The effects of acute stress on episodic memory: A meta-analysis and integrative review

Context Matters: Situational Stress Impedes Functional Reorganization of Intrinsic Brain Connectivity during Problem-Solving

Extensive research has established a relationship between individual differences in brain activity in a resting state and individual differences in behavior. Conversely, when individuals are engaged in various tasks, certain task-evoked reorganization occurs in brain functional connectivity, which can consequently influence individuals' performance as well. Here, we show that resting state and task-dependent state brain patterns interact as a function of contexts engendering stress. Findings revealed that when the resting state connectome was examined during performance, the relationship between connectome strength and performance only remained for participants under stress (who also performed worse than all other groups on the math task), suggesting that stress preserved brain patterns indicative of underperformance whereas non-stressed individuals spontaneously transitioned out of these patterns. Results imply that stress may impede the reorganization of a functional network in task-evoked brain states. This hypothesis was subsequently verified using graph theory measurements on a functional network, independent of behavior. For participants under stress, the functional network showed less topological alterations compared to non-stressed individuals during the transition from resting state to task-evoked state. Implications are discussed for network dynamics as a function of context.

Stress and long-term memory retrieval: a systematic review

Introduction

The experience of stressful events can alter brain structures involved in memory encoding, storage and retrieval. Here we review experimental research assessing the impact of the stress-related hormone cortisol on long-term memory retrieval.

Method

A comprehensive literature search was conducted on PubMed, Web of Science and PsycNet databases with the following terms: “stress,” “long-term memory,” and “retrieval.” Studies were included in the review if they tested samples of healthy human participants, with at least one control group, and with the onset of the stress intervention occurring after the encoding phase and shortly (up to one hour) before the final memory test.

Results

Thirteen studies were included in the qualitative synthesis (N = 962) and were classified according to the time elapsed between stress induction and memory retrieval (stress-retrieval delay), the stress-inducing protocol (stressor), the time of day in which stress induction took place, sex, and age of participants. Most studies induced stress with the Trier Social Stress Test (TSST) between 15 and 25 minutes before the final memory (mostly recall) test and showed significant increases in cortisol levels and memory impairment.

Discussion

The reviewed studies indicate that stress does impair retrieval, particularly when induced with the TSST, in the afternoon, up to 45 minutes before the onset of the final memory test, in healthy young men. These results may inform future research on the impact of stress-induced cortisol surges on memory retrieval.

Stress Impairs Intentional Memory Control through Altered Theta Oscillations in Lateral Parietal Cortex

Accumulating evidence suggests that forgetting is not necessarily a passive process but that we can, to some extent, actively control what we remember and what we forget. Although this intentional control of memory has potentially far-reaching implications, the factors that influence our capacity to intentionally control our memory are largely unknown. Here, we tested whether acute stress may disrupt the intentional control of memory and, if so, through which neural mechanism. We exposed healthy men and women to a stress (n = 27) or control (n = 26) procedure before they aimed repeatedly to retrieve some previously learned cue-target pairs and to actively suppress others. While control participants showed reduced memory for suppressed compared with baseline pairs in a subsequent memory test, this suppression-induced forgetting was completely abolished after stress. Using magnetoencephalography (MEG), we show that the reduced ability to suppress memories after stress is associated with altered theta activity in the inferior temporal cortex when the control process (retrieval or suppression) is triggered and in the lateral parietal cortex when control is exerted, with the latter being directly correlated with the stress hormone cortisol. Moreover, the suppression-induced forgetting was linked to altered connectivity between the hippocampus and right dorsolateral prefrontal cortex (PFC), which in turn was negatively correlated to stress-induced cortisol increases. These findings provide novel insights into conditions under which our capacity to actively control our memory breaks down and may have considerable implications for stress-related psychopathologies, such as posttraumatic stress disorder (PTSD), that are characterized by unwanted memories of distressing events.SIGNIFICANCE STATEMENT It is typically assumed that forgetting is a passive process that can hardly be controlled. There is, however, evidence that we may actively control, to some extent, what we remember and what we forget. This intentional memory control has considerable implications for mental disorders in which patients suffer from unwanted (e.g., traumatic) memories. Here, we demonstrate that the capacity to intentionally control our memory breaks down after stress. Using magnetoencephalography (MEG), we show that this stress-induced memory control deficit is linked to altered activity in the lateral parietal cortex and the connectivity between the hippocampus and right prefrontal cortex (PFC). These findings provide novel insights into conditions under which memory control fails and are highly relevant in the context of stress-related psychopathologies.

Stress Impairs Episodic Retrieval by Disrupting Hippocampal and Cortical Mechanisms of Remembering

Despite decades of science investigating the neural underpinnings of episodic memory retrieval, a critical question remains: how does stress influence remembering and the neural mechanisms of recollection in humans? Here, we used functional magnetic resonance imaging and multivariate pattern analyses to examine the effects of acute stress during retrieval. We report that stress reduced the probability of recollecting the details of past experience, and that this impairment was driven, in part, by a disruption of the relationship between hippocampal activation, cortical reinstatement, and memory performance. Moreover, even memories expressed with high confidence were less accurate under stress, and this stress-induced decline in accuracy was explained by reduced posterior hippocampal engagement despite similar levels of category-level cortical reinstatement. Finally, stress degraded the relationship between the engagement of frontoparietal control networks and retrieval decision uncertainty. Collectively, these findings demonstrate the widespread consequences of acute stress on the neural systems of remembering.

Salivary Cortisol Levels Are Associated with Craving and Cognitive Performance in Cocaine-Abstinent Subjects: A Pilot Study

Cortisol is a glucocorticoid hormone secreted by the adrenal cortex upon the activation of the hypothalamic-pituitary-adrenal (HPA) axis. Assessment of cortisol in saliva has emerged as a reliable way of evaluating HPA function. We examined the relationships between salivary cortisol levels with both craving and cognitive performance, as a possible biomarker of cocaine addiction. Cognitive performance (attention, declarative and working memory, executive functions and recognition of emotions) was assessed in 14 abstinent cocaine-dependent subjects in outpatient treatment and 13 control participants. Three salivary samples were collected at home by all the participants in the morning, afternoon and at bedtime. Patients showed higher levels of cortisol in the morning, as well as higher area under the curve with respect to the ground (AUCg). Regarding cognitive performance, cocaine-abstinent subjects showed worse performance in attention (d2 test), verbal memory (Spanish Complementary Verbal Learning Test, TAVEC) and executive tests (Tower of Hanoi and phonological fluency test) with respect to the control group. Morning cortisol levels and the AUCg index were negatively associated with the age of onset of drug consumption and the AUCg index was also positively associated with craving in our patients' group. Moreover, morning cortisol levels, as well as the AUCg index, were negatively associated with verbal memory performance. Therefore, our pilot study suggests that salivary cortisol measurements could be a good avenue to predict craving level, as well as cognitive status, especially the declarative memory domain.

