1. Department of Neurology, Division of Clinical Medicine, Faculty of Medicine, University of Tsukuba, Tsukuba, Ibaraki, Japan
2. Department of Physiology, Division of Biomedical Science, Faculty of Medicine, University of Tsukuba, Tsukuba, Ibaraki, Japan
3. Department of Neurology, Fuji Heavy Industries Health Insurance Society Ota Memorial Hospital, Gunma, Japan