Systematic Fluctuations of TMS-induced motor evoked potentials

Objectives: While latencies of transcranial magnetic stimulation (TMS) induced motor responses are relatively stable, measure of amplitude are notoriously variable (Kiers 1993) This leads to a wide range of normal values and limits its usefulness for single subjects or groups with minor differences (Magistris 1999; Wassermann 2002). The aim of this study was to investigate the correlation of motor evoked potentials (MEP) sweep-to-sweep variability with the variations of physical parameters of TMS. This should allow us to differentiate physiological and physical origins. Previous results show that trial variabili…