Cognitive Benefits of Aerobic Exercise Across the Age Span

Inclusion Criteria: 1. Age 20-68 2. English-speaking 3. strongly right-handed 4. BMI \< 35 5. Pre-menopausal (women only): no oral contraceptive use Post-menopausal: no estrogen replacement therapy 6. sedentary: VO2 max \< 41 and 31.6 ml/kg/min for men age 20-40 and 50-68 and \< 35.2 and 26.6 ml/kg/min for women age 20-40 and 50-68 respectively 7. participants over age 60 must have ECG within past 3 months Exclusion Criteria: 1. MRI contraindications (e.g., metallic implants, pacemaker, weight \> 350 lbs, waist \> 55") 2. Hearing impaired/hearing aids, unable to read newspaper at arm's length with corrective lenses 3. Objective cognitive impairment 4. Ischemic changes, abnormal blood pressure responses, or any significant ectopy during aerobic capacity testing 5. Cardiovascular disease 6. Uncontrolled high blood pressure (systolic blood pressure ≥ 140 mmHg; or diastolic blood pressure ≥ 90 mmHg on two measures) 7. Current or recent (evidence of disease x 5 years) non-skin neoplastic disease or melanoma 8. Active hepatic disease (not a history of hepatitis) or primary renal disease requiring dialysis, primary untreated endocrine diseases, e.g., Cushing's disease or primary hypothalamic failure or insulin dependent diabetes (Type I or II). 9. HIV infection 10. Pregnant or lactating (participation allowed 3 months after ceasing lactation 11. Medications that target CNS (central nervous system, e.g., neuroleptics, anticonvulsants, antidepressants, benzodiazepines) within the last month 12. Women: any selective estrogen receptor modulator or aromatase inhibitor Men: androgen ablation/deprivation hormonal therapies 13. Any history of psychosis or electroconvulsive therapy 14. Psychotic disorder (lifetime) 15. Current or recent (within past 12 months) alcohol or substance abuse or dependence. Recent use (past month) of recreational drugs. 16. Brain disorder such as stroke, tumor, infection, epilepsy, multiple sclerosis, degenerative diseases, head injury, mental retardation 17. Imaged cortical stroke or large subcortical lacunae or infarct or space-occupying lesion (≥ 2 cubic cm). Other findings, e.g., periventricular caps or small white matter hyperintensities, do not result in exclusion 18. Diagnosed learning disability, dyslexia 19. Current or recent (Past 5 years) Major Depressive Disorder, Bipolar Disorder, or Anxiety Disorder 20. Dementia Rating Scale \< 135