The authors wish to thank Dr. D. Leibovici and Prof. P.A. Valdés-Sosa for helpful discussions on multi-way analysis, Dr. D.J. McGonigle for granting access to the FMRI data, Prof. P.M. Matthews and Dr. H. Johansen-Berg for their advice on neuroanatomy and Prof. M.S. Cohen for helpful discussions about MR physics. The authors gratefully acknowledge the financial support from the UK EPSRC and GlaxoSmithKline.