[1] Imperial Coll London, Dept Brain Sci, London, England
[2] Univ Cambridge, Dept Med, Div Anaesthesia, Cambridge, England
[3] Cambridge Univ Hosp Natl Hlth Serv Fdn Trust, Cambridge, England
[4] Univ Cambridge, Dept Clin Neurosci, Wolfson Brain Imaging Ctr, Cambridge, England