Basal amygdala inputs to the medial prefrontal cortex mediate fear memory strengthening

Abstract

Survival critically depends on the memorization of stimuli recurrently predicting pleasant or aversive experiences. Memory strengthening by additional learning is a critical process allowing the long-term stabilization of learned aversive experience. However, the underlying neuronal circuits and mechanisms are still largely unknown. Using a combination of single unit recordings and optogenetic manipulations, we observed that strengthened fear responses following successive fear learning episodes led to a remapping in the population of basal amygdala (BA) neurons encoding the conditioned stimulus. Moreover, strengthened fear responses were preferentially carried by BA neurons projecting to the medial prefrontal cortex (mPFC). Selective optogenetic inhibition of BA terminals in the mPFC during a second learning episode prevented fear memory strengthening. Together, our findings suggest that fear memory strengthening with additional training critically depends on the selective remapping of a subpopulation of BA neurons projecting to the mPFC.