1. Department of Neurology University of Groningen, University Medical Center Groningen Groningen the Netherlands
2. Department of Neurology, Division of Clinical Neuropsychology University of Groningen, University Medical Center Groningen the Netherlands
3. Department of Radiology University of Michigan Ann Arbor Michigan USA
4. Morris K. Udall Center of Excellence for Parkinson's Disease Research University of Michigan Ann Arbor Michigan USA
5. Department of Neurology University of Michigan Ann Arbor Michigan USA
6. Neurology Service and GRECC, Veterans Administration Ann Arbor Healthcare System Ann Arbor Michigan USA
7. University of Michigan Parkinson's Foundation Center of Excellent Ann Arbor Michigan USA