Learning under stress: The inverted-U-shape function revisited

Cognitive training prevents stress-induced working memory deficits

BACKGROUND

Working memory is a fundamental cognitive process that is critically involved in planning, comprehension, reasoning, or problem-solving. Acute stress has been shown to impair working memory. This stress-induced working memory deficit has profound implications for our cognitive functioning in everyday life as well as for stress-related mental disorders. Here, we tested whether a cognitive training intervention can make working memory more resistant to disruptive effects of acute stress.

METHODS

In a pre-registered, fully-crossed between-subjects design with the factors stress (vs. control) and cognitive training (vs. sham), one hundred twenty-three healthy men and women (aged 18-35 years) completed a daily cognitive training program targeting working memory-related processes or a sham training over a period of six weeks. After this six-week training intervention, participants underwent a standardized stress or control manipulation shortly before their working memory performance was tested.

RESULTS

As expected, the exposure to acute stress led to a significant working memory impairment in the sham training group. Critically, although the subjective, autonomic, and endocrine stress responses were comparable in the two training groups, this stress-induced working memory impairment was abolished in the intervention training group.

CONCLUSIONS

These results are the first to show that a cognitive training intervention directed at prefrontal and hippocampal functioning can prevent the detrimental effects of stressful events on working memory performance.

Acute psychosocial stress modulates neural and behavioral substrates of cognitive control

Acute psychosocial stress affects learning, memory, and attention, but the evidence for the influence of stress on the neural processes supporting cognitive control remains mixed. We investigated how acute psychosocial stress influences performance and neural processing during the Go/NoGo task-an established cognitive control task. The experimental group underwent the Trier Social Stress Test (TSST) acute stress induction, whereas the control group completed personality questionnaires. Then, participants completed a functional magnetic resonance imaging (fMRI) Go/NoGo task, with self-report, blood pressure and salivary cortisol measurements of induced stress taken intermittently throughout the experimental session. The TSST was successful in eliciting a stress response, as indicated by significant Stress > Control between-group differences in subjective stress ratings and systolic blood pressure. We did not identify significant differences in cortisol levels, however. The stress induction also impacted subsequent Go/NoGo task performance, with participants who underwent the TSST making fewer commission errors on trials requiring the most inhibitory control (NoGo Green) relative to the control group, suggesting increased vigilance. Univariate analysis of fMRI task-evoked brain activity revealed no differences between stress and control groups for any region. However, using multivariate pattern analysis, stress and control groups were reliably differentiated by activation patterns contrasting the most demanding NoGo trials (i.e., NoGo Green trials) versus baseline in the medial intraparietal area (mIPA, affiliated with the dorsal attention network) and subregions of the cerebellum (affiliated with the default mode network). These results align with prior reports linking the mIPA and the cerebellum to visuomotor coordination, a function central to cognitive control processes underlying goal-directed behavior. This suggests that stressor-induced hypervigilance may produce a facilitative effect on response inhibition which is represented neurally by the activation patterns of cognitive control regions.

Potential interactive effect of positive expectancy violation and sleep on memory consolidation in dogs

In dogs, as in humans, both emotional and learning pretreatment affect subsequent behaviour and sleep. Although learning often occurs in an emotional-social context, the emotion-learning interplay in such context remain mainly unknown. Aims were to assess the effects of Controlling versus Permissive (emotional factors) training (learning factors) styles on dogs' behaviour, learning performance, and sleep. Family dogs (N = 24) participated in two command learning sessions employing the two training styles with each session followed by assessment of learning performance, a 2-h-long non-invasive sleep EEG measurement, and a retest of learning performance. Pre- to post-sleep improvement in learning performance was evident in dogs that received the Permissive training during the second learning session, indicating that dogs that experienced a more rewarding situation than expected (positive expectancy violation) during the second training session showed improved learning success after their afternoon sleep. These results possibly indicate an interactive effect of expectancy violation and sleep on enhancing learning.

Teaching Before, During, and After a Surgical Resuscitation

Teaching during a surgical resuscitation can be difficult due to the infrequency of these events. Furthermore, when these events do occur, the trainee can experience cognitive overload and an overwhelming amount of stress, thereby impairing the learning process. The emergent nature of these scenarios can make it difficult for the surgical educator to adequately teach. Repeated exposure through simulation, role play, and "war games" are great adjuncts to teaching and preparation before crisis. However, surgical educators can further enhance the knowledge of their trainees during these scenarios by using tactics such as talking out loud, targeted teaching, and debriefing.

A Multidimensional Evaluation of the Factors in the Animal Welfare Assessment Grid (AWAG) That Are Associated with, and Predictive of, Behaviour Disorders in Dogs

Behavioural disorders in dogs are common and have severe welfare consequences for dogs. This study aimed to assess the factors that are significant and predictive of behaviour problems in dogs using the animal welfare assessment grid (AWAG) to further understand what factors influence their welfare. 177 AWAG assessments were undertaken across 129 dogs that clinicians deemed to have a behavioural disorder. Wilcoxon rank-sum tests were used to assess the difference in scores between dogs with behaviour disorders and a cohort of healthy dogs (n = 117). This analysis showed that all physical factors besides body condition, all procedural factors besides procedure pain, and all psychological, and environmental factors were significantly different between healthy dogs and dogs with behaviour disorders. Spearman rank correlation coefficient (RS) revealed several significant strong positive correlations including the procedural impact on the dog's daily routine with aggression towards unfamiliar people and procedure pain, as well as other correlations between the dog's behaviour during assessment with the frequency at which they encounter fears and anxieties, clinical assessment and procedure pain, and reaction to stressors and social interactions. These findings highlight the interdependent nature of the various influences of welfare. Logistic regression analysis identified that aggression towards the caregiver, fears and anxieties frequency, and choice, control, and predictability were all significant predictors of behaviour disorders. The findings have important implications for veterinary, behaviour, and animal welfare professionals as any changes across these factors may indicate poor welfare linked to emotional disorders in dogs.

