The goal of this research project is to determine the role of cholinergic neuromodulation in the functional organization of memory and attention in humans, using functional neuroimaging techniques. The study of human cognition with functional brain imaging in conjunction with pharmacologic probes that alter cognitive processes provides an opportunity to examine another dimension of the organization of human neural systems. In addition to identifying the anatomical structures that participate in specific cognitive functions, this approach can reveal how different neuromodulators can influence processing in those structures. Additionally, the combined use of functional brain imaging and pharmacological manipulation can be used to evaluate the role of neurotransmitter dysfunction in disease states that produce cognitive impairment and may direct us to potential therapeutic approaches.