Item

Abstract

This chapter directly compares the current direction effect of monophasic pulses on thresholds in the visual and motor system using two different stimulator types. With a frameless stereotactic positioning system, the chapter demonstrates a dependency of phosphene maps from the visual cortex on current direction. Phosphene mapping revealed that stimulation sites evoking phosphenes bilaterally in the left and right visual field depend on the induced current direction. Under the assumption that the generator of a unilateral phosphene sits in the contralateral hemisphere bilateral phosphenes require a suprathreshold stimulation of both occipital lobes. The shift of the border from bilateral to unilateral stimulation can be directly explained because of threshold differences. The suprathreshold stimulation of the hemisphere stimulated in the preferred current direction still works with a coil position shifted over the nonpreferred hemisphere.