Binding neutral information to emotional contexts: Brain dynamics of long-term recognition memory

Differentiating the DF effect in episodic memory: evaluating the contribution of the procedures of collaborative memory

Existing research has demonstrated a significant directed forgetting (DF) effect in memory. However, it remains unclear whether this phenomenon would occur in the context of interpersonal collaboration. Additionally, the contribution of emotional valence to the DF effect in item memory and source memory (which are subtypes of episodic memory) also needs to be explored. To address these issues, we conducted two experiments that combined the collaborative memory paradigm with the item-method procedure of DF. In both experiments, positive, neutral, or negative words were presented as stimuli, each followed by an R/F cue during encoding. We conducted two recalls, labeled Recall 1 and Recall 2, which consisted of both memory tasks. Recall 1 was performed either individually or collaboratively, whereas Recall 2 was done individually. Experiment 1 and Experiment 2 adopted the free-flowing procedure and the turn-taking procedure of collaborative memory, respectively. We obtained three implications from our current findings. (a) The occurrence of the DF effect in item memory was found regardless of the procedure of collaborative memory, and it was insensitive to the emotional valence of words or to whether participants had collaborated or not. These patterns demonstrate that both the mechanisms of elaborative rehearsal and active suppression/encoding blocking were engaged across words of different emotional valences and in nominal and collaborative circumstances. (b) In source memory, the DF effect showed different patterns in ongoing and post-collaborative memory, which underpins the dual-process models. (c) The amplitude of the DF effect was sensitive to the interaction of emotional valence by the status of collaboration, and the impact of collaboration differed between the two experiments, offering telling evidence of different aspects of the retrieval strategy disruption hypothesis (RSDH). Directions for identifying more influential factors are put forward.

Emotional state dynamics impacts temporal memory

Emotional fluctuations are ubiquitous in everyday life, but precisely how they sculpt the temporal organisation of memories remains unclear. Here, we designed a novel task - the Emotion Boundary Task - wherein participants viewed sequences of negative and neutral images surrounded by a colour border. We manipulated perceptual context (border colour), emotional-picture valence, as well as the direction of emotional-valence shifts (i.e., shifts from neutral-to-negative and negative-to-neutral events) to create events with a shared perceptual and/or emotional context. We measured memory for temporal order and temporal distances for images processed within and across events. Negative images processed within events were remembered as closer in time compared to neutral ones. In contrast, temporal distances were remembered as longer for images spanning neutral-to-negative shifts - suggesting temporal dilation in memory with the onset of a negative event following a previously-neutral state. The extent of negative-picture induced temporal dilation in memory correlated with dispositional negativity across individuals. Lastly, temporal order memory was enhanced for recently-presented negative (versus neutral) images. These findings suggest that emotional-state dynamics matters when considering emotion-temporal memory interactions: While persistent negative events may compress subjectively remembered time, dynamic shifts from neutral-to-negative events produce temporal dilation in memory, with implications for adaptive emotional functioning.

Enhanced source memory for emotionally valenced sources: does an affective orienting task make the difference?

Previous research on whether source memory is enhanced for emotionally valenced sources yielded inconclusive results. To identify potential boundary conditions, we tested whether encoding instructions that promote affective versus different types of non-affective item-source-processing foster versus hamper source-valence effects. In both experiments, we used neutral words as items superimposed on emotional (positive & negative) or neutral pictures as sources. Source pictures were selected based on valence and arousal ratings collected in a pre-study such that only valence varied across sources. Source memory was measured via multinomial modelling. In Experiment 1, we applied an affective, item-focused orienting task (OT; i.e. word-pleasantness ratings) during item-source encoding and found enhanced source memory for emotionally valenced (positive & negative) compared to neutral sources. In Experiment 2, we systematically manipulated encoding instructions and again found enhanced source memory for emotionally valenced sources with an affective OT. No such effects occurred in the non-affective conditions, where participants were instructed to integrate item and source (item-source-fit judgments), to focus on the item (living-non-living judgments), or to encode the items only, respectively. With intentional item encoding, however, source memory was surprisingly better for positive than negative sources. We conclude that source-valence effects might unfold only under affective processing.

Negative emotions enhance memory-guided attention in a visual search task by increasing frontoparietal, insular, and parahippocampal cortical activity

Previous literature demonstrated that long-term memory representations guide spatial attention during visual search in real-world pictures. However, it is currently unknown whether memory-guided visual search is affected by the emotional content of the picture. During functional magnetic resonance imaging (fMRI), participants were asked to encode the position of high-contrast targets embedded in emotional (negative or positive) or neutral pictures. At retrieval, they performed a visual search for targets presented at the same location as during encoding, but at a much lower contrast. Behaviorally, participants detected more accurately targets presented in negative pictures compared to those in positive or neutral pictures. They were also faster in detecting targets presented at encoding in emotional (negative or positive) pictures than in neutral pictures, or targets not presented during encoding (i.e., memory-guided attention effect). At the neural level, we found increased activation in a large circuit of regions involving the dorsal and ventral frontoparietal cortex, insular and parahippocampal cortex, selectively during the detection of targets presented in negative pictures during encoding. We propose that these regions might form an integrated neural circuit recruited to select and process previously encoded target locations (i.e., memory-guided attention sustained by the frontoparietal cortex) embedded in emotional contexts (i.e., emotional contexts recollection supported by the parahippocampal cortex and emotional monitoring supported by the insular cortex). Ultimately, these findings reveal that negative emotions can enhance memory-guided visual search performance by increasing neural activity in a large-scale brain circuit, contributing to disentangle the complex relationship between emotion, attention, and memory.

