Hyperpolarization-activated cyclic nucleotide-gated 1 channels (HCN1) mediate the I h cationic current and play a central role in regulating neuronal excitability and synaptic integration. HCN1 is predominantly expressed in the neocortex and hippocampus. Pathogenic variants in HCN1 have been increasingly identified in individuals presenting with a broad spectrum of epileptic disorders, ranging from severe developmental and epileptic encephalopathy (DEE) to milder epilepsies. Here, we used patch-...