Fig. 2.

Deficient reconsolidation of contextual fear memory in older 5XFAD mice. Experimental design used is presented at the top of each panel. (A) 5XFAD mice at 10–12 months of age and their wild-type littermate mice were trained with 5 CS/US pairings for contextual fear conditioning. Mice received a single 3-min re-exposure to the conditioning context 24 h after training, and were then tested for contextual memory 24 h later. Levels of freezing during re-exposure were not different between 5XFAD and wild-type mice. In contrast, levels of freezing during subsequent memory testing in 5XFAD mice were significantly lower than those of wild-type controls (* p < 0.05) and as compared to those during re-exposure (^#p < 0.05) (n = 12–14 mice per group). (B) When mice received no re-exposure intervening between training with 5 CS/US pairings and memory testing 48 h later, no difference in freezing levels was found between 5XFAD mice and wild-type controls (n = 11–14 mice per group). (C) Weaker training with 1 CS/US pairing dramatically reduced freezing during re-exposure in wild-type mice, but similar levels of freezing were retained during memory testing 24 h later (n = 12 mice per group). All data are presented as mean ± SEM.