Figure 1: Physiological effects of tDCS. (a) Illustration of the typical placement of the anode (red square) and cathode (blue square) during stimulation of the primary motor cortex. The direction of stimulation causes differential effects on neuronal activation and plasticity. (b) Illustration of anodal (red) and cathodal (blue) transcranial direct current stimulation on spike activity in animals (modified from [39]). Anodal stimulation increased subsequent spike activity by lowering the membrane potential, whereas cathodal stimulation reduced subsequent spike activity in the stimulated area by increasing the membrane potential. (c) DCS promotes LTP in motor cortical slices. The sample of fEPSPs showing a 2-hour time course after DCS (vertical gray line) (from [40]).