SIMULATION STUDIES OF MULTIPLE DIPOLE NEUROMAGNETIC SOURCE LOCALIZATION - MODEL ORDER AND LIMITS OF SOURCE RESOLUTION

Numerical simulation studies were performed using a multiple dipole so urce model and a spherical approximation of the head to examine how th e resolution of simultaneously active neuromagnetic sources depends up on: 1) source modeling assumptions (i.e., number of assumed dipoles); 2) actual source parameters (e.g., location, orientation, and moment); and 3) measurement errors. Forward calculations were conducted for a series of source configurations in which the number of dipoles, specif ic dipole parameters, and noise levels were systematically varied. Sim ulated noisy field distributions were fit by multiple dipole models of increasing model order (1, 2,..., 6 and alternative statistical appro aches (i.e., percent of variance, reduced chi-square, and F-ratio) wer e compared for their effectiveness in determining adequate model order . Limits of spatial resolution were established for a variety of multi -source configurations and noise conditions. Implications for the anal ysis of empirical data are discussed.