Impact of music-based intervention on verbal memory: an experimental behavioral study with older adults

Normal age-related declines have been reported in different cognitive functions, such as episodic memory. Some environmental factors have the potential to reduce cognitive decline and promote healthy aging. In this research, we employed musical improvisation as a focal music-based intervention to explore its effects as a modulator of verbal memory. We evaluated two types of verbal memory: a neutral one, employing the Rey Auditory Verbal Learning Test (Study 1), and an emotional one, implementing the Spanish version of Affective Norms for English Words (Study 2) in a volunteer group of older adults. After the acquisition of neutral (Study 1) or emotional (Study 2) verbal information, the participants were exposed to musical improvisation (experimental condition) or two control conditions (rhythmic reproduction as a musically active control condition or a rest condition as a passive control condition) for 3 min. Then, memory was evaluated through two memory tasks (immediate and deferred free-recall and recognition tests). In both studies, we compared memory performance among musicians (with five or more years of music training) and non-musicians. We found a significant improvement in neutral verbal memory among participants involved in musical improvisation, who remembered more words than those in the control conditions. Differences were also found according to the musical experience of the sample, with musicians outperforming non-musicians. The current research supports the late-life cognitive benefits of music-based intervention and music training.

Eyewitness identifications after witnessing threatening and non-threatening scenes in 360-degree virtual reality (or 2D) from first and third person perspectives

In eyewitness research the frequent use of video playback presented on a computer screen (i.e., 2D videos) in laboratory-based research is problematic due to the low realism of this method when presenting, for example, threatening (and non-threatening) first-person (and third-person) scenarios. However, in contrast to 2D videos, 360-degree videos presented in virtual reality (VR) presents the opportunity of achieving more realistic and immersive scenarios that might be better suited to mimic real-life incidents, as for example, in the case of a threatening first-person robbery. In the present study, we asked 37 participants to watch eight pre-recorded threatening or non-threatening 2D and VR videos, viewed from either a first- or third-person perspective. After each video, participants assessed the observed target’s appearance and were then presented with either a target present (TP) or target absent (TA) six-person photograph line-up. We expected that VR would result in higher degrees of accuracy in both TP and TA line-ups compared with 2D and that the differences between manipulations would be more pronounced within VR compared with 2D. We found that TP (but not TA) accuracy was higher in 2D compared with VR videos (91 vs. 66%), that there was no main effect of perspective, and that threatening scenes increased TP (but not TA) accuracy compared to non-threatening scenes (86 vs. 70%). Furthermore, in VR (but not in 2D), threatening scenes increased TP (but not TA) accuracy compared with non-threatening scenes (85 vs. 40%). The results go against the expected increased accuracy in VR (vs. 2D) videos but support the notion that threatening (vs. non-threatening) scenes can increase identification accuracy in VR but not necessarily in 2D.

Stress-induced cortisol modulates the control of memory retrieval towards the dorsal striatum

Stress can modulate the recruitment of multiple memory systems during learning, favouring dorsal striatal "habit" learning over hippocampal "cognitive" learning. Here, we tested whether stress may also bias the engagement of "cognitive" and "habit" systems during retrieval and thereby affect the nature of remembering. To this end, participants first performed a probabilistic classification learning task that can be solved by both the "cognitive" and the "habit" system. Twenty-four hours later, participants underwent either a stress manipulation or a non-stressful control procedure before they completed a retention test for the previously learned task in the MRI scanner. During this retention test, stress-induced cortisol levels were linked to a relative bias towards behavioural strategies indicative for the "habit" system. At the neural level, stress led to increased dorsal striatal activity during retrieval. Elevated cortisol levels were directly correlated with increased activity in the dorsal striatum and further linked to reduced functional connectivity between the hippocampus and the amygdala, which is assumed to orchestrate the stress-related shift from "cognitive" to "habitual" control. Together, our data suggest that stress may bias the contributions of multiple memory systems also at retrieval, in a manner that promotes dorsal striatal "habit" processes and most likely driven by cortisol.

Spousal Loss and Change in Cognitive Functioning: An Examination of Temporal Patterns and Gender Differences

OBJECTIVES

The study investigates whether the disadvantaged position of men in the adverse consequences of widowhood for health and mortality also exists for changes in cognitive health.

METHODS

We used data of up to 1,269 men and women aged 65 years and older who participated in the Longitudinal Aging Study Amsterdam in 3-yearly assessments between 1992 and 2012 (5,123 person-observations). All were married and without cognitive impairment (Mini-Mental State Examination ≥ 24) at baseline and up to 419 lost their spouse. In fixed effects regression models, the effect of spousal loss on change in four domains of cognitive functioning was estimated independently of age-related cognitive change.

RESULTS

For women, a robust temporary decrease was found in the second year after spousal loss in the reasoning domain, but not in global cognitive functioning, processing speed, or memory. No robust effects were found for men.

DISCUSSION

Considering that only one cognitive domain was affected and effects were temporary, cognitive functioning seems rather robust to the experience of spousal loss. Despite men having often been reported to be in a disadvantaged position in other health domains, our analyses indicate no such pattern for cognitive functioning.

Stress Alters the Neural Context for Building New Memories

Stressful events affect mnemonic processing, in particular for emotionally arousing events. Previous research on the mechanisms underlying stress effects on human memory focused on stress-induced changes in the neural activity elicited by a stimulus. We tested an alternative mechanism and hypothesized that stress may already alter the neural context for successful memory formation, reflected in the neural activity preceding a stimulus. Therefore, 69 participants underwent a stress or control procedure before encoding neutral and negative pictures. During encoding, we recorded high-density EEG and analyzed-based on multivariate searchlight analyses-oscillatory activity and cross-frequency coupling patterns before stimulus onset that were predictive of memory tested 24 hr later. Prestimulus theta predicted subsequent memory in controls but not in stressed participants. Instead, prestimulus gamma predicted successful memory formation after stress, specifically for emotional material. Likewise, stress altered the patterns of prestimulus theta-beta and theta-gamma phase-amplitude coupling predictive of subsequent memory, again depending on the emotionality of the presented material. Our data suggest that stress changes the neural context for building new memories, tuning this neural context specifically to the encoding of emotionally salient events. These findings point to a yet unknown mechanism through which stressful events may change (emotional) memory formation.

Registered nurse perceptions of factors contributing to the inconsistent brand image of the nursing profession

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An outdated brand image projects nurses as lacking in influence and autonomy.

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Nurses could use branding principles to develop and promote their desired image.

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Branding is most effective when members agree on a set of shared values.

