Spatial localization of neural sources using the magnetoencephalogram

An array of superconducting quantum interference device (SQUID) biomagnetometers may be used to measure the spatio-temporal neuromagnetic field or magnetoencephalogram (MEG) produced by the brain in response to a given sensory stimulus. A popular model for the neural activity that produces these fields is a set of current dipoles. It is assumed that the location, orientation, and magnitude of the dipoles are unknown. The authors show how the problem may be decomposed into the estimation of the dipole locations using nonlinear minimization followed by linear estimation of the associated moment time series. The methods described are demonstrated in a simulated application to a three dipole problem. Cramer-Rao lower bounds are derived for the white Gaussian noise case.<>