Emotional state dynamics impacts temporal memory

Emotional fluctuations are ubiquitous in everyday life, but precisely how they sculpt the temporal organization of memories remains unclear. Here, we designed a novel task-the Emotion Boundary Task-wherein participants viewed sequences of negative and neutral images surrounded by a color border. We manipulated perceptual context (border color), emotional valence, as well as the direction of emotional-valence shifts (i.e., shifts from neutral-to-negative and negative-to-neutral events) to create encoding events comprised of image sequences with a shared perceptual and/or emotional context. We measured memory for temporal order and subjectively remembered temporal distances for images processed within and across events. Negative images processed within events were remembered as closer in time compared to neutral ones. In contrast, temporal distance was remembered as longer for images spanning neutral-to-negative shifts-suggesting temporal dilation in memory with the onset of a negative event following a previously-neutral state. The extent of this negative-picture induced temporal dilation in memory correlated with dispositional negativity across individuals. Lastly, temporal order memory was enhanced for recently presented negative (compared to neutral) images. These findings suggest that emotional-state dynamics matters when considering emotion-temporal memory interactions: While persistent negative events may compress subjectively remembered time, dynamic shifts from neutral to negative events produce temporal dilation in memory, which may be relevant for adaptive emotional functioning.

Dynamic emotional states shape the episodic structure of memory

Human emotions fluctuate over time. However, it is unclear how these shifting emotional states influence the organization of episodic memory. Here, we examine how emotion dynamics transform experiences into memorable events. Using custom musical pieces and a dynamic emotion-tracking tool to elicit and measure temporal fluctuations in felt valence and arousal, our results demonstrate that memory is organized around emotional states. While listening to music, fluctuations between different emotional valences bias temporal encoding process toward memory integration or separation. Whereas a large absolute or negative shift in valence helps segment memories into episodes, a positive emotional shift binds sequential representations together. Both discrete and dynamic shifts in music-evoked valence and arousal also enhance delayed item and temporal source memory for concurrent neutral items, signaling the beginning of new emotional events. These findings are in line with the idea that the rise and fall of emotions can sculpt unfolding experiences into memories of meaningful events.

Does Expecting Matter? The Impact of Experimentally Established Expectations on Subsequent Memory Retrieval of Emotional Words

Previous studies have confirmed that different degrees of expectation, including the bipolarity of the expected and unexpected, as well as an intermediate level (no expectation), can affect memory. However, only a few investigations have manipulated expectation through experimentally established schema, with no consideration of how expectation impacts both item and source memory. Furthermore, stimulus emotionality may also impact memory. Therefore, we conducted a study to investigate the effects of three levels of expectation on item and source memory while considering the impact of stimulus emotionality. The experiment began with a phase dedicated to learning the rules. In the subsequent study phase, negative and neutral words were manipulated as expected, no expectation, and unexpected, based on these rules. This was followed by tasks focused on item and source memory. The study found that there was a "U-shape" relationship between expectation and item memory. Additionally, the study revealed the distinct impacts of expectation on item and source memory. When it came to item memory, both expected and unexpected words were better remembered than those with no expectations. In source memory, expected words showed memory inferiority for expectation-irrelevant source information, but an advantage for expectation-relevant source information. Stimulus emotionality modulated the effect of expectation on both item and source memory. Our findings provide behavioral evidence for the schema-linked interactions between medial prefrontal and medial temporal regions (SLIMM) theory, which proposes that congruent and incongruent events enhance memory through different brain regions. The different patterns between item and source memory also support dual-process models. Moreover, we speculate that processing events with varying levels of emotionality may undermine the impact of expectation, as implied by other neural investigations.

Sensitivity of late ERP old/new effects in source memory to self-referential encoding focus and stimulus emotionality

In episodic memory, the old/new effect, the contrast of the waveforms elicited by the correctly recognized studied items and the correctly rejected novel items, has been broadly concerned. However, the contribution of self-referential encoding to the old/new effect in source memory (i.e., source-SRE), is far from clarification; further, it remains unclear whether the contribution is susceptible to the factor of stimulus emotionality. To address these issues, adopting the event-related potential (ERP) technique, this study applied words of three types of emotional valences (positive, neutral, vs. negative) in the self-focus vs. external-focus encoding tasks. In the course of the test, four ERP old/new effects were identified: (a) the familiarity- and recollection-reflected mid-frontal effect (FN400) and late positive component (LPC) were both independent of source-SRE and stimulus emotionality; (b) the reconstruction-driven late posterior negativity (LPN) exhibited an adverse pattern of source-SRE and was susceptible to the emotional valence by encoding focus; and (c) the right frontal old/new effect (RFE), reflecting post-retrieval process, exhibited a source-SRE in emotional words. These effects provide compelling evidence for the influences of both stimulus valence and encoding focus on SRE in source memory, especially during the late processes. Further directions considering more perspectives are put forward.

