1. Human Motor Control Section, Medical Neurology Branch; National Institutes of Neurological Disease and Stroke; National Institutes of Health; Bethesda Maryland USA
2. Institute of Cognitive Neuroscience; University College London; 17 Queen Square London United Kingdom
3. Department of Psychology Goldsmiths; University of London; United Kingdom
4. Sobell Department of Motor Neuroscience and Movement Disorders; Institute of Neurology; University College London; London United Kingdom
5. Department of Clinical Neurosciences, Neurology Unit; University of Cambridge; Cambridge United Kingdom
6. Department of Psychiatry; University of Cambridge; Cambridge United Kingdom
7. Center for Imaging Sciences; University of Sussex; Falmer United Kingdom
8. Behavioural and Clinical Neurosciences Institute; University of Cambridge; Cambridge United Kingdom