4-AP blocks voltage-dependent K+ channels like Kv1.5 and others18, and may improve spike precision in SCA684Q/84Q mice through an enhancement of the action potential afterhyperpolarization18, Although the precise mechanism of action of 4-AP is not fully understood, it has been shown to selectively restore firing precision18 and firing rate21 in other ataxia mouse models, suggesting that the action of 4-AP on Purkinje cell firing depends on the underlying pathological changes that may differ in different ataxias. The gene discussed is KCNA5; the disease is cerebellar ataxia.