The effects of social anxiety on recognition memory for social threat words: An ERP study

In this study, the effect of social anxiety on item recognition memory was examined by adopting a study-test paradigm. Participants with high and low social anxiety (31 HSA vs. 30 LSA) memorized neutral target and threat target (NT vs. TT) words while threat distracters were simultaneously presented. The behavioral results did not exhibit group differences in recognition performance. The event-related potentials (ERP) results showed that the HSA and LSA participants all did not exhibit significant old/new effects for neutral targets, while only the LSA participants exhibited significant old/new effects for threat targets. For the distracters, the HSA participants did not exhibit evident old/new effects under the NT and TT conditions; while LSA participants showed a reversed LPC old/new effect for the threat distracters under the NT condition. The old/new effects for threat targets were impaired in HSA participants but presented in LSA participants. These findings suggest that social anxiety modulates the effect of recognition memory for social threat words.

Effect of the congruity of emotional contexts at encoding on source memory: Evidence from ERPs

Emotion's influence on source memory has proven more elusive and the lack of studies investigates the effect of the congruent emotional contexts on source memory. Here, we investigated these issues using event-related potentials (ERPs) to assess emotional-induced neural correlates. During encoding, congruent word-picture (a word 'shoes' - a picture described shoes) and incongruent word-picture (a word 'pepper' - a picture described shoes) with a prompt (Common? or Natural?) were presented. At retrieval, participants indicated which prompts were concomitantly presented with the word during encoding. Behavioral results revealed that source memory accuracy was enhanced in the neutral contexts compared to the negative contexts, and enhanced in the incongruent condition relative to the congruent condition, suggesting that emotional contexts impaired source memory performance, and incongruent information enhanced source memory. ERPs results showed that early P2 old/new effect (150-250 ms) and FN400 old/new effect (300-450 ms) were observed for words with correct source that had been encoded in the congruent emotional contexts, and that a larger parietal old/new effect, between 500 and 700 ms, was observed for words with correct source that had been encoded in the incongruent condition than in the congruent condition, irrespective the nature of context. The ERPs results indicate that retrieval of source details for the associated emotionally congruent information supports the idea that emotional events could attract more attentional resources, and reflects the contribution of familiarity-based process. Meanwhile, retrieval of source details for the associated incongruent information reflects a stronger contribution of recollection-based process.

Social threat and safety learning in individuals with adverse childhood experiences: electrocortical evidence on face processing, recognition, and working memory

BACKGROUND

Adverse childhood experiences (ACEs) are often associated with stress and anxiety-related disorders in adulthood, and learning and memory deficits have been suggested as a potential link between ACEs and psychopathology.

OBJECTIVE

In this preregistered study, the impact of social threat learning on the processing, encoding, and recognition of unknown faces as well as their contextual settings was measured by recognition performance and event-related brain potentials.

METHOD

Sixty-four individuals with ACEs encoded neutral faces within threatening or safe context conditions. During recognition, participants had to decide whether a face was new or had been previously presented in what context (item-source memory), looking at old and new faces. For visual working memory, participants had to detect changes in low and high load conditions during contextual threat or safety.

RESULTS

Results showed a successful induction of threat expectation in persons with ACEs. In terms of face and source recognition, overall recognition of safe and new faces was better compared to threatening face-compounds, with more socially anxious individuals having an advantage in remembering threatening faces. For working memory, an effect of task load was found on performance, irrespective of threat or safety context. Regarding electrocortical activity, an old/new recognition effect and threat-selective processing of face-context information was observed during both encoding and recognition. Moreover, neural activity associated with change detection was found for faces in a threatening context, but only at high task load, suggesting reduced capacity for faces in potentially harmful situations when cognitive resources are limited.

CONCLUSION

While individuals with ACE showed intact social threat and safety learning overall, threat-selective face processing was observed for item/source memory, and a threatening context required more processing resources for visual working memory. Further research is needed to investigate the psychophysiological processes involved in functional and dysfunctional memory systems and their importance as vulnerability factors for stress-related disorders.

Better memory for emotional sources? A systematic evaluation of source valence and arousal in source memory

Emotion-enhanced memory (EEM) describes the robust memory advantage of emotional over non-emotional stimuli. While extensively investigated with emotional items, it is unclear whether the EEM effect extends to source memory for a neutral item's emotional context. In two pre-registered studies, we systematically manipulated source valence (positive, negative) between participants and source arousal (high, low, neutral-low) within participants. In Experiment 1 (lab study, N = 80), we used emotional sound sources and presented them together with neutral pictures as items. In Experiment 2 (online study, N = 172), we used emotional background pictures with superimposed neutral item words to similarly manipulate source emotionality. Multinomial model-based analysis showed no general effects of valence or arousal on source memory across both experiments. Source memory was impaired for the negative high-arousing source in Experiment 1 but this did not replicate in Experiment 2. Altogether, we conclude that there are no memory-enhancing effects of source emotionality (valence, arousal, or any specific combination thereof) on source memory, dissociating emotionality effects between source and item memory. Additionally, we propose that material-dependent influences carry more weight if the used emotional material is limited in number, as is the case in the standard source-monitoring paradigm employing few sources only.

