1. Center for Education in Health Sciences Northwestern University, Chicago, IL, USA
2. National Parkinson Foundation, Miami, FL, USA
3. Department of Biostatistics, University of Texas Health Science Center at Houston, Houston, TX, USA
4. Morton and Gloria Shulman Movement Disorders Centre and the Edmond J Safra Program in Parkinson’s disease, Toronto Western Hospital, University of Toronto, Toronto, Canada
5. Thomas L. Davis, Division of Movement Disorders, Department of Neurology, Vanderbilt University, Nashville, TN, USA
6. Division of Neurology, Department of Medicine, University of Toronto, Toronto, Canada
7. Department of Neurology, Northwestern University, Chicago, IL, USA