Additional Study Information: For more than 30 years, The Columbia University Alzheimer's Disease Research Center (ADRC) has worked with thousands of participants who have helped provide important insights into how the brain ages and why Alzheimer's disease may develop. We are actively recruiting adults 65 years of age and older who share our commitment to be part of this nationwide study. Younger participants are welcome if there is a personal or family history of memory loss. Participants, both with and without memory problems, will be comprehensively evaluated beginning with a physician taking a history and performing a neurological exam, and a blood draw, followed by more in-depth memory and cognitive testing. All participants are encouraged to have an MRI and participate in a lumbar puncture at some point during study participation. With each annual visit, history, examination, and a blood draw will occur. Some of these steps can be done online. Participants are compensated for some procedures. Please contact our staff if you are interested in learning more.