The overarching purpose of this study is to further our understanding of the individual and interactive effects of the hormone estrogen and the neurotransmitter serotonin on certain aspects of cognition and brain activation in menopausal women ages 48 to 60 years. Women will undergo cognitive testing and fMRI sessions both before and after 6 weeks of either estrogen or placebo administration. We will recruit women who are across the first 10 years since their last menstrual period so that the investigators can gather information regarding the potential impact of time since menopause on our outcomes of interest. We anticipate that findings from this study will help scientist and clinicians to refine their use of estrogen therapy in menopausal women. In addition, should the role of serotonin be of utmost importance for maintenance of healthy cognition, these data aid future drug development to preserve health cognition and/or to treat dementias in which serotonin is an important factor. This proposal is both novel and timely as results from this study are likely to provide information critical to the on-going discussion regarding the risks and benefits of ET use in menopausal women.