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A strong brand message is built on “consistency of message and action over time.”

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Research is needed which could inform an accurate brand image for nursing.

Background

Nurses have been overlooked as autonomous healthcare providers due to an inaccurate image which projects them as caring and trusted, yet lacking in influence and autonomy. It is important for nurses to understand the image their profession wishes to convey, how the image falls short, and what can be done to improve it.

Purpose

To examine responses of Registered Nurses (n = 286) describing factors influencing nursing's inconsistent brand image.

Methods

Qualitative data were thematically coded, analyzed, and grouped into eight influencing factors.

Findings

Factors contributing to nursing's inconsistent image included: variety of education/credentials, image not a priority, lack of leadership development, lack of professionalism, portrayals in the media and online, patients’ personal experiences, treatment by other professional colleagues and gender role assumptions.

Discussion

A strong brand image could dispel outdated and inaccurate views while communicating new visionary leadership which aligns with priorities for the nursing profession.

The Forward Testing Effect is Immune to Acute Psychosocial Encoding/Retrieval Stress

The forward testing effect (FTE) refers to the finding that testing of previously studied information enhances memory for subsequently studied other information. Previous research demonstrated that the FTE is a robust phenomenon that generalizes across different materials and populations. The present study examined whether the FTE is robust under acute psychosocial encoding/retrieval stress. In each of two experimental conditions, participants studied three item lists in anticipation of final cumulative recall testing. In the testing condition, participants were tested immediately on lists 1 and 2, whereas in the restudy condition, they restudied lists 1 and 2. In both conditions, participants were tested immediately on list 3. Acute psychosocial stress was induced in participants prior to the encoding of item lists using the Trier social stress test for groups protocol. No stress was induced in a control group. Salivary cortisol, alpha amylase, and subjective stress were measured repeatedly to capture the biopsychological stress response. The results showed a significant FTE on list 3 recall, that is, testing of lists 1 and 2 enhanced the recall of list 3. No significant effect of stress on the FTE was observed, suggesting that the FTE is robust under acute psychosocial encoding/retrieval stress. The discussion provides suggestions for future research directions.

Effects of stress on 6- and 7-year-old children's emotional memory differs by gender

Understanding effects of emotional valence and stress on children's memory is important for educational and legal contexts. This study disentangled the effects of emotional content of to-be-remembered information (i.e., items differing in emotional valence and arousal), stress exposure, and associated cortisol secretion on children's memory. We also examined whether girls' memory is more affected by stress induction. A total of 143 6- and 7-year-old children were randomly allocated to the Trier Social Stress Test for Children (n = 103) or a control condition (n = 40). At 25 min after stressor onset, children incidentally encoded 75 objects varying in emotional valence (crossed with arousal) together with neutral scene backgrounds. We found that response bias corrected memory was worse for low-arousing negative items than for neutral and positive items, with the latter two categories not being different from each other. Whereas boys' memory was largely unaffected by stress, girls in the stress condition showed worse memory for negative items, especially the low-arousing ones, than girls in the control condition. Girls, compared with boys, reported higher subjective stress increases following stress exposure and had higher cortisol stress responses. Whereas a higher cortisol stress response was associated with better emotional memory in girls in the stress condition, boys' memory was not associated with their cortisol secretion. Taken together, our study suggests that 6- and 7-year-old children, more so girls, show memory suppression for negative information. Girls' memory for negative information, compared with that of boys, is also more strongly modulated by stress experience and the associated cortisol response.

Sex Differences in Work-Stress Memory Bias and Stress Hormones

Mental health problems related to chronic stress in workers appear to be sex-specific. Psychosocial factors related to work-life balance partly explain these sex differences. In addition, physiological markers of stress can provide critical information on the mechanisms explaining how chronic stress gets "under the skull" to increase vulnerability to mental health disorders in working men and women. Stress hormones access the brain and modulate attentional and memory process in favor of threatening information. In the present study, we tested whether male and female workers present a memory bias towards work-stress related information, and whether this bias is associated with concentrations of stress hormones in reactivity to a laboratory stressor (reactive levels) and samples taken in participants' workday (diurnal levels). In total, 201 participants (144 women) aged between 18 and 72 years underwent immediate and delayed recall tasks with a 24-word list, split as a function of valence (work-stress, positive, neutral). Participants were exposed to a psychosocial stressor in between recalls. Reactivity to stress was measured with saliva samples before and after the stressor. Diurnal cortisol was also measured with five saliva samples a day, during 2 workdays. Our exploratory results showed that men presented greater cortisol reactivity to stress than women, while women recalled more positive and neutral words than men. No sex difference was detected on the recall of work-stress words, before or after exposure to stress. These results do not support the hypothesis of a sex-specific cognitive bias as an explanatory factor for sex differences in stress-related mental health disorders in healthy male and female workers. However, it is possible that such a work-stress bias is present in individuals who have developed a mental-health disorder related to workplace stress or who have had one in the recent past. Consequently, future studies could use our stress memory bias task to assess this and other hypotheses in diverse working populations.

Acute psychosocial stress during retrieval impairs pattern separation processes on an episodic memory task

Numerous studies have shown that the presence of psychosocial stress impairs the ability to retrieve episodic memories, which raise questions about the specific cognitive processes that underlie this impairment. Here, we tested the hypothesis that stress targets retrieval processes needed to reliability discriminate previously learned from new information within episodic memory, pattern separation processing by measuring the effects of retrieval-induced stress on a modified version of the Mnemonic Similarity Task. In a two-part between-subjects design, all participants studied a series of object images in an initial testing session. In a second session, held 24 h later, half of the participants completed a stress induction task (stress group) and half performed a similarly structured but non-stressful task (control group) and all were then given a recognition memory test for the previously studied images which included new images similar to those studied (lures), and images that were completely novel (foils). Both groups performed equally well in terms of overall recognition memory, but the stress group was significantly impaired in discriminating new and similar (lure) items from studied items. This pattern of results suggests that stress specifically targets pattern separation processing when retrieving information from episodic memory. We discuss the implications of this effect, specifically how stress at retrieval reduces the ability to discriminate new from learned information.

Stress-Induced Increase in Cortisol Negatively Affects the Consolidation of Contextual Elements of Episodic Memories

Stress can modulate episodic memory in various ways. The present study asks how post-encoding stress affects visual context memory. Participants encoded object images centrally positioned on background scenes. After encoding, they were either exposed to cold pressure stress (CPS) or a warm water control procedure. Forty-right hours later, participants were cued with object images, and for each image, they were asked to select the background scene with which it was paired during study among three highly similar options. Only male but not female participants reacted with a significant increase in salivary cortisol to CPS, and the stress and control group did not differ in recognition performance. Comparing recognition performance between stress responders and non-responders, however, revealed a significant impairment in context memory in responders. Additionally, proportional increase in cortisol was negatively correlated with the number of correctly recognized scenes in responders. Due to the small number of responders, these findings need to be interpreted with caution but provide preliminary evidence that stress-induced cortisol increase negatively affects the consolidation of contextual elements of episodic memories.

