Contextual fear conditioning promotes robust remote fear memory. (A) Mouse breeding strategy. (B) Experimental protocol: Immediately following conditioning, all mice received 100 mg/kg 4-OHT i.p. to “TRAP” the CeA neuronal Fos ensemble (tdTomato+) activated during conditioning and 21 d later were perfused 90 min after the remote memory recall session to capture the Fos neuronal ensemble activated during recall using Fos immunostaining. (C) Fear conditioning (shocks [blue circles]; n = 5) resulted in fear acquisition relative to baseline and relative to context-conditioned mice (no shocks [open squares]; n = 5). Values represent total time spent freezing during a 30-sec time bin immediately after each shock or dummy shock. (*) P = 0.0203, (****) P < 0.0001 versus shock group baseline (BL); (##) P = 0.0056, (#) P = 0.0044 between groups. Two-way ANOVA with Sidak's posttest. (D) Remote memory recall at day 21 after conditioning. (####) P < 0.0001. Unpaired t-test. Data are mean ± SEM. Biorender.com was used to generate mouse images.