The effects of early-life and intergenerational stress on the brain

Stress experienced during ontogeny can have profound effects on the adult phenotype. However, stress can also be experienced intergenerationally, where an offspring's phenotype can be moulded by stress experienced by the parents. Although early-life and intergenerational stress can alter anatomy, physiology, and behaviour, nothing is known about how these stress contexts interact to affect the neural phenotype. Here, we examined how early-life and intergenerational stress affect the brain in eastern fence lizards (Sceloporus undulatus). Some lizard populations co-occur with predatory fire ants, and stress from fire ant attacks exerts intergenerational physiological and behavioural changes in lizards. However, it is unclear if intergenerational stress, or the interaction between intergenerational and early-life stress, modulates the brain. To test this, we captured gravid females from fire ant invaded and uninvaded populations, and subjected offspring to three early-life stress treatments: (1) fire ant attack, (2) corticosterone, or (3) a control. Corticosterone and fire ant attack decreased some aspects of the neural phenotype while population of origin and the interaction of early-life stress and population had no effects on the brain. These results suggest that early-life stressors may better predict adult brain variation than intergenerational stress in this species.

Sex-dependent differences in animal cognition

The differences in cognitive processes driven by biological sex are the issues that have gotten growing attention recently. Considering the increasing population suffering from various cognitive impairments and the development of therapeutic strategies, it is essential that we recognize the mechanisms responsible for discrepancies observed in male and female learning and memory functions. In this review, we discuss recent reports from preclinical studies on rodents regarding selected cognitive domains to explore the state of knowledge on sex-dependent differences and point to challenges encountered during such research. We focus on spatial, recognition, and emotional memory, as well as on executive functions, such as attention, cognitive flexibility, and working memory. This review will help to acknowledge sex-related differences in cognition and indicate some fields that lack sufficient data.

Acute Stress Modulates Social Approach and Social Maintenance in Adult Zebrafish

Stress alters social functioning in a complex manner. An important variable determining the final effects of stress is stressor intensity. However, the precise relationship between stressor intensity and social behavior is not well understood. Here, we investigate the effects of varying acute stressor intensity exposure on social behavior using adult zebrafish. We first establish a novel test using adult zebrafish that allows distinguishing fish's drive to approach a social cue and its ability to engage and maintain social interaction within the same behavioral paradigm. Next, we combined this test with a new method to deliver an acute stress stimulus of varying intensities. Our results show that both social approach and social maintenance are reduced in adult zebrafish on acute stress exposure in an intensity-dependent manner. Interestingly, lower stress intensity reduces social maintenance without affecting the social approach, while a higher stress level is required to alter social approach. These results provide evidence for a direct correlation between acute stressor intensity and social functioning and suggest that distinct steps in social behavior are modulated differentially by the acute stress level.

Effects of a True Prophylactic Treatment on Hippocampal and Amygdala Synaptic Plasticity and Gene Expression in a Rodent Chronic Stress Model of Social Defeat

Post-traumatic stress disorder (PTSD) is a complex stress-related disorder induced by exposure to traumatic stress that is characterized by symptoms of re-experiencing, avoidance, and hyper-arousal. While it is widely accepted that brain regions involved in emotional regulation and memory-e.g., the amygdala and hippocampus-are dysregulated in PTSD, the pathophysiology of the disorder is not well defined and therefore, pharmacological interventions are extremely limited. Because stress hormones norepinephrine and cortisol (corticosterone in rats) are heavily implicated in the disorder, we explored whether preemptively and systemically antagonizing β-adrenergic and glucocorticoid receptors with propranolol and mifepristone are sufficient to mitigate pathological changes in synaptic plasticity, gene expression, and anxiety induced by a modified social defeat (SD) stress protocol. Young adult, male Sprague Dawley rats were initially pre-screened for anxiety. The rats were then exposed to SD and chronic light stress to induce anxiety-like symptoms. Drug-treated rats were administered propranolol and mifepristone injections prior to and continuing throughout SD stress. Using competitive ELISAs on plasma, field electrophysiology at CA1 of the ventral hippocampus (VH) and the basolateral amygdala (BLA), quantitative RT-PCR, and behavior assays, we demonstrate that our SD stress increased anxiety-like behavior, elevated long-term potentiation (LTP) in the VH and BLA, and altered the expression of mineralocorticoid, glucocorticoid, and glutamate receptors. These measures largely reverted to control levels with the administration of propranolol and mifepristone. Our findings indicate that SD stress increases LTP in the VH and BLA and that prophylactic treatment with propranolol and mifepristone may have the potential in mitigating these and other stress-induced effects.

Neurocognitive effects of stress: a metaparadigm perspective

Stressful experiences, both physical and psychological, that are overwhelming (i.e., inescapable and unpredictable), can measurably affect subsequent neuronal properties and cognitive functioning of the hippocampus. At the cellular level, stress has been shown to alter hippocampal synaptic plasticity, spike and local field potential activity, dendritic morphology, neurogenesis, and neurodegeneration. At the behavioral level, stress has been found to impair learning and memory for declarative (or explicit) tasks that are based on cognition, such as verbal recall memory in humans and spatial memory in rodents, while facilitating those that are based on emotion, such as differential fear conditioning in humans and contextual fear conditioning in rodents. These vertically related alterations in the hippocampus, procedurally observed after subjects have undergone stress, are generally believed to be mediated by recurrently elevated circulating hypothalamic-pituitary-adrenal (HPA) axis effector hormones, glucocorticoids, directly acting on hippocampal neurons densely populated with corticosteroid receptors. The main purposes of this review are to (i) provide a synopsis of the neurocognitive effects of stress in a historical context that led to the contemporary HPA axis dogma of basic and translational stress research, (ii) critically reappraise the necessity and sufficiency of the glucocorticoid hypothesis of stress, and (iii) suggest an alternative metaparadigm approach to monitor and manipulate the progression of stress effects at the neural coding level. Real-time analyses can reveal neural activity markers of stress in the hippocampus that can be used to extrapolate neurocognitive effects across a range of stress paradigms (i.e., resolve scaling and dichotomous memory effects issues) and understand individual differences, thereby providing a novel neurophysiological scaffold for advancing future stress research.

