1. Department of Neurophysiology, Graduate School of Medicine, The University of Tokyo, Tokyo 113-0033, Japan.
2. Department of Anatomy, Hokkaido University Graduate School of Medicine, Sapporo 060-8638, Japan.
3. Laboratory of Animal Resources, Center for Disease Biology and Integrated Medicine, Graduate School of Medicine, The University of Tokyo, Tokyo 113-0033, Japan.
4. Department of Neurophysiology, Gunma University Graduate School of Medicine, Maebashi, Gunma 371-8511, Japan.