Neuromodulators such as dopamine and serotonin are fundamental to learning processes and central to a wide array of brain disorders, making them prime targets for neuropsychiatric drugs. However, we have a limited understanding of how neuromodulators influence the dynamics of downstream neural populations. This project aims to elucidate how multiple neuromodulators drive neural computations underlying flexible decision-making by combining opto- and electrophysiological recordings and genetic perturbation with quantitative mouse behavior.