Amygdala activity related to enhanced memory for pleasant and aversive stimuli

Unpleasant emotions and task-unrelated thoughts and their associations with amygdala activity during emotional distraction: A functional magnetic resonance imaging study

Previous emotion regulation studies revealed that emotional distraction decreases unpleasant emotions. This study examined whether distraction tasks decrease unpleasant task-unrelated thoughts (TUTs) and unpleasant emotions when recalling stressful daily interpersonal events. Amygdala activity was examined to assess implicit emotional changes using functional magnetic resonance imaging (fMRI). The behavioral data of 20 university students (mean age: 20.35 ± 1.42 years; range: 18-24 years) and fMRI data of 18 students were examined. As an emotion induction procedure, participants initially freely recalled memories of daily stressful interpersonal events and then responded to a series of questions about their recalled memories presented on a monitor. In the distraction experiment, the questions were re-represented as an emotional stimulation; a distraction task (nonconstant or constant finger tapping) or rest condition was then performed, and ratings were given for attentional state, thought types conceived during the tasks, and emotional state. Decreases in unpleasant emotions and TUTs were defined as distraction effects. We found that unpleasant TUTs decreased in the nonconstant relative to rest condition (p < .05). Furthermore, increased right amygdala activation positively correlated with unpleasant emotions, and bilateral amygdala activation correlated with unpleasant TUTs only in the rest condition, indicating the existence of amygdala activation associated with unpleasant emotions and thoughts. However, such associations were not under nonconstant or constant conditions, indicating distraction effects. Notably, this study showed that emotional distraction can decrease the degree of unpleasant emotions and the occurrence of unpleasant thoughts regarding common daily emotions.

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.

Data-centric artificial olfactory system based on the eigengraph

Recent studies of electronic nose system tend to waste significant amount of important data in odor identification. Until now, the sensitivity-oriented data composition has made it difficult to discover meaningful data to apply artificial intelligence in terms of in-depth analysis for odor attributes specifying the identities of gas molecules, ultimately resulting in hindering the advancement of the artificial olfactory technology. Here, we realize a data-centric approach to implement standardized artificial olfactory systems inspired by human olfactory mechanisms by formally defining and utilizing the concept of Eigengraph in electrochemisty. The implicit odor attributes of the eigengraphs were mathematically substantialized as the Fourier transform-based Mel-Frequency Cepstral Coefficient feature vectors. Their effectiveness and applicability in deep learning processes for gas classification have been clearly demonstrated through experiments on complex mixed gases and automobile exhaust gases. We suggest that our findings can be widely applied as source technologies to develop standardized artificial olfactory systems.

Memory biases in Alzheimer's disease and mild cognitive impairment. A systematic review and metanalysis

Several studies demonstrated that individuals are more likely to remember emotional than neutral information; this phenomenon is known as emotional enhancement of memory (EEM). Adults generally tend to remember negative information more efficiently than neutral or positive items. In contrast, healthy elders seem to show an opposite bias for positive information, but results are inconsistent, also because during aging, elaboration of emotional information could change as a consequence of cognitive impairment. In this systematic review and meta-analysis, we conducted literature search of studies investigating emotion memory biases in mild cognitive impairment (MCI) and Alzheimer's disease (AD) on PubMed, Scopus and PsycINFO databases following PRISMA guidelines. The findings showed that emotional memory biases are still present despite the presence of cognitive impairment, both in MCI and at least in early stages of AD. However, the direction of emotion memory biases is not consistent across studies. These results suggest that patients with cognitive impairment might still benefit from EEM and help to define targets of intervention for cognitive rehabilitation in pathological aging.

How to Understand Them? A Review of Emotional Indicators in Horses

Stabled horses often experience negative emotions due to the inappropriate living conditions imposed by humans. However, identifying what emotions horses experience and what can trigger positive and negative emotions in stabled horses can be challenging. In this article we present a brief history of the study of emotions and models that explain emotions from a scientific point of view and the physiological bases and functions of emotions. We then review and discuss physiological and behavioral indicators and cognitive bias tests developed to assess emotions in horses. Hormone concentrations, body temperature, the position of the ears, facial expressions and behaviors, such as approach and avoidance behaviors, can provide valuable information about emotional states in horses. The cognitive bias paradigm is a recent and robust tool to assess emotions in horses. Knowing how to evaluate the intensity and frequency of an individual's emotions can guide horse owners and caretakers to identify practices and activities that should be stimulated, avoided or even banned from the individual's life, in favor of a life worth living. The development and validation of novel indicators of emotions considering positive and negative contexts can help in these actions.

The amygdala mediates the facilitating influence of emotions on memory through multiple interacting mechanisms

Emotionally arousing experiences are better remembered than neutral ones, highlighting that memory consolidation differentially promotes retention of experiences depending on their survival value. This paper reviews evidence indicating that the basolateral amygdala (BLA) mediates the facilitating influence of emotions on memory through multiple mechanisms. Emotionally arousing events, in part by triggering the release of stress hormones, cause a long-lasting enhancement in the firing rate and synchrony of BLA neurons. BLA oscillations, particularly gamma, play an important role in synchronizing the activity of BLA neurons. In addition, BLA synapses are endowed with a unique property, an elevated post-synaptic expression of NMDA receptors. As a result, the synchronized gamma-related recruitment of BLA neurons facilitates synaptic plasticity at other inputs converging on the same target neurons. Given that emotional experiences are spontaneously remembered during wake and sleep, and that REM sleep is favorable to the consolidation of emotional memories, we propose a synthesis for the various lines of evidence mentioned above: gamma-related synchronized firing of BLA cells potentiates synapses between cortical neurons that were recruited during an emotional experience, either by tagging these cells for subsequent reactivation or by enhancing the effects of reactivation itself.

Anteromedial thalamus gates the selection and stabilization of long-term memories

Memories initially formed in hippocampus gradually stabilize to cortex over weeks-to-months for long-term storage. The mechanistic details of this brain re-organization remain poorly understood. We recorded bulk neural activity in circuits that link hippocampus and cortex as mice performed a memory-guided virtual-reality task over weeks. We identified a prominent and sustained neural correlate of memory in anterior thalamus, whose inhibition substantially disrupted memory consolidation. More strikingly, gain amplification enhanced consolidation of otherwise unconsolidated memories. To gain mechanistic insights, we developed a technology for simultaneous cellular-resolution imaging of hippocampus, thalamus, and cortex throughout consolidation. We found that whereas hippocampus equally encodes multiple memories, the anteromedial thalamus preferentially encodes salient memories, and gradually increases correlations with cortex to facilitate tuning and synchronization of cortical ensembles. We thus identify a thalamo-cortical circuit that gates memory consolidation and propose a mechanism suitable for the selection and stabilization of hippocampal memories into longer-term cortical storage.

