1 Department of Human Neurosciences, Sapienza University of Rome, Rome, Italy.
2 IRCCS Neuromed, Pozzilli, Italy.
3 Gardner Family Center for Parkinson's Disease and Movement Disorders, Department of Neurology, University of Cincinnati, Cincinnati, Ohio, USA.
4 Edmond J. Safra Program in Parkinson's Disease, Morton and Gloria Shulman Movement Disorders Clinic, Toronto Western Hospital, UHN, Toronto, Ontario, Canada.
5 Division of Neurology, University of Toronto, Toronto, Ontario, Canada.
6 Krembil Brain Institute, Toronto, Ontario, Canada.
7 Human Motor Control Section, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland, USA.