1. Tokyo Metropolitan Institute of Medical Science Neural Prosthetics Project, , Setagaya, Tokyo 156-8506 , Japan
2. National Institute for Physiological Sciences Section of Brain Function Information, , Okazaki, Aichi 444-8585 , Japan
3. The Graduate University for Advanced Studies, SOKENDAI , Hayama, Kanagawa 340-0193 , Japan
4. Ritsumeikan University Research Organization of Science and Technology, , Kusatsu, Shiga 525-8577 , Japan