Fish and chips: Using machine learning to estimate the effects of basal cortisol on fish foraging behavior

Foraging is an essential behavior for animal survival and requires both learning and decision-making skills. However, despite its relevance and ubiquity, there is still no effective mathematical framework to adequately estimate foraging performance that also takes interindividual variability into account. In this work, foraging performance is evaluated in the context of multi-armed bandit (MAB) problems by means of a biological model and a machine learning algorithm. Siamese fighting fish (Betta splendens) were used as a biological model and their ability to forage was assessed in a four-arm cross-maze over 21 trials. It was observed that fish performance varies according to their basal cortisol levels, i.e., a reduced average reward is associated with low and high levels of basal cortisol, while the optimal level maximizes foraging performance. In addition, we suggest the adoption of the epsilon-greedy algorithm to deal with the exploration-exploitation tradeoff and simulate foraging decisions. The algorithm provided results closely related to the biological model and allowed the normalized basal cortisol levels to be correlated with a corresponding tuning parameter. The obtained results indicate that machine learning, by helping to shed light on the intrinsic relationships between physiological parameters and animal behavior, can be a powerful tool for studying animal cognition and behavioral sciences.

Stressfulness of the design influences consistency of cognitive measures and their correlation with animal personality traits in wild mice (Mus musculus)

Individual variation in cognition is being increasingly recognized as an important evolutionary force but contradictory results so far hamper a general understanding of consistency and association with other behaviors. Partly, this might be caused by external factors imposed by the design. Stress, for example, is known to influence cognition, with mild stress improving learning abilities, while strong or chronic stress impairs them. Also, there might be intraspecific variation in how stressful a given situation is perceived. We investigated two personality traits (stress coping and voluntary exploration), spatial learning with two mazes, and problem-solving in low- and high-stress tests with a group of 30 female wild mice (Mus musculus domesticus). For each test, perceived stress was assessed by measuring body temperature change with infrared thermography, a new non-invasive method that measures skin temperature as a proxy of changes in the sympathetic system activity. While spatial learning and problem-solving were found to be repeatable traits in mice in earlier studies, none of the learning measures were significantly repeatable between the two stress conditions in our study, indicating that the stress level impacts learning. We found correlations between learning and personality traits; however, they differed between the two stress conditions and between the cognitive tasks, suggesting that different mechanisms underlie these processes. These findings could explain some of the contradictory findings in the literature and argue for very careful design of cognitive test setups to draw evolutionary implications.

Pathophysiological aspects of complex PTSD - a neurobiological account in comparison to classic posttraumatic stress disorder and borderline personality disorder

Despite a great diagnostic overlap, complex posttraumatic stress disorder (CPTSD) has been recognised by the ICD-11 as a new, discrete entity and recent empirical evidence points towards a distinction from simple posttraumatic stress disorder (PTSD) and borderline personality disorder (BPD). The development and maintenance of these disorders is sustained by neurobiological alterations and studies using functional magnetic resonance imaging (fMRI) may further contribute to a clear differentiation of CPTSD, PTSD and BPD. However, there are no existing fMRI studies directly comparing CPTSD, PTSD and BPD. In addition to a summarization of diagnostic differences and similarities, the current review aims to provide a qualitative comparison of neuroimaging findings on affective, attentional and memory processing in CPTSD, PTSD and BPD. Our narrative review alludes to an imbalance in limbic-frontal brain networks, which may be partially trans-diagnostically linked to the degree of trauma symptoms and their expression. Thus, CPTSD, PTSD and BPD may underlie a continuum where similar brain regions are involved but the direction of activation may constitute its distinct symptom expression. The neuronal alterations across these disorders may conceivably be better understood along a symptom-based continuum underlying CPTSD, PTSD and BPD. Further research is needed to amend for the heterogeneity in experimental paradigms and sample criteria.

HBK-15, a Multimodal Compound, Showed an Anxiolytic-Like Effect in Rats

Anxiety is a common mental disorder, and its prevalence has lately increased because of the COVID-19 pandemic. Unfortunately, the available anxiolytics are often ineffective, and most possess addictive potential. Thus, searching for novel compounds is essential. In our previous studies, we selected a multimodal compound, HBK-15, which showed a fast antidepressant-like effect in animal models of depression. HBK-15 demonstrated a high affinity for serotonin 5-HT_1A receptors and moderate for 5-HT₇, dopamine D₂, and α₁-adrenoceptors. Based on the receptor profile and preliminary studies, we aimed to investigate the anxiolytic potential of HBK-15 using the conditioned-response rat model of anxiety, i.e., the Vogel drinking test. We performed hot plate and free-drinking tests to exclude false positive results in the Vogel test. Using radioligand binding studies, we also investigated the affinity of the compound for the selected biological targets, which play a role in anxiety. Our experiments revealed that HBK-15 showed an anxiolytic-like effect in rats (5 mg/kg) without influencing the pain threshold or the amount of water consumed in the free-drinking test. Furthermore, the tested compound did not show a significant affinity for the selected biological targets, which suggests that its anxiolytic-like mechanism of action could be connected with the interaction with other receptors. This study indicates that multimodal compounds with a receptor profile similar to HBK-15 could be an attractive therapeutic option for patients with a generalized anxiety disorder. However, more studies are required to determine the exact mechanism of action of HBK-15 and its safety profile.

Sexual dimorphism in spatial learning and brain metabolism after exposure to a western diet and early life stress in rats

Prolonged daily intake of Western-type diet rich in saturated fats and sugars, and exposure to early life stress have been independently linked to impaired neurodevelopment and behaviour in animal models. However, sex-specific effects of both environmental factors combined on spatial learning and memory, behavioural flexibility, and brain oxidative capacity have still not been addressed. The current study aimed to evaluate the impact of maternal and postnatal exposure to a high-fat and high-sugar diet (HFS), and exposure to early life stress by maternal separation in adult male and female Wistar rats. For this purpose, spatial learning and memory and behavioural flexibility were evaluated in the Morris water maze, and regional brain oxidative capacity and oxidative stress levels were measured in the hippocampus and medial prefrontal cortex. Spatial memory, regional brain oxidative metabolism, and levels of oxidative stress differed between females and males, suggesting sexual dimorphism in the effects of a HFS diet and early life stress. Males fed the HFS diet performed better than all other experimental groups independently of early life stress exposure. However, behavioural flexibility evaluated in the spatial reversal leaning task was impaired in males fed the HFS diet. In addition, exposure to maternal separation or the HFS diet increased the metabolic capacity of the prefrontal cortex and dorsal hippocampus in males and females. Levels of oxidative stress measured in the latter brain regions were also increased in groups fed the HFS diet, but maternal separation seemed to dampen regional brain oxidative stress levels. Therefore, these results suggest a compensatory effect resulting from the interaction between prolonged exposure to a HFS diet and early life stress.

