How the nature of weak learning and retention interval affects behavioral tagging of episodic memory

Emotional experiences can promote memory consolidation of weakly learned events encoded around the same time. This memory enhancement through temporal convergence between a weak and strong event accords with the behavioral tagging hypothesis, a behavioral analog of the synaptic tagging model for cellular plasticity. There is evidence for a behavioral tagging process in human episodic memory. However, the conditions necessary to stabilize episodic memory through association with a more meaningful event remain vague. Here, we investigated whether the nature of the "weak" event and length of the retention interval are boundary conditions underlying selective retroactive memory enhancements. Participants encoded trial-unique items from two semantic categories before, during, and after fear conditioning that involved pairing one category with electric shock. Memory was tested either 24 hr or 1 month later. Importantly, some participants did not expect shocks during weak learning and were administered electric shocks only after weak learning, while other participants experienced shocks before weak learning and expected shocks throughout every encoding phase. Results showed that participants who weakly encoded category exemplars without presumed threat of shock prior to fear conditioning exhibited selective retroactive memory enhancements that survived up to 1 month later. By contrast, altering the nature of "weak" encoding through prearousal and threat expectancy prevented selective retroactive enhancements at 24 hr; however, a selective retroactive enhancement did emerge when memory was tested 1 month later. These findings suggest that sufficiently encoded events fail to profit from additional modulation by subsequent emotional learning when tested at relatively short retention intervals. However, selective retroactive preservation for information conceptually related to an emotional event is revealed over longer retention intervals. (PsycInfo Database Record (c) 2025 APA, all rights reserved).