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.

A multinomial modelling approach to face identity recognition during instructed threat

To organise future behaviour, it is important to remember both the central and contextual aspects of a situation. We examined the impact of contextual threat or safety, learned through verbal instructions, on face identity recognition. In two studies (N = 140), 72 face-context compounds were presented each once within an encoding session, and an unexpected item/source recognition task was performed afterwards (including 24 new faces). Hierarchical multinomial processing tree modelling served to estimate individual parameters of item (face identity) and source memory (threat or safety context) as well as guessing behaviour. Results show that language was highly effective in establishing threatening and safe context conditions. In Study 1, a fleeting picture stream (1 s per picture) led to poor item and source recognition. Prolonged presentation times (Study 2 with 6 s per picture) improved face memory but no contextual modulation was observed. Thus, incidental face learning was surprisingly poor and rapidly changing contextual settings might have interfered with the accurate encoding of face identity information and item-source binding.

Professional discrepancies of doctors and lawyers in episodic memory: Modulations of professional morality and warning

Past investigations have consistently demonstrated the robust stereotype-consistent effect in the circumstance of source memory but not always in item memory, including the case of professional stereotype. However, it remains unclear whether the effect still occurs in professional stereotype when considering the attributes of negative (or bad) or positive (or good); besides, it has not been concerned about how does warning work in remembering the professional stereotypical stimuli. The current experiments aimed to address these issues by adopting descriptive sentences as stimuli, which were related or unrelated to doctors and lawyers, and with different professional moral valences (negative, neutral, or positive). Item memory and source memory were tested successively. Experiment 1 without the explicit warning confirmed the reliable stereotype-consistent effect solely in source memory; the modulation of professional morality on memory behaved differently between doctor and lawyer, that is, negativity bias versus positivity bias. When giving an explicit warning (Experiment 2), the stereotype-consistent effect attenuated in the lawyer case, and the occurrence of negativity bias was sensitive to the memory task. Thus, our findings further reinforce the dual-process model; both professional morality and warning work in memory of professional stereotype, depending upon the nature of the profession, the concerned memory task, and also the presence of warning. Implications are made for future research to consider more perspectives.

Is color source retrieval sensitive to emotion? Electrophysiological evidence from old/new effects

It has been proved that item memory and source memory are two dissociable processes, as reflected by differential influence at behavioral and electrophysiological levels, the latter being evidenced by the ERP old/new effects. Specially for source memory, the retrieval of color source may be unique from recollecting other types of contextual information, which can be seen from the late posterior negativity (LPN). However, the mediation of emotional valence on the old/new effects for verbal stimuli encoded in colors remains unknown. Adopting words of three emotional valences (i.e., positive, neutral, and negative), with their displayed colors serving as sources, the current experiment aimed to explore the sensitivity of old/new effects to emotion for both item memory and source memory. Results demonstrated that: the FN400 that reflects familiarity was recorded and it was sensitive to emotional valence across both memory tasks; the mediation of emotional valence was absent in recollection-reflected LPC, neither for item memory nor for source memory; an association between LPN and color source retrieval was confirmed, with reliable amplitudes for neutral words but not for emotional words. These data were discussed in terms of the dual-process model and other accounts. Future research directions were recommended.

Neural substrates of long-term item and source memory for emotional associates: An fMRI study

Since Tulving's influential work on the distinction between familiarity and recollection-based retrieval, numerous studies have found evidence for differential contribution of these retrieval mechanisms on emotional episodic memory. Particularly, retrieval advantage for emotional, compared to neutral, information has been related to recollection-, but not familiarity-mediated processes. Neuroimaging studies suggest that this recollection-based retrieval for emotional information is related to stronger engagement of regions in the medial temporal lobe (MTL), posterior parietal cortex (PPC), and prefrontal cortex (PFC). In the present study, we investigated neural correlates related to long-term memory of neutral information that has been associated with emotional and neutral contexts, using functional magnetic resonance imaging (fMRI). During encoding, different neutral objects integrated with emotional or neutral scenes were presented. One week later, the encoded objects were intermixed with new ones and participants had to indicate whether the objects were previously seen or not, using the Remember/Know procedure (item memory). Furthermore, memory for the correct scene background category was also tested (contextual source memory). First, replicating previous findings, we observed a preference for recollection-dependent memory retrieval versus familiarity-dependent memory retrieval for those neutral objects encoded in emotional compared to neutral contexts. Second, consistent with these behavioral effects, objects encoded with emotional, compared to neutral, scenes produced larger memory-related activity in recollection-sensitive brain regions, including PPC and PFC regions. Third, correctly retrieved emotional compared to neutral contextual information was associated with increased activity in these brain areas. Together, these results suggest that memory for information encoded in emotional contexts is remarkably robust over time and mediated by recollection-based processes.

