Data for "Corticosterone differentially modulates time-dependent fear generalization following mild or stronger fear conditioning"
Stressful and emotionally arousing experiences create strong memories that seem to lose specificity over time. It is uncertain, however, how the stress system contributes to the phenomenon of time-dependent fear generalization. Here, we investigated whether the glucocorticoid hormonal system affects the specificity of contextual fear memories at several timepoints. We trained male Wistar rats on the context fear conditioning (CFC) task using two footshock intensities (mild CFC, 3 footshocks of 0.3 mA, or moderate CFC, 3x 0.6 mA) and immediately after the training session we administered corticosterone (CORT-HBC) systemically. We first tested the animals in a novel context and then in the training context at different intervals following the training (2, 14, 28 or 42 days). By contrasting freezing times shown in both contexts, we inferred contextual fear generalization for each rat. Following mild CFC training, the glucocorticoid induced the consolidation of an increased discriminative contextual memory that lasted from two up to 28 days. In contrast, after moderate CFC training, CORT-HBC elicited contextual generalization at 14 days, contrarily to the control group that maintained contextual discrimination at this timepoint. For this training intensity, however, CORT-HBC did not have any effect on recent memory specificity. These findings indicate that manipulating glucocorticoid levels after mild or strongly arousing experiences may differentially modulate memory consolidation and time-dependent fear generalization, possibly suggesting there may be a minimum level of emotional arousal that is necessary for CORT-HBC to modulate the creation of generalizable fear memories.