The timing-dependent effects of stress-induced cortisol release on evaluative conditioning

The neuro-physiological response to stress has far-reaching implications for learning and memory processes. Here, we examined whether and how the stress-induced release of cortisol, following the socially-evaluated cold pressor test, influenced the acquisition of preferences in an evaluative conditioning (EC) procedure. We found that when the stressor preceded the evaluation phase, cortisol responders showed decreased evaluative conditioning effects. By contrast, impairing effects of a stressor-induced cortisol release before encoding were not found. Moreover, explicit memory was not found to be affected by the stressor or its timing. Implications of the timing-dependent effects of stress-induced cortisol release on EC and the relation between stress and associative memory are discussed.

Activation of the hypothalamic-pituitary adrenal axis in response to a verbal fluency task and associations with task performance

Speech fluency can be impaired in stressful situations. In this study, it was investigated whether a verbal fluency task by itself, i.e. without the presence of any further stressors, induces responses of the hypothalamic-pituitary adrenal (HPA) axis and of the sympathetic nervous system (SNS). The sample consisted of n = 85 participants (68.2% female; 33.3 ± 15.2 years) who performed two consecutive verbal fluency tasks for two minutes each. The categories were either ‘stress’ or ‘disease’ and ‘animals’ or ‘foods’ which were presented in a randomized order. Three saliva samples were collected, prior to the task (t₀), immediately after (t₁), and ten minutes after it (t₂). Salivary α-amylase and cortisol were assessed. Furthermore, blood pressure, heart rate, and ratings of actual stress perception, level of effort, and tiredness were measured. The verbal fluency task induced a HPA axis response with a maximum cortisol level at t₂ which was independent of task performance. Furthermore, perceived stress and effort, as well as tiredness increased after the task. Moreover, tiredness immediately after the task was negatively correlated with task performance. No α-amylase, blood pressure, or heart rate, and therefore SNS, responses were found. Implications for the integrated specificity model are discussed. We conclude that a verbal fluency task acts like an acute stressor that induces a cortisol and a perceived stress response without the need for further (e.g., social-evaluative) stress components. Therefore, it is a less time-consuming alternative to other stress tasks that can be used in field studies with little effort.

Stress Disrupts Human Hippocampal-Prefrontal Function during Prospective Spatial Navigation and Hinders Flexible Behavior

The ability to anticipate and flexibly plan for the future is critical for achieving goal-directed outcomes. Extant data suggest that neural and cognitive stress mechanisms may disrupt memory retrieval and restrict prospective planning, with deleterious impacts on behavior. Here, we examined whether and how acute psychological stress influences goal-directed navigational planning and efficient, flexible behavior. Our methods combined fMRI, neuroendocrinology, and machine learning with a virtual navigation planning task. Human participants were trained to navigate familiar paths in virtual environments and then (concurrent with fMRI) performed a planning and navigation task that could be most efficiently solved by taking novel shortcut paths. Strikingly, relative to non-stressed control participants, participants who performed the planning task under experimentally induced acute psychological stress demonstrated (1) disrupted neural activity critical for mnemonic retrieval and mental simulation and (2) reduced traversal of shortcuts and greater reliance on familiar paths. These neural and behavioral changes under psychological stress were tied to evidence for disrupted neural replay of memory for future locations in the spatial environment, providing mechanistic insight into why and how stress can alter planning and foster inefficient behavior.

Balancing Between Goal-Directed and Habitual Responding Following Acute Stress

Abstract. Instrumental learning is regulated by two memory systems: a relatively rigid but efficient habit system and a flexible but resource-demanding goal-directed system. Previous work has demonstrated that exposure to acute stress may shift the balance between these systems toward the habitual system. In the current study, we used a 2-day outcome devaluation paradigm with a 75% reward contingency rate and altered food reward categories to replicate and extend our previous findings. Participants learned neutral stimulus–response–reward associations on the first day. On the second day, rewards were devalued by eating to satiety. Subsequently, acute stress was induced in half of the participants using the Maastricht Acute Stress Test, while the other half engaged in a nonstressful control task. Finally, relative goal-directed versus habitual behavior was evaluated in a slips-of-action phase, where more slips-of-action indicate a shift toward the habitual system. Results showed that participants successfully acquired the stimulus–response–reward associations, that devaluation was effective, and that stressed participants displayed significant increases in cortisol and blood pressure. Stress led participants to commit more slips-of-action compared with nonstressed controls. The current study extends previous work, showing that the employed paradigm and outcome devaluation procedure are boundary conditions to the stress-induced shift in instrumental responding.

Acute stress reduces out-group related safety signaling during fear reinstatement in women

When using in-group and out-group faces as conditional stimuli (CS) in fear conditioning designs, extinction learning is selectively impaired for out-group faces. Additionally, stress seems to inhibit extinction retrieval leading to a higher return of fear, which might be especially the case for out-group faces. To test this hypothesis, 51 healthy women underwent fear acquisition training, consisting of repeated presentations of two in-group and two out-group faces. One of each (CS+) was paired with an electrical stimulation (unconditional stimulus, UCS), whereas the other was not coupled with the UCS (CS-). During immediate extinction training, all CS were presented again. On the next day, a retrieval and reinstatement test took place after a stress or a control procedure. Confirming previous research, impaired extinction learning occurred for out-group relative to in-group faces. During the reinstatement test, stress specifically increased responding towards the out-group CS-, thus reducing its safety signaling properties. So, stress seems to reduce the ability to adequately distinguish threat and safety cues after aversive experiences mimicked by reinstatement shocks.

Basolateral Amygdala Connectivity With Subgenual Anterior Cingulate Cortex Represents Enhanced Fear-Related Memory Encoding in Anxious Humans

BACKGROUND

The amygdala can enhance emotional memory encoding as well as anxiogenesis via corticotropin-releasing factor neurons. However, the amygdala's explicit role in emotional encoding remains unclarified in humans. We examined how functional connectivity (FC) of amygdala subnuclei affects emotional encoding, considering its mechanism in which anxiety, attention, and cortisol conceivably participate.

METHODS

A total of 65 healthy humans underwent resting-state functional magnetic resonance imaging scans and saliva collection at 10 points in time over 2 days. FC analysis was performed for basolateral amygdala subnucleus (BLA) and centromedial amygdala subnucleus. We assessed attentional control via an emotional Stroop task and assessed emotional encoding via a facial identification task that examines how strongly a neutral face is memorized when accompanied by an emotional face (fearful, sad, or happy). FC and task performance were compared between high-anxious and non-high-anxious groups classified by anxious personality scores.

