Effects of tissue dielectric properties on the electric field induced in tDCS: a sensitivity analysis.

Numerical modeling studies remain the only viable way to accurately predict the electric field (E-field) distribution in transcranial direct current stimulation (tDCS). Despite the existence of multiple studies of this kind, a wide range of different values and properties for the electrical conductivities of the tissues represented is employed. This makes it difficult to predict whether the changes observed between models are due to differences in the geometries of the volume conductors or to the different electrical properties of the tissues. In this study we used the finite element method to calculate the E-field distribution in several spherical head models whose tissues were represented with different isotropic and anisotropic conductivity profiles. Results show that the distribution of the E-field is especially sensitive to the conductivity of the skull, skin and GM. These results might help comparing numerical modeling studies that employ different conductivity values.