1 From the Department of Rehabilitation (J.N., L.V., B.P.V.D.W., B.R.B.), Radboud University Medical Centre, Donders Institute for Brain, Cognition and Behaviour, Center of Expertise for Parkinson & Movement Disorders, Nijmegen, The Netherlands; and Reta Lila Weston Institute of Neurological Studies (A.J.L.), University College London, London, UK.