The Mental Activity and eXercise Trial for Seniors

Inclusion Criteria: * Age \> 64 * Self-report of recent decline in memory or thinking * Low/no physical activity (\<2 days/week for \<30 minutes/session of moderate intensity activity over past 3 months) * Low/no computer mental activity (\<2 days/week for \<30 minutes/session over past 3 months) * Fluent in English * Willingness to perform study activities Exclusion Criteria: * Evidence of dementia (based on self-report, physician diagnosis or score \< 19 on Telephone Interview for Cognitive Status) * Significant central nervous system disorder (Parkinson's disease, multiple sclerosis, ALS \[Lou Gerig's disease\]) * Major, current psychiatric disorder (major depressive disorder, schizophrenia, bipolar disorder, post-traumatic stress disorder, obsessive-compulsive disorder, psychiatric hospitalization in past 20 years) * Major central nervous system event (stroke, transient ischemic attack/mini-stroke, seizure, or traumatic brain injury that has left a residual deficit) * Significant heart disease (severe congestive heart failure, severe aortic stenosis, cardiac arrest, uncontrolled angina) * Significant lung disease (requiring supplemental oxygen or oral or injected steroids) * Other condition that would make participation potentially dangerous (cancer requiring treatment in past 3 years, severe arthritis, history of cardiac defibrillation, dialysis) * Lack of physician approval * Severe hearing or visual impairment * History of learning disability * Starting prescription medication to enhance cognitive function (e.g., memantine, aricept) * Dependent in any basic activity of daily living (eating, dressing, bathing, toileting, getting out of bed/chair) * History of alcohol abuse/heavy alcohol use * History of drug abuse/heavy drug use * Currently enrolled in another research study * Fibromyalgia or tremor severe enough to prevent use of a computer mouse * Planning to travel \> 4 exercise class days during study period * Behaviors during screening or baseline visit that, in the judgement of research staff, are likely to present significant problems (e.g., uncooperative, anger, inappropriate physical contact) * Unable to perform neuropsychological evaluations * Unable to complete consent process