Shrinking LORETA-FOCUSS: a recursive approach to estimating high spatial resolution electrical activity in the brain

To image the neural current source from the measurements of EEG, this paper describes a new approach that integrates the ideas of Low Resolution Electromagnetic Tomography(LORETA) and Focal Underdetermined System Solution(FOCUSS). Basically a weighted minimum norm inverse method, this new algorithm-termed Shrinking LORETA-FOCUSS-recursively adjusts the weighting matrix and solution space until a sparse focal solution is achieved. The computer simulation compares its performance with LORETA and FOCUSS. The results suggest this method is able to reconstruct the 3D source distribution in brain volume with very small localization error and small energy error.