1. IEEE Member, Prof., Head, Department Medical Engineering and Neural Prosthetics, Fraunhofer Institute for Biomedical Engineering, Ensheimer Straße 48, 66386 St. Ingbert, Germany. e-mail: klaus.hoffmann@ibmt.fraunhofer.de
2. Group Neuromonitoring, Department Medical Engineering and Neural Prosthetics, Fraunhofer Institute for Biomedical Engineering, Ensheimer Straße 48, 66386 St. Ingbert, Germany. e-mail: roman.ruff@ibmt.fraunhofer.de