1. Humanoid and Cognitive Robotics Laboratory, Department of Automatics, Biocybernetics, and Robotics, Jožef Stefan Institute, 1000 Ljubljana, Slovenia.
2. Humanoid and Cognitive Robotics Laboratory, Department of Automatics, Biocybernetics, and Robotics, Jožef Stefan Institute, 1000 Ljubljana, Slovenia, and also with ATR Computational Neuroscience Laboratories, Department of Brain-Robot Interface, Advanced Telecommunications Research Institute International, Kyoto 619-0237, Japan.
3. ATR Computational Neuroscience Laboratories, Department of Brain-Robot Interface, Advanced Telecommunications Research Institute International, Kyoto 619-0237, Japan, and also with the Graduate School of Informatics, Kyoto University, Kyoto 606-8501, Japan.