When neutral turns significant: brain dynamics of rapidly formed associations between neutral stimuli and emotional contexts

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.

Incidental learning of faces during threat: No evidence for enhanced physiological responses to former threat identities

Remembering an unfamiliar person and the contextual conditions of that encounter is important for adaptive future behavior, especially in a potentially dangerous situation. Initiating defensive behavior in the presence of former dangerous circumstances can be crucial. Recent studies showed selective electrocortical processing of faces that were previously seen in a threat context compared to a safety context, however, this was not reflected in conscious recognition performance. Here, we investigated whether previously seen threat-faces, that could not be remembered, were capable to activate defensive psychophysiological response systems. During an encoding phase, 50 participants with low to moderate levels of anxiety viewed 40 face pictures with neutral expressions (6 s each), without an explicit learning instruction (incidental learning task). Each half of the faces were presented with contextual background colors that signaled either threat-of-shock or safety. In the recognition phase, all old and additional new faces (total of 60) were presented intermixed without context information. Participants had to decide whether a face was new or had been presented previously in a threatening or a safe context. Results show moderate face recognition independent of context conditions. Startle reflex and skin conductance responses (SCR) were more pronounced for threat compared to safety during encoding. For SCR, this differentiation was enhanced with higher levels of depression and anxiety. There were no differential startle reflex or SCR effects during recognition. From a clinical perspective, these findings do not support the notion that perceptual biases and physiological arousal directly relate to threat-associated identity recognition deficits in healthy and clinical participants with anxiety and trauma-related disorders.

Motivated attention and task relevance in the processing of cross-modally associated faces: Behavioral and electrophysiological evidence

It has repeatedly been shown that visually presented stimuli can gain additional relevance by their association with affective stimuli. Studies have shown effects of associated affect in event-related potentials (ERP) like the early posterior negativity (EPN), late positive complex (LPC), and even earlier components as the P1 or N170. However, findings are mixed as to the extent associated affect requires directed attention to the emotional quality of a stimulus and which ERP components are sensitive to task instructions during retrieval. In this preregistered study ( https://osf.io/ts4pb ), we tested cross-modal associations of vocal affect-bursts (positive, negative, neutral) to faces displaying neutral expressions in a flash-card-like learning task, in which participants studied face-voice pairs and learned to correctly assign them to each other. In the subsequent EEG test session, we applied both an implicit ("old-new") and explicit ("valence-classification") task to investigate whether the behavior at retrieval and neurophysiological activation of the affect-based associations were dependent on the type of motivated attention. We collected behavioral and neurophysiological data from 40 participants who reached the preregistered learning criterium. Results showed EPN effects of associated negative valence after learning and independent of the task. In contrast, modulations of later stages (LPC) by positive and negative associated valence were restricted to the explicit, i.e., valence-classification, task. These findings highlight the importance of the task at different processing stages and show that cross-modal affect can successfully be associated to faces.

Altered beta band spatial-temporal interactions during negative emotional processing in major depressive disorder: An MEG study

BACKGROUND

The mood-concordance bias is a key feature of major depressive disorder (MDD), but the spatiotemporal neural activity associated with emotional processing in MDD remains unclear. Understanding the dysregulated connectivity patterns during emotional processing and their relationship with clinical symptoms could provide insights into MDD neuropathology.

METHODS

We enrolled 108 MDD patients and 64 healthy controls (HCs) who performed an emotion recognition task during magnetoencephalography recording. Network-based statistics (NBS) was used to analyze whole-brain functional connectivity (FC) across different frequency ranges during distinct temporal periods. The relationship between the aberrant FC and affective symptoms was explored.

RESULTS

MDD patients exhibited decreased FC strength in the beta band (13-30 Hz) compared to HCs. During the early stage of emotional processing (0-100 ms), reduced FC was observed between the left parahippocampal gyrus and the left cuneus. In the late stage (250-400 ms), aberrant FC was primarily found in the cortex-limbic-striatum systems. Moreover, the FC strength between the right fusiform gyrus and left thalamus, and between the left calcarine fissure and left inferior temporal gyrus were negatively associated with Hamilton Depression Rating Scale (HAMD) scores.

LIMITATIONS

Medication information was not involved.

CONCLUSION

MDD patients exhibited abnormal temporal-spatial neural interactions in the beta band, ranging from early sensory to later cognitive processing stages. These aberrant interactions involve the cortex-limbic-striatum circuit. Notably, aberrant FC in may serve as a potential biomarker for assessing depression severity.

On the dynamics of gain and loss: Electrophysiological evidence from associative learning

Associated relevance affects the sensory encoding of low-level visual features of symbolic stimuli. It is unclear, however, which dimension of low-level visual features benefits from prioritized processing, and how these effects develop throughout the course of relevance acquisition. Moreover, previous evidence is inconclusive regarding the preservation of processing advantage once the association is no longer relevant, as well as its generalization to perceptually similar but novel stimuli. The present study addresses these questions by employing an associative learning paradigm. In two experiments (N = 24 each, between-subject design), different dimensions of low-level visual features of symbolic stimuli were associated with monetary gain, loss, or zero outcome. In a consecutive old/new decision task, associated stimuli were presented together with perceptually similar but novel stimuli. Event-related brain potentials (P1, EPN, LPC) were measured throughout both sessions. Early sensory encoding (P1) was boosted by loss association and appeared to be sensitive to the dimension of the associated low-level visual features. Gain association influenced post-perceptual processing stages (LPC), arising over the course of the learning phase, and are preserved even when the associated outcome was no longer relevant. Gain association also resulted in EPN modulations similar to the effects observed in the case of emotional words. None of the observed effects generalized to perceptually similar stimuli. These results show that acquired relevance can influence the sensory processing of specific dimensions of low-level visual features. Moreover, this study extends previous evidence of a dissociation of early and late neural effects of associated motivational relevance.