Emotionally-loaded Visual Stimuli to Alter Brain Arousal: A Flicker Fusion Study

Background: Human brain performance and arousal are still challenging and critical, especially in environments such as power plants. Since different emotions are common in daily work life and have inevitable effects on cognitive performance, it is important to evaluate whether or not emotional interventions can, in any way, alter brain arousal, leading to mental fatigue in control room operators (CROs) and affecting their cognitive emotion regulation. To address this issue, flicker fusion frequency (FFF) was employed as a simple and reproducible surrogate index for mental fatigue. Objectives: This study aimed to investigate whether or not emotionally loaded visual stimuli can alter brain arousal (brain fatigue) or is associated with cognitive emotion regulation (CER) ability. Methods: Flicker fusion frequency was assessed by RT-961, and the International Affective Picture System (IAPS) was adopted as the picture database of stimuli. Additionally, the Cognitive Emotion Regulation Questionnaire (CERQ) was used to determine the participants’ cognitive emotion CER ability. Twenty volunteer CROs from Fars Combined Cycle Power Plant participated in this study. They completed CERQ and then were assessed at two different time points, i.e., before and after presenting emotional stimuli. At each round, FFF was assessed 20 times, and the average frequency was recorded. Emotionally-loaded images were considered as stimuli. The stimuli sets were classified based on their arousal level and valence, yet they were presented in a random order. Subjects were exposed to each image for five seconds (30 minutes in total). Results: The participants’ mean age was 39.55 ± 7.02 years. The first and second FFFs were 42.15 ± 3.90 and 41.96 ± 3.98 in the appropriate group and 42.82 ± 3.59 and 42.26 ± 4.07 in the inappropriate group, respectively. Based on the statistical tests, there were no significant relationships between the measurements (P > 0.05). Conclusions: Our findings suggest that CROs may positively maintain their brain arousal during specific emotional stimuli when the intervention lasts less than 30 minutes. Considering the prolonged working hours in such industries (roughly over eight hours a day) and the importance of cognitive aptitude in preventing work-related errors, we propose this line of research to gain momentum.

Exogenous estradiol and oxytocin modulate sex differences in hippocampal reactivity during the encoding of episodic memories

Considerable evidence supports sex differences in episodic memory. The hormones estradiol and oxytocin both affect episodic memory and may contribute to these sex differences, but possible underlying hormonal interactions have not been tested in a sample involving both sexes. To this end, we conducted a randomized, placebo-controlled, parallel-group functional magnetic resonance imaging (fMRI) study including healthy free-cycling women (n = 111) and men (n = 115). The fMRI session was conducted under four experimental conditions: 1. transdermal estradiol (2 mg) and intranasal oxytocin (24 IU), 2. transdermal placebo and intranasal oxytocin, 3. transdermal estradiol and intranasal placebo, 4. transdermal placebo and intranasal placebo. Participants were scanned during the encoding of positive, neutral, and negative scenes. Recognition memory was tested three days following the scanning sessions without additional treatments. Under placebo, women showed a significantly better recognition memory and increased hippocampal responses to subsequently remembered items independent of the emotional valence compared to men. The separate treatments with either hormone significantly diminished this mnemonic sex difference and reversed the hippocampal activation pattern. However, the combined treatments produced no significant effect. Collectively, the results suggest that both hormones play a crucial role in modulating sex differences in episodic memory. Furthermore, possible antagonistic interactions between estradiol and oxytocin could explain previously observed opposing hormonal effects in women and men.

Human cerebellum and corticocerebellar connections involved in emotional memory enhancement

Enhanced memory for emotional stimuli is crucial for survival, but it may also contribute to the development and maintenance of fear-related disorders in case of highly aversive experiences. This large-scale functional brain imaging study identifies the cerebellum and cerebellar–cerebral connections involved in the phenomenon of superior memory for emotionally arousing visual information. These findings expand knowledge on the role of the cerebellum in complex cognitive and emotional processes and may be relevant for the understanding of psychiatric disorders with aberrant emotional circuitry, such as posttraumatic stress disorder or autism spectrum disorder.

Emotional information is better remembered than neutral information. Extensive evidence indicates that the amygdala and its interactions with other cerebral regions play an important role in the memory-enhancing effect of emotional arousal. While the cerebellum has been found to be involved in fear conditioning, its role in emotional enhancement of episodic memory is less clear. To address this issue, we used a whole-brain functional MRI approach in 1,418 healthy participants. First, we identified clusters significantly activated during enhanced memory encoding of negative and positive emotional pictures. In addition to the well-known emotional memory–related cerebral regions, we identified a cluster in the cerebellum. We then used dynamic causal modeling and identified several cerebellar connections with increased connection strength corresponding to enhanced emotional memory, including one to a cluster covering the amygdala and hippocampus, and bidirectional connections with a cluster covering the anterior cingulate cortex. The present findings indicate that the cerebellum is an integral part of a network involved in emotional enhancement of episodic memory.

Synergistic effects of disgust and anger on amygdala activation while recalling memories of interpersonal stress: An fMRI study

Occurrence of an unpleasant interpersonal event in daily life may cause an individual to experience unpleasant emotions and recall memories regarding it. These emotions, manifesting in daily social interactions, are often complex and mixed. In the laboratory, autobiographical recall is frequently used to induce emotions; however, it often involves recalling memories associated with a specific discrete emotion (e.g., sadness). To examine the neural activity of emotions similar to real-life experiences, we examined neural activity while recalling memories of stressful interpersonal events in daily life, without specifying a discrete emotion. Of the 23 university students recruited, 21 were analyzed and asked to freely recall memories and answer a series of questions on a monitor concerning their recalled memories while their neural activity was measured with functional magnetic resonance imaging. Amygdala activity increased while receiving the instructions, followed by a decrease in activity. This indicates that the participants' arousal and vigilance initially increased in response to a novel stimulus, and then decreased by habituation. Disgust and anger, which frequently occur as negative interpersonal feelings, were most prominently produced with strong associations with each other. More importantly, activation of the right amygdala while responding to questions regarding the recalled memories was positively correlated with disgust or anger only when not controlling for anger or disgust, respectively. These results indicate that responding to questions facilitated the generation of a mixed emotional response compared to during free recall alone. Furthermore, disgust and anger as a mixed emotion can synergistically activate amygdala.

Immature excitatory neurons in the amygdala come of age during puberty

The human amygdala is critical for emotional learning, valence coding, and complex social interactions, all of which mature throughout childhood, puberty, and adolescence. Across these ages, the amygdala paralaminar nucleus (PL) undergoes significant structural changes including increased numbers of mature neurons. The PL contains a large population of immature excitatory neurons at birth, some of which may continue to be born from local progenitors. These progenitors disappear rapidly in infancy, but the immature neurons persist throughout childhood and adolescent ages, indicating that they develop on a protracted timeline. Many of these late-maturing neurons settle locally within the PL, though a small subset appear to migrate into neighboring amygdala subnuclei. Despite its prominent growth during postnatal life and possible contributions to multiple amygdala circuits, the function of the PL remains unknown. PL maturation occurs predominately during late childhood and into puberty when sex hormone levels change. Sex hormones can promote developmental processes such as neuron migration, dendritic outgrowth, and synaptic plasticity, which appear to be ongoing in late-maturing PL neurons. Collectively, we describe how the growth of late-maturing neurons occurs in the right time and place to be relevant for amygdala functions and neuropsychiatric conditions.

Neural correlates of perceived emotions in human insula and amygdala for auditory emotion recognition

The emotional status of a speaker is an important non-linguistic cue carried by human voice and can be perceived by a listener in vocal communication. Understanding the neural circuits involved in processing emotions carried by human voice is crucial for understanding the neural basis of social interaction. Previous studies have shown that human insula and amygdala responded more selectively to emotional sounds than non-emotional sounds. However, it is not clear whether the neural selectivity to emotional sounds in these brain structures is determined by the emotion presented by a speaker which is associated with the acoustic properties of the sounds or by the emotion perceived by a listener. In this study, we recorded intracranial electroencephalography (iEEG) responses to emotional human voices while subjects performed emotion recognition tasks. We found that the iEEG responses of Heschl's gyrus (HG) and posterior insula were determined by the presented emotion, whereas the iEEG responses of anterior insula and amygdala were driven by the perceived emotion. These results suggest that the anterior insula and amygdala play a crucial role in conscious perception of emotions carried by human voice.

