Hippocampal somatostatin neurons gate context generalization during fear memory updating

Freezing is used as a readout of fear memory in rodents, but it remains unclear how distinct freezing features reflect discrimination and generalization of threatening and neutral contexts. Using pose-tracking and unsupervised analysis in male and female mice undergoing contextual fear conditioning, we show that fear in neutral a context is expressed through fragmented freezing that resist experience-dependent updating, in contrast with more sustained, uninterrupted, and adaptable freezing in a threatening context. Neuronal recordings revealed that recalling neutral context fear is associated with increased activity of dentate gyrus somatostatin inhibitory neurons (SST INs). Chemogenetic suppression of SST INs during fear memory updating selectively facilitated neutral context freezing adaptation while activation prevented generalization of contextual information by restricting long-term fear reduction in contexts that differed from the updating context. These findings identify DG SST INs as context-specific modulators of fear memory updating and suggest that freezing dynamics serve as a behavioral signature of generalization.