Investigation of coil tilt by transcranial magnetic stimulation (TMS) of the motor cortex using a navigation system

Introduction: It has been assumed that the maximum induced electrical field (mIEF) evoked by a TMS coil occurs at the point at which a line perpendicular to the coil surface and through its center intercepts the cortical surface (P-line point). This concept implies that a change of the angle of incidence (I-angle) at a point on the cortical surface does not cause a migration of the mIEF. We challenged this assumption by examining the effect of two types of coil rotation. Methods: We used a neuronavigation system to calculate the relative position of the volunteer's head to the coil. MRI scans of 11 healthy adult…