After advanced age, female sex is the major risk factor for Alzheimer’s disease, the most common form of dementia affecting 5 million patients in the United States alone. For every three patients with AD, two are women. Brain imaging studies implicate the menopause transition in the increased AD risk in women by showing that perimenopausal and postmenopausal women exhibit altered brain bioenergetics as compared with age-matched men and premenopausal women. There is evidence that the ebb in estrogen heralding the onset of menopause causes the loss of a key neuroprotective element in the female brain, with an aggressively higher vulnerability to brain aging and Alzheimer’s disease. In this project, we will perform in vivo imaging of brain mitochondrial function to determine how bioenergetic systems might be compromised in postmenopausal women. This project seeks to unravel the biological mechanism that increases AD vulnerability in women by using novel brain imaging techniques that allow quantification of energy production in the brain.