title: Beamformer reconstruction of correlated sources using a modified source model.
abstract: This paper introduces a lead field formulation for use in beamformer analysis of MEG data. This 'dual source beamformer' is a technique to image two temporally correlated sources using beamformer methodology. We show that while the standard, single source beamformer suppresses the reconstructed power of two spatially separate but temporally correlated sources, the dual source beamformer allows for their accurate reconstruction. The technique is proven to be accurate using simulations. We also show that it can be used to image accurately the auditory steady state response, which is correlated between the left and right auditory cortices. We suggest that this technique represents a useful way of locating correlated sources, particularly if a seed location can be defined a priori for one of the two sources. Such a priori information could be based on previous studies using similar paradigms, or from other functional neuroimaging techniques.
authors.affiliation: The Sir Peter Mansfield Magnetic Resonance Centre, School of Physics and Astronomy, University of Nottingham, University Park, Nottingham, NG7 2RD, UK. brookes@magres.nottingham.ac.uk
authors.forename: Matthew J
authors.initials: MJ
authors.lastname: Brookes
authors.forename: Claire M
authors.initials: CM
authors.lastname: Stevenson
authors.forename: Gareth R
authors.initials: GR
authors.lastname: Barnes
authors.forename: Arjan
authors.initials: A
authors.lastname: Hillebrand
authors.forename: Michael I G
authors.initials: MI
authors.lastname: Simpson
authors.forename: Susan T
authors.initials: ST
authors.lastname: Francis
authors.forename: Peter G
authors.initials: PG
authors.lastname: Morris
mesh_terms: D001303:Auditory Cortex / Q000000981:diagnostic imaging*; D001931:Brain Mapping / Q000379:methods; D003198:Computer Simulation; D004574:Electromagnetic Fields; D007839:Functional Laterality; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D008959:Models, Neurological; D011859:Radiography; D015203:Reproducibility of Results