Small, tightly-packed granule cells (GrCs) in the cerebellum have been associated with sensory and motor events, but their specific roles remain unclear due to their close packing. Dr. Broussard aims to precisely record from and perturb GrCs and measure the resulting effects on neural firing patterns and activity in mice. The researcher will develop a spike-counting method for genetically encoded indicators by optimizing the kinetics of the calcium sensor GCaMP. After developing a cleared skull preparation to access the full posterior cerebellum in mice, the new indicator will be used to map the neocortical drivers of GrC activity across the cerebellum, and rodent behavioral tasks will be used to disambiguate sensory, motor and internal-state contributions to granule cell activity patterns. Better knowledge of GrCs activity will further our understanding of neural circuits that guide sensory processing and plays roles in neurological disorders.