title: Dealing with the shortcomings of spatial normalization: multi-subject parcellation of fMRI datasets.
abstract: The analysis of functional magnetic resonance imaging (fMRI) data recorded on several subjects resorts to the so-called spatial normalization in a common reference space. This normalization is usually carried out on a voxel-by-voxel basis, assuming that after coregistration of the functional images with an anatomical template image in the Talairach reference system, a correct voxel-based inference can be carried out across subjects. Shortcomings of such approaches are often dealt with by spatially smoothing the data to increase the overlap between subject-specific activated regions. This procedure, however, cannot adapt to each anatomo-functional subject configuration. We introduce a novel technique for intra-subject parcellation based on spectral clustering that delineates homogeneous and connected regions. We also propose a hierarchical method to derive group parcels that are spatially coherent across subjects and functionally homogeneous. We show that we can obtain groups (or cliques) of parcels that well summarize inter-subject activations. We also show that the spatial relaxation embedded in our procedure improves the sensitivity of random-effect analysis.
authors.affiliation: Service Hospitalier Frédéric Joliot, Département de Recherche Médicale-CEA-DSV-UNAF, Orsay Cedex, France. thirion@shfj.cea.fr
authors.forename: Bertrand
authors.initials: B
authors.lastname: Thirion
authors.forename: Guillaume
authors.initials: G
authors.lastname: Flandin
authors.forename: Philippe
authors.initials: P
authors.lastname: Pinel
authors.forename: Alexis
authors.initials: A
authors.lastname: Roche
authors.forename: Philippe
authors.initials: P
authors.lastname: Ciuciu
authors.forename: Jean-Baptiste
authors.initials: JB
authors.lastname: Poline
mesh_terms: D000465:Algorithms; D001921:Brain / Q000033:anatomy & histology / Q000502:physiology; D001931:Brain Mapping / Q000379:methods*; D016000:Cluster Analysis; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D008279:Magnetic Resonance Imaging / Q000379:methods*