1. Human Informatics and Interaction Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), 1-1-1 Higashi, Tsukuba, Ibaraki 305-8566, Japan
2. Center for Neuroscience and Biomedical Engineering, The University of Electro-Communications, 1-5-1 Choufuga-oka, Choufu, Tokyo 182-8585, Japan
3. School of Veterinary Medicine, Azabu University, 1-17-71 Fuchinobe, Chuou-ku, Sagamihara, Kanagawa 252-5201, Japan