1. Oxford Centre for Functional MRI of the Brain, Nuffield Department of Clinical Neurosciences (Division of Anaesthetics), University of Oxford, OX3 9DU Oxford, UK.
2. NeuroImage Nord, Department of Neurology, University Medical Center Hamburg-Eppendorf, 20246 Hamburg, Germany.
3. Division of Anaesthesia, Cambridge University, Addenbrookes Hospital, CB2 0QQ Cambridge, UK.
4. Department of Neurology, Technische Universität München, 81675 Munich, Germany.