Neurobiological insights into twice-exceptionality: Circuits, cells, and molecules

Twice-exceptional learners face a unique set of challenges arising from the intersection of extraordinary talent and disability. Neurobiology research has the capacity to complement pedagogical research and provide support for twice-exceptional learners. Very few studies have attempted to specifically address the neurobiological underpinnings of twice-exceptionality. However, neurobiologists have built a broad base of knowledge in nervous system function spanning from the level of neural circuits to the molecular basis of behavior. It is known that distinct neural circuits mediate different neural functions, which suggests that 2e learning may result from enhancement in one circuit and disruption in another. Neural circuits are known to adapt and change in response to experience, a cellular process known as neuroplasticity. Plasticity is controlled by a bidirectional connection between the synapse, where neural signals are received, and the nucleus, where regulated gene expression can return to alter synaptic function. Complex molecular mechanisms compose this connection in distinct neural circuits, and genetic alterations in these mechanisms are associated with both memory enhancements and psychiatric disorder. Understanding the consequences of these changes at the molecular, cellular, and circuit levels will provide critical insights into the neurobiological bases of twice-exceptionality.

Examining the impact of social stressor stimuli in eliciting physiological reactivity in children and adolescents with autism spectrum disorder: a systematic review and meta-analysis protocol

INTRODUCTION

Stress is not experienced the same by everyone. Some individuals, such as individuals with autism spectrum disorder (ASD), are at risk of heightened sensitivity to stress responses. ASD is a neurodevelopmental disorder commonly characterised by deficits in social communication and social interaction. Among different stressor stimuli, social stressors are particularly worth our attention due to the social and communication challenges inherent in ASD. This study aims to systematically evaluate different social stressor stimuli in eliciting physiological reactivity in ASD, focusing on the children and adolescent population.

METHODS AND ANALYSIS

We designed a study protocol for this study and submitted it to PROSPERO for systematic review registration. Any studies with children and adolescents with ASD between the ages of 0 and 18 in clinical and community settings will be included. All types of social stressor interventions will be included. The outcome of interest will include studies with physiological activity of the participants being measured, for example, measures related to autonomic functioning, electrodermal functioning and cortisol level. The primary literature sources will be across four electronic databases: MEDLINE, Embase, PsycInfo and CINAHL in August 2021. The second source of literature will be across grey literature, including ProQuest Dissertations & Theses Global and across clinical trial registries in August 2021. Hand searching of references will be performed on the reference lists of all included studies. Two volunteers pursuing postgraduate-level studies will independently search and screen potential studies for eligibility. Finally, all references considered by hand searching will be reviewed by two researchers. The methodological quality of the research will be assessed by adopting the quality assessment used by a previous study. The assessment consists of four primary categories: descriptive validity, internal validity, external validity and statistical conclusion validity.

ETHICS AND DISSEMINATION

No ethical approval is required for this study. Results will be disseminated through conferences and publications in relevant peer-reviewed journals.

PROSPERO REGISTRATION NUMBER

CRD42021244039.

Acute effects of physical activity patterns on plasma cortisol and brain-derived neurotrophic factor in relation to corticospinal excitability

Brain-derived neurotrophic factor (BDNF) and cortisol are both capable of modulating synaptic plasticity, but it is unknown how physical activity-induced changes in their plasma levels relate to corticospinal plasticity in humans. Sixteen inactive middle-aged men and women participated in three separate interventions consisting of 3hours prolonged sitting (SIT); 3hours sitting interrupted every 30minutes with frequent short physical activity breaks (FPA); and 2.5hours prolonged sitting followed by 25minutes of moderate intensity exercise (EXE). These 3hour sessions were each followed by a 30min period of paired associative stimulation over the primary motor cortex (PAS). Blood samples were taken and corticospinal excitability measured at baseline, pre PAS, 5min and 30min post PAS. Here we report levels of plasma BDNF and cortisol over three activity conditions and relate these levels to previously published changes in corticospinal excitability of a non-activated thumb muscle. There was no interaction between time and condition in BDNF, but cortisol levels were significantly higher after EXE compared to after SIT and FPA. Higher cortisol levels at pre PAS predicted larger increases in corticospinal excitability from baseline to all subsequent time points in the FPA condition only, while levels of BDNF at pre PAS did not predict such changes in any of the conditions. Neither BDNF nor cortisol modified changes from pre PAS to the subsequent time points, suggesting that the increased corticospinal excitability was not mediated though an augmented effect of the PAS protocol. The relationship between cortisol and plasticity has been suggested to be U-shaped. This is possibly why the moderately high levels of cortisol seen in the FPA condition were positively associated with changes AURC, while the higher cortisol levels seen after EXE were not. A better understanding of the mechanisms for how feasible physical activity breaks affect neuroplasticity can inform the theoretical framework for how work environments and schedules should be designed. DATA AVAILABILITY: Data are available from the corresponding author upon reasonable request.

