Comparison of cephalic and extracephalic montages for Transcranial Direct Current Stimulation - A numerical study

While studies have shown that the application of Transcranial Direct Current Stimulation (tDCS) has been beneficial in the stimulation of cortical activity and treatment of neurological disorders in humans, open questions remain regarding the placement of electrodes for optimal targeting of currents for a given functional area. Placement of electrodes has traditionally relied on knowledge of human anatomy and physiology, producing electrode montages that are believed to be best suited to a desired cortical region of stimulation. Given the difficulty of obtaining in vivo measurements of current density, modeling of conventional and alternative electrode montages via the Finite Element Method (FEM) has been utilized to provide insight into tDCS montage performance. Accurate simulations using a high definition, anatomically correct female human model based on the Visible Human Project dataset (the VHP-F model) have given evidence that extracephalic cathode locations provide deeper stimulation of the primary motor cortex than the traditional cephalic electrode montage.