An increased in vivo [F-18]-AV-1451 retention in midbrain, basal ganglia and choroid plexus has been observed in a high percentage of elderly individuals regardless of their clinical diagnosis; including not only patients clinically diagnosed with AD [5, 8, 18, 40] and other non-AD tauopathies [7, 9, 11, 13, 19, 32, 38, 44, 45, 47, 49], but also patients with Parkinson’s disease (PD) and other synucleinopathies [9, 10, 21] as well as clinically normal individuals [5, 8, 9, 18, 26, 40, 45] whose brains are not anticipated to harbor tau pathology in those regions. This evidence concerns the gene MAPT and Alzheimer disease.