1Center for Information and Neural Networks (CiNet), Advanced ICT Research Institute, National Institute of Information and Communications Technology (NICT), Suita, Osaka, 565-0871 Japan
2Graduate School of Frontier Biosciences, Osaka University, Suita, Osaka, 565-0871 Japan
4Center for Human Nature, Artificial Intelligence, and Neuroscience, Hokkaido University, Sapporo, Hokkaido, 060-0812 Japan
