838-44. doi: 10.1016/j.clinph.2005.10.029. Epub 2006 Feb 21.
To compare half sine transcranial magnetic stimuli (TMS) with conventional monophasic and biphasic stimuli, measuring resting and active motor threshold, motor evoked potential (MEP) input/output curve, MEP latency, and silent period duration.
We stimulated the dominant hand representation of the motor cortex in 12 healthy subjects utilising two different MagPro stimulators to generate TMS pulses of distinct monophasic, half sine and biphasic shape with anteriorly or posteriorly directed current flow.
The markedly asymmetric monophasic pulse with a posterior current flow in the brain yielded a higher motor threshold, a less steep MEP input/output curve and a longer latency than all other TMS types. Similar but less pronounced results were obtained with a less asymmetric half sine pulses. The biphasic stimuli yielded the lowest motor threshold and a short latency, particularly with the posterior current direction.
The more asymmetric the monophasic pulse, the stronger the difference to biphasic pulses. The 3rd and 4th quarter cycle of the biphasic waveform make it longer than any other waveform studied here and likely contribute to lowering motor threshold, shortening MEP latency and reversing the influence of current direction.
This systematic comparison of 3 waveforms and two current directions allows a better understanding of the mechanisms of TMS.
比较半正弦经颅磁刺激（TMS）与传统单相和双相刺激，测量静息和主动运动阈值、运动诱发电位（MEP）输入/输出曲线、MEP潜伏期和静息期持续时间。
我们使用两种不同的MagPro刺激器刺激12名健康受试者运动皮层的优势手代表区，以产生具有不同单相、半正弦和双相形状且电流流向为向前或向后的TMS脉冲。
大脑中电流向后流动的明显不对称单相脉冲产生的运动阈值高于所有其他TMS类型，MEP输入/输出曲线较平缓，潜伏期更长。不对称程度较低的半正弦脉冲也得到了类似但不太明显的结果。双相刺激产生的运动阈值最低，潜伏期最短，尤其是电流向后时。
单相脉冲越不对称，与双相脉冲的差异就越大。双相波形的第三和第四季度周期使其比此处研究的任何其他波形都长，这可能有助于降低运动阈值、缩短MEP潜伏期并扭转电流方向的影响。
对三种波形和两种电流方向的这种系统比较有助于更好地理解TMS的机制。