A Biologically Inspired Neural Network Model to Gain Insight Into the Mechanisms of Post-Traumatic Stress Disorder and Eye Movement Desensitization and Reprocessing Therapy

Eye movement desensitization and reprocessing (EMDR) therapy is a well-established therapeutic method to treat post-traumatic stress disorder (PTSD). However, how EMDR exerts its therapeutic action has been studied in many types of research but still needs to be completely understood. This is in part due to limited knowledge of the neurobiological mechanisms underlying EMDR, and in part to our incomplete understanding of PTSD. In order to model PTSD, we used a biologically inspired computational model based on firing rate units, encompassing the cortex, hippocampus, and amygdala. Through the modulation of its parameters, we fitted real data from patients treated with EMDR or classical exposure therapy. This allowed us to gain insights into PTSD mechanisms and to investigate how EMDR achieves trauma remission.

Representing the Good and Bad: fMRI signatures during the encoding of multisensory positive, negative, and neutral events

Few studies have examined how multisensory emotional experiences are processed and encoded into memory. Here, we aimed to determine whether, at encoding, activity within functionally-defined visual- and auditory-processing brain regions discriminated the emotional category (i.e., positive, negative, or neutral) of the multisensory (audio-visual) events. Participants incidentally encoded positive, negative, and neutral multisensory stimuli during event-related functional magnetic resonance imaging (fMRI). Following a 3-h post-encoding delay, their memory for studied stimuli was tested, allowing us to identify emotion-category-specific subsequent-memory effects focusing on medial temporal lobe regions (i.e., amygdala, hippocampus) and visual- and auditory-processing regions. We used a combination of univariate and multivoxel pattern fMRI analyses (MVPA) to examine emotion-category-specificity in mean activity levels and neural patterning, respectively. Univariate analyses revealed many more visual regions that showed negative-category-specificity relative to positive-category-specificity, and auditory regions only showed negative-category-specificity. These results suggest that negative emotion is more closely tied to information contained within sensory regions, a conclusion that was supported by the MVPA analyses. Functional connectivity analyses further revealed that the visual amplification of category-selective processing is driven, in part, by mean signal from the amygdala. Interestingly, while stronger representations in visuo-auditory regions were related to subsequent-memory for neutral multisensory stimuli, they were related to subsequent-forgetting of positive and negative stimuli. Neural patterning in the hippocampus and amygdala were related to memory for negative multisensory stimuli. These results provide new evidence that negative emotional stimuli are processed with increased engagement of visuosensory regions, but that this sensory engagement-that generalizes across the entire emotion category-is not the type of sensory encoding that is most beneficial for later retrieval.

Mechanisms of memory under stress

It is well established that stress has a major impact on memory, driven by the concerted action of various stress mediators on the brain. Recent years, however, have seen considerable advances in our understanding of the cellular, neural network, and cognitive mechanisms through which stress alters memory. These novel insights highlight the intricate interplay of multiple stress mediators, including-beyond corticosteroids, catecholamines, and peptides-for instance, endocannabinoids, which results in time-dependent shifts in large-scale neural networks. Such stress-induced network shifts enable highly specific memories of the stressful experience in the long run at the cost of transient impairments in mnemonic flexibility during and shortly after a stressful event. Based on these recent discoveries, we provide a new integrative framework that links the cellular, systems, and cognitive mechanisms underlying acute stress effects on memory processes and points to potential targets for treating aberrant memory in stress-related mental disorders.

Medial prefrontal and occipito-temporal activity at encoding determines enhanced recognition of threatening faces after 1.5 years

Studies demonstrated that faces with threatening emotional expressions are better remembered than non-threatening faces. However, whether this memory advantage persists over years and which neural systems underlie such an effect remains unknown. Here, we employed an individual difference approach to examine whether the neural activity during incidental encoding was associated with differential recognition of faces with emotional expressions (angry, fearful, happy, sad and neutral) after a retention interval of > 1.5 years (N = 89). Behaviorally, we found a better recognition for threatening (angry, fearful) versus non-threatening (happy and neutral) faces after a delay of > 1.5 years, which was driven by forgetting of non-threatening faces compared with immediate recognition after encoding. Multivariate principal component analysis (PCA) on the behavioral responses further confirmed the discriminative recognition performance between threatening and non-threatening faces. A voxel-wise whole-brain analysis on the concomitantly acquired functional magnetic resonance imaging (fMRI) data during incidental encoding revealed that neural activity in bilateral inferior occipital gyrus (IOG) and ventromedial prefrontal/orbitofrontal cortex (vmPFC/OFC) was associated with the individual differences in the discriminative emotional face recognition performance measured by an innovative behavioral pattern similarity analysis (BPSA). The left fusiform face area (FFA) was additionally determined using a regionally focused analysis. Overall, the present study provides evidence that threatening facial expressions lead to persistent face recognition over periods of > 1.5 years, and that differential encoding-related activity in the medial prefrontal cortex and occipito-temporal cortex may underlie this effect.

Modulation of Emotion Perception via Amygdala Stimulation in Humans

Background

Multiple lines of evidence show that the human amygdala is part of a neural network important for perception of emotion from environmental stimuli, including for processing of intrinsic attractiveness/“goodness” or averseness/“badness,” i.e., affective valence.

Objective/Hypothesis

With this in mind, we investigated the effect of electrical brain stimulation of the human amygdala on perception of affective valence of images taken from the International Affective Picture Set (IAPS).

Methods

Using intracranial electrodes in patients with epilepsy, we first obtained event-related potentials (ERPs) in eight patients as they viewed IAPS images of varying affective valence. Next, in a further cohort of 10 patients (five female and five male), we measured the effect of 50 Hz electrical stimulation of the left amygdala on perception of affective valence from IAPS images.

Results

We recorded distinct ERPs from the left amygdala and found significant differences in the responses between positively and negatively valenced stimuli (p = 0.002), and between neutral and negatively valenced stimuli (p = 0.017) 300–500 ms after stimulus onset. Next, we found that amygdala stimulation did not significantly affect how patients perceived valence for neutral images (p = 0.58), whereas stimulation induced patients to report both positively (p = 0.05) and negatively (< 0.01) valenced images as more neutral.

Conclusion

These results render further evidence that the left amygdala participates in a neural network for perception of emotion from environmental stimuli. These findings support the idea that electrical stimulation disrupts this network and leads to partial disruption of perception of emotion. Harnessing this effect may have clinical implications in treatment of certain neuropsychiatric disorders using deep brain stimulation (DBS) and neuromodulation.

Impairment of aversive episodic memories during Covid-19 pandemic: The impact of emotional context on memory processes

The threatening context of the COVID-19 pandemic provided a unique setting to study the effects of negative psychological symptoms on memory processes. Episodic memory is an essential function of the human being related to the ability to store and remember experiences and anticipate possible events in the future. Studying this function in this context is crucial to understand what effects the pandemic will have on the formation of episodic memories. To study this, the formation of episodic memories was evaluated by free recall, recognition, and episode order tasks for an aversive and neutral content. The results indicated that aversive episodic memory is impaired both in the free recall task and in the recognition task. Even the beneficial effect that emotional memory usually has for the episodic order was undermined as there were no differences between the neutral and aversive condition. The present work adds to the evidence that indicates that the level of activation does not modify memory processes in a linear way, which also depends on the type of recall and the characteristics of the content to be encoded.

