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

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 post-encoding, 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), one day (N = 40), one week (N = 39), or two 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 time-dependent transformation of emotional episodic memories, thereby shedding light on the ways healthy and maladaptive human memories may develop.

Mnemonic prediction errors promote detailed memories

When our experience violates our predictions, it is adaptive to update our knowledge to promote a more accurate representation of the world and facilitate future predictions. Theoretical models propose that these mnemonic prediction errors should be encoded into a distinct memory trace to prevent interference with previous, conflicting memories. We investigated this proposal by repeatedly exposing participants to pairs of sequentially presented objects (A → B), thus evoking expectations. Then, we violated participants’ expectations by replacing the second object in the pairs with a novel object (A → C). The following item memory test required participants to discriminate between identical old items and similar lures, thus testing detailed and distinctive item memory representations. In two experiments, mnemonic prediction errors enhanced item memory: Participants correctly identified more old items as old when those items violated expectations during learning, compared with items that did not violate expectations. This memory enhancement for C items was only observed when participants later showed intact memory for the related A → B pairs, suggesting that strong predictions are required to facilitate memory for violations. Following up on this, a third experiment reduced prediction strength prior to violation and subsequently eliminated the memory advantage of violations. Interestingly, mnemonic prediction errors did not increase gist-based mistakes of identifying old items as similar lures or identifying similar lures as old. Enhanced item memory in the absence of gist-based mistakes suggests that violations enhanced memory for items’ details, which could be mediated via distinct memory traces. Together, these results advance our knowledge of how mnemonic prediction errors promote memory formation.

EPISODIC MEMORY PROCESSES FOR NEUTRAL STIMULI IN THE EMOTIONAL CONTEXT

Emotional stimuli are processed differently in memory with respect to neutral stimuli; because they are more distinct, salient, and biologically significant. Episodic memory is about remembering the events as related to each other. In everyday life, because of the nature of episodic memories, emotional and neutral stimuli are exposed together, not separately. Thus, emotional stimuli become related to nearby neutral stimuli and affect their processing. In the emotional episodic memory literature, how emotional stimuli affect episodic memory processes about neutral stimuli has been widely studied. In addition to the approaches arguing this effect is either enhancing or weakening, there are also other approaches suggesting that it is selective. This selective effect emphasizes that emotion might enhance or weaken the memory for neutral stimuli with respect to different occasions. In addition to the item memory for nearby neutral stimuli, emotional stimuli have effects on the associative memory established with these stimuli. Research has shown that emotional stimuli affect item and associative memory in different ways. In summary, this review tries to analyze emotional episodic memory literature in the scope of neutral stimuli. For this aim, how emotional stimuli affect episodic memory for nearby neutral stimuli is evaluated extensively. Keywords Emotional stimuli, neutral stimuli, episodic memory, item memory, associative memory

Relationship Between Item and Source Memory: Explanation of Connection-Strength Model

The controversy in the relationship between item memory and source memory is a focus of episodic memory. Some studies show the trade-off between item memory and source memory, some show the consistency between them, and others show the independence between them. This review attempts to point out the connection-strength model, implying the different types and strengths of the important role of the item–source connections in the relationship between item memory and source memory, which is based on the same essence in the unified framework. The logic of the model is that when item memory and source memory share the same or relevant connection between item and source, they positively connect, or they are independently or negatively connected. This review integrates empirical evidence from the domains of cognition, cognitive neuroscience, and mathematical modeling to validate our hypothesis.

Effects of emotional study context on immediate and delayed recognition memory: Evidence from event-related potentials

