[1] UCL, Inst Neurol, Wellcome Dept Imaging Neurosci, London WC1N 3AR, England
[2] UCL, Inst Cognit Neurosci, London, England
[3] UCL, Univ Coll London Hosp Trust, Natl Hosp Neurol & Neuorsurg, Inst Neurol,Autonom Unit, London, England
[4] Univ Sussex, Brighton & Sussex Med Sch, Dept Psychiat, Brighton BN1 9PX, E Sussex, England