Effects of novelty and reward-based fear extinction on memory generalization

Fear extinction forms new memories that are typically weaker and less generalizable than the original fear memory. Using a test of behavioral pattern completion and separation, we previously found that fear conditioning is associated with greater episodic memory generalization (pattern completion) of conditioned stimuli (CS), whereas extinction generates more precise, stimulus-specific, long-term memory representations. Here, we tested the hypothesis that enhancing extinction, via novelty or counterconditioning, shifts the precision of extinction memory towards greater generalization, which may promote more flexible long-term retrieval of safety learning. Participants underwent threat acquisition (shock-paired CS+, unpaired CS-), followed by extinction involving either standard shock-omission (EXT, N = 40), novelty-facilitated extinction replacing shock with an auditory tone (NFE, N = 30), or counterconditioning replacing shock with positive images (CCX, N = 42). The next day, participants completed tests of generalized extinction retention and item-level episodic memory-including old, similar, and new CS category items. On day 2, NFE and EXT showed equivalent reduction of physiological fear recovery towards novel CS items during the retention test, but in terms of episodic memory, NFE showed enhanced accuracy and generalization-greater pattern completion-for CS + items encoded during extinction. Although CCX evoked strong positive affect on day 1, extinction memory was highly specific, indicating reward-based extinction may bias memory toward pattern separation (discrimination). Overall, NFE promoted generalizable episodic memory, whereas positively-valenced extinction rendered specific learning that may fail to generalize to similar events in future scenarios. The long-term efficacy of extinction-based interventions may therefore benefit from novelty-based approaches.