Gonadal hormones have profound effects on the brain and behavior but have mostly been studied in the context of reproduction. My research examines how gonadal hormones affect cognitive and motor functions, using the rhesus monkey as a model. The primary focus of my current studies is to characterize sex differences in cognition, and to elucidate the role of gonadal hormones in shaping patterns of cognitive and brain aging in male and female monkeys. Parallel studies in non-primate species are also planned to further our understanding of the interactions between brain aging and the neuroendocrine system.