Our goal is to understand the functional flexibility of cortical circuits. The physical elements of a neural circuit, cells and synapses, are largely stable over short time periods. In contrast, the functional circuit—the subset of cells that are active participants—changes on a millisecond timescale, as does the output of the circuit. Using a multilevel approach combining intra- and extracellular electrophysiology, 2-photon calcium imaging, and behavior, we hope to understand how excitatory and inhibitory neurons interact to promote flexible circuit function underlying perception and cognition.