The brain's magnetic field: some effects of multiple sources on localization methods.

The theoretical basis for magnetic field recording (MEG) methods is briefly summarized. Lines of constant radial magnetic field on a spherical surface, which are typically used in MEG applications to locate sources, are shown for various multiple dipole sources. It is shown that the usual localization methods are subject to relatively large error if only one additional dipole is present. New methods to improve spatial resolution are discussed.