Time-dependent emotional memory transformation: Divergent pathways of item memory and contextual dependency.

Abstract

Emotional memory can persist strikingly long, but it is believed that not all its elements are protected against the fading effects of time. So far, studies of emotional episodic memory have mostly investigated retention up to 24h postencoding and revealed that central emotional features (items) are usually strengthened, while contextual binding of the event is reduced. However, even though it is known for neutral memories that central versus contextual elements evolve differently with longer passage of time, the time-dependent evolution of emotional memories remains unclear. Hypothetically, compared to neutral memories, emotional item memory becomes increasingly stronger, accompanied by accelerated decay of-already fragile-links with their original encoding contexts, resulting in progressive reductions in contextual dependency. Here, we tested these predictions in a large-scale study. Participants encoded emotional and neutral episodes, and were assessed 30 minutes (N = 40), 1 day (N = 40), 1 week (N = 39), or 2 weeks (N = 39) later on item memory, contextual dependency, and subjective quality of memory. The results show that, with the passage of time, emotional memories were indeed characterized by increasingly stronger item memory and weaker contextual dependency. Interestingly, analyses of the subjective quality of memories revealed that stronger memory for emotional items with time was expressed in familiarity, whereas increasingly smaller contextual dependency for emotional episodes was reflected in recollection. Together, these findings uncover the timedependent transformation of emotional episodic memories, thereby shedding light on the ways healthy and maladaptive human memories may develop.

Context reexposure to bolster contextual dependency of emotional episodic memory

“…S2 A, right pane), but here recognition was only elevated in the original versus similar context ( Test in Original Context versus Test in Similar Context , F 1,28 = 8.50, p = 0.01, η p 2 = 0.23, BF 10 = 6.23; Test in Similar Context versus Test in New Context , F 1,28 = 1.04, p = 0.32, η p 2 = 0.04, BF 10 = 0.32). In short, these results largely replicate earlier studies showing context-dependent memory 1 , 2 , 4 – 6 , and smaller contextual dependency for emotional versus neutral memories 4 – 6 .…”

“…To assess whether correct recognition depended on context, and this contextual dependency was lower for emotional than neutral memories, we analyzed d-prime scores in the No Exposure control group . We only included the control group for this analysis, because in earlier studies that we aimed to replicate here no exposure to context was included between encoding and testing 4 – 6 . To test if contextual dependency of emotional memories is impaired relative to neutral memories, we performed two independent t-tests.…”

“…When one returns to the spatial environment in which an event has previously occurred, retrieval or recognition of that event often happens readily, whereas memories can be more difficult to reinstate in different contexts 1 – 3 . Such contextual dependency of memory is, however, less pronounced for emotional compared to neutral memories, an observation that is partly attributed to relatively weak embedding of emotional events in their encoding context 4 – 6 . The reduced contextual dependency of emotional memory is believed to lie at the heart of dysfunctional memory development, resulting in symptoms that characterize a multitude of affective disorders 7 .…”

“…Based on these insights, it thus seems likely that stronger retrieval during context reexposure predicts larger increases in contextual dependency. This may especially be true for emotional memories that typically depend less on context than neutral memories 4 – 6 . Stronger retrieval during exposure to a similar context may also amplify memory integration, but in this case of the original learning event with a different context 41 .…”

“…On the third and final day, all participants underwent a recognition test during which they were presented with targets (i.e., faces seen during encoding) and lures (i.e., unfamiliar faces). As a test of contextual dependency of memory 4 – 6 , one third of the targets and lures were presented on one of the contexts that were seen on the first day, i.e., the same context for targets and random contexts for lures ( Test in Original Context condition ). Another third of the faces was shown on a similar context ( Test in Similar Context condition ) and the final third was shown on a completely new context ( Test in New Context condition ).…”