1. Center for International Research on Integrative Biomedical Systems, Institute of Industrial Science, University of Tokyo, Tokyo 153-8505, Japan.
2. Department of Mechanical Engineering, Keio University, Yokohama, Kanagawa 223-8522, Japan.
3. International Research Center for Neurointelligence, University of Tokyo Institutes for Advanced Study, University of Tokyo, Tokyo 153-8505, Japan.