 Over 5 million people in the United States have heart failure, and 500,000 more develop this condition each year. Up to 80 of people with heart failure experience cognitive functioning difficulties, including problems with memory, attention, and other thinking skills. People with heart failure often participate in a cardiac rehabilitation program, which is an individualized program that aims to improve a persons physical and mental health while dealing with a heart-related condition. Cardiac rehabilitation is different for each person, but it can include medical counseling on how to manage a heart condition and how to modify risk factors for further heart problems, including lowering blood pressure and cholesterol levels, stopping smoking, and losing weight. Nutritional counseling and an exercise program may also be a part of cardiac rehabilitation. Preliminary research has shown that people with heart failure who participate in a cardiac rehabilitation program may experience improved cognitive function. This is thought to be a result of increased blood flow to the brain and improved autonomic nervous system function, which is responsible for regulating various body functions. In this study, researchers will explore the relationship between heart failure and cognitive function, examine how cognitive function changes over time in heart failure patients, and evaluate how cardiac rehabilitation may affect cognitive function in older adults. Specifically, researchers will examine how physical activity and patterns of blood flow affect cognitive function. 