1. Department of Otorhinolaryngology and Head and Neck Surgery, Ohtawara Red Cross Hospital, 2-7-3, Sumiyoshi-cho, Ohtawara City, Tochigi 324-8686, Japan
2. National Institute of Sensory Organs, National Tokyo Medical Center, 2-5-1, Higashigaoka, Meguro, Tokyo 152-8902, Japan
3. Department of Oral Function and Molecular Biology, Ohu University, 31-1, Mitsumido, Tomita-machi, Koriyama City, Fukushima 963-8611, Japan