Emotional learning retroactively enhances item memory but distorts source attributions

Abstract

An adaptive memory system should prioritize select information surrounding a powerful learning event that may prove useful for predicting future meaningful events. The behavioral tagging hypothesis provides a mechanistic framework to interpret how weak experiences persist as durable memories through temporal association with a strong experience. Importantly, memories are composed of multiple elements, and different mnemonic aspects of the same experience may be uniquely affected by mechanisms that retroactively modulate weakly encoded memory. Here we investigated how emotional learning affects item and source memory for related events encoded close in time. Participants encoded trial-unique category exemplars before, during, and after Pavlovian fear conditioning. Results showed selective retroactive enhancements in 24-hour item memory were accompanied by a bias to misattribute items to the temporal context of fear conditioning. The strength of this source memory bias correlated with participants’ retroactive item memory enhancement, and source misattribution to the emotional context predicted whether items were remembered overall. In the framework of behavioral tagging: memory attribution was biased to the temporal context of the stronger event (fear conditioning) that provided the putative source of memory stabilization for the weaker event (non-emotional learning). We additionally found that fear conditioning selectively and retroactively enhanced stimulus typicality ratings for related items, and that stimulus typicality also predicted overall item memory. Collectively, these results provide new evidence that items related to an emotional event are misattributed to the temporal context of the emotional event and judged to be more representative of their semantic category. Both processes may help facilitate memory retrieval for related events encoded close in time.