Post-training intra-basolateral complex of the amygdala infusions of clenbuterol enhance memory for conditioned place preference and increase ARC protein expression in dorsal hippocampal synaptic fractions

The basolateral complex of the amygdala (BLA) is critically involved in modulation of memory by stress hormones. Noradrenergic activation of the BLA enhances memory consolidation and plays a necessary role in the enhancing or impairing effects of stress hormones on memory. The BLA is not only involved in the consolidation of aversive memories but can regulate appetitive memory formation as well. Extensive evidence suggests that the BLA is a modulatory structure that influences consolidation of arousing memories through modulation of plasticity and expression of plasticity-related genes, such as the activity regulated cytoskeletal-associated (Arc/Arg 3.1) protein, in efferent brain regions. ARC is an immediate early gene whose mRNA is localized to the dendrites and is necessary for hippocampus-dependent long-term potentiation and long-term memory formation. Post-training intra-BLA infusions of the β-adrenoceptor agonist, clenbuterol, enhances memory for an aversive task and increases dorsal hippocampus ARC protein expression following training on that task. To examine whether this function of BLA noradrenergic signaling extends to the consolidation of appetitive memories, the present studies test the effect of post-training intra-BLA infusions of clenbuterol on memory for the appetitive conditioned place preference (CPP) task and for effects on ARC protein expression in hippocampal synapses. Additionally, the necessity of increased hippocampal ARC protein expression was also examined for long-term memory formation of the CPP task. Immediate post-training intra-BLA infusions of clenbuterol (4 ng/0.2 µL) significantly enhanced memory for the CPP task. This same memory enhancing treatment significantly increased ARC protein expression in dorsal, but not ventral, hippocampal synaptic fractions. Furthermore, immediate post-training intra-dorsal hippocampal infusions of Arc antisense oligodeoxynucleotides (ODNs), which reduce ARC protein expression, prevented long-term memory formation for the CPP task. These results suggest that noradrenergic activity in the BLA influences long-term memory for aversive and appetitive events in a similar manner and the role of the BLA is conserved across classes of memory. It also suggests that the influence of the BLA on hippocampal ARC protein expression and the role of hippocampal ARC protein expression are conserved across classes of emotionally arousing memories.

Separate neural networks of implicit emotional processing between pictures and words: A coordinate-based meta-analysis of brain imaging studies

Both pictures and words are frequently employed as experimental stimuli to investigate the neurocognitive mechanisms of emotional processing. However, it remains unclear whether emotional picture processing and emotional word processing share neural underpinnings. To address this issue, we focus on neuroimaging studies examining the implicit processing of affective words and pictures, which require participants to meet cognitive task demands under the implicit influence of emotional pictorial or verbal stimuli. A coordinate-based activation likelihood estimation meta-analysis was conducted on these studies, which revealed no common activation maximum between the picture and word conditions. Specifically, implicit negative picture processing (35 experiments, 393 foci, and 932 subjects) engages the bilateral amygdala, left hippocampus, fusiform gyri, and right insula, which are mainly located in the subcortical network and visual network associated with bottom-up emotional responses. In contrast, implicit negative word processing (34 experiments, 316 foci, and 799 subjects) engages the default mode network and fronto-parietal network including the ventrolateral prefrontal cortex, dorsolateral prefrontal cortex, and dorsomedial prefrontal cortex, indicating the involvement of top-down semantic processing and emotion regulation. Our findings indicate that affective pictures (that intrinsically have an affective valence) and affective words (that inherit the affective valence from their object) modulate implicit emotional processing in different ways, and therefore recruit distinct brain systems.

Haloperidol rescues the schizophrenia-like phenotype in adulthood after rotenone administration in neonatal rats

Neuropsychiatric disorders are multifactorial disturbances that encompass several hypotheses, including changes in neurodevelopment. It is known that brain development disturbances during early life can predict psychosis in adulthood. As we have previously demonstrated, rotenone, a mitochondrial complex I inhibitor, could induce psychiatric-like behavior in 60-day-old rats after intraperitoneal injections from the 5th to the 11th postnatal day. Because mitochondrial deregulation is related to psychiatric disorders and the establishment of animal models is a high-value preclinical tool, we investigated the responsiveness of the rotenone (Rot)-treated newborn rats to pharmacological agents used in clinical practice, haloperidol (Hal), and methylphenidate (MPD). Taken together, our data show that Rot-treated animals exhibit hyperlocomotion, decreased social interaction, and diminished contextual fear conditioning response at P60, consistent with positive, negative, and cognitive deficits of schizophrenia (SZ), respectively, that were reverted by Hal, but not MPD. Rot-treated rodents also display a prodromal-related phenotype at P35. Overall, our results seem to present a new SZ animal model as a consequence of mitochondrial inhibition during a critical neurodevelopmental period. Therefore, our study is crucial not only to elucidate the relevance of mitochondrial function in the etiology of SZ but also to fulfill the need for new and trustworthy experimentation models and, likewise, provide possibilities to new therapeutic avenues for this burdensome disorder.

Neural Responses of Pet Dogs Witnessing Their Caregiver's Positive Interactions with a Conspecific: An fMRI Study

We have limited knowledge on how dogs perceive humans and their actions. Various researchers investigated how they process human facial expressions, but their brain responses to complex social scenarios remain unclear. While undergoing fMRI, we exposed pet dogs to videos showing positive social and neutral nonsocial interactions between their caregivers and another conspecific. Our main interest was how the dogs responded to their caregivers (compared to a stranger) engaging in a pleasant interaction with another dog that could be seen as social rival. We hypothesized that the dogs would show activation increases in limbic areas such as the amygdala, hypothalamus, and insula and likely show higher attention and arousal during the positive caregiver-dog interaction. When contrasting the social with the nonsocial interaction, we found increased activations in the left amygdala and the insular cortex. Crucially, the dogs' hypothalamus showed strongest activation when the caregiver engaged in a positive social interaction. These findings indicate that dogs are sensitive to social affective human-dog interactions and likely show higher valence attribution and arousal in a situation possibly perceived as a potential threat to their caregiver bonds. Our study provides a first window into the neural correlates of social and emotional processing in dogs.

Neural correlates of cognitive bias modification for interpretation

The effectiveness of cognitive bias modification for interpretation (CBM-I), a treatment method employed to reduce social anxiety (SA), has been examined. However, the neural correlates of CBM-I remain unclear, and we aimed to elucidate brain activities during intervention and activity changes associated with CBM-I effectiveness in a pre–post intervention comparison. Healthy participants divided into two groups (CBM, control) were scanned before, during and after intervention using functional magnetic resonance imaging. Ambiguous social situations followed by positive outcomes were repeatedly imagined by the CBM group during intervention, while half of the outcomes in the control group were negative. Whole-brain analysis revealed that activation of the somatomotor and somatosensory areas, occipital lobe, fusiform gyrus and thalamus during intervention was significantly greater in the CBM than in the control group. Furthermore, altered activities in the somatomotor and somatosensory areas, occipital lobe and posterior cingulate gyrus during interpreting ambiguous social situations showed a significant group × change in SA interaction. Our result suggests that when facing ambiguous social situations, positive imagery instilled by CBM-I is recalled, and interpretations are modified to contain social reward. These findings may help to suggest an alternative manner of enhancing CBM-I effectiveness from a cognitive-neuroscience perspective.