Decision neuroscience and neuroeconomics: Recent progress and ongoing challenges

In the past decade, decision neuroscience and neuroeconomics have developed many new insights in the study of decision making. This review provides an overarching update on how the field has advanced in this time period. Although our initial review a decade ago outlined several theoretical, conceptual, methodological, empirical, and practical challenges, there has only been limited progress in resolving these challenges. We summarize significant trends in decision neuroscience through the lens of the challenges outlined for the field and review examples where the field has had significant, direct, and applicable impacts across economics and psychology. First, we review progress on topics including reward learning, explore-exploit decisions, risk and ambiguity, intertemporal choice, and valuation. Next, we assess the impacts of emotion, social rewards, and social context on decision making. Then, we follow up with how individual differences impact choices and new exciting developments in the prediction and neuroforecasting of future decisions. Finally, we consider how trends in decision-neuroscience research reflect progress toward resolving past challenges, discuss new and exciting applications of recent research, and identify new challenges for the field. This article is categorized under: Psychology > Reasoning and Decision Making Psychology > Emotion and Motivation.

Sex Differences in the Spatial Behavior Functions of Adult-Born Neurons in Rats

Adult neurogenesis modifies hippocampal circuits and behavior, but removing newborn neurons does not consistently alter spatial processing, a core function of the hippocampus. Additionally, little is known about sex differences in neurogenesis since few studies have compared males and females. Since adult-born neurons regulate the stress response, we hypothesized that spatial functions may be more prominent under aversive conditions and may differ between males and females given sex differences in stress responding. We therefore trained intact and neurogenesis-deficient rats in the spatial water maze at temperatures that vary in their degree of aversiveness. In the standard water maze, ablating neurogenesis did not alter spatial learning in either sex. However, in cold water, ablating neurogenesis had divergent sex-dependent effects: relative to intact rats, male neurogenesis-deficient rats were slower to escape the maze and female neurogenesis-deficient rats were faster. Neurogenesis promoted temperature-related changes in search strategy in females, but it promoted search strategy stability in males. Females displayed greater recruitment (Fos expression) of the dorsal hippocampus than males, particularly in cold water. However, blocking neurogenesis did not alter Fos expression in either sex. Finally, morphologic analyses revealed greater experience-dependent plasticity in males. Adult-born neurons in males and females had similar morphology at baseline but training increased spine density and reduced presynaptic terminal size, specifically in males. Collectively, these findings indicate that adult-born neurons contribute to spatial learning in stressful conditions and they provide new evidence for sex differences in their behavioral functions.

The roles of intensity, exposure duration, and modulation on the biological effects of radiofrequency radiation and exposure guidelines

In this paper, we review the literature on three important exposure metrics that are inadequately represented in most major radiofrequency radiation (RFR) exposure guidelines today: intensity, exposure duration, and signal modulation. Exposure intensity produces unpredictable effects as demonstrated by nonlinear effects. This is most likely caused by the biological system's ability to adjust and compensate but could lead to eventual biomic breakdown after prolonged exposure. A review of 112 low-intensity studies reveals that biological effects of RFR could occur at a median specific absorption rate of 0.0165 W/kg. Intensity and exposure duration interact since the dose of energy absorbed is the product of intensity and time. The result is that RFR behaves like a biological "stressor" capable of affecting numerous living systems. In addition to intensity and duration, man-made RFR is generally modulated to allow information to be encrypted. The effects of modulation on biological functions are not well understood. Four types of modulation outcomes are discussed. In addition, it is invalid to make direct comparisons between thermal energy and radiofrequency electromagnetic energy. Research data indicate that electromagnetic energy is more biologically potent in causing effects than thermal changes. The two likely functionthrough different mechanisms. As such, any current RFR exposure guidelines based on acute continuous-wave exposure are inadequate for health protection.

Opposite effects of stress on effortful motivation in high and low anxiety are mediated by CRHR1 in the VTA

Individuals frequently differ in their behavioral and cognitive responses to stress. However, whether motivation is differently affected by acute stress in different individuals remains to be established. By exploiting natural variation in trait anxiety in outbred Wistar rats, we show that acute stress facilitates effort-related motivation in low anxious animals, while dampening effort in high anxious ones. This model allowed us to address the mechanisms underlying acute stress-induced differences in motivated behavior. We show that CRHR1 expression levels in dopamine neurons of the ventral tegmental area (VTA)-a neuronal type implicated in the regulation of motivation-depend on animals' anxiety, and these differences in CRHR1 expression levels explain the divergent effects of stress on both effortful behavior and the functioning of mesolimbic DA neurons. These findings highlight CRHR1 in VTA DA neurons-whose levels vary with individuals' anxiety-as a switching mechanism determining whether acute stress facilitates or dampens motivation.

A Mixed-Methods Realist Analysis of an Interdisciplinary Simulation Intervention for Psychiatry Residents

OBJECTIVES

Simulation research in postgraduate psychiatry remains limited, with minimal studies on interdisciplinary involvement and mechanisms of change. To address these gaps, the authors implemented a mixed-methods realist analysis of an interdisciplinary simulation intervention administered to psychiatry residents.

METHODS

The University of Calgary implemented a simulation intervention for psychiatry residents. Eight junior residents participated in or observed 4 scenarios and eighteen senior residents participated in or observed 8 scenarios. Scenarios lasted 15 minutes with a pre-simulation orientation and post-scenario debrief. Most scenarios involved interdisciplinary staff. Scenarios included agitated and suicidal patients; treatment-related emergencies; and challenging conversations. All residents completed pre- and post-simulation surveys reporting confidence levels. Changes in confidence were analyzed using paired t tests and differences between junior and senior residents' confidence using ANOVA. Eleven residents participated in 2 focus groups. Transcripts were analyzed using a constant comparative model to identify contexts, mechanisms, outcomes, and the relationship between these realist categories. Key themes were extracted using generic theme analysis.

RESULTS

Aggregated survey data demonstrated statistically significant improvements in self-reported confidence for 7 of 8 proposed scenarios, with variations in confidence outcomes between junior and senior residents. Four themes emerged: (1) How Simulations Facilitate Learning, (2) The Role of Pre-simulation Instructions, (3) Factors Facilitating Confidence, (4) Positive Effects of Interdisciplinary Involvement.

CONCLUSIONS

This study identifies possible mechanisms for residents' self-reported improvements in learning and confidence, which may help programs tailor interventions. Furthermore, this study suggests there may be benefits to interdisciplinary simulations, with self-reported outcomes of improved collaboration and safety planning.

