1 Radboud University Medical Centre, Donders Institute for Brain, Cognition and Behaviour, Department of Neurology, Center of Expertise for Parkinson and Movement Disorders, Nijmegen 6500, Netherlands.
2 CHDI Management for the CHDI Foundation, Princeton NJ, USA.
3 Radboud University Medical Centre, Donders Institute for Brain, Cognition and Behaviour, Department of Neurology, Center of Expertise for Parkinson and Movement Disorders, Nijmegen 6500, Netherlands. Electronic address: bas.bloem@radboudumc.nl.