HOW WELL DOES A 3-SPHERE MODEL PREDICT POSITIONS OF DIPOLES IN A REALISTICALLY SHAPED HEAD

The electrical potential produced by a dipole in the temporal or front al lobe was calculated for a realistically shaped scalp, skull, and br ain. This potential distribution was then used with a 3-sphere model t o predict the position, orientation, and strength of the dipole source . The original and predicted dipole positions differed by an average o f 1.97 cm, with a difference of more than 4 cm in some cases. Control calculations demonstrated that this difference was not caused by numer ical artifacts in the computation, but instead was due to a true diffe rence between the 3-sphere and realistically shaped head models.