A method to localize source activity in neocortex using measured scalp potential

Spline based surface Laplacians are used as an accurate method for estimating the source activities in the brain. The spline-Laplacian accurately estimates distributed sources and it is insensitive to subcortical sources including the sources which are located outside the boundaries of the electrode array which the author uses to record EEG. It also acts as a bandpass spatial filter improving the spatial resolution obtained by this method over that obtained with conventional EEG by at least a factor of three. The author outlines the surface Laplacian method for general ellipsoidal surfaces in terms of the spline function.