1. Division of Experimental Medicine, Department of Medicine, Imperial College London, Hammersmith Hospital, London, UK
2. Clinical Imaging Centre, GlaxoSmithKline Research and Development, Hammersmith Hospital, London, UK
3. Genetics, GlaxoSmithKline Research and Development, Stevenage, UK and King of Prussia, PA and Research Triangle Park, North Carolina, USA
4. Centre for Neuroscience, Department of Medicine, Imperial College London, Hammersmith Hospital, London, UK
5. Department of Engineering Science, University of Oxford, Oxford, UK