Imaging of Brain Structural/Functional Connectivity and Amyloid and Tau Lesions in APOE4 Carriers.

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 * Females of childbearing potential without documented history of menopause or hysterectomy who do participate must not be pregnant or breastfeeding at screening * (negative urine β-HCG within 24 hours prior to injection), and must agree to avoid becoming pregnant. Females of childbearing potential who do not agree to use reliable contraception or refrain from sexual activity for 24 hours following administration of flortaucipir injection. * Enrollment in DCE-MRI study * Capacity to give informed consent and follow study procedures Exclusion Criteria: * Any illness preventing cooperation with testing or longitudinal participation * Exclusion from the Knight ADRC or DIAN referring project * Has a high risk for Torsades de Pointes or is taking medications known to prolong or may prolong QT interval (refer to study attachment "Restricted Medication List"). * MRI contraindications (e.g. electronic medical devices, severe claustrophobia, inability to lie still for long periods) that make it unsafe to participate in an MRI scan, using standard screening processes implemented by Washington University and Barnes-Jewish Hospital * Currently pregnant or breastfeeding