Effects of posed smiling on memory for happy and sad facial expressions

The perception and storage of facial emotional expressions constitutes an important human skill that is essential for our daily social interactions. While previous research revealed that facial feedback can influence the perception of facial emotional expressions, it is unclear whether facial feedback also plays a role in memory processes of facial emotional expressions. In the present study we investigated the impact of facial feedback on the performance in emotional visual working memory (WM). For this purpose, 37 participants underwent a classical facial feedback manipulation (FFM) (holding a pen with the teeth—inducing a smiling expression vs. holding a pen with the non-dominant hand—as a control condition) while they performed a WM task on varying intensities of happy or sad facial expressions. Results show that the smiling manipulation improved memory performance selectively for happy faces, especially for highly ambiguous facial expressions. Furthermore, we found that in addition to an overall negative bias specifically for happy faces (i.e. happy faces are remembered as more negative than they initially were), FFM induced a positivity bias when memorizing emotional facial information (i.e. faces were remembered as being more positive than they actually were). Finally, our data demonstrate that men were affected more by FFM: during induced smiling men showed a larger positive bias than women did. These data demonstrate that facial feedback not only influences our perception but also systematically alters our memory of facial emotional expressions.

Understanding heterosexual women's erotic flexibility: the role of attention in sexual evaluations and neural responses to sexual stimuli

Many women experience desires, arousal and behavior that run counter to their sexual orientation (orientation inconsistent, 'OI'). Are such OI sexual experiences cognitively and neurobiologically distinct from those that are consistent with one's sexual orientation (orientation consistent, 'OC')? To address this question, we employed a mindful attention intervention-aimed at reducing judgment and enhancing somatosensory attention-to examine the underlying attentional and neurobiological processes of OC and OI sexual stimuli among predominantly heterosexual women. Women exhibited greater neural activity in response to OC, compared to OI, sexual stimuli in regions associated with implicit visual processing, volitional appraisal and attention. In contrast, women exhibited greater neural activity to OI, relative to OC, sexual stimuli in regions associated with complex visual processing and attentional shifting. Mindfully attending to OC sexual stimuli reduced distraction, amplified women's evaluations of OC stimuli as sexually arousing and deactivated the superior cerebellum. In contrast, mindfully attending to OI sexual stimuli amplified distraction, decreased women's evaluations of OI stimuli as sexually arousing and augmented parietal and temporo-occipital activity. Results of the current study constrain hypotheses of female erotic flexibility, suggesting that sexual orientation may be maintained by differences in attentional processing that cannot be voluntarily altered.

Testosterone and Resting State Connectivity of the Parahippocampal Gyrus in Men With History of Deployment-Related Mild Traumatic Brain Injury

INTRODUCTION

The purpose of this study was to explore the effect of low testosterone level on whole-brain resting state (RS) connectivity in male veterans with symptoms such as sleep disturbance, fatiguability, pain, anxiety, irritability, or aggressiveness persisting after mild traumatic brain injury (mTBI). Follow-up analyses were performed to determine if sleep scores affected the results.

MATERIALS AND METHODS

In our cross-sectional design study, RS magnetic resonance imaging scans on 28 veterans were performed, and testosterone, sleep quality, mood, and post-traumatic stress symptoms were measured. For each participant, we computed the average correlation of each voxel's time-series with the rest of the voxels in the brain, then used AFNI's 3dttest++ on the group data to determine whether the effects of testosterone level on whole-brain connectivity were significant. We then performed follow-up region of interest-based RS analyses of testosterone, with and without sleep quality as a covariate. The study protocol was approved by the National Institute of Health's Combined Neuroscience Institutional Review Board.

RESULTS

Sixteen participants reported repeated blast exposure in theater, leading to symptoms; the rest reported exposure to a single blast or a nonblast TBI. Thirty-three percent had testosterone levels <300 ng/dL. Testosterone level was lower in participants who screened positive for post-traumatic stress disorder compared to those who screened negative, but it did not reach statistical significance. Whole-brain connectivity and testosterone level were positively correlated in the left parahippocampal gyrus (LPhG), especially in its connectivity with frontal areas, the lingual gyrus, cingulate, insula, caudate, and right parahippocampal gyrus. Further analysis revealed that the effect of testosterone on LPhG connectivity is only partially mediated by sleep quality. Sleep quality by itself had an effect on connectivity of the thalamus, cerebellum, precuneus, and posterior cingulate.

CONCLUSION

Lower testosterone levels were correlated with lower connectivity of the LPhG. Weaknesses of this study include a retrospective design based on self-report of mTBI and the lack of a control group without TBI. Without a control group or pre-injury testosterone measures, we were not able to attribute the rate of low testosterone in our participants to TBI per se. Also testosterone levels were checked only once. The high rate of low testosterone level that we found suggests there may be an association between low testosterone level and greater post-traumatic stress disorder symptoms following deployment, but the causality of the relationships between TBI and deployment stress, testosterone level, behavioral symptomatology, and LPhG connectivity remains to be determined. Our study on men with persistent symptoms postdeployment and post-mTBI may help us understand the role of low testosterone and sleep quality in persistent symptoms and may be important in developing therapeutic interventions. Our results highlight the role of the LPhG, as we found that whole-brain connectivity in that region was positively associated with testosterone level, with only a limited portion of that effect attributable to sleep quality.

Neural correlates of episodic memory modulated by temporally delayed rewards

When a stimulus is associated with an external reward, its chance of being consolidated into long-term memory is boosted via dopaminergic facilitation of long-term potentiation in the hippocampus. Given that higher temporal distance (TD) has been found to discount the subjective value of a reward, we hypothesized that memory performance associated with a more immediate reward will result in better memory performance. We tested this hypothesis by measuring both behavioral memory performance and brain activation using functional magnetic resonance imaging (fMRI) during memory encoding and retrieval tasks. Contrary to our hypothesis, both behavioral and fMRI results suggest that the TD of rewards might enhance the chance of the associated stimulus being remembered. The fMRI data demonstrate that the lateral prefrontal cortex, which shows encoding-related activation proportional to the TD, is reactivated when searching for regions that show activation proportional to the TD during retrieval. This is not surprising given that this region is not only activated to discriminate between future vs. immediate rewards, it is also a part of the retrieval-success network. These results provide support for the conclusion that the encoding-retrieval overlap provoked as the rewards are more delayed may lead to better memory performance of the items associated with the rewards.

Does Napping Enhance the Consolidation of Clinically Relevant Information? A Comparison of Individuals with Low and Elevated Depressive Symptoms

PURPOSE

Sleep, both overnight and daytime naps, can facilitate the consolidation of declarative memories in healthy humans. However, it is unclear whether such beneficial effects of sleep occur in special populations, such as individuals with elevated neuropsychiatric symptoms, and if they apply to clinically relevant material that may have personal significance to those populations.

METHODS

We examined memory retention over a 60-minute interval of wakefulness or nap opportunity in participants with low or elevated scores (≤13 and ≥21, respectively) on the Beck Depression Inventory-II (BDI-II). Memory for depression-related information was assessed by (a) free-recall of a video depicting a personal experience narrative of the impact of depression on cognition and workplace performance; and (b) a paired-associates task linking depression-related cognitive symptoms to appropriate coping strategies.

RESULTS

The results showed no overall difference in recall between the nap and waking condition. However, across the full sample of participants, there were significant positive correlations between total sleep time and paired associates recall, and slow wave sleep (SWS) percentage and story free recall performance. Unexpectedly, participants with elevated BDI-II scores exhibited better free-recall performance compared to those with low scores.

