Abstract: Normal aging is characterized by cognitive deficits that cross multiple domains and impair the ability of some older individuals to lead productive, high-quality lives. One of the primary goals of research in our laboratories is to study age-related alterations in neural mechanisms that underlie a wide range of cognitive processes so that we may generate a unifying principle of cognitive aging. Top-down modulation is the mechanism by which we enhance neural activity associated with relevant information and suppress activity for irrelevant information, thus establishing a foundation for both attention and memory processes. We use three converging technologies of human neurophysiology to study top-down modulation in aging: functional magnetic resonance imaging (fMRI), electroencephalography (EEG), and transcranial magnetic stimulation (TMS). Using these tools we have discovered that healthy older adults exhibit a selective inability to effectively suppress neural activity associated with distracting information and that this top-down suppression deficit is correlated with their memory impairment. We are now further characterizing the basis of these age-related alterations in top-down modulation and investigating interventions to remedy them.