Common and separable behavioral and neural mechanisms underlie the generalization of fear and disgust

Generalization represents the transfer of a conditioned responses to stimuli that resemble the conditioned stimulus (CS). Previous studies on generalization of defensive avoidance responses have primarily focused on fear and have neglected disgust generalization, which represents a key pathological mechanism in some anxiety disorders. In the present study we examined common and distinct mechanisms of fear and disgust generalization by means of a fear or disgust multi-CS conditioning and generalization paradigm with concomitant event-related potential (ERPs) acquisition in n = 62 subjects. We demonstrate that compared to fear, disgust-relevant generalized stimuli (GS) elicited larger expectancy ratings and longer reaction times (RTs) reflecting stronger ratings of 'risk'. On the electrophysiological level, increased P2 amplitudes were found in response to conditioned CS+ versus CS- across both domains, possibly reflecting higher motivational and attentional salience of aversive conditioned stimuli per se. Contingent negative variation (CNV) amplitude was significantly larger for disgust-CS+ than disgust-CS-, reflecting a stronger preparation of the disgust US. Additionally, we found that the contingent negative variation (CNV) fear generalization gradient, and CNV amplitude were increased with similarity to CS+. In contrast the CNV to disgust-GS did not differ and did not reflect disgust generalization. Together this may indicate that the CNV represents a highly fear-specific index for generalization learning. This study provides the first neurobiological evidence for common and distinct generalization learning in fear versus disgust suggesting that dysregulations in separable defensive avoidance mechanisms may underly different anxiety disorder subtypes.

Subsequent memory effects on event-related potentials in associative fear learning

Studies of human fear learning suggest that a reliable discrimination between safe and threatening stimuli is important for survival and mental health. In the current study, we applied the subsequent memory paradigm in order to identify neurophysiological correlates of successful threat and safety learning. We recorded event-related potentials, while participants incidentally learned associations between multiple neutral faces and an aversive outcome [unconditioned stimulus (US)/conditioned stimulus (CS)+] or no outcome (noUS/CS-). We found that an enhanced late positive potential (LPP) to both CS+ and CS- during learning predicted subsequent memory. A quadratic relationship between LPP and confidence in memory indicates a possible role in both correct and false fear memory. Importantly, the P300 to the omission of the US (following CS-) was enhanced for remembered CS-, while there was a positive correlation between P300 amplitude to both US occurrence and omission and individual memory performance. A following re-exposure phase indicated that memory was indeed related to subjective fear of the CS+/CS-. These results highlight the importance of cognitive resource allocation to both threat and safety for the acquisition of fear and suggest a potential role of the P300 to US omission as an electrophysiological marker of successful safety learning.

Inferential affective tracking reveals the remarkable speed of context-based emotion perception

Understanding the emotional states of others is important for social functioning. Recent studies show that context plays an essential role in emotion recognition. However, it remains unclear whether emotion inference from visual scene context is as efficient as emotion recognition from faces. Here, we measured the speed of context-based emotion perception, using Inferential Affective Tracking (IAT) with naturalistic and dynamic videos. Using cross-correlation analyses, we found that inferring affect based on visual context alone is just as fast as tracking affect with all available information including face and body. We further demonstrated that this approach has high precision and sensitivity to sub-second lags. Our results suggest that emotion recognition from dynamic contextual information might be automatic and immediate. Seemingly complex context-based emotion perception is far more efficient than previously assumed.

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.

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.

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.

Latent profiles of maternal neural response to infant emotional stimuli: Associations with maternal sensitivity

In the current study, we examined how latent profiles reflecting maternal neural response to infant emotional expressions predict observed parenting behavior. Participants included 86 mothers of infants. Maternal sensitivity was coded from video-recorded distress and play interactions; mothers' event-related potentials (ERPs) to child emotional expressions were measured from EEG activity recorded during a categorization task. Latent profile analysis of mothers' P200 and late positive potential (LPP) responses to crying and laughing child expressions identified three latent profiles, characterized by enhanced or attenuated responses to crying and laughing expressions at early and late stages of processing. Mothers' probability of being assigned to the "attenuated to distress" profile, characterized by undifferentiated early and late response to infant emotional expressions, was associated with reduced maternal sensitivity. Probability of being assigned to this profile was also correlated with sociodemographic risk. Profiles of maternal neural response to infant emotional expressions may enhance our understanding of the phenomenology of insensitive caregiving.

Differential effects of learned associations with words and pseudowords on event-related brain potentials

Associated stimulus valence affects neural responses at an early processing stage. However, in the field of written language processing, it is unclear whether semantics of a word or low-level visual features affect early neural processing advantages. The current study aimed to investigate the role of semantic content on reward and loss associations. Participants completed a learning session to associate either words (Experiment 1, N = 24) or pseudowords (Experiment 2, N = 24) with different monetary outcomes (gain-associated, neutral or loss-associated). Gain-associated stimuli were learned fastest. Behavioural and neural response changes based on the associated outcome were further investigated in separate test sessions. Responses were faster towards gain- and loss-associated than neutral stimuli if they were words, but not pseudowords. Early P1 effects of associated outcome occurred for both pseudowords and words. Specifically, loss-association resulted in increased P1 amplitudes to pseudowords, compared to decreased amplitudes to words. Although visual features are likely to explain P1 effects for pseudowords, the inversed effect for words suggests that semantic content affects associative learning, potentially leading to stronger associations.

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.