1. Department of Neurorehabilitation Engineering, Bernstein Focus Neurotechnology Göttingen, Bernstein Center for Computational Neuroscience, University Medical Center Göttingen, Georg-August University, D–37075 Göttingen, Germany.
2. CD Laboratory for Restoration of Extremity Function, Division of Plastic and Reconstructive Surgery, Medical University of Vienna, A-1090 Vienna, Austria.