[1] Univ Cambridge, Wolfson Brain Imaging Ctr, Dept Clin Neurosci, Cambridge CB2 0QQ, England
[2] Univ Cambridge, Mol Imaging Chem Lab, Dept Clin Neurosci, Cambridge CB2 0QQ, England
[3] Univ Cambridge, Behav & Clin Neurosci Inst, Cambridge CB2 0QQ, England
[4] Univ Cambridge, Lab Mol Imaging, Dept Clin Neurosci, Cambridge CB2 0QQ, England
[5] Univ Cambridge, Dept Expt Psychol, Cambridge CB2 0QQ, England
[6] Univ Cambridge, Dept Clin Neurosci, Neurol Unit, Cambridge CB2 0QQ, England
[7] Univ Paris, INSERM, U894, Ctr Psychiat & Neurosci, F-75252 Paris, France
[8] Univ Cambridge, Dept Psychiat, Cambridge CB2 0QQ, England