Cognitive impairment following experimental febrile seizures is determined by sex and seizure duration

BACKGROUND

Febrile seizures are the most common type of seizures in children. While in most children the outcome is favorable, children with febrile status epilepticus may exhibit modest cognitive impairment. Whether children with other forms of complex febrile seizure, such as repetitive febrile seizures within the same illness are at risk of cognitive deficits is not known. In this study, we used a well-established model of experimental febrile seizures in rat pups to compare the effects of febrile status epilepticus and recurrent febrile seizures on subsequent spatial cognition and anxiety.

METHODS

Male and female rat pups were subjected to hyperthermic seizures at postnatal day 10 and were divided into groups of rats with continuous seizures for ≥40 min or recurrent febrile seizures. They were then tested as adults in the active avoidance and spatial accuracy tests to assess spatial learning and memory and the elevated plus maze to measure anxiety.

RESULTS

Febrile status epilepticus rats demonstrated impaired spatial cognition in active avoidance and spatial accuracy and exhibited reduced anxiety-like behavior in the elevated plus maze. Rats with recurrent febrile seizures did not differ significantly from the controls on any measures. There were also significant sex-related differences with females with FSE performing far better than males with FSE in active avoidance but demonstrating a navigational learning impairment relative to CTL females in spatial accuracy. However, once learned, females with FSE performed the spatial accuracy task as well as CTL females.

CONCLUSION

There is a duration-dependent effect of febrile seizures on subsequent cognitive and behavioral outcomes. Febrile status epilepticus resulted in spatial cognitive deficits and reduced anxiety-related behaviors whereas rats with recurrent febrile seizures did not differ from controls. Sex had a remarkable effect on spatial cognitive outcome where males with FSE fared worse than females with FSE. The results demonstrate that sex should be considered as a biological variable in studies evaluating the effects of seizures on the developing brain.

Exploring the relationship between emotion and cognitive load types during patient handovers

Cognitive Load Theory has emerged as an important approach to improving instruction in the health professions workplace, including patient handovers. At the same time, there is growing recognition that emotion influences learning through numerous cognitive processes including motivation, attention, working memory, and long-term memory. This study explores how emotion influences the cognitive load experienced by trainees performing patient handovers. From January to March 2019, 693 (38.7%) of 1807 residents and fellows from a 24-hospital health system in New York city completed a survey after performing a handover. Participants rated their emotional state and cognitive load. The survey included questions about features of the learner, task, and instructional environment. The authors used factor analysis to identify the core dimensions of emotion. Regression analyses explored the relationship between the emotion factors and cognitive load types. Two emotion dimensions were identified representing invigoration and tranquility. In regression analyses, higher levels of invigoration, tranquility, and their interaction were independently associated with lower intrinsic load and extraneous load. The interaction of invigoration and tranquility predicted lower germane load. The addition of the emotion variables to multivariate models including other predictors of cognitive load types significantly increased the amount of variance explained. The study provides a model for measuring emotions in workplace learning. Because emotion appears to have a significant influence on cognitive load types, instructional designers should consider strategies that help trainees regulate emotion in order to reduce cognitive load and improve learning and performance.

Different underlying mechanisms for high and low arousal in probabilistic learning in humans

Humans are uniquely capable of adapting to highly changing environments by updating relevant information and adjusting ongoing behaviour accordingly. Here we show how this ability -termed cognitive flexibility- is differentially modulated by high and low arousal fluctuations. We implemented a probabilistic reversal learning paradigm in healthy participants as they transitioned towards sleep or physical extenuation. The results revealed, in line with our pre-registered hypotheses, that low arousal leads to diminished behavioural performance through increased decision volatility, while performance decline under high arousal was attributed to increased perseverative behaviour. These findings provide evidence for distinct patterns of maladaptive decision-making on each side of the arousal inverted u-shaped curve, differentially affecting participants' ability to generate stable evidence-based strategies, and introduces wake-sleep and physical exercise transitions as complementary experimental models for investigating neural and cognitive dynamics.

Early-life stress does not alter spatial memory performance, hippocampal neurogenesis, neuroinflammation, or telomere length in 20-month-old male mice

Early-life stress (ES) increases the risk for psychopathology and cognitive decline later in life. Because the neurobiological substrates affected by ES (i.e., cognition, neuroplasticity, and neuroinflammation) are also altered in aging, we set out to investigate if and how ES in the first week of life affects these domains at an advanced age, and how ES modulates the aging trajectory per se. We subjected C57BL/6j mice to an established ES mouse model from postnatal days 2–9. Mice underwent behavioral testing at 19 months of age and were sacrificed at 20 months to investigate their physiology, hippocampal neuroplasticity, neuroinflammation, and telomere length. ES mice, as a group, did not perform differently from controls in the open field or Morris water maze (MWM). Hippocampal neurogenesis and synaptic marker gene expression were not different in ES mice at this age. While we find aging-associated alterations to neuroinflammatory gene expression and telomere length, these were unaffected by ES. When integrating the current data with those from our previously reported 4- and 10-month-old cohorts, we conclude that ES leads to a ‘premature’ shift in the aging trajectory, consisting of early changes that do not further worsen at the advanced age of 20 months. This could be explained e.g. by a ‘floor’ effect in ES-induced impairments, and/or age-induced impairments in control mice. Future studies should help understand how exactly ES affects the overall aging trajectory.

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Early-life stress (ES) exposure does not worsen water maze learning in aged male mice.

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ES does not affect brain plasticity markers at 20 months of age.

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Hippocampal telomere length is reduced by aging but unaffected by ES.

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ES leads to a premature aging trajectory that does not worsen with aging.

Neural systems and the emotion-memory link

The present brief review for this Special Issue summarizes some of the original research on the emotional modulation of memory. The review begins by highlighting the pioneering research from James L. McGaugh and colleagues demonstrating modulatory effects of post-training drug administration on memory consolidation, in particular the stress hormone epinephrine. The subsequent discovery of a critical role for the basolateral amygdala in emotional modulation of memory is described. Within the context of a multiple systems approach to memory focusing on selective roles for the hippocampus and dorsolateral striatum in cognitive and habit memory, the original studies indicating that robust emotional arousal can bias animals and humans toward the predominant use of habit memory are reviewed. This effect of emotional arousal on the relative use of multiple memory systems depends on a modulatory role of the basolateral amygdala. Finally, we briefly consider how an emotion-induced enhancement of dorsolateral striatal-dependent memory may be relevant to understanding maladaptive habitual behaviors in certain human psychopathologies.

