We use behavioral, computational, electrophysiological, neuroimaging, and noninvasive neuromodulation approaches to understand the large-scale causal mechanisms of perception and cognition in the healthy adult brain, and how these mechanisms go awry in normal and pathological aging, and psychiatric illnesses, such as schizophrenia and obsessive-compulsive disorder. We also build unique neuromodulation protocols, grounded in fundamental science, to control components of perception and cognition in healthy individuals and to protect or restore abilities in aging and clinical populations.