1 Department of Diagnostic Medicine, Dell Medical School, The University of Texas at Austin, Austin, USA.
2 Département d'Informatique et Recherche Opérationnelle, Université de Montréal, Montréal, Canada; Centre de recherche de l'institut Universitaire de Gériatrie de Montréal, Montréal, Canada. Electronic address: pierre.bellec@criugm.qc.ca.
3 Oxford Centre for Functional MRI of the Brain (FMRIB), Wellcome Centre for Integrative Neuroimaging, Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, United Kingdom.