The investigators have provided proof-of principle evidence for persisting improvement of cognitive planning by a polarity-specific learning-stage dependent coupling of training and stimulation. The investigators have demonstrated that working memory and deficient cognitive control can be enhanced with anodal tDCS in depression and that the effects of tDCS are modulated by genetic polymorphisms. The investigators were the first to show impaired cortical plasticity following tDCS in schizophrenia patients at different disease states. Finally, the investigators have just successfully finished the world-wide largest clinical trial investigating the efficacy of non-invasive brain stimulation (rTMS) on negative symptoms in schizophrenia (DFG 241/10-1, Falkai, Hasan).