Loo C K, Taylor J L, Gandevia S C, McDarmont B N, Mitchell P B, Sachdev P S
Schools of Psychiatry, Faculty of Medicine, University of New South Wales, Sydney, New South Wales, Australia.
Biol Psychiatry. 2000 Feb 15;47(4):325-31. doi: 10.1016/s0006-3223(99)00285-1.
Carefully designed controlled studies are essential in further evaluating the therapeutic efficacy of transcranial magnetic stimulation (TMS) in psychiatric disorders. A major methodological concern is the design of the "sham" control for TMS. An ideal sham would produce negligible cortical stimulation in conjunction with a scalp sensation akin to real treatment. Strategies employed so far include alterations in the position of the stimulating coil, but there has been little systematic study of their validity. In this study, we investigated the effects of different coil positions on cortical activation and scalp sensation.
In nine normal subjects, single TMS pulses were administered at a range of intensities with a "figure eight" coil held in various positions over the left primary motor cortex. Responses were measured as motor-evoked potentials in the right first dorsal interosseus muscle. Scalp sensation to TMS with the coil in various positions over the prefrontal area was also assessed.
None of the coil positions studied met the criteria for an ideal sham. Arrangements associated with a higher likelihood of scalp sensation were also more likely to stimulate the cortex.
The choice of a sham for TMS involves a trade-off between effective blinding and truly inactive "stimulation." Further research is needed to develop the best sham condition for a range of applications.
精心设计的对照研究对于进一步评估经颅磁刺激（TMS）在精神疾病中的治疗效果至关重要。一个主要的方法学问题是TMS“假刺激”对照的设计。理想的假刺激应在产生可忽略不计的皮层刺激的同时，伴有类似于真实治疗的头皮感觉。迄今为止采用的策略包括改变刺激线圈的位置，但对其有效性的系统研究很少。在本研究中，我们调查了不同线圈位置对皮层激活和头皮感觉的影响。
对9名正常受试者，使用“8”字形线圈在左侧初级运动皮层上方的不同位置，以一系列强度给予单个TMS脉冲。以右侧第一背侧骨间肌的运动诱发电位作为反应指标。还评估了线圈在前额叶区域不同位置时对TMS的头皮感觉。
所研究的线圈位置均不符合理想假刺激的标准。与头皮感觉可能性较高相关的设置也更有可能刺激皮层。
TMS假刺激的选择涉及有效盲法与真正无活性“刺激”之间的权衡。需要进一步研究以开发适用于一系列应用的最佳假刺激条件。
