A Follow-On Study of Donanemab (LY3002813) With Video Assessments in Participants With Alzheimer's Disease (TRAILBLAZER-EXT)

Inclusion Criteria: * Participated in a double-blind treatment period of a sponsor-approved originating donanemab trial, for example the TRAILBLAZER-ALZ study. * Have a study partner * Stable symptomatic Alzheimer's Disease (AD) medications and other medication that may impact cognition for at least 30 days prior to randomization into Part A Exclusion Criteria: * Current serious or unstable illnesses including cardiovascular, hepatic, renal, gastroenterologic, respiratory, endocrinologic, neurologic (other than AD), psychiatric, immunologic, or hematologic disease and other conditions that, in the investigator's opinion, could interfere with outcome assessments or the analyses in this study. * Have received treatment with a passive anti-amyloid immunotherapy after completion of originating donanemab study or received active immunization against Aβ in any other study. * Poor venous access * Contraindication to PET or MRI imaging