Whilst research has largely focused on the recognition of emotional items, emotion may be a more subtle part of our surroundings and conveyed by context rather than by items. Using ERPs, we investigated which effects an arousing context during encoding may have for item-context binding and subsequent familiarity-based and recollection-based item-memory. It has been suggested that arousal could facilitate item-context bindings and by this enhance the contribution of recollection to subsequent memory judgements. Alternatively, arousal could shift attention onto central features of a scene and by this foster unitisation during encoding. This could boost the contribution of familiarity to remembering. Participants learnt neutral objects paired with ecologically highly valid emotional faces whose names later served as neutral cues during an immediate and delayed test phase. Participants identified objects faster when they had originally been studied together with emotional context faces. Items with both neutral and emotional context elicited an early frontal ERP old/new difference (200-400 ms). Neither the neurophysiological correlate for familiarity nor recollection were specific to emotionality. For the ERP correlate of recollection, we found an interaction between stimulus type and day, suggesting that this measure decreased to a larger extend on Day 2 compared with Day 1. However, we did not find direct evidence for delayed forgetting of items encoded in emotional contexts at Day 2. Emotion at encoding might make retrieval of items with emotional context more readily accessible, but we found no significant evidence that emotional context either facilitated familiarity-based or recollection-based item-memory after a delay of 24 h.

Comprehension of Morse Code Predicted by Item Recall From Short-Term Memory

Purpose Morse code as a form of communication became widely used for telegraphy, radio and maritime communication, and military operations, and remains popular with ham radio operators. Some skilled users of Morse code are able to comprehend a full sentence as they listen to it, while others must first transcribe the sentence into its written letter sequence. Morse thus provides an interesting opportunity to examine comprehension differences in the context of skilled acoustic perception. Measures of comprehension and short-term memory show a strong correlation across multiple forms of communication. This study tests whether this relationship holds for Morse and investigates its underlying basis. Our analyses examine Morse and speech immediate serial recall, focusing on established markers of echoic storage, phonological-articulatory coding, and lexical-semantic support. We show a relationship between Morse short-term memory and Morse comprehension that is not explained by Morse perceptual fluency. In addition, we find that poorer serial recall for Morse compared to speech is primarily due to poorer item memory for Morse, indicating differences in lexical-semantic support. Interestingly, individual differences in speech item memory are also predictive of individual differences in Morse comprehension. Conclusions We point to a psycholinguistic framework to account for these results, concluding that Morse functions like “reading for the ears” ( Maier et al., 2004 ) and that underlying differences in the integration of phonological and lexical-semantic knowledge impact both short-term memory and comprehension. The results provide insight into individual differences in the comprehension of degraded speech and strategies that build comprehension through listening experience. Supplemental Material https://doi.org/10.23641/asha.16451868

A selective benefit of transient, but not sustained, reward to memory formation

Reward benefits to memory formation have been robustly linked to dopaminergic activity. Despite established characterization of dopaminergic mechanisms as operating at multiple timescales, potentially supporting distinct functional outcomes, the temporal dynamics by which reward might modulate memory encoding are just beginning to be investigated. In the present study, we leveraged a mixed block/event experimental design to disentangle transient and sustained reward influences on task engagement and subsequent recognition memory in an adapted monetary-incentive encoding (MIE) paradigm. Across three behavioral experiments, transient and sustained reward modulation of item and context memory was probed, at both 24-hour and ~10-minute retention intervals, to investigate the importance of overnight consolidation. In general, we observed that transient reward was associated with enhanced item memory encoding, while sustained reward modulated task engagement at encoding (specifically, increasing response speed) but did not confer a benefit to subsequent memory performance. Notably, reward benefits to item memory performance were somewhat inconsistent across the three experiments, and in contrast to predictions, we did not observe reward modulation of context memory performance or amplification of reward effects by overnight consolidation. Taken together, the observed pattern of behavior suggests potentially distinct roles for transient and sustained reward in memory encoding and cognitive performance and suggests that further investigation of the temporal dynamics of dopaminergic contributions to memory formation will advance understanding of motivated memory.

Tracking the relation between gist and item memory over the course of long-term memory consolidation

Our experiences in the world support memories not only of specific episodes but also of the generalities (the ‘gist’) across related experiences. It remains unclear how these two types of memories evolve and influence one another over time. In two experiments, 173 human participants encoded spatial locations from a distribution and reported both item memory (specific locations) and gist memory (center for the locations) across one to two months. Experiment 1 demonstrated that after one month, gist memory was preserved relative to item memory, despite a persistent positive correlation between them. Critically, item memories were biased towards the gist over time. Experiment 2 showed that a spatial outlier item changed this relationship and that the extraction of gist is sensitive to the regularities of items. Our results suggest that the gist starts to guide item memories over longer durations as their relative strengths change.