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. 2020 Jan 30;9:e51207. doi: 10.7554/eLife.51207

Figure 2. Deconditioning-update weakens both remote and strong fear memories.

(A) Experimental design for remote memory: rats were fear-conditioned with five tone-shock pairings (context A; 5 CS + US, 0.5mA). Starting 40 days later, the no-footshock and footshock (deconditioning-update) groups were exposed to daily reactivation sessions (context B). Then, all groups underwent test (context B), renewal (context A) and spontaneous recovery (context B) sessions. Black circles represent context A, while white rectangles represent context B. (B) Freezing levels during reactivation sessions. Rats exposed to weak footshocks during reactivation sessions showed similar freezing levels to no-footshock animals during the test session (C) and lower freezing levels at the renewal (D) and spontaneous recovery (E) ones. (F) Experimental design for strong training (5CS+US, 1mA). (G) Freezing levels during reactivation sessions. Rats exposed to weak footshocks during reactivation sessions showed a significant reduction in freezing responses that was maintained during the test (H), renewal (I) and spontaneous recovery (J) sessions. Bars represent mean ± SEM. Statistical comparisons 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 and spontaneous recovery). *p<0.05; **p<0.005; ***p<0.0005; ****p<0.0001. For full statistics, see Supplementary file 2. For pre-CS freezing, see Supplementary file 13.

Figure 2—source data 1. Raw data of Figure 2.

Figure 2.

Figure 2—figure supplement 1. Deconditioning-update weakens strong fear memories in females.

Figure 2—figure supplement 1.

(A) Experimental design: rats were fear-conditioned with five tone-shock pairings (context A; 5 CS + US, 1mA). Starting 48 hr later, animals were exposed to three daily reactivation sessions (context B) with or without a weak footshock (0.1 mA) at the end of tones. Subsequently, all groups underwent test (context B) and renewal (context A) sessions. Black circles represent context A and white rectangles represent context B. (B) Freezing levels during reactivation sessions. Rats exposed to weak footshocks during reactivation sessions showed a decrease in freezing responses that was maintained in the test session (C). Bars represent mean ± SEM. Statistical comparisons 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 and renewal). *p<0.05; **p<0.005. ****p<0.0001. For full statistics, see Supplementary file 9. For pre-CS freezing, see Supplementary file 19.