1. Department of Neurology, Universitätsklinikum Schleswig-Holstein, Kiel Campus; Christian Albrechts University Kiel; Kiel Germany
2. Sobell Department of Motor Neuroscience and Movement Disorders; University College London Institute of Neurology; London UK
3. Southern Illinois University School of Medicine; Springfield Illinois USA
4. Human Motor Control Section, National Institute of Neurological Disorders and Stroke; National Institutes of Health; Bethesda Maryland USA