Simulated ECD locations. Two tangential ECDs of unit length were seeded (at the back ends of the red arrows) in the auditory cortices. The corresponding forward field is shown in the bottom-right panel. The spherical head model was applied, and the green sphere was fitted using FieldTrip , based on 192 surface points selected from head digitization. Only the points close to the two auditory cortices were used for the fit. The blue lines intersect at the anterior commissure.