Approximately 1200 healthy participants aged 36 years and older will be studied by a consortium of investigators at WUSTL, Massachusetts General Hospital, UCLA and the University of Minnesota. In addition, Oxford University, with which WUSTL has executed a Data Use Agreement to allow sharing of the Limited Data Set, will participate in data analysis. Participants will undergo several MR scans during their study visit(s) to assess structural and functional brain connectivity at rest and during activation by certain tasks done in the scanner. To correlate and contrast with connectivity patterns, they will also be asked to answer questions demonstrating their cognitive and learning ability, and their emotional characteristics. They will be characterized for major factors relevant to general health and brain aging, including vascular burden (e.g., obesity, hypertension, smoking), genetic status of several aging-related genes (e.g., APOE), diet, physical activity, systemic health, (insulin, HbA1C, glucose, creatinine, cholesterol, total protein), hormonal status (estrogen, testosterone, luteinizing hormone, follicle stimulating hormone), and life history of stress, sleep patterns, social/community engagement, and adversity.