Anodal occipital tDCS enhances spontaneous alpha activity

Transcranial direct current stimulation (tDCS) is a form of brain stimulation technique that modulates neuronal excitability changes in targeted cerebral areas through a constant low current. The existing studies mainly concentrated in tDCS effects on motor cortex. The number of tDCS studies targeting visual area is sparse. And parameters of tDCS on the visual cortex are not well optimized yet. Therefore, this study explored the effect of anodal occipital tDCS in eyes-open resting state to disclose possible modulation to spontaneous brain activity by electroencephalography (EEG). Fifteen healthy subjects were involved in this study. Each subject endured sham and anodal tDCS in turn. 2 mA tDCS was applied over 21 min with Oz-Cz montage. Amplitudes of spontaneous brain activities were evaluated for each experimental condition. Compared with pre-stimulation and sham tDCS, anodal tDCS caused an obvious increment in parieto-occipital alpha activity. These results demonstrated electrophysiological changes in EEG oscillations induced by anodal occipital tDCS, and would help to improve the understanding of modulation of tDCS-induced visual cortex excitability changes in humans.