1. Department of Neurodegeneration, Hertie Institute for Clinical Brain Research; University of Tuebingen; Tuebingen Germany
2. Neurology Unit, Department of Clinical and Experimental Sciences; University of Brescia, Brescia, Italy and Parkinson's Disease Rehabilitation Centre, FERB ONLUS S.Isidoro Hospital, Trescore Balneario (BG); Italy
3. Department of Neurology; Christian-Albrechts-University; Kiel Germany
4. German Center for Neurodegenerative Diseases; Tuebingen Germany
5. Department of Psychiatry and Psychotherapy, Geriatric Center; Tuebingen University Hospital; Tuebingen Germany
6. Department of Neurology; Montreal General Hospital; Montreal Quebec Canada