CONCLUSION

These results suggest that sleep, specifically SWS, may stabilize memories for clinically relevant information in populations with low and elevated depressive symptoms. The superior recall in participants with elevated-BDI scores may be related to the personal significance and stronger encoding of depression-related information. These observations raise the possibility that mnemonic deficits in depressed patients may be, at least in part, related to the type of information used to assess memory performance.

Accumbal D2R-medium spiny neurons regulate aversive behaviors through PKA-Rap1 pathway

The nucleus accumbens (NAc) plays a crucial role in various mental activities, including positive and negative reinforcement. We previously hypothesized that a balance between dopamine (DA) and adenosine signals regulates the PKA-Rap1 pathway in medium spiny neurons expressing DA D1 receptors (D1R-MSNs) or D2 receptors (D2R-MSNs) and demonstrated that the PKA-Rap1 pathway in D1R-MSNs is responsible for positive reinforcement. Here, we show the role of the PKA-Rap1 pathway in accumbal D2R-MSNs in negative reinforcement. Mice were exposed to electric foot shock as an aversive stimulus. We monitored the phosphorylation level of Rap1gap S563, which leads to the activation of Rap1. Electric foot shocks increased the phosphorylation level of GluN1 S897 and Rap1gap S563 in the NAc. The aversive stimulus-evoked phosphorylation of Rap1gap S563 was detected in accumbal D2R-MSNs and inhibited by pretreatment with adenosine A2a receptor (A2aR) antagonist. A2aR antagonist-treated mice showed impaired aversive memory in passive avoidance tests. AAV-mediated inhibition of PKA, Rap1, or MEK1 in accumbal D2R-MSNs impaired aversive memory in passive avoidance tests, whereas activation of this pathway potentiated aversive memory. Optogenetic inactivation of mesolimbic DAergic neurons induced place aversion in real-time place aversion tests. Aversive response was attenuated by inhibition of PKA-Rap1 signaling in accumbal D2R-MSNs. These results suggested that accumbal D2R-MSNs regulate aversive behaviors through the A2aR-PKA-Rap1-MEK pathway. Our findings provide a novel molecular mechanism for regulating negative reinforcement.

Amygdalar and hippocampal beta rhythm synchrony during human fear memory retrieval

BACKGROUND

Fear, as one of the basic emotions, is crucial in helping humans to perceive hazards and adapt to social activities. Clinically, fear memory is also involved in a wide spectrum of psychiatric disorders. A better understanding of the neural mechanisms of fear thereby has both neuroscientific and clinical significance. In recent years, data from animal models have demonstrated the key role of the amygdala-hippocampal circuit in the development of fear. However, the neural processing of fear memory remains unclear in humans, which is mainly due to the limitation of indirect measure of neural activity.

METHODS

Herein, we investigated fear memory by direct intracranial recordings from 8 intractable epilepsy patients with depth electrodes in both the hippocampus and ipsilateral amygdala. All the patients were subjected to a well-established Pavlovian fear memory paradigm consisted of the familiarization task, conditioning task, and retrieval task, respectively. Simultaneous local field potentials from the hippocampus and amygdala were recorded during different stages. The oscillatory activities from the amygdala and hippocampus were analyzed during fear memory retrieval compared with neutral stages.

RESULTS

Consistent with previous rodent studies, our results showed that the amygdala was involved in fear memory retrieval rather than neutral memory retrieval, while the hippocampus was involved both in fear memory retrieval and neutral memory retrieval. In particular, we found that there was an enhanced synchronized activity between the amygdala and hippocampus at beta frequencies (14-30 Hz), which suggested that enhanced synchronized activity at beta frequencies between the amygdala and hippocampus play a pivotal role during retrieval of fear memory in human.

CONCLUSIONS

Thus, our observation that the amygdala-hippocampal system contributing to fear memory retrieval in human with frequency-depended specificity has provided new insights into the mechanism of fear and have potential clinical relevance.

The effects of acute cannabidiol on cerebral blood flow and its relationship to memory: An arterial spin labelling magnetic resonance imaging study

BACKGROUND

Cannabidiol (CBD) is being investigated as a potential treatment for several medical indications, many of which are characterised by altered memory processing. However, the mechanisms underlying these effects are unclear.

AIMS

Our primary aim was to investigate how CBD influences cerebral blood flow (CBF) in regions involved in memory processing. Our secondary aim was to determine if the effects of CBD on CBF were associated with differences in working and episodic memory task performance.

METHODS

We used a randomised, crossover, double-blind design in which 15 healthy participants were administered 600 mg oral CBD or placebo on separate days. We measured regional CBF at rest using arterial spin labelling 3 h after drug ingestion. We assessed working memory with the digit span (forward, backward) and n-back (0-back, 1-back, 2-back) tasks, and we used a prose recall task (immediate and delayed) to assess episodic memory.

RESULTS

CBD increased CBF in the hippocampus (mean (95% confidence intervals) = 15.00 (5.78-24.21) mL/100 g/min, t₁₄ = 3.489, Cohen's d = 0.75, p = 0.004). There were no differences in memory task performance, but there was a significant correlation whereby greater CBD-induced increases in orbitofrontal CBF were associated with reduced reaction time on the 2-back working memory task ( r= -0.73, p = 0.005).

CONCLUSIONS

These findings suggest that CBD increases CBF to key regions involved in memory processing, particularly the hippocampus. These results identify potential mechanisms of CBD for a range of conditions associated with altered memory processing, including Alzheimer's disease, schizophrenia, post-traumatic stress disorder and cannabis-use disorders.

The Impact of Emotion on Musical Long-Term Memory

The influence of emotional dimensions such as arousal and valence on memory has been a topic of particularly intense inquiry. As stimuli go, music is capable of provoking strong emotional responses from listeners, which can in turn influence memory. However, few studies have examined the effect of musical emotions on memory, and even fewer the effect of valence and arousal. In order to shed light on the ways in which emotional dimensions affect musical memory as study-test delay intervals increase, we tested recognition after a short delay and after a long delay. In line with the literature, we hypothesized an emotional enhancement of music memory induced by post-encoding processes leading to better recognition of musical excerpts in delayed condition, as compared to the immediate condition. The effects of arousal and valence were expected to become exaggerated after a long delay. We also predicted that the two emotional dimensions would be differently affected by the study-test intervals. Our results showed that the emotional enhancement of memory depends upon the valence, with remembering of positive and negative stimuli being differently affected by the duration of the study-test delay interval. Furthermore, our data demonstrated that musical excerpts were better recognized after a long delay than after a short delay, illustrating that memory consolidation for musical information is taking place during the long study-test interval. Moreover, musical memory consolidation is strongly related to the characteristics of the positive valence, which have been discussed in relation to its pleasantness. This original finding provides new insights into the modulatory effects of emotional valence on memory consolidation and could offer promising therapeutic possibilities for the rehabilitation of memory disorders.

What causes the insight memory advantage?

Prior research indicates that solutions accompanied by an Aha! experience are remembered better than those missing this feeling of epiphany. The question for the present studies was whether this insight memory advantage for problem solutions is modulated by the affective component of insight (the strong feelings that typically accompany the Aha! experience), or by the cognitive component (the restructuring or representational change that occurs during insightful problem solving). In both studies, participants viewed a set of magic trick videos to generate solutions for how each trick was done, and memory for the generated solutions was tested after a week delay. They also indicated the extent to which they experienced an Aha! moment at solution along with other perceptions of their experience. In the second study, they additionally rated the relevance of five action verbs for each trick (including one that implied the correct solution) multiple times during solution as a measure of restructuring the problem representation. The explanation for the insight memory advantage that was best supported by the results is that it is the joint consequence of finding correct solutions, the subjective feeling that one has found a correct solution (certainty), and experiencing an emotional pleasurable reaction during the problem solving process that all contribute to better memory for the solution. However, it did not seem to rely on having reached the solution via a sudden restructuring process.

