Understanding how cellular and synaptic mechanisms interact within neural circuits to control behavior is a fundamental goal of neuroscience. To achieve that goal, we need a thorough understanding of behavior as well as a detailed knowledge of the underlying neural circuit. With this in mind, we focus our research on the cerebellum, a brain area that is critical for coordinated motor control and motor learning and whose circuitry is well characterized. Many of the neuron types in the cerebellum are molecularly identifiable, and existing technologies allow us to target transgenes to specific neuronal populations. By comparing specific aspects of behavior and neural activity across mice in which we have targeted genetic perturbations to different cell types, we aim to determine links between cellular function, circuit activity, and behavior.