1. Department of Experimental Medicine, Section of Human Physiology, University of Genoa, I-16132 Genoa, Italy;
2. Institut National de la Santéet de la Recherche Médicale, Motricité & Plasticité, University of Burgundy, F-21078 Dijon, France; and
3. Physiological Institute, University of Pavia, and Human Movement Laboratory, Fondazione Salvatore Maugeri, Istituto di Ricovero e Cura a Carattere Scientifico, I-27100 Pavia, Italy