Our goal is to understand how sensory input is represented in the brain and transformed into behavioral commands. We study this problem in the superior colliculus (SC), a structure comprising functionally diverse sensory and motor neurons interleaved with fibers from myriad cortical and subcortical areas. This remarkable neuroanatomy poises SC as an integrative hub, but has also hindered efforts to dissect SC circuitry using classical methods, such as lesions, that offer poor spatial and temporal resolution. In order to record from and manipulate genetically defined cell types, we study the mouse SC, where we capitalize on an experimental preparation I developed (Feinberg and Meister, Nature, 2015) that allows two-photon imaging of neuronal population activity in SC of awake animals. We apply these methods to decipher computations in the context of quantitative behavioral assays. Our long-term aim is to understand how the brain encodes information from input to output.