RESULTS

BLA connected with subgenual anterior cingulate cortex (sgACC) in proportion to the strength of fear-related encoding, whereas centromedial subnucleus connected with caudate nucleus for happy-related encoding. The high-anxious group showed more enhanced fear-related encoding but impaired happy-related encoding compared with the non-high-anxious group. BLA-sgACC FC was more intensified in the high-anxious group than in the non-high-anxious group; however, centromedial-caudate FC did not differ between them. Although emotional encoding was uncorrelated with either attentional control or cortisol, BLA-sgACC was positively correlated with cortisol increase after awakening.

CONCLUSIONS

The study revealed that neural interactions of BLA, specifically with sgACC, might play a critical role in fear-related memory encoding, depending on the individual's level of anxiety. These findings aid in understanding the complicated mechanisms of emotional memory in anxiety disorders.

Stress and cognition: A user's guide to designing and interpreting studies

Fueling the rapid growth in our understanding of how stress influences cognition, the number of studies examining the effects of stress on various cognitive processes has grown substantially over the last two decades. Despite this growth, few published guidelines exist for designing these studies, and divergent paradigm designs can diminish typical effects of stress or even reverse them. The goal of this review, therefore, is to survey necessary considerations (e.g., validating a stress induction), important considerations (e.g., specifying the timing of the stressor and cognitive task), and best practices (e.g., using Bayesian analyses) when designing a study that aims at least in part to examine the effects of acute stress on some cognitive process or function. These guidelines will also serve to help readers of these studies interpret what may otherwise be very confusing, anomalous results. Designing and interpreting studies with these considerations and practices in mind will help to move the field of stress and cognition forward by clarifying how, exactly, stress influences performance on a given cognitive task in a population of interest.

Acute and Chronic Insomnia: What Has Time and/or Hyperarousal Got to Do with It?

Nearly one-third of the population reports new onset or acute insomnia in a given year. Similarly, it is estimated that approximately 10% of the population endorses sleep initiation and maintenance problems consistent with diagnostic criteria for chronic insomnia. For decades, acute and chronic insomnia have been considered variations of the same condition or disorder, only really differentiated in terms of chronicity of symptoms (days/weeks versus months). Whether or not acute and chronic insomnia are part of the same phenomena is an important question, one that has yet to be empirically evaluated. The goal of the present theoretical review was to summarize the definitions of acute and chronic insomnia and discuss the role that hyperarousal may have in explaining how the pathophysiology of acute and chronic insomnia is likely different (i.e., what biopsychological factors precipitate and/or perpetuate acute insomnia, chronic insomnia, or both?).

Emotional Objectivity: Neural Representations of Emotions and Their Interaction with Cognition

Recent advances in our understanding of information states in the human brain have opened a new window into the brain's representation of emotion. While emotion was once thought to constitute a separate domain from cognition, current evidence suggests that all events are filtered through the lens of whether they are good or bad for us. Focusing on new methods of decoding information states from brain activation, we review growing evidence that emotion is represented at multiple levels of our sensory systems and infuses perception, attention, learning, and memory. We provide evidence that the primary function of emotional representations is to produce unified emotion, perception, and thought (e.g., “That is a good thing”) rather than discrete and isolated psychological events (e.g., “That is a thing. I feel good”). The emergent view suggests ways in which emotion operates as a fundamental feature of cognition, by design ensuring that emotional outcomes are the central object of perception, thought, and action.

Effects of Exercise on Memory Interference in Neuropsychiatric Disorders

There are several mechanisms that cause memory impairment, including motivated forgetting, active forgetting, natural decay, and memory interference. Interference occurs when one is attempting to recall something specific, but there is conflicting information making it more difficult to recall the target stimuli. In laboratory settings, it is common to measure memory interference with paired associate tasks-usually utilizing the AB-CD, AB-AC, AB-ABr, or AB-DE AC-FG method. Memory impairments are frequent among those with neuropsychiatric disorders such as depression, schizophrenia, and multiple sclerosis. The memory effects of each condition differ, but are all related to alterations in brain physiology and general memory deterioration. Exercise, or physical activity, has been demonstrated to attenuate memory interference in some cases, but the mechanisms are still being determined. Further research is needed on memory interference, in regard to exercise and neuropsychiatric disorders.

Hippocampal µ-opioid receptors on GABAergic neurons mediate stress-induced impairment of memory retrieval

Stressful life events induce abnormalities in emotional and cognitive behaviour. The endogenous opioid system plays an essential role in stress adaptation and coping strategies. In particular, the µ-opioid receptor (μR), one of the major opioid receptors, strongly influences memory processing in that alterations in μR signalling are associated with various neuropsychiatric disorders. However, it remains unclear whether μR signalling contributes to memory impairments induced by acute stress. Here, we utilized pharmacological methods and cell-type-selective/non-cell-type-selective μR depletion approaches combined with behavioural tests, biochemical analyses, and in vitro electrophysiological recordings to investigate the role of hippocampal μR signalling in memory-retrieval impairment induced by acute elevated platform (EP) stress in mice. Biochemical and molecular analyses revealed that hippocampal μRs were significantly activated during acute stress. Blockage of hippocampal μRs, non-selective deletion of μRs or selective deletion of μRs on GABAergic neurons (μR_GABA) reversed EP-stress-induced impairment of memory retrieval, with no effect on the elevation of serum corticosterone after stress. Electrophysiological results demonstrated that stress depressed hippocampal GABAergic synaptic transmission to CA1 pyramidal neurons, thereby leading to excitation/inhibition (E/I) imbalance in a μR_GABA-dependent manner. Pharmaceutically enhancing hippocampal GABA_A receptor-mediated inhibitory currents in stressed mice restored their memory retrieval, whereas inhibiting those currents in the unstressed mice mimicked the stress-induced impairment of memory retrieval. Our findings reveal a novel pathway in which endogenous opioids recruited by acute stress predominantly activate μR_GABA to depress GABAergic inhibitory effects on CA1 pyramidal neurons, which subsequently alters the E/I balance in the hippocampus and results in impairment of memory retrieval.

