1Centre for Cognitive Neuroscience, Neuroscience and Behavioural Disorders Programme, Duke-National University of Singapore Graduate Medical School, Singapore, Singapore, 2Department of Pharmacology, National University Health System, Clinical Research Centre, Singapore, Singapore, 3Memory Ageing & Cognition Centre, National University Health System, Singapore, Singapore, 4Duke-National University of Singapore Graduate Medical School, Singapore, Singapore, 5St. Luke's Hospital, Singapore, Singapore, 6Raffles Neuroscience Centre, Raffles Hospital, Singapore, Singapore, 7Clinical Imaging Research Centre, The Agency for Science, Technology and Research and National University of Singapore, Singapore, Singapore