Differential Impact of Acute and Chronic Stress on CA1 Spatial Coding and Gamma Oscillations

Chronic and acute stress differentially affect behavior as well as the structural integrity of the hippocampus, a key brain region involved in cognition and memory. However, it remains unclear if and how the facilitatory effects of acute stress on hippocampal information coding are disrupted as the stress becomes chronic. To examine this, we compared the impact of acute and chronic stress on neural activity in the CA1 subregion of male mice subjected to a chronic immobilization stress (CIS) paradigm. We observed that following first exposure to stress (acute stress), the spatial information encoded in the hippocampus sharpened, and the neurons became increasingly tuned to the underlying theta oscillations in the local field potential (LFP). However, following repeated exposure to the same stress (chronic stress), spatial tuning was poorer and the power of both the slow-gamma (30–50 Hz) and fast-gamma (55–90 Hz) oscillations, which correlate with excitatory inputs into the region, decreased. These results support the idea that acute and chronic stress differentially affect neural computations carried out by hippocampal circuits and suggest that acute stress may improve cognitive processing.

Title: "Labels Matter: Is it stress or is it Trauma?"

In neuroscience, the term 'Stress' has a negative connotation because of its potential to trigger or exacerbate psychopathologies. Yet in the face of exposure to stress, the more common reaction to stress is resilience, indicating that resilience is the rule and stress-related pathology the exception. This is critical because neural mechanisms associated with stress-related psychopathology are expected to differ significantly from those associated with resilience.Research labels and terminology affect research directions, conclusions drawn from the results, and the way we think about a topic, while choice of labels is often influenced by biases and hidden assumptions. It is therefore important to adopt a terminology that differentiates between stress conditions, leading to different outcomes.Here, we propose to conceptually associate the term 'stress'/'stressful experience' with 'stress resilience', while restricting the use of the term 'trauma' only in reference to exposures that lead to pathology. We acknowledge that there are as yet no ideal ways for addressing the murkiness of the border between stressful and traumatic experiences. Yet ignoring these differences hampers our ability to elucidate the mechanisms of trauma-related pathologies on the one hand, and of stress resilience on the other. Accordingly, we discuss how to translate such conceptual terminology into research practice.

A randomized experimental study to test the effects of discussing uncertainty during cancer genetic counseling: different strategies, different outcomes?

Uncertainty is increasingly discussed during genetic counseling due to innovative techniques, e.g., multigene panel testing. Discussions about uncertainty may impact counselees variably, depending on counselors' communication styles. Ideally, the discussion of uncertainty enables counselees to cope with uncertainty and make well-informed decisions about testing. We examined the impact of how counselors convey uncertainty and address counselees' uncertainty, and explored the role of individual characteristics. Therefore, a randomized controlled experiment using videos was conducted. Former counselees (N = 224) viewed one video depicting a genetic consultation about multigene panel testing. The extent of counselors' communication of uncertainty (comprehensive vs. the essence) and their response to counselees' uncertainty expressions (providing information vs. providing space for emotions vs. normalizing and counterbalancing uncertainty) were systematically manipulated. Individual characteristics, e.g., uncertainty tolerance, were assessed, as well as outcome variables (primary outcomes: feelings of uncertainty and information recall). No effects were found on primary outcomes. Participants were most satisfied when the essence was communicated, combined with providing information or providing space responses (p = 0.002). Comprehensive information resulted in less perceived steering toward testing (p = 0.005). Participants with lower uncertainty tolerance or higher trait anxiety were less confident about their understanding when receiving comprehensive information (p = 0.025). Participants seeking information experienced less uncertainty (p = 0.003), and trusted their counselor more (p = 0.028), when the counselor used information providing responses. In sum, the impact of discussing uncertainty primarily depends on individual characteristics. Practical guidelines should address how to tailor the discussion of uncertainty.

Differential Susceptibility to the Impact of the COVID-19 Pandemic on Working Memory, Empathy, and Perceived Stress: The Role of Cortisol and Resilience

There are important individual differences in adaptation and reactivity to stressful challenges. Being subjected to strict social confinement is a distressful psychological experience leading to reduced emotional well-being, but it is not known how it can affect the cognitive and empathic tendencies of different individuals. Cortisol, a key glucocorticoid in humans, is a strong modulator of brain function, behavior, and cognition, and the diurnal cortisol rhythm has been postulated to interact with environmental stressors to predict stress adaptation. The present study investigates in 45 young adults (21.09 years old, SD = 6.42) whether pre-pandemic diurnal cortisol indices, overall diurnal cortisol secretion (AUCg) and cortisol awakening response (CAR) can predict individuals' differential susceptibility to the impact of strict social confinement during the Coronavirus Disease 2019 (COVID-19) pandemic on working memory, empathy, and perceived stress. We observed that, following long-term home confinement, there was an increase in subjects' perceived stress and cognitive empathy scores, as well as an improvement in visuospatial working memory. Moreover, during confinement, resilient coping moderated the relationship between perceived stress scores and pre-pandemic AUCg and CAR. In addition, in mediation models, we observed a direct effect of AUCg and an indirect effect of both CAR and AUCg, on change in perceived self-efficacy. These effects were parallelly mediated by the increase in working memory span and cognitive empathy. In summary, our findings reveal the role of the diurnal pattern of cortisol in predicting the emotional impact of the COVID-19 pandemic, highlighting a potential biomarker for the identification of at-risk groups following public health crises.

