[1] Natl Inst Quantum & Radiol Sci & Technol, Dept Funct Brain Imaging, Chiba, Japan
[2] Natl Inst Quantum & Radiol Sci & Technol, Dept Radiopharmaceut Dev, Chiba, Japan
[3] Keio Univ, Sch Med, Dept Neurol, Tokyo, Japan
[4] Scripps Res Inst, Dept Neurosci, La Jolla, CA 92037 USA