Figure 3. Deconditioning-update weakens fear memory in different behavioral tasks.

(A) Experimental design in contextual fear conditioning: rats were fear-conditioned with five contextual-shock pairings (4 min context + 4 US, 0.5mA). Starting 48 hr later, the no-footshock and footshock groups were exposed to daily reactivation sessions. 24 hr after the last reactivation, all groups were tested; 20 days later, they were tested for spontaneous recovery. (B) Freezing levels during reactivation sessions. Rats exposed to weak footshocks during reactivation sessions showed a significant reduction in freezing responses maintained during the test (C) and spontaneous recovery (D) sessions. (E) Experimental design in inhibitory avoidance: rats were placed in the lighted compartment and received footshocks (4 US, 0.5mA) upon entering the dark one. Starting 48 hr later, the no-footshock and footshock groups were exposed to daily 30-s reactivation sessions in the dark compartment; 24 hr after the last reactivation, all groups were tested. Rats exposed to weak footshocks during reactivation sessions showed lower latencies to cross to the dark compartment (F) and spent more time in it during the test (G). Bars represent mean ± SEM or median with interquartile range (in F and G). Statistical comparisons for contextual fear conditioning are performed using two-way repeated-measures ANOVA followed by a Bonferroni post-hoc (reactivation sessions) or one-way ANOVA followed by a Tukey post-hoc (test, renewal, and spontaneous recovery). For inhibitory avoidance, a Kruskal-Wallis test followed by a Dunn post-hoc was performed. *p<0.05; **p<0.005; ***p<0.0005; ****p<0.0001. For full statistics, see Supplementary file 3.