In control mice, showing normal fear memory, the concentrations of the adaptive memory-promoting proteins P-Erk1/2MAPK progressively increased after the conditioning session, whilst it decreased to below basal levels in animals that developed PTSD-like memories (Fig. 3e, i; interaction time × treatment: F4,40 = 1.375, p = 0.2598; time: F4,40 = 2.988, p = 0.0300; treatment: F1,10 = 14.96, p = 0.0031) as shown by the analysis of the area under the curve (Fig. 3f; t = 5.362, df = 10, p = 0.0003). Here, MAPK3 is linked to post-traumatic stress disorder.