A real electro-magnetic placebo (REMP) device for sham transcranial magnetic stimulation (TMS

Objective: There is growing interest in neuropsychiatry for repetitive transcranial magnetic stimulation (rTMS) as a neuromodulatory treatment. However, there are limitations in interpreting rTMS effects as a real consequence of physiological brain changes or as placebo-mediated unspecific effects, which may be particularly strong in psychiatric patients. This is due to the fact that existing sham rTMS procedures are less than optimal. A new placebo tool is introduced here, called real electro-magnetic placebo (REMP) device, which can simulate the scalp sensation induced by the real TMS, while leaving both the visual impact and acoustic sensation of real TMS unaltered. Methods: Physical, neurophysiological and behavioural variables of monophasic and biphasic single-pulse TMS and biphasic 1 Hz and 20 Hz rTMS procedures (at different intensities) were tested in subjects who were expert or naive of TMS. Results of the real TMS were compared with those induced by the REMP device and with two other currently used sham procedures, namely the commercially available Magstim sham coil and tilting the real coil by 90 degrees. Results: The REMP device, besides producing scalp sensations similar to the real TMS, attenuated the TMS-induced electric field (as measured by a dipole probe) to a biologically inactive level. Behaviourally, neither expert nor naive TMS subjects identified the coil at 90 degrees or the Magstim sham coil as a real TMS intervention, whilst naive subjects were significantly more likely to identify the REMP-attenuated TMS as real. Conclusions: The goodness of sham of the REMP device is demonstrated by physical, neurophysiological, and behavioural results. Significance: Such placebo TMS is superior to the available sham procedures when applied on subjects naive to TMS, as in case of patients undergoing a clinical rTMS trial. (c) 2006 International Federation of Clinical Neurophysiology. Published by Elsevier Ireland Ltd. All rights reserved.