Across time and space: spatial-temporal binding under stress

Successful episodic memory requires binding of event details across spatial and temporal gaps. The neural processes underlying mnemonic binding, however, are not fully understood. Moreover, although acute stress is known to modulate memory, if and how stress changes mnemonic integration across time and space is unknown. To elucidate these issues, we exposed participants to a stressor or a control manipulation shortly before they completed, while electroencephalography was recorded, an encoding task that systematically varied the demands for spatial and temporal integration. Associative memory was tested 24 h later. While early event-related potentials, including the P300 and Late Positive Component, distinguished different levels of spatiotemporal discontinuity, only later Slow Waves were linked to subsequent remembering. Furthermore, theta oscillations were specifically associated with successful mnemonic binding. Although acute stress per se left mnemonic integration largely unaffected, autonomic activity facilitated object memory and glucocorticoids enhanced detail memory, indicative for mnemonic integration. At the neural level, stress amplified the effects of spatiotemporal discontinuity on early information processing. Together, our results indicate that temporal and spatial gaps recruit early neural processes, providing attentional resources. The actual binding success, however, appears to depend on later processes as well as theta power and may be shaped by major stress response systems.

Cortisol-related hippocampal-extrastriate functional connectivity explains the adverse effect of cortisol on visuospatial retrieval

Cortisol is known to affect visuospatial memory through its major binding site in the brain, the hippocampus. The synchronization of neural activity between the hippocampus, prefrontal cortex (PFC), and visual cortex is presumed to be essential for the formation of visuospatial memory because of their visuospatial learning-dependent neuroplasticity. However, it remains unclear how hippocampal connectivity with the PFC and visual cortex is involved in the relationship between cortisol and visuospatial memory in humans. We thus investigated whether functional connectivity (FC) of the hippocampus, specifically its rostral and caudal subdivisions, mediates the relationship between visuospatial memory and endogenous cortisol. One-hundred sixty-six healthy young adults underwent standard neuropsychological tests to assess visuospatial construction (a complex figure copying test) and retrieval (the corresponding recall test) and collected their saliva at 6-time points across 2 consecutive days for measurement of daily cortisol concentrations (dCOR). Ninety of them received resting-state fMRI scans. Greater dCOR was significantly associated with better figure copying performance, but contrastingly with poorer figure recall. In proportion to dCOR, the rostral hippocampus (rHC) showed significantly increased FC with the PFC (including its dorsolateral and medial parts) and the inferior lateral occipital cortex (iLOC), while the caudal hippocampus had increased FC with the anterior middle temporal cortex. Of the cortisol-related hippocampal connectivity, the rHC-iLOC FC was specifically correlated with figure recall and showed complete mediation for the negative relationship of dCOR with figure recall. These results suggest that cortisol might have enhancing effects on visuospatial encoding as well as impairing effects on visuospatial retrieval, possibly due to its occupancy patterns of corticosteroid receptors. Cortisol's adverse effects on visuospatial retrieval might be explained through cortisol-related rostral hippocampal connectivity with the iLOC, which is a part of the extrastriate cortex implicated in visuospatial perception. Thorough dissection of hippocampal-prefrontal-extrastriate connectivity might facilitate the understanding of neural mechanisms underlying cortisol's contrasting effects on encoding (or consolidation) and retrieval of visuospatial information.

Effects of hydrocortisone on autobiographical memory retrieval in patients with posttraumatic stress disorder and borderline personality disorder: the role of childhood trauma

In a previous study, we found that patients with posttraumatic stress disorder (PTSD) and borderline personality disorder (BPD) showed better autobiographical memory (AM) retrieval after hydrocortisone administration than after placebo administration. Here we investigate the neural correlates of AM retrieval after hydrocortisone administration in patients with PTSD or BPD. We recruited 78 female participants for this placebo-controlled crossover study: 40 healthy controls, 20 patients with PTSD, and 18 patients with BPD (all without medication). All participants received an oral placebo or 10 mg hydrocortisone in a randomized order before performing an AM task. Neural activity was monitored during the task by functional magnetic resonance imaging. Neural activation did not differ between the three groups during AM retrieval, neither in the placebo condition nor after hydrocortisone intake. Multiple regression analysis revealed that Childhood Trauma Questionnaire scores correlated positively with hydrocortisone effects on activation in the anterior medial prefrontal cortex (amPFC), ventrolateral prefrontal cortex (vlPFC), posterior cingulate cortex (PCC), angular gyrus, and cerebellum. These results suggest that hydrocortisone-induced neural activation pattern during AM retrieval is related to childhood trauma. Previously described effects in the hippocampus, which were absent in the current study, might be related to PTSD caused by trauma in adulthood. The effects of hydrocortisone on brain activation and how these effects are influenced by childhood trauma, trauma in adulthood, and PTSD symptoms should be determined in future studies.

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

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

Mild acute stress improves response speed without impairing accuracy or interference control in two selective attention tasks: Implications for theories of stress and cognition

Acute stress is generally thought to impair performance on tasks thought to rely on selective attention. This effect has been well established for moderate to severe stressors, but no study has examined how a mild stressor-the most common type of stressor-influences selective attention. In addition, no study to date has examined how stress influences the component processes involved in overall selective attention task performance, such as controlled attention, automatic attentional activation, decision-making, and motor abilities. To address these issues, we randomly assigned 107 participants to a mild acute stress or control condition. As expected, the mild acute stress condition showed a small but significant increase in cortisol relative to the control condition. Following the stressor, we assessed attention with two separate flanker tasks. One of these tasks was optimized to investigate component attentional processes using computational cognitive modeling, whereas the other task employed mouse-tracking to illustrate how response conflict unfolded over time. The results for both tasks showed that mild acute stress decreased response time (i.e., increased response speed) without influencing accuracy or interference control. Further, computational modeling and mouse-tracking analyses indicated that these effects were due to faster motor action execution time for chosen actions. Intriguingly, however, cortisol responses were unrelated to any of the observed effects of mild stress. These results have implications for theories of stress and cognition, and highlight the importance of considering motor processes in understanding the effects of stress on cognitive task performance.

Determining the biological associates of acute cold pressor post-encoding stress effects on human memory: The role of salivary interleukin-1β

Stress generally hurts many aspects of memory, but an interesting finding to emerge from the stress and memory literature is that stress that occurs shortly after learning (i.e., post-encoding stress) usually benefits memory. Although this effect is well established, the biological mechanisms underpinning this effect are not-especially in humans. We addressed this gap in the present study by collecting saliva samples from 80 participants who were randomized to a post-encoding stress (i.e., cold pressor for 3 min) or control task (i.e., warm water for 3 min) and 48 h later completed a recognition memory task. Saliva was collected both prior to and 15 min after the offset of (18 min after the onset of) the stress/control manipulation. Drawing on animal and human work, we examined how five stress-responsive biomarkers-cortisol, salivary α-amylase, progesterone, estradiol, and the proinflammatory cytokine interleukin (IL)-1β, all assessed in saliva-related to the effects of stress on memory. We found that stress enhanced recollection of negative images and that these effects were selectively related to salivary IL-1β. Moreover, we found that the beneficial effects of stress on memory were statistically mediated by salivary IL-1β. We found no robust associations-either linear or quadratic-between memory and any other biomarker, nor did we find significant interactions between biomarkers in predicting memory. These results suggest that immune system activity indexed by salivary IL-1β may play an important role in contributing to post-encoding stress effects on human memory.

