[1] Washington Univ, Sch Med, Dept Neurosci, St Louis, MO 63110 USA
[2] Univ Oxford, John Radcliffe Hosp, Nuffield Dept Clin Neurosci, FMRIB Ctr, Oxford OX3 9DU, England
[3] Imperial Coll, Dept Comp, London SW7 2AZ, England
[4] Washington Univ, Dept Biomed Engn, St Louis, MO 63110 USA
[5] Univ Minnesota, Ctr Magnet Resonance Res, Minneapolis, MN 55455 USA
[6] Radboud Univ Nijmegen, Donders Inst Brain Cognit & Behav, NL-6525 EN Nijmegen, Netherlands
[7] Radboud Univ Nijmegen, Med Ctr Nijmegen, Dept Cognit Neurosci, NL-6500 HB Nijmegen, Netherlands