The effects of positive and negative emotional text content on knowledge revision

Across three experiments, we sought to determine the effects of positive and negative emotional content in refutation texts on misconceptions about vaccines. The addition of negative emotional content to texts that identify, refute, and explain vaccine misconceptions improved knowledge revision observed during reading (Experiment 1). However, the addition of positive emotional content to refutation texts weakened this effect (Experiment 2). A direct comparison between negative and positive emotional content provided corroborating evidence for these findings (Experiment 3). Across experiments, results show that all refutation texts (with or without positive or negative emotional content) improved learning assessed after reading. These findings show the differential effects of emotional content on processing misconceptions about an important socio-scientific topic and provide consistent support for refutation texts as a potentially useful tool in these corrective efforts.

False memory production in schizophrenia: A neurophysiological investigation

Background

The topic of false memory in schizophrenia has been well documented in earlier research contributions. To date, there is no study exploring the implications of specific neural networks during this phenomenon in patients suffering from schizophrenia.

Methods

We compared 17 patients suffering from psychosis (SCZ) to 33 healthy controls (HC) performing a verbal memory task designed to produce false memories, i.e. the Deese-Roediger-McDermott paradigm (DRM). Electroencephalography was used to specifically analyze the P2 and N400 event-related potentials components.

Results

The SCZ patients showed a reduced ability to distinguish between true and false memories as assessed by the A' index which was calculated based on the false and true memory rates. The morphology of the P2 differed in frontal electrode region with a lower amplitude in SCZ. In addition, the amplitude of N400 was more pronounced (more negative) in HC than in SCZ in centro-parietal electrode site.

Conclusions

We suggest that the differences found in P2 amplitude are associated with difficulties of SCZ patients to efficiently compare item-specific features of a mnesic elements to incoming stimuli which impair the subsequent verbal memory information processing reflected by the N400 component amplitude decrease. These results are consistent with the idea that SCZ use a different strategy while they perform the DRM paradigm.

Is internal source memory recognition modulated by emotional encoding contexts?

The influence of emotion on memory has been mainly examined by manipulating the emotional valence and/or arousal of critical items. Few studies probed how emotional information presented during the encoding of critical neutral items modulates memory recognition, particularly when considering source memory features. In this study, we specified the role of emotional encoding contexts in internal source memory performance (discrimination between encoding tasks) using a mixed (Experiment 1) and a blocked design (Experiment 2). During the study phase, participants were required to evaluate a set of neutral words, using either a self-referential or a semantic (common judgment) encoding strategy. Prior and concomitantly with each word, negative, neutral or positive pictures were presented in the background. The beneficial effect of self-referential encoding was observed for both item and internal source memory in both experiments. Remarkably, item and internal source memory recognition was not modulated by emotion, even though a secondary analysis indicated that the consistent exposure to negative (vs. positive) information led to worse source memory performance. These findings suggest that internal source memory of neutral items is not always affected by changing or repetitive emotional encoding contexts.

Behavioral and neural evidence of enhanced long-term memory for untrustworthy faces

In daily life, we automatically form impressions of other individuals on basis of subtle facial features that convey trustworthiness. Because these face-based judgements influence current and future social interactions, we investigated how perceived trustworthiness of faces affects long-term memory using event-related potentials (ERPs). In the current study, participants incidentally viewed 60 neutral faces differing in trustworthiness, and one week later, performed a surprise recognition memory task, in which the same old faces were presented intermixed with novel ones. We found that after one week untrustworthy faces were better recognized than trustworthy faces and that untrustworthy faces prompted early (350–550 ms) enhanced frontal ERP old/new differences (larger positivity for correctly remembered old faces, compared to novel ones) during recognition. Our findings point toward an enhanced long-lasting, likely familiarity-based, memory for untrustworthy faces. Even when trust judgments about a person do not necessarily need to be accurate, a fast access to memories predicting potential harm may be important to guide social behaviour in daily life.

The Effect of Emotional Valence and Arousal on Visuo-Spatial Working Memory: Incidental Emotional Learning and Memory for Object-Location

Remembering places in which emotional events occur is essential for individual's survival. However, the mechanisms through which emotions modulate information processing in working memory, especially in the visuo-spatial domain, is little understood and controversial. The present research was aimed at investigating the effect of incidentally learned emotional stimuli on visuo-spatial working memory (VSWM) performance by using a modified version of the object-location task. Eight black rectangles appeared simultaneously on a computer screen; this was immediately followed by the sequential presentation of eight pictures (selected from IAPS) superimposed onto each rectangle. Pictures were selected considering the two main dimensions of emotions: valence and arousal. Immediately after presentation, participants had to relocate the rectangles in the original position as accurately as possible. In the first experiment arousal and valence were manipulated either as between-subject (Experiment 1A) or as within-subject factors (Experiment 1B and 1C). Results showed that negative pictures enhanced memory for object location only when they were presented with neutral ones within the same encoding trial. This enhancing effect of emotion on memory for object location was replicated also with positive pictures. In Experiment 2 the arousal level of negative pictures was manipulated between-subjects (high vs. low) while maintaining valence as a within-subject factor (negative vs. neutral). Objects associated with negative pictures were better relocated, independently of arousal. In Experiment 3 the role of emotional valence was further ascertained by manipulating valence as a within-subject factor (neutral vs. negative in Experiment 3A; neutral vs. positive in Experiment 3B) and maintaining similar levels of arousal among pictures. A significant effect of valence on memory for location was observed in both experiments. Finally, in Experiment 4, when positive and negative pictures were encoded in the same trial, no significant effect of valence on memory for object location was observed. Taken together results suggest that emotions enhance spatial memory performance when neutral and emotional stimuli compete with one another for access into the working memory system. In this competitive mechanism, an interplay between valence and arousal seems to be at work.

