Spatiotemporal source imaging of brain magnetic fields associated with short-term memory by linear and nonlinear optimization methods

In the biomagnetic inverse problem, it is important that the optimal method be selected, especially when estimating internal electrical sources for higher functions with poor information about their source profile. In this paper, internal sources of brain magnetic fields associated with short-term memory processes were estimated by: 1) a nonlinear parameter optimization method using a multidipole model and 2) a linear optimization method using an L1 minimum norm estimation (L1-MNE) technique. Both methods showed almost the same sources: in the inferior part of the occipital lobe, the supramarginal gyrus and the angular gyrus, and the inferior frontal gyrus. These results indicate the reliability and availability of these methods for brain magnetic data associated with higher brain functions.