Fig. 1

Frontal view of the simulated electric field (normal component (En) with tDCS configuration used in the study. The simulated electric field was obtained with StimViewer (Neuroelectrics®), using the realistic head model described in Miranda et al. [60]. Briefly, tissue boundaries were derived from MR images (scalp, skull, cerebrospinal fluid (CSF) – including ventricles, grey matter and white matter) and the Finite Element Method was used to calculate the electric potential in the head, with circular electrodes with a 3.14 cm2 area. Tissues were assumed to be uniform and isotropic and values for their electric conductivity were taken from the literature. A positive value for the component of the electric field normal to the cortical surface means the electric field normal component is pointing into the cortex, and such a field would be excitatory. On the other hand, an electric field pointing out of the cortex (negative normal component) would be inhibitory. Details of the simulation parameters are taken from https://www.neuroelectrics.com/wiki/index.php/Simulating_tCS_Electric_Fields_in_the_Brain