Spinocerebellar ataxia type 13 (SCA13) and Spinocerebellar ataxia type 19/22 (SCA19/22) are caused by function-impairing mutations in the genes encoding the potassium channels Kv3.3 [55] and Kv4.3 [56], respectively, and studies of these channels or their paralogs have demonstrated that they limit dendritic excitability [28, 57]. This evidence concerns the gene KCNA3 and spinocerebellar ataxia type 13.