Neuronal activity in the dorsal dentate gyrus during extinction regulates fear memory extinction and renewal.

Memory extinction and renewal are major factors that limits the efficacy of exposure therapy. The dorsal dentate gyrus (dDG) plays a crucial role in spatial memory, and epigenetic modifications in the dDG play an important role in fear memory renewal. However, whether dDG activity regulates fear memory extinction and renewal remains unclear. In this study, we showed that an extinction procedure that prevents fear memory renewal (extinction within the reconsolidation window) leads to increased c-fos expression in the dDG. Chemicogenetic activation of dDG excitatory neurons during extinction training elevated fear memory extinction and prevented renewal, whereas inhibition of dDG excitatory neurons inhibited fear memory extinction. We also demonstrated that inhibiting fear engram cells (neurons active during fear acquisition) during extinction training inhibits fear memory extinction. Therefore, dDG activity during fear extinction plays an important role in fear memory extinction and renewal.