Disrupters as Well as Monitors: Roles of Others During and After Collaborative Remembering in the DRM Procedure

Influence of others on true and inauthentic memory both during and after collaborative remembering have drawn extensive attention in recent years. Collaborative research has recorded three typical effects: collaborative inhibition and error pruning (i.e., nominal groups recall more true information but also bear higher erroneous intrusions than collaborative groups) during collaboration, as well as post-collaborative recall benefit after collaboration. This study introduced Deese-Roediger-McDermott (DRM) lists not only to investigate these phenomena in semantically related information, but also set a course to explore false memory in the collaborative context. Another issue is the sensitivity of these effects to different episodic memory tests (i.e., item memory and source memory tests). In views of these, the current study instructed participants to study several DRM lists and then recall previously studied words (item recall) together with their displayed colors (source retrieval) twice (Recall 1 and 2). Recall 1 was performed either individually or collaboratively, whereas Recall 2 was conducted individually. The cost of collaborative inhibition was obtained, along with three different beneficial effects: error pruning, false memory reduction, and post-collaborative recall benefit. Furthermore, the novel implication of the current study is that it reveals the sensitivity of collaborative inhibition and error pruning in DRM lists to testing conditions and demonstrates that the modulation of collaboration on false memory occurs in the same way both during and after collaboration. These results are discussed in terms of the retrieval strategy disruption hypothesis and other accounts.

How do word frequency and memory task influence directed forgetting: An ERP study

In daily life, it is important either to remember sometimes or to intentionally forget on other occasions. The issue of forgetting following instructions (i.e. directed forgetting, DF) has been broadly studied; however, whether the frequency of contents would matter in DF remains unclear, and the understanding of its neural mechanism in both circumstances of item memory and source memory requires improvement in depth. For these purposes, the current study manipulated word frequency and memory task to investigate relevant behavioral features and neural activities of DF. Adopting event-related potential (ERP) technique, this study applied two-character Chinese words of two types of word frequency (high vs low) in the item-method DF paradigm. During encoding, we found that the increased frontal positivity, an index of active inhibition, was regulated by both word frequency and memory task, while the enhanced parietal positivity reflecting selective rehearsal didn't fluctuate across conditions. In the course of test, three ERP old/new effects were identified: the familiarity-based FN400 and the recollection-driven LPC were both modulated by word frequency and memory task, but the right frontal old/new effect was significant solely in source memory; also, these effects provided compelling evidence for the influences of word frequency and memory task on DF. Our results reinforce the differentiation between absolute familiarity and relative familiarity in memory, reveal their sensitivity to DF, and also support the dual-process interpretation. Implications are made to examine more influential factors for future research.

Time-dependent effects of psychosocial stress on the contextualization of neutral memories

Memories about stressful experiences need to be both specific and generalizable to adequately guide future behavior. Memory strength is influenced by emotional significance, and contextualization (i.e., encoding experiences with their contextual details) enables selective context-dependent retrieval and protects against overgeneralization. The current randomized-controlled study investigated how the early and late phase of the endogenous stress response affects the contextualization of neutral and negative information. One hundred healthy male participants were randomly divided into three experimental groups that performed encoding either 1) without stress (control), 2) immediately after acute stress (early) or 3) two hours after acute stress (late). Stress was induced via the Trier Social Stress Test and salivary alpha-amylase and cortisol levels were measured throughout the experiment. In the Memory Contextualization Task, neutral and angry faces (items) were depicted against unique context pictures during encoding. During testing 24 h later, context-dependent recognition memory of the items was assessed by presenting these in either congruent or incongruent contexts (relative to encoding). Multilevel analyses revealed that neutral information was more contextualized when encoding took place two hours after psychosocial stress, than immediately after the stressor. Results suggest that the late effects in the unique, time-dependent sequence of a healthy endogenous stress response, could complement reduced contextualization immediately after stress. The contextualization of negative information was not influenced by psychosocial stress, as opposed to earlier reported effects of exogenous hydrocortisone administration. An imbalance between the early and late effects of the endogenous stress response could increase vulnerability for stress-related psychopathology.