A Functional Near-Infrared Spectroscopy Study on the Cortical Haemodynamic Responses During the Maastricht Acute Stress Test

In order to better understand stress responses, neuroimaging studies have investigated the underlying neural correlates of stress. Amongst other brain regions, they highlight the involvement of the prefrontal cortex. The aim of the present study was to explore haemodynamic changes in the prefrontal cortex during the Maastricht Acute Stress Test (MAST) using mobile functional Near-Infrared Spectroscopy (fNIRS), examining the stress response in an ecological environment. The MAST includes a challenging mental arithmic task and a physically stressful ice-water task. In a between-subject design, participants either performed the MAST or a non-stress control condition. FNIRS data were recorded throughout the test. Additionally, subjective stress ratings, heart rate and salivary cortisol were evaluated, confirming a successful stress induction. The fNIRS data indicated significantly increased neural activity of brain regions of the dorsolateral prefrontal cortex (dlPFC) and the orbitofrontal cortex (OFC) in response to the MAST, compared to the control condition. Furthermore, the mental arithmetic task indicated an increase in neural activity in brain regions of the dlPFC and OFC; whereas the physically stressful hand immersion task indicated a lateral decrease of neural activity in the left dlPFC. The study highlights the potential use of mobile fNIRS in clinical and applied (stress) research.

Burden of Environmental Adversity Associated With Psychopathology, Maturation, and Brain Behavior Parameters in Youths

IMPORTANCE

Low socioeconomic status (L-SES) and the experience of traumatic stressful events (TSEs) are environmental factors implicated in behavioral deficits, abnormalities in brain development, and accelerated maturation. However, the relative contribution of these environmental factors is understudied.

OBJECTIVE

To compare the association of L-SES and TSEs with psychopathology, puberty, neurocognition, and multimodal neuroimaging parameters in brain maturation.

DESIGN, SETTING, AND PARTICIPANTS

The Philadelphia Neurodevelopmental Cohort is a community-based study examining psychopathology, neurocognition, and neuroimaging among participants recruited through the Children's Hospital of Philadelphia pediatric network. Participants are youths aged 8 to 21 years at enrollment with stable health and fluency in English. The sample of 9498 participants was racially (5298 European ancestry [55.8%], 3124 African ancestry [32.9%], and 1076 other [11.4%]) and economically diverse. A randomly selected subsample (n = 1601) underwent multimodal neuroimaging. Data were collected from November 5, 2009, through December 30, 2011, and analyzed from February 1 through November 7, 2018.

MAIN OUTCOMES AND MEASURES

The following domains were examined: (1) clinical, including psychopathology, assessed with a structured interview based on the Schedule for Affective Disorders and Schizophrenia for School-Age Children, and puberty, assessed with the Tanner scale; (2) neurocognition, assessed by the Penn Computerized Neurocognitive Battery; and (3) multimodal magnetic resonance imaging parameters of brain structure and function.

RESULTS

A total of 9498 participants were included in the analysis (4906 [51.7%] female; mean [SD] age, 14.2 [3.7] years). Clinically, L-SES and TSEs were associated with greater severity of psychiatric symptoms across the psychopathology domains of anxiety/depression, fear, externalizing behavior, and the psychosis spectrum. Low SES showed small effect sizes (highest for externalizing behavior, 0.306 SD; 95% CI, 0.269 to 0.342), whereas TSEs had large effect sizes, with the highest in females for anxiety/depression (1.228 SD; 95% CI, 1.156 to 1.300) and in males for the psychosis spectrum (1.099 SD; 95% CI, 1.032 to 1.166). Both were associated with early puberty. Cognitively, L-SES had moderate effect sizes on poorer performance, the greatest being on complex cognition (-0.500 SD 95% CI, -0.536 to -0.464), whereas TSEs were associated with slightly better memory (0.129 SD; 95% CI, 0.084 to 0.174) and poorer complex reasoning (-0.109 SD; 95% CI, -0.154 to -0.064). Environmental factors had common and distinct associations with brain structure and function. Structurally, both were associated with lower volume, but L-SES had correspondingly lower gray matter density, whereas TSEs were associated with higher gray matter density. Functionally, both were associated with lower regional cerebral blood flow and coherence and with accelerated brain maturation.

CONCLUSIONS AND RELEVANCE

Low SES and TSEs are associated with common and unique differences in symptoms, neurocognition, and structural and functional brain parameters. Both environmental factors are associated with earlier completion of puberty by physical features and brain parameters. These findings appear to underscore the need for identifying and preventing adverse environmental conditions associated with neurodevelopment.

The 'paradox' of converging evidence

We explore the implication of viewing a psychological theory as the logical conjunction of all its predictions. Even if several predictions derived from a theory are descriptive of behavior in separate studies, the theory as a whole may fail to be descriptive of any single individual. We discuss what proportion of a population satisfies a theory's joint predictions as a function of the true effect sizes and the proportion of variance attributable to individual differences. Unless there are no individual differences, even very well replicated effects may fail to establish that the combination of predictions that have been tested accurately describes even one person. Every additional study that contributes another effect, rather than strengthening support for the theory, may further limit its scope. Using four illustrative examples from cognitive and social psychology, we show how, in particular, small effect sizes dramatically limit the scope of psychological theories unless every small effect coincides with little to no individual differences. In some cases, this 'paradox' can be overcome by casting theories in such a way that they apply to everyone in a target population, without exception. Rather than relegating heterogeneity to a nuisance component of statistical models and data analysis, explicitly keeping track of heterogeneity in hypothetical constructs makes it possible to understand and quantify theoretical scope. (PsycINFO Database Record (c) 2019 APA, all rights reserved).

Reports of recovered memories of childhood abuse in therapy in France

Recovered memories of abuse in therapy are especially controversial if the clients were not aware they were abused before therapy. In the past, such memory recovery has led to legal action, as well as a debate about whether such memories might be repressed, forgotten, or false memories. More than two decades after the height of the controversy, it is unclear to what degree such memories are still recovered today, and to what extent it occurs in France. In our French survey of 1312 participants (M_age = 33; 53% female), 551 reported having done therapy at some point. Of that 551, 33 (6%) indicated they had recovered memories of abuse in therapy that they did not know about before therapy. Sexual abuse was the most commonly reported type that was recovered in therapy (79%). As in past research, discussing the possibility of repressed memories with therapists was associated with reports of recovered memories of abuse. Surprisingly, memory recovery occurred just as much in behavioural and cognitive therapies as it did in therapies focused on trauma. We found recovered memories in a proportion of clients who began therapy recently. Recovered memories in therapy appears to be an ongoing concern in France.