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.

Transcutaneous Vagus Nerve Stimulation (tVNS) Improves High-Confidence Recognition Memory but Not Emotional Word Processing

Previous clinical research found that invasive vagus nerve stimulation (VNS) enhanced word recognition memory in epileptic patients, an effect assumed to be related to the activation of brainstem arousal systems. In this study, we applied non-invasive transcutaneous auricular VNS (tVNS) to replicate and extend the previous work. Using a single-blind, randomized, between-subject design, 60 healthy volunteers received active or sham stimulation during a lexical decision task, in which emotional and neutral stimuli were classified as words or non-words. In a subsequent recognition memory task (1 day after stimulation), participants' memory performance on these words and their subjective memory confidence were tested. Salivary alpha-amylase (sAA) levels, a putative indirect measure of central noradrenergic activation, were also measured before and after stimulation. During encoding, pleasant words were more accurately detected than neutral and unpleasant words. However, no tVNS effects were observed on task performance or on overall sAA level changes. tVNS also did not modulate overall recognition memory, which was particularly enhanced for pleasant emotional words. However, when hit rates were split based on confidence ratings reflecting familiarity- and recollection-based memory, higher recollection-based memory performance (irrespective of emotional category) was observed during active stimulation than during sham stimulation. To summarize, we replicated prior findings of enhanced processing and memory for emotional (pleasant) words. Whereas tVNS showed no effects on word processing, subtle effects on recollection-based memory performance emerged, which may indicate that tVNS facilitates hippocampus-mediated consolidation processes.

Memory facilitation for emotional faces: Visual working memory trade-offs resulting from attentional preference for emotional facial expressions

Visual working memory (VWM) for faces is facilitated when they display negative facial expressions. The present study manipulated the emotional heterogeneity of the encoding display in a change detection task to examine whether VWM is enhanced by having a separate memory store or by a bias in the allocation of limited attentional resource. When the encoding display was emotionally heterogeneous, regardless of whether happy or fearful facial expressions were presented, memory for emotional faces increased while memory for neutral faces decreased, indicating a memory trade-off. To investigate whether this occurred as a result of preferential allocation of attentional resource towards emotional expressions over neutral ones, faces were shown sequentially in different quadrants of the display. The memory trade-off between happy and neutral faces disappeared but persisted between fearful and neutral faces at trailing serial positions. When blank intervals were inserted between faces to prevent fearful faces from having prolonged processing that consumes attentional resource that should be shared with neutral faces, the memory trade-off disappeared. Findings support the argument that emotional expressions facilitate VWM due to their bias in obtaining attentional resource but the exact mechanisms through which limited resource is allocated between happy and fearful expressions may differ.

Enhanced mnemonic discrimination for emotional memories: the role of arousal in interference resolution

In the present study we investigated the long-standing question whether and why emotionally arousing memories are more distinct as compared to neutral experiences. We assumed that memory benefits from the distinctiveness of emotional information, and that emotions affect encoding by reducing interference among overlapping memory representations. Since pattern separation is the process which minimizes interference between memory representations with similar features, we examined the behavioral manifestation of putative neural mechanisms enabling pattern separation (i.e. mnemonic discrimination) for emotionally arousing materials using the Mnemonic Similarity Task with negative, positive, and neutral images as stimuli. Immediately after incidental encoding, subjects were presented with stimuli they had seen at encoding and also with new items. Crucially, participants were also presented with lure images that were visually similar to ones they had seen before. Response options were old, new, and similar. Our results showed that individuals were better in discriminating between similar, emotionally arousing memories, when compared to the neutral stimuli. Moreover, this so-called lure discrimination performance was better for the negative images, than it was for the positive stimuli. Finally, we showed that the high arousing negative stimuli were better separated than the low arousing negative stimuli, and a similar pattern of results was found for the positive items. Altogether, these findings suggest that lure discrimination is modulated by arousal and not by valence. We argue that noradrenergic activity might facilitate interference resolution among memory representations with similar features, and that superior pattern separation might play a key role in memory enhancement for emotional experiences.

Interplay between midbrain and dorsal anterior cingulate regions arbitrates lingering reward effects on memory encoding

Rewarding events enhance memory encoding via dopaminergic influences on hippocampal plasticity. Phasic dopamine release depends on immediate reward magnitude, but presumably also on tonic dopamine levels, which may vary as a function of the average accumulation of reward over time. Using model-based fMRI in combination with a novel associative memory task, we show that immediate reward magnitude exerts a monotonically increasing influence on the nucleus accumbens, ventral tegmental area (VTA), and hippocampal activity during encoding, and enhances memory. By contrast, average reward levels modulate feedback-related responses in the VTA and hippocampus in a non-linear (inverted U-shape) fashion, with similar effects on memory performance. Additionally, the dorsal anterior cingulate cortex (dACC) monotonically tracks average reward levels, while VTA-dACC functional connectivity is non-linearly modulated (inverted U-shape) by average reward. We propose that the dACC computes the net behavioral impact of average reward and relays this information to memory circuitry via the VTA.

Opioid withdrawal and memory consolidation

It is well established that learning and memory are central to substance dependence. This paper specifically reviews the effect of opioid withdrawal on memory consolidation. Although there is evidence that opioid withdrawal can interfere with initial acquisition and retrieval of older memories, there are several reasons to postulate a facilitatory action on the consolidation of newly acquired memories. In fact, there is substantial evidence that memory consolidation is facilitated by the release of stress hormones, that it requires the activation of the amygdala, of central noradrenergic and cholinergic pathways, and that it involves long-term potentiation. This review highlights evidence that very similar neurobiological processes are involved in opioid withdrawal, and summarizes recent results indicating that naltrexone-precipitated withdrawal enhanced consolidation in rats. From this neurocognitive perspective, therefore, opioid use may escalate during the addiction cycle in part because memories of stimuli and actions experienced during withdrawal are strengthened.

The impact of focused attention on subsequent emotional recollection: A functional MRI investigation

In his seminal works, Endel Tulving argued that functionally distinct memory systems give rise to subjective experiences of remembering and knowing (i.e., recollection- vs. familiarity-based memory, respectively). Evidence shows that emotion specifically enhances recollection, and this effect is subserved by a synergistic mechanism involving the amygdala (AMY) and hippocampus (HC). In extreme circumstances, however, uncontrolled recollection of highly distressing memories may lead to symptoms of affective disorders. Therefore, it is important to understand the factors that can diminish such detrimental effects. Here, we investigated the effects of Focused Attention (FA) on emotional recollection. FA is an emotion regulation strategy that has been proven quite effective in reducing the impact of emotional responses associated with the recollection of distressing autobiographical memories, but its impact during emotional memory encoding is not known. Functional MRI and eye-tracking data were recorded while participants viewed a series of composite negative and neutral images with distinguishable foreground (FG) and background (BG) areas. Participants were instructed to focus either on the FG or BG content of the images and to rate their emotional responses. About 4 days later, participants' memory was assessed using the R/K procedure, to indicate whether they Recollected specific contextual details about the encoded images or the images were just familiar to them - i.e., participants only Knew that they saw the pictures without being able to remember specific contextual details. First, results revealed that FA was successful in decreasing memory for emotional pictures viewed in BG Focus condition, and this effect was driven by recollection-based retrieval. Second, the BG Focus condition was associated with decreased activity in the AMY, HC, and anterior parahippocampal gyrus for subsequently recollected emotional items. Moreover, correlation analyses also showed that reduced activity in these regions predicted greater reduction in emotional recollection following FA. These results demonstrate the effectiveness of FA in mitigating emotional experiences and emotional recollection associated with unpleasant emotional events.