Enhanced spontaneous retrieval of cues from emotional events: An ERP study

Recent evidence points to enhanced episodic memory retrieval not only for emotional items but also for neutral information encoded in emotional contexts. However, prior research only tested instructed explicit recognition, and hence here we investigated whether memory retrieval is also heightened for cues from emotional contexts when retrieval is not explicitly probed. During the first session of a two-session experiment, neutral objects were presented on different background scenes varying in emotional and neutral contents. One week later, objects were presented again (with no background) intermixed with novel objects. In both sessions, participants were instructed to attentively watch the stimuli (free viewing procedure), and during the second session, ERPs were also collected to measure the ERP Old/New effect, an electrophysiological correlate of episodic memory retrieval. Analyses were performed using cluster-based permutation tests in order to identify reliable spatio-temporal ERP differences. Based on this approach, old relative to new objects, were associated with larger ERP positivity in an early (364-744 ms) and late time window (760-1148 ms) over distinct central electrode clusters. Interestingly, significant late ERP Old/New differences were only observed for objects previously encoded with emotional, but not neutral scenes (504 to 1144 ms). Because these ERP differences were observed in a non-instructed retrieval context, our results indicate that long-term, spontaneous retrieval for neutral objects, is particularly heightened if encoded within emotionally salient contextual information. These findings may assist in understanding mechanisms underlying spontaneous retrieval of emotional associates and the utility of ERPs to study maladaptive involuntary memories in trauma- and stress-related disorders.

Echoes of Emotions Past: How Neuromodulators Determine What We Recollect

We tend to re-live emotional experiences more richly in memory than more mundane experiences. According to one recent neurocognitive model of emotional memory, negative events may be encoded with a larger amount of sensory information than neutral and positive events. As a result, there may be more perceptual information available to reconstruct these events at retrieval, leading to memory reinstatement patterns that correspond with greater memory vividness and sense of recollection for negative events. In this commentary, we offer an alternative perspective on how emotion may influence such sensory cortex reinstatement that focuses on engagement of the noradrenergic (NE) and dopaminergic (DA) systems rather than valence. Specifically, we propose that arousal-related locus coeruleus-norepinephrine (LC-NE) system activation promotes the prioritization of the most salient features of an emotional experience in memory. Thus, a select few details may drive lower-level sensory cortical activity and a stronger sense of recollection for arousing events. By contrast, states of high behavioral activation, including novelty-seeking and exploration, may recruit the DA system to broaden the scope of cognitive processing and integrate multiple event aspects in memory. These more integrated memory representations may be reflected in higher-order cortical reinstatement at retrieval. Thus, the balance between activation in these neuromodulatory systems at encoding, rather than the valence of the event, may ultimately determine the quality of emotional memory recollection and neural reinstatement.

Emotional Content and Source Memory for Language: Impairment in an Incidental Encoding Task

Research into the effects of emotion on source memory (i.e., memory for certain contextual details of a stimulus, such as its location, color, or temporal context) has yielded inconsistent findings. Mather and her co-workers tried to account for such inconsistencies by pointing out the relevance of the characteristics of the feature examined. Specifically, they distinguished between intrinsic and extrinsic features (Mather, 2007) and between goal-relevant and goal-irrelevant information (Mather and Sutherland, 2011). In the current study, we investigated source memory for language, which is an intrinsic feature or words. Catalan-Spanish bilinguals were tested in three experiments involving a recognition task in which they were asked about the language of presentation (Catalan or Spanish) of emotional and neutral words. In Experiments 1 and 2, source memory for negative and neutral words was assessed. In Experiment 1 participants performed an intentional encoding task in which language was a goal-relevant feature. In Experiment 2, they did an incidental encoding task in which language was also goal-relevant. Experiment 3 replicated Experiment 2 but negative words were replaced by positive words. The results showed an impairment in source memory for the language of presentation of emotional words when the encoding task was incidental, but not when it was intentional. Such impairment was observed with both negative words and positive words. The results are discussed in relation to the proposals of Mather and co-workers and point to the relevance of modulating factors, such as the intentional/incidental nature of encoding.

Distinctions between autobiographical memory specificity and detail: Trajectories across cue presentations

Autobiographical memory is central to identity and self-awareness, but individuals with depression and Post-Traumatic Stress Disorder tend to have overgeneral memories. Recent research has suggested that the ability to retrieve specific memories and individual differences in the amount of detail in specific memories are independent (Kyung, Yanes-Lukin, & Roberts, 2016). We re-analyzed data from Kyung et al. to test whether these constructs are distinct in terms of their trajectories over cue presentations. Results indicated a U-shaped trajectory for specificity, but a inverted-U trajectory for detail, suggesting a dissociation in which periods of decreasing probability of retrieving specific memories correspond to increasing amounts of detail. Further, trajectories had similar forms when memories included emotional content, but differed for recollections that did not include emotional content. Finally, at the individual level, slopes for specificity and detail across trials were uncorrelated. These findings provide further support for the independence of these constructs.

Effects of early morning nap sleep on associative memory for neutral and emotional stimuli

Emotional events are preferentially retained in episodic memory. This effect is commonly attributed to enhanced consolidation and has been linked specifically to rapid eye movement (REM) sleep physiology. While several studies have demonstrated an enhancing effect of REM sleep on emotional item memory, it has not been thoroughly explored whether this effect extends to the retention of associative memory. Moreover, it is unclear how non-rapid eye movement (NREM) sleep contributes to these effects. The present study thus examined associative recognition of emotional and non-emotional material across an early morning nap (N = 23) and sustained wakefulness (N = 23). Nap group subjects demonstrated enhanced post-sleep associative memory performance, which was evident across both valence categories. Subsequent analyses revealed significant correlations between NREM spindle density and pre-sleep memory performance. Moreover, NREM spindle density was positively correlated with post-sleep neutral associative memory performance but not with post-sleep emotional associative memory. Accordingly, only neutral associative memory, but not emotional associative memory, was significantly correlated with spindle density after an additional night of sleep (+24 h). These results illustrate a temporally persistent relationship between spindle density and memory for neutral associations, whereas post-sleep emotional associative memory appears to be disengaged from NREM-sleep-dependent processes.

