1. Sobell Department of Motor Neuroscience and Movement Disorders; University College London (UCL) Institute of Neurology; London United Kingdom
2. Department of Neurosciences, Charing Cross Hospital; Imperial College London; United Kingdom
3. Division of Neurology; Nottingham University Hospital; Nottingham United Kingdom
4. Southern Illinois University School of Medicine; Springfield Illinois USA
5. Human Motor Control Section, National Institute of Neurological Disorders and Stroke; NIH; Bethesda Maryland USA
6. Division of Movement Disorders, Department of Neurology, Yale School of Medicine, Yale University, New Haven, Connecticut, USA, and Department of Chronic Disease Epidemiology, Yale School of Public Health; Yale University; New Haven Connecticut USA
7. Department of Neurology, Universitätsklinikum Schleswig-Holstein, Kiel Campus; Christian Albrechts University Kiel; Kiel Germany
8. Department of Neurology, Philipps University, Marburg, Germany; Department of Neurology, Attikon Hospital; University of Athens; Athens Greece
9. Virginia Commonwealth University; Richmond Virginia USA