Linearly constrained minimum variance beamformers, synthetic aperture magnetometry, and MUSIC in MEG applications

MUSIC and minimum variance beamformers operated without specific determination of the source orientation (LCMV) or including the orientation (SAM) are methods for discriminating among uncorrelated MEG sources by point-by-point search through the brain volume. Both beamformer types give similar dipole positions, however SAM exhibits better spatial resolution than the LCMV. For spontaneous brain activity when averaging is not possible and in the presence of multiple sources, SAM performs well, while MUSIC is sensitive to the subspace partitioning, and no clear indication about the correct partitioning can be obtained from the eigenspectra.