Current orientation induced by magnetic stimulation influences a cognitivetask

The direction of the current induced by transcranial magnetic stimulation ( TMS) over the motor cortex has been observed to influence the threshold and latency of evoked muscle responses. This study investigates the effect of TMS-induced current orientation (ICO) over the prefrontal cortex, on a spec ific cognitive task (memory-guided saccade). TMS was applied with a figure- of-eight coil, placed at one of eight different orientations over the prefr ontal cortex. The most effective ICO was antero-lateral, which is a differe nt optimal ICO from that seen over the hand area of the motor cortex. This demonstrates that ICO can alter the effect of TMS on cognitive functions an d that ICO is an independent variable that should not be ignored when desig ning TMS studies. NeuroReport 11:3257-3259 (C) 2000 Lippincott Williams & W ilkins.