Prefrontal somatostatin interneurons encode fear memory.

Theories stipulate that memories are encoded within networks of cortical projection neurons. Conversely, GABAergic interneurons are thought to function primarily to inhibit projection neurons and thereby impose network gain control, an important but purely modulatory role. Here we show in male mice that associative fear learning potentiates synaptic transmission and cue-specific activity of medial prefrontal cortex somatostatin (SST) interneurons and that activation of these cells controls both memory encoding and expression. Furthermore, the synaptic organization of SST and parvalbumin interneurons provides a potential circuit basis for SST interneuron-evoked disinhibition of medial prefrontal cortex output neurons and recruitment of remote brain regions associated with defensive behavior. These data suggest that, rather than constrain mnemonic processing, potentiation of SST interneuron activity represents an important causal mechanism for conditioned fear.