Sex hormones play a role in the organization of behavior during development and an activating role at sexual maturity. However, there is very little known about the modulatory role hormones play on the neural control of behavior in the adult, or the cognitive and behavioral consequences of sex hormone decline in the aged. Therefore, the objective of this proposal is to determine the influence of sex hormones on cognition in older men and women, the changes in cognition induced by hormone supplementation in the aged, and the cognitive and neural specificity of these hormone actions. In this research project, the cognitive performance of normal older men and women receiving hormone supplementation (testosterone and estrogen, respectively) will be compared to age-matched subjects who show the normal age-related declines in sex hormones, as well as to younger subjects whose hormone levels are normally high. Cognitive performance on tasks of spatial cognition and motor planning that have been shown to be influenced by estrogen and testosterone will be compared (Studies 1 & 2). In addition, the performance on tests that dissociate spatial cognition into its visual attention, visual perception and visual memory components will be assessed (Study 3). The neural bases of these components of spatial cognition are known and will provide information about the neural specificity of sex steroid effects on spatial cognition. Sex steroid replacement, supplementation and inhibition are used in the elderly to treat a variety of disorders. The effects of steroids on behavior, and particularly their effects on spatial cognition will provide information that is critically important for safe and effective medical care for the growing aged population in this country. In addition, these studies will provide new information on the role of sex hormones on cognition and brain function throughout life.