What is Leadfield

In this article, we propose a novel preprocessing method in the spherical harmonics domain to decompose the MEG signal into specific parts, whose sources arise from user-prescribed concentric spherical regions. A particular case of this approach is presented to separate the data into parts corresponding to deep and superficial regions of the brain, without using inverse solutions. Throughout this article, plain italics denote scalars, lower case boldface symbols denote vectors, uppercase boldface symbols denote matrices, superscripts T and H stand for transpose and Hermitian transpose, and ||.||, tr(.), * indicate Euclidean norm, and trace and complex conjugate operations, respectively.