1. Department of Medical Physiology, Kyorin University, Tokyo 181-8611, Japan
2. Department of Neurology, University of Tokyo, Tokyo 113-8655, Japan
3. Yoshiko Nomura Neurological Clinic for Children, Tokyo 113-0034, Japan
4. Segawa Memorial Neurological Clinic for Children, Tokyo 101-0062, Japan
5. Section of Neuronal Networks, Laboratory of Sensorimotor Research, National Eye Institute, Bethesda, MD 20892-2510, USA
6. Department of Human Neurophysiology, Fukushima Medical University, Fukushima 960-1295, Japan