Influence of current direction in transcranial magnetic stimulation (TMS) on MEP amplitude and latency – opportunity of I wave specific evaluation and stimulation

Introduction: It has been shown from invasive epidural recordings that in transcranial magnetic stimulation (TMS) a current in the brain flowing from a posterior to an anterior (p.a.) direction mainly evokes I1, I2 and I3 waves whereas a current flowing from an anterior to a posterior direction mainly evokes I3 waves. This leads to the hypotheses that in p.a. current direction the motor threshold (MT) is lower, motor evoked potentials (MEPs) are higher and latency is shorter than in a.p. direction. The aim of this study was to re-evaluate the inconsistent results in literature by means of a stimulation technique…