Emerging Directions in Emotional Episodic Memory

Building upon the existing literature on emotional memory, the present review examines emerging evidence from brain imaging investigations regarding four research directions: (1) Social Emotional Memory, (2) The Role of Emotion Regulation in the Impact of Emotion on Memory, (3) The Impact of Emotion on Associative or Relational Memory, and (4) The Role of Individual Differences in Emotional Memory. Across these four domains, available evidence demonstrates that emotion- and memory-related medial temporal lobe brain regions (amygdala and hippocampus, respectively), together with prefrontal cortical regions, play a pivotal role during both encoding and retrieval of emotional episodic memories. This evidence sheds light on the neural mechanisms of emotional memories in healthy functioning, and has important implications for understanding clinical conditions that are associated with negative affective biases in encoding and retrieving emotional memories.

Local context influences memory for emotional stimuli but not electrophysiological markers of emotion-dependent attention

Emotional enhancement of free recall can be context dependent. It is readily observed when emotional and neutral scenes are encoded and recalled together in a “mixed” list, but diminishes when these scenes are encoded separately in “pure” lists. We examined the hypothesis that this effect is due to differences in allocation of attention to neutral stimuli according to whether they are presented in mixed or pure lists, especially when encoding is intentional. Using picture stimuli that were controlled for semantic relatedness, our results contradicted this hypothesis. The amplitude of well‐known electrophysiological markers of emotion‐related attention—the early posterior negativity (EPN), the late positive potential (LPP), and the slow wave (SW)—was higher for emotional stimuli. Crucially, the emotional modulation of these ERPs was insensitive to list context, observed equally in pure and mixed lists. Although list context did not modulate neural markers of emotion‐related attention, list context did modulate the effect of emotion on free recall. The apparent decoupling of the emotional effects on attention and memory, challenges existing hypotheses accounting for the emotional enhancement of memory. We close by discussing whether findings are more compatible with an alternative hypothesis, where the magnitude of emotional memory enhancement is, at least in part, a consequence of retrieval dynamics.

ERP evidence for the control of emotional memories during strategic retrieval

Neural evidence for the strategic retrieval of task-relevant 'target' memories at the expense of less relevant 'nontarget' memories has been demonstrated across a wide variety of studies. In ERP studies, this evidence consists of the ERP correlate of recollection (i.e. the 'left parietal old/new effect') being evident for targets and attenuated for nontargets. It is not yet known, however, whether this degree of strategic control can be extended to emotionally valenced words, or whether these items instead reactivate associated memories. The present study used a paradigm previously employed to demonstrate the strategic retrieval of neutral words (Herron & Rugg, Psychonomic Bulletin and & Review, 10(3), 703--710, 2003b) to assess the effects of stimulus valence on behavioural and event-related potential (ERP) measures of strategic retrieval. While response accuracy and reaction times associated with targets were unaffected by valence, negative nontargets and new items were both associated with an elevated false alarm rate and longer RTs than their neutral equivalents. Both neutral and negative targets and nontargets elicited early old/new effects between 300 and 500 ms. Critically, whereas neutral and negative targets elicited robust and statistically equivalent left parietal old/new effects between 500 and 800 ms, these were absent for neutral and negative nontargets. A right frontal positivity associated with postretrieval monitoring was evident for neutral targets versus nontargets, for negative versus neutral nontargets, and for targets versus new items. It can therefore be concluded that the recollection of negatively valenced words is subject to strategic control during retrieval, and that postretrieval monitoring processes are influenced by emotional valence.

Memory for objects and startle responsivity in the immediate aftermath of exposure to the Trier Social Stress Test

Previously, we observed enhanced long-term memory for objects used (central objects) by committee members in the Trier Social Stress Test (TSST) on the next day. In addition, startle responsivity was increased. However, response specificity to an odour involved in the stressful episode was lacking and recognition memory for the odour was poor. In the current experiments, immediate effects of the stressor on memory and startle responsivity were investigated. We hypothesised memory for central objects of the stressful episode and startle response specificity to an odour ambient during the TSST to be enhanced shortly after it, in contrast to the control condition (friendly TSST). Further, memory for this odour was also assumed to be increased in the stress group. We tested 70 male (35) and female participants using the TSST involving objects and an ambient odour. After stress induction, a startle paradigm including olfactory and visual stimuli was conducted. Indeed, memory for central objects was significantly enhanced in immediate aftermath of the stressor. Startle responsivity increased at a trend level, particularly with regard to the odour involved in the stressful episode. Moreover, the stress group descriptively tended towards a better recognition of the odour involved. The study shows that stress enhances memory for central aspects of a stressful situation before consolidation processes come into play. In addition, results preliminarily suggest that the impact of stress on startle responsivity increases in strength but decreases in specificity during the first 24h after stress exposure.