Aberrant Thalamic-Centered Functional Connectivity in Patients with Persistent Somatoform Pain Disorder

PURPOSE

Recent task-based fMRI studies have shown that Persistent Somatoform Pain Disorder (PSPD) patients demonstrated aberrant activity in a wide range of brain regions associated with sensation, cognition and emotion. However, these specific task-based studies could not clearly uncover the alterations in the spontaneous brain networks that were associated with the general pain-related symptoms in PSPD.

PATIENTS AND METHODS

In the present study, 13 PSPD patients and 23 matched healthy controls (HCs) were enrolled. Resting state and 3D structural imaging data were collected during magnetic resonance imaging (MRI) scans. Ninety regions of interest (ROIs) were selected from the automated anatomical labeling (AAL) template. The functional connectivity toolbox "CONN" was used to calculate the functional connectivity (FC) coefficients.

RESULTS

Our results showed that PSPD patients exhibited increased FCs between the left thalamus and the right amygdala, the right hippocampus, and multiple sub-regions of the occipital lobe when compared to HCs. Correlation analysis revealed a negative correlation between the left thalamus-right amygdala FC and the level of anxiety in PSPD patients.

CONCLUSION

These findings suggest that the altered FC between thalamus and amygdala may be the neural mechanisms underlying the pain-related anxiety in PSPD.

Emotion, Respiration, and Heart Rate Variability: A Mathematical Model and Simulation Analyses

Although the generation mechanism of the low-frequency (LF) component of heart rate variability (HRV) is controversial, HRV is a potential candidate in designing objective measurement methodologies for emotions. These methodologies could be valuable for several biosignal applications. Here, we have conducted a simulation analysis using a novel mathematical model that integrates emotion, respiration, the nervous system, and the cardiovascular system. Our model has well reproduced experimental results, specifically concerning HRV with respiratory sinus arrhythmia and LF, the relation between HRV total power and the respiration frequency, and the homeostatic maintenance by the baroreflex. Our model indicates the following possibilities: (i) The delay in the heart rate control process of the parasympathetic activity works as a low-pass filter and the HRV total power decreases with a higher respiration frequency; (ii) the LF component of HRV and the Mayer wave are generated as transient responses of the baroreflex feedback control to perturbations induced by an emotional stimulus; and (iii) concentration on breathing to reduce the respiration frequency can reduce LF/HF and the reduction can be fed back to the emotional status.

Fornix Stimulation Induces Metabolic Activity and Dopaminergic Response in the Nucleus Accumbens

The Papez circuit, including the fornix white matter bundle, is a well-known neural network that is involved in multiple limbic functions such as memory and emotional expression. We previously reported a large-animal study of deep brain stimulation (DBS) in the fornix that found stimulation-induced hemodynamic responses in both the medial limbic and corticolimbic circuits on functional resonance imaging (fMRI) and evoked dopamine responses in the nucleus accumbens (NAc), as measured by fast-scan cyclic voltammetry (FSCV). The effects of DBS on the fornix are challenging to analyze, given its structural complexity and connection to multiple neuronal networks. In this study, we extend our earlier work to a rodent model wherein we characterize regional brain activity changes resulting from fornix stimulation using fludeoxyglucose (¹⁸F-FDG) micro positron emission tomography (PET) and monitor neurochemical changes using FSCV with pharmacological confirmation. Both global functional changes and local changes were measured in a rodent model of fornix DBS. Functional brain activity was measured by micro-PET, and the neurochemical changes in local areas were monitored by FSCV. Micro-PET images revealed increased glucose metabolism within the medial limbic and corticolimbic circuits. Neurotransmitter efflux induced by fornix DBS was monitored at NAc by FSCV and identified by specific neurotransmitter reuptake inhibitors. We found a significant increase in the metabolic activity in several key regions of the medial limbic circuits and dopamine efflux in the NAc following fornix stimulation. These results suggest that electrical stimulation of the fornix modulates the activity of brain memory circuits, including the hippocampus and NAc within the dopaminergic pathway.

Emotionally expressed voices are retained in memory following a single exposure

Studies of voice recognition in biology suggest that long exposure may not satisfactorily represent the voice acquisition process. The current study proposes that humans can acquire a newly familiar voice from brief exposure to spontaneous speech, given a personally engaging context. Studies have shown that arousing and emotionally engaging experiences are more likely to be recorded and consolidated in memory. Yet it remains undemonstrated whether this advantage holds for voices. The present study examined the role of emotionally expressive context in the acquisition of voices following a single, 1-minute exposure by comparing recognition of voices experienced in engaging and neutral contexts at two retention intervals. Listeners were exposed to a series of emotionally nuanced and neutral videotaped narratives produced by performers, and tested on the recognition of excerpted voice samples, by indicating whether they had heard the voice before, immediately and after a one-week delay. Excerpts were voices from exposed videotaped narratives, but utilized verbal material taken from a second (nonexposed) narrative provided by the same performer. Overall, participants were consistently able to distinguish between voices that were exposed during the video session and voices that were not exposed. Voices experienced in emotional, engaging contexts were significantly better recognized than those in neutral ones both immediately and after a one-week delay. Our findings provide the first evidence that new voices can be acquired rapidly from one-time exposure and that nuanced context facilitates initially inducting new voices into a repertory of personally familiar voices in long-term memory. The results converge with neurological evidence to suggest that cerebral processes differ for familiar and unfamiliar voices.

The Cancer Bell: Too Much of a Good Thing?

PURPOSE

Patients around the world often ring a bell on the final day of radiation therapy (RT) to celebrate treatment completion. Patients appear to enjoy ringing the bell, but its psychological impact is unexamined. Applying a psychological principle named the "peak-end rule," we hypothesized that ringing the bell would improve patients' perceptions of the overall distress from cancer treatment.

METHODS AND MATERIALS

We enrolled 2 cohorts of patients completing definitive RT in a single-center outpatient radiation oncology clinic. Patients in the control arm completed treatment and filled out the survey mentioned below. A bell was then installed in the clinic, and patients in the intervention arm rang the bell on the final day of RT and filled out the same survey. Patients evaluated their overall distress from cancer treatment using a survey composed of an 11-point numerical rating scale in combination with the Verbal Rating Scale. At follow-up, a shorter survey was completed that asked the same questions about distress from cancer treatment.

RESULTS

Two hundred ten patients were enrolled, 107 in the bell group and 103 in the control group. One hundred sixty-three patients completed follow-up surveys, n = 86 (80%) and n = 77 (75%) in the bell and control groups, respectively. Demographics and treatment characteristics were well balanced. The bell group reported worse overall distress scores than those not ringing the bell (mean [standard deviation] 5.6 [2.8] vs 4.7 [2.7], P = .045). This difference worsened further at follow-up (6.4 [2.9] vs 5.1 [3.0], P = .009; mean 103 vs 130 days, P = .056).

CONCLUSIONS

Counter to our hypothesis, ringing the bell on the final day of RT worsens patients' evaluation of overall distress from cancer treatment, and this distress persists and even worsens in the months after treatment. Emotional arousal created by ringing the bell may magnify the distress from cancer treatment and subsequently worsen the perception of distress from treatment.