Orth M, Rothwell J C
Sobell Department of Motor Neuroscience and Movement Disorders, The National Hospital for Neurology and Neurosurgery, Royal Free and University College Medical School, Institute of Neurology, London, UK.
Clin Neurophysiol. 2004 May;115(5):1076-82. doi: 10.1016/j.clinph.2003.12.025.
To assess the variability of the duration of the contralateral cortical silent period (CSP) between individuals and to assess the effect of different transcranial magnetic stimulation (TMS) pulse waveforms.
In Expt. 1, CSP duration, and the motor-evoked potential (MEP) amplitude and area were measured in the first dorsal interosseous muscle (FDI) of 11 subjects on 3 separate occasions using a TMS intensity of 150% active motor threshold (AMT). In Expt. 2, the stimulation intensity was varied between 100% AMT and 150% AMT. In both sets of experiments, 3 types of TMS pulse were used: monophasic posterior-anterior (PA) induced current in the brain, monophasic anterior-posterior induced current (AP), and biphasic PA/AP stimulation.
Experiment 1: Between-subject variation in CSP duration was high. In addition, the duration after PA stimulation was significantly shorter than after AP or PA/AP stimulation. However, there was a good correlation between CSP duration and the area, or amplitude, of the MEP. This meant that calculating the ratio of duration/amplitude or duration/area reduced intersubject variability and eliminated differences between TMS pulses. Experiment 2: increasing stimulation intensity increased the mean value of all parameters, but with significantly lower values for PA than other forms of stimulation. The ratios of duration/amplitude or duration/area did not differ between current flow directions and were relatively constant for intensities 130-150% AMT.
Between-subject variation in the duration of the CSP is high. A given intensity of stimulation (expressed in %AMT) produces a shorter CSP for PA stimulation than for AP or PA/AP stimulation.
If the ratio (CSP duration)/(MEP size) is calculated, then intersubject variability is reduced, and TMS pulse type differences are eliminated.
评估个体间对侧皮质静息期（CSP）持续时间的变异性，并评估不同经颅磁刺激（TMS）脉冲波形的影响。
在实验1中，使用150%运动阈强度（AMT）的TMS，在3个不同时间点测量11名受试者第一背侧骨间肌（FDI）的CSP持续时间、运动诱发电位（MEP）幅度和面积。在实验2中，刺激强度在100%AMT至150%AMT之间变化。在两组实验中，使用了3种类型的TMS脉冲：在大脑中诱导单相后-前（PA）电流、单相前-后诱导电流（AP）以及双相PA/AP刺激。
实验1：CSP持续时间的个体间差异很大。此外，PA刺激后的持续时间明显短于AP或PA/AP刺激后的持续时间。然而，CSP持续时间与MEP的面积或幅度之间存在良好的相关性。这意味着计算持续时间/幅度或持续时间/面积的比值可降低个体间变异性，并消除TMS脉冲之间的差异。实验2：增加刺激强度会增加所有参数的平均值，但PA刺激的值明显低于其他形式的刺激。持续时间/幅度或持续时间/面积的比值在电流方向之间没有差异，并且在130 - 150%AMT强度下相对恒定。
CSP持续时间的个体间差异很大。给定强度的刺激（以%AMT表示）对PA刺激产生的CSP比对AP或PA/AP刺激产生的CSP短。
如果计算（CSP持续时间）/（MEP大小）的比值，则个体间变异性会降低，并且TMS脉冲类型差异会消除。
