[1] Osaka City Univ, Sch Med, Dept Neurosci, Abeno Ku, Osaka 5458585, Japan
[2] Tokyo Inst Psychiat, Dept Mol Biol, Setagaya Ku, Tokyo 156, Japan
[3] Univ Washington, Div Gerontol & Geriatr Med, Seattle, WA 98195 USA
[4] Harvard Univ, Brigham & Womens Hosp, Sch Med, Ctr Neurol Dis, Boston, MA 02115 USA