1 Department of Cognitive Sciences, Department of Computer Science, University of California, Irvine, USA. Electronic address: jkrichma@uci.edu.
2 Center of Competence on NeuroEngineering, Department of Electrical and Computer Engineering, Technical University Munich, Germany. Electronic address: conradt@tum.de.
3 Department of Adaptive Machine Systems, Graduate School of Engineering, Osaka University, Yamadaoka 2-1, Suita, Osaka, Japan. Electronic address: asada@ams.eng.osaka-u.ac.jp.