Effects of estrogen on patterns of brain activity at rest and during cognitive activity: A review of neuroimaging studies

Animal and human studies provide evidence of systematic effects of estrogen on cerebral activity and cognitive function. In this article, we review st udies of the activational effects of estrogen on cerebral activity during r est and during the performance of cognitive tasks in pre- and postmenopausa l women. The goal is twofold-to better understand evidence suggesting that estrogen influences brain functioning and argue for the importance of consi dering hormone effects when designing neuroimaging studies. Hormone-related increases in blood flow during the resting state have been documented in h ealthy elderly women, elderly women with cerebrovascular disease, and middl e-aged postmenopausal women with early menopause. There is no reliable infl uence of estrogen on blood flow during the resting state in women with Alzh eimer's disease. Hormone therapy has been associated with changes in brain activation patterns in middle-aged and elderly postmenopausal women during performance of verbal and figural memory tasks, providing critical biologic al support for the view that estrogen might protect against age-associated changes in cognition and lower the risk of Alzheimer's disease. There is a paucity of studies examining changes in brain activation patterns across th e menstrual cycle and a need for randomized studies of hormone therapy in p ostmenopausal women to confirm findings from observational studies. General procedural guidelines for controlling and investigating hormone effects in neuroimaging studies are discussed.