1. ATR Computational Neuroscience Laboratories, Department of Humanoid Robotics and Computational Neuroscience, Kyoto, 619-0288, Japan
2. Computational Brain Project, ICORP, Japan Science and Technology Agency, Kyoto, Japan
3. Carnegie Mellon University, Robotics Institute, Pittsburgh, PA, USA
4. Jožef Stefan Institute, Department of Automatics, Biocybernetics and Robotics, Ljubljana, Slovenia