The primary objective of this study is to measure the concentration and the regional brain distribution of pathologic tau deposition using the PET tracer AV-1451 in participants in the UAB-ADC cohort. The amount and distribution of AV-1451 in the brain will be correlated to demographic, clinical, genetic, and biospecimen data acquired through the separate ongoing UAB-ADC study. Assessment of interactions between race and vascular risk factors, brain tau levels measured with AV-1451-PET, and cognitive status will be the primary outcome of this imaging study. Individuals participating in this AV-1451-PET/MRI study will also be enrolled in an ongoing [C-11]PiB-PET/MRI study (IRB-300001005, IND-138128), and their amyloid, tau and cognitive statuses will be compared in terms of race and vascular risk factors.

Inclusion Criteria:

1. Enrollment in the UAB-ADC study under a separate IRB-approved research protocol.
2. Enrollment in the UAB-ADC amyloid-PET substudy under a separate IRB-approved research protocol. The amyloid-PET study does not have to have been completed prior to enrollment and participation in this tau-PET study.
3. Negative urine or serum hCG test within 2 days of [F-18]AV-1451 administration in women of child bearing potential. Women who are post-menopausal with at least 1 year since last menses or documented surgical sterilization will not require pregnancy testing.

Exclusion Criteria:

1. Meets any exclusion criteria for the UAB-ADC study.
2. Inability or contraindication for undergoing MRI and/or PET imaging
3. Inability to participate in the imaging studies due to severity of dementia