Training with a strong footshock followed by a strong RS elicits extinction-resistant memories. Experimental schedule is shown above each panel. Data are expressed as the mean ± SEM of latency (in seconds) to enter the dark compartment. A, Memory was tested for 5 consecutive days from day 2 after 3 mA-induced training (E1–E5). At the end of each testing session, animals were enclosed for 5 min into the dark compartment of the IA chamber to promote memory extinction. An RS of the same intensity as that received at training was delivered 1 d after E5 and memory was tested for reinstatement 1 d later (T1). #p < 0.05 (vs T1); §§p < 0.01 (E5 vs T1). B, Memory was tested 2 d after training elicited with 0.6 or 3 mA intensity. One day after T1, an RS of 0.6 or 3 mA intensity was delivered, and memory was tested for 5 consecutive days (E1–E5) with the same protocol described in A. An RS of the same intensity as that received at training was delivered 1 d after E5, and memory was tested 1 d later for reinstatement (T2). Data are expressed as the mean ± SEM of latency (in seconds) to enter the dark compartment. ***p < 0.001; §p < 0.05 and §§p < 0.01 (E5 vs T2). C, Rats trained with 0.6 or 3 mA intensity footshock were tested 2 d after training (T1). An RS of the same intensity as during training was delivered 1 d later, and rats were tested twice a day with an intra-testing interval of 30 min for 7 consecutive days (E1–E14). One day after E14, an RS (RS2) was delivered, and memory was tested 1 d later (T2). *p < 0.05, **p < 0.01, ***p < 0.001; §p < 0.05 (T15 vs T16). D, Re-experiencing the same traumatic experience does not elicit a traumatic memory phenotype. Memory was tested at 2 d after a 3 mA training (T1). At the end of T1, rats were either retrained at 3 mA intensity (TR2) or were exposed to a 3 mA RS. Extinction protocol was given for 5 consecutive days (E1–E5). One day after E5, an 3 mA RS was delivered, and memory was tested 1 d later (T2) for reinstatement. *p < 0.05, **p < 0.01, ***p < 0.001; §§p < 0.01 and §§§p < 0.001 (E5 vs T2). E, Two days after training elicited with a 3 mA footshock, rats were left in their home cages (−), retrained at 3 mA, or exposed to a 3 mA RS, and memory was tested for IA generalization in a modified context (ctx B) 1 d later (T1). *p < 0.05, **p < 0.01.