FOS and Ataxia: The FN contains glutamatergic and GABAergic neuron subtypes.17,18 To determine the neuronal subtypes involved in ataxia behavior, the c-fos expression was examined.19 We injected AAV-DIO-eNpHR3.0 into the IV/V lobe of L7-Cre mice, in which optical fibers were implanted above the FN to allow the light-mediated inhibition of IV/V lobe PC inhibitory inputs in the FN.