MAPT and Alzheimer disease: As noted above, elevated in vivo [F-18]-AV-1451 retention in basal ganglia has been observed in a significant proportion of elderly individuals with different clinical diagnosis, including AD [5, 8, 18, 40] and non-AD tauopathies [7, 10, 11, 13, 19, 27, 32, 36, 38, 44, 45, 47, 49], but also in cases without suspected underlying tau pathology like PD [9, 20] and MSA [10] as well as in clinically normal individuals [5, 8, 9, 18, 26, 40, 45].