Realistic simulation of transcranial direct current stimulation via 3-d high-resolution finite element analysis: Effect of tissue anisotropy

Recently, transcranial direct current stimulation (tDCS) is getting an attentions as a promising technique with a capability of noninvasive and nonconvulsive stimulation to treat ill conditions of the brain such as depression. However, knowledge on how exactly tDCS affects the activity of neurons in the brain is still not sufficient. Precise analysis on the electromagnetic effect of tDCS on the brain requires finite element analysis (FEA) with realistic head models including anisotropy of the white matter and the skull. In this paper, we have simulated tDCS via 3-D high-resolution FEA and investigated the effect of tissue anisotropy on tDCS. The results show that the skull anisotropy induces a strong shunting effect, causing a shift of the stimulated areas, and the white matter anisotropy affects strongly the current flow directions, changing the current field distribution inside the human brain. Our presented methodology and results should be useful for more effective guiding and treatment using tDCS.