Bioelectric and biomagnetic localization of deep sources in the brain: a model study

The inverse problem of localizing deep sources in a spherical head model is considered in terms of an equivalent current dipole. To locate the source from the electric surface potential the equivalent current dipole is obtained using the well-known Gabor-Nelson equations. For the external magnetic field a corresponding system of eight equations is derived on the basis of the multipole expansion. Both sets of equations are solved for a single current dipole source. In addition, an extended source modeled as a rectangular current dipole layer is considered in more detail. The analytical results show that the features of the deep sources have different effects on the bioelectric and biomagnetic localization using an equivalent current dipole.