title: Response from Menon, Owen and Pickard.
authors.affiliation: aWolfson Brain Imaging Centre and Department of Anaesthesia, University of Cambridge School of Clinical Medicine, Addenbrooke's Hospital, Cambridge, UK CB2 2QQ.
authors.initials: DK
authors.lastname: Menon
authors.initials: AM
authors.lastname: Owen
authors.initials: JD
authors.lastname: Pickard