[1] UCL, Inst Neurol, Dept Clin & Expt Epilepsy, London, England
[2] Univ Manchester, Imaging Sci & Biomed Engn, Manchester, Lancs, England
[3] UCL, Dept Comp Sci, London, England
[4] UCL, Inst Neurol, NMR Res Unit, London, England
[5] Kings Coll London, Inst Psychiat, Dept Neurol, Ctr Neuroimaging Sci, London WC2R 2LS, England