Neuroimaging in Healthy Aging and Senile Dementia (HASD_IND)

Inclusion Criteria: * Male or female, any race * Age \> 18 years * Participation in one of the ongoing projects affiliated with the Knight ADRC at Washington University and referred by the MAP staff and a Washington University physician. * Normal cognition or early-stage symptomatic AD * Willing and able to undergo study procedures. * Capacity to give informed consent and follow study procedures Exclusion Criteria: * Has any condition that, in the Investigator's opinion, could increase risk to the participant, limit the participant's ability to tolerate the research procedures, or interfere with the collection/analysis of the data (e.g., participants with severe chronic back pain might not be able to lie still during the scanning procedures); * Has hypersensitivity to either AV-1451 or PIB or any of its excipients; * Contraindications to PET, CT or MRI (e.g. electronic medical devices, inability to lie still for extended periods) that make it unsafe for the individual to participate; * Severe claustrophobia; * Currently pregnant or breast-feeding. Women must agree to avoid becoming pregnant and must agree to refrain from sexual activity or to use reliable contraceptive methods for 24 hours following administration of Flortaucipir injection; * Must not have participated in any clinical trial involving a study drug or device within the 30-days prior to study enrollment; * Must not participate in another drug or device study prior to the end of this study participation; * Current or recent (within 12 months prior to screening) participation in research studies involving radioactive agents such that the total research-related radiation dose to the participant in any given year would exceed the limits set forth in the U.S. Code of Federal Regulations (CFR) Title 21 Section 361.1. https://www.accessdata.fda.gov/scripts/cdrh/cfdocs/cfcfr/CFRSearch.cfm?FR=361.1