1. Department of Medical Physiology, University of Copenhagen, Blegdamsvej 3, Copenhagen 2200, Denmark
2. The Prince of Wales Medical Research Institute, University of New South Wales, Sydney, Australia
3. Neurophysiologie Clinique, Rééducation, Hôpital de la Salpétrière, Paris, France
4. Sobell Department of Neurophysiology, University College London, London, UK
5. Faculty of Human Movement Sciences, Vrije University, Amsterdam, The Netherlands