1. Institute of Biophysics and Biomedical Engineering, Bulgarian Academy of Sciences, Sofia, Bulgaria
2. Institute for Neurorehabilitation Research (InFo), Hannover Medical School (MHH), Hessisch Oldendorf, Germany
3. Institut für Infomationstechnik, Universität der Bundeswehr München, Neubiberg, Germany
4. Department of Neurology, Hannover Medical School (MHH), Germany