Does repetitive anodal tDCS applied on the visual cortex induce long-term improvements in visual contrast perception?

Introduction: Anodal transcranial direct current stimulation (tDCS) can induce upward excitability shifts in the primary visual cortex, e.g. as measured by an altered TMS phosphene threshold in V1 (Nitsche et al. 2008). However the effect of a singular stimulation is limited to 10–20 minutes (Antal et al. 2006). In the motor system it was demonstrated that anodal tDCS over multiple days facilitated motor skill acquisition through an effect of consolidation. The skill acquisition measure remained greater for anodal tDCS even after three months (Reis et al. 2009). In analogy to the motor system we investigate in t…