1. Center for Information and Neural Networks (CiNet), National Institute of Information and Communications Technology, and Osaka University, 2B6, CiNet, 1-4 Yamadaoka, Suita, Osaka 565-0871, Japan
2. Graduate School of Frontier Biosciences, Osaka University, 1-4 Yamadaoka, Suita, Osaka, 565-0871, Japan
3. Graduate School of Information Science and Engineering, Ritsumeikan University, 1-1-1 Noji-higashi, Kusatsu, Shiga 525-8577, Japan
4. College of Information Science and Engineering, Ritsumeikan University, 1-1-1 Noji-higashi, Kusatsu, Shiga 525-8577, Japan