PB20. Comparison between static transcranial magnetic stimulation (TMS), repetitive TMS and transcranial direct current stimulation

Abstract

Objective To investigate and compare the strength of the neuroinhibitory effect of three different techniques of non-invasive brain stimulation. Methods Transcranially evoked motor evoked potentials (MEPs) were recorded via a surface EMG of the abductor digiti minimi (ADM) in 14 healthy subjects (7 female). 25 consecutive single pulses of TMS were applied at the ADM hot spot at the stimulation intensity eliciting MEPs with an average amplitude of about 1 mV before and in regular time-intervals after the intervention. As intervention, static magnetic stimulation, slow repetitive 1 Hz TMS (rTMS) and cathodal tDCS and respective sham conditions were applied for 20 min each. EMG amplitudes were averaged and compared for each condition and each time point by a repeated measures analysis of variance with the dependent variable EMG-amplitude and the conditioning factors time-point and type of stimulation. Results In this analysis with 14 participants included there is no significant difference in effect between any of the conditions ( Fig. 1 ). Discussion Variability of data is high and thus none of the inhibitory stimulation techniques is consistently effective. Additionally, duration of stimulation in our study differed from classical protocols e.g. for cathodal tDCS (5–9 min Nitsche et al., 2003 ) and static magnetic stimulation (10 min Oliviero et al., 2011 ) which may alter their effectivity. Conclusions Due to a high variability of MEPs no significant aftereffects have been found. Significance The reproducibility of transcranial stimulation aftereffects depends on many physical stimulation and protocol parameters. Optimal parameters warranting comparison need to be identified.