1Parkinson's Foundation Centre of Excellence, King's College Hospital NHS Foundation Trust, London, United Kingdom
2Department of Psychiatry, Ng Teng Fong General Hospital, Singapore, Singapore
3Department of Basic and Clinical Neuroscience, Institute of Psychiatry, Psychology & Neuroscience, King's College London, London, United Kingdom
4Department of Neurology, Centre of Expertise for Parkinson & Movement Disorders, Donders Institute for Brain, Cognition and Behaviour, Radboud University Medical Center, Nijmegen, the Netherlands
5Duke-NUS Medical School, National Neuroscience Institute, Singapore, Singapore