1. Department of Biomedical and Dental Sciences and Morphofunctional Imaging, University of Messina, 98124 Messina, Italy
2. Laboratory of Neuromotor Physiology, IRCCS Fondazione Santa Lucia, 00179 Rome, Italy
3. Center for Information and Neural Networks (CiNet), Advanced ICT Research Institute, National Institute of Information and Communications Technology, Suita City 565-0871, Osaka, Japan
4. Institut fur Technische Informatik (ZITI), Heidelberg University, 69120 Heidelberg, Germany
5. Department of Mechanical and Aerospace Engineering, Politecnico di Torino, 10129 Turin, Italy