Effects of transcranial direct current stimulation on steady-state visual evoked potentials.

Recently, transcranial direct current stimulation (tDCS) has attracted increasing attention in the field of neuro-modulation because of its capacity to modulate cortical excitability noninvasively. Previous findings have demonstrated its effectiveness in visual studies. However, few studies have referred to steady-state visual evoked potential (SSVEP), a promising visual evoked potential that has been widely used in brain-computer interfaces. The present work investigated the effects of tDCS on SSVEPs. Sham and 1 mA real tDCS (anodal and cathodal) in a PO7-PO8 montage were administered for 15 min in 12 healthy subjects. Compared with sham conditions, both anodal and cathodal tDCS significantly decreased 7-Hz SSVEP power. Also, anodal tDCS increased 10-Hz SSVEP power. Our study demonstrated that tDCS over occipital areas altered brain activity evoked by visual stimuli.