Stress and the medial temporal lobe at rest: Functional connectivity is associated with both memory and cortisol

When acute stress is experienced immediately after memory encoding (i.e., post-encoding stress) it can significantly impact subsequent memory for that event. For example, recent work has suggested that post-encoding stress occurring in a different context from encoding impairs memory. However, the neural processes underlying these effects are poorly understood. We aimed to expand this understanding by conducting an analysis of resting functional connectivity in the period following post-encoding stress that occurred in a different context than encoding, using seed regions in the medial temporal lobes known for their roles in memory. In the current study of 44 males randomized to stress (n = 23) or control (n = 21) groups, we found that stress increased cortisol, impaired recollection of neutral materials, and altered functional connectivity with medial temporal lobe regions. Although stress did not significantly alter hippocampus-amygdala functional connectivity, relative to participants in the control group, participants in the post-encoding stress group showed lower functional connectivity between the hippocampus and a region with a peak in the superior temporal gyrus. Across participants in both groups, functional connectivity between these regions was related to greater increases in cortisol, and it was also inversely related to recollection of neutral materials. In contrast, the stress group showed greater parahippocampal cortex functional connectivity with a region in the left middle temporal gyrus than the control group. Moreover, greater functional connectivity between the parahippocampal cortex and the observed cluster in the middle temporal gyrus was associated with greater cortisol changes from pre- to post-manipulation, but was not related to differences in memory. The results show that post-encoding stress can alter the resting-state functional connectivity between the medial temporal lobe and neocortex, which may help explain how stress impacts memory.

Cortisol suppression after memory reactivation impairs later memory performance

Experiencing stressful or traumatic events can result in disabling clinical symptoms of maladaptive emotional memory retrieval, which are only partly addressed by the currently proposed treatments. Cortisol modulation has been shown to affect emotional memory retrieval and potentially reconsolidation, offering an opportunity for developing more efficient treatments for disorders with an emotional memory component. Here, we investigated if cortisol suppression after reactivation of emotional memories weakens later memory thereof. Forty healthy young men were tested in a randomized, placebo controlled, double-blind, and between-subject design, assigned either to a cortisol suppression (metyrapone) group or a placebo group. Participants of both groups, were presented with two emotional stories at an encoding session (Day 1). One of the two stories was later reactivated and followed by metyrapone vs. placebo administration (Day 3). Memory for both stories was tested at a recognition memory session (Day 7). In the group undergoing cortisol suppression after memory reactivation memory performance was weaker compared to the placebo group, tested four days after reactivation. This study shows that cortisol suppression can weaken memory for past events, possibly by altering reconsolidation processes and thus exerting long-lasting weakening effects on the original memory.

Interactive effects of stress reactivity and rapid eye movement sleep theta activity on emotional memory formation

Sleep and stress independently enhance emotional memory consolidation. In particular, theta oscillations (4-7 Hz) during rapid eye movement (REM) sleep increase coherence in an emotional memory network (i.e., hippocampus, amygdala, and prefrontal cortex) and enhance emotional memory. However, little is known about how stress during learning might interact with subsequent REM theta activity to affect emotional memory. In the current study, we examined whether the relationship between REM theta activity and emotional memory differs as a function of pre-encoding stress exposure and reactivity. Participants underwent a psychosocial stressor (the Trier Social Stress Task; n = 32) or a comparable control task (n = 32) prior to encoding. Task-evoked cortisol reactivity was assessed by salivary cortisol rise from pre- to post-stressor, and participants in the stress condition were additionally categorized as high or low cortisol responders via a median split. During incidental encoding, participants studied 150 line drawings of negative, neutral, and positive images, followed by the complete color photo. All participants then slept overnight in the lab with polysomnographic recording. The next day, they were given a surprise recognition memory task. Results showed that memory was better for emotional relative to neutral information. Critically, these findings were observed only in the stress condition. No emotional memory benefit was observed in the control condition. In stressed participants, REM theta power significantly predicted memory for emotional information, specifically for positive items. This relationship was observed only in high cortisol responders. For low responders and controls, there was no relationship between REM theta and memory of any valence. These findings provide evidence that elevated stress at encoding, and accompanying changes in neuromodulators such as cortisol, may interact with theta activity during REM sleep to promote selective consolidation of emotional information.

Prospective memory under acute stress: The role of (output) monitoring and ongoing-task demands

Prospective memory (PM) refers to the ability to postpone retrieval and execution of intended actions until the appropriate situation (PM cue) has come, while engaging in other ongoing activities or tasks. In everyday live we often perform PM tasks in stressful situations. While it has been shown that acute stress does not impair PM-cue identification and intention retrieval, little is known about acute stress effects on PM performance and memory for having performed an action (output monitoring) under varying ongoing-task demands. Here we investigated this in eighty healthy participants who performed event-based PM tasks during low- and high-demanding ongoing working memory tasks after having undergone either a standardized stress induction (Maastricht Acute Stress Test) or a standardized control protocol. Successful stress induction in the stress group compared to the no-stress group was confirmed by increased salivary cortisol, an indicator of stress-related hypothalamus-pituitaryadrenal axis activity, throughout the event-based PM tasks. Nevertheless, not-only PM-cue identification but also output monitoring remained fully intact after stress induction. The absence of these effects was independent of ongoing-task demands. Nonetheless, we replicated recent findings of a stress-induced reduction in performance cost of monitoring for PM-cue occurrences. Taken together our findings suggest that acute stress alters PM monitoring by enhancing selective attention, decreasing PM response thresholds or by shifting performance towards more automatic processes in PM, while not affecting PM-cue identification and output monitoring.

Stress impacts the fidelity but not strength of emotional memories

Psychological stress during memory encoding influences resulting memory representations. However, open questions remain regarding how stress interacts with emotional memory. This interaction has mainly been studied by characterizing the correct identification of previously observed material (memory "hits"), with few studies investigating how stress influences the endorsement of unobserved material as remembered (memory "false alarms"). While hits can provide information about the presence or strength of a memory representation, false alarms provide insight into memory fidelity, indicating to what extent stored memories are confused with similar information presented at retrieval. This study examined the effects of stress on long-term memory for negative and neutral images, considering the separate contributions of hits and false alarms. Participants viewed images after repeated exposure to either a stress or a control manipulation. Stress impaired memory performance for negative pictures and enhanced memory performance for neutral pictures. These effects were driven by false alarms rather than hits: stressed participants false alarmed more often for negative and less often for neutral images. These data suggest that stress undermines the benefits of emotion on memory by changing individuals' susceptibility towards false alarms, and highlight the need to consider both memory strength and fidelity to characterize differences in memory performance.