Amphetamine Modulation of Long-Term Object Recognition Memory in Rats: Influence of Stress

Amphetamine is a potent psychostimulant that increases brain monoamine levels. Extensive evidence demonstrated that norepinephrine is crucially involved in the regulation of memory consolidation for stressful experiences. Here, we investigated amphetamine effects on the consolidation of long-term recognition memory in rats exposed to different intensities of forced swim stress immediately after training. Furthermore, we evaluated whether such effects are dependent on the activation of the peripheral adrenergic system. To this aim, male adult Sprague Dawley rats were subjected to an object recognition task and intraperitoneally administered soon after training with amphetamine (0.5 or 1 mg/kg), or its corresponding vehicle. Rats were thereafter exposed to a mild (1 min, 25 ± 1°C) or strong (5 min, 19 ± 1°C) forced swim stress procedure. Recognition memory retention was assessed 24-h after training. Our findings showed that amphetamine enhances the consolidation of memory in rats subjected to mild stress condition, while it impairs long-term memory performance in rats exposed to strong stress. These dichotomic effects is dependent on stress-induced activation of the peripheral adrenergic response.

Heart Rate Variability-Measured Stress and Academic Achievement in Medical Students

OBJECTIVES

Stress can affect learning and memory in students. Previous studies on stress in students were conducted mainly through surveys. We investigated how heart rate variability (HRV)-measured stress is related to academic achievement in medical students during clerkship.

SUBJECTS AND METHODS

A cross-sectional study was conducted. HRV measurements were performed in 97 third-year medical students during their family medicine clerkship course. Data on written and skilled examination scores of the end of the school year were also collected. We assessed the association between HRV-measured stress and written/skilled examination scores.

RESULTS

Written examination scores showed a positive correlation with standard deviation of the normal-to-normal intervals (SDNNs) (r = 0.245, p = -0.016), sympathetic nervous system/parasympathetic nervous system (SNS/PNS) balance (r = 0.218, p = 0.033), and stress index (r = 0.381, p = 0.004). Students with an unhealthy SDNN, a dominant SNS, and a high stress index had higher scores in written examinations than students with a healthy SDNN, a balanced SNS/PNS, and a normal stress index, respectively (p = 0.004, 0.018, and 0.012, respectively). Moreover, skilled examination scores were negatively correlated with BMI (r = -0.249, p = 0.014) and were higher in female students (r = 0.240, p = 0.018). Students with an abnormal autonomic balance diagram (ABD) had a higher score than students with a normal ABD (p = 0.03).

CONCLUSIONS

This study shows that medical students with higher stress measured by HRV have higher academic achievement, especially in written examinations. Further studies are needed to confirm the results of this study and to assess the long-term effects of HRV-measured stress on medical students.

PAI-1 protein is a key molecular effector in the transition from normal to PTSD-like fear memory

Moderate stress increases memory and facilitates adaptation. In contrast, intense stress can induce pathological memories as observed in post-traumatic stress disorders (PTSD). A shift in the balance between the expression of tPA and PAI-1 proteins is responsible for this transition. In conditions of moderate stress, glucocorticoid hormones increase the expression of the tPA protein in the hippocampal brain region which by triggering the Erk1/2^MAPK signaling cascade strengthens memory. When stress is particularly intense, very high levels of glucocorticoid hormones then increase the production of PAI-1 protein, which by blocking the activity of tPA induces PTSD-like memories. PAI-1 levels after trauma could be a predictive biomarker of the subsequent appearance of PTSD and pharmacological inhibition of PAI-1 activity a new therapeutic approach to this debilitating condition.

Brain activity during a post-stress working memory task differs between the hormone-present and hormone-absent phase of hormonal contraception

Taking hormonal contraceptives (HCs) affects the magnitude of the hormonal stress response and cognition. HCs are usually administered in a monthly cycle with both synthetic-hormone-containing and synthetic-hormone-absent phases. The synthetic hormones contained in HCs affect a wide range of neurophysiological systems, suggesting that effects of the medication might only be observed during the synthetic-hormone-containing phase of the HC cycle. To test this, women were seen twice, once during the hormone-present phase and once during the hormone-absent phase of the HC cycle. In each session, women performed an n-back working memory task to assess pre-stress performance outside of the magnetic resonance imaging scanner, were then exposed to cold pressor stress, and again completed the n-back task during functional magnetic resonance imaging. The free cortisol response to stress remained the same across the HC cycle. Women also performed comparably on the n-back task after stress exposure across the two phases. However, despite these similarities, women displayed greater disengagement of default mode network as task demands increased during the hormone-present phase only, a pattern more in line with working memory-related brain activation under non-stressful conditions reported in other studies. The results suggest that the synthetic hormones contained in HCs may mitigate stress-related disruptions of typical brain activation patterns during the hormone-present phase of the HC cycle, despite exhibiting comparable cortisol responses across the HC cycle. Additional research is required to determine the mechanisms contributing to, and the extent of, such mitigating effects.

Programming effects of peripubertal stress on spatial learning

Exposure to adversity during early life can have profound influences on brain function and behavior later in life. The peripubertal period is emerging as an important time-window of susceptibility to stress, with substantial evidence documenting long-term consequences in the emotional and social domains. However, little is known about how stress during this period impacts subsequent cognitive functioning. Here, we assessed potential long-term effects of peripubertal stress on spatial learning and memory using the water maze task. In addition, we interrogated whether individual differences in stress-induced behavioral and endocrine changes are related to the degree of adaptation of the corticosterone response to repeated stressor exposure during the peripubertal period. We found that, when tested at adulthood, peripubertally stressed animals displayed a slower learning rate. Strikingly, the level of spatial orientation in the water maze completed on the last training day was predicted by the degree of adaptation of the recovery -and not the peak-of the corticosterone response to stressor exposure (i.e., plasma levels at 60 min post-stressor) across the peripubertal stress period. In addition, peripubertal stress led to changes in emotional and glucocorticoid reactivity to novelty exposure, as well as in the expression levels of the plasticity molecule PSA-NCAM in the hippocampus. Importantly, by assessing the same endpoints in another peripubertally stressed cohort tested during adolescence, we show that the observed effects at adulthood are the result of a delayed programming manifested at adulthood and not protracted effects of stress. Altogether, our results support the view that the degree of stress-induced adaptation of the hypothalamus-pituitary-adrenal axis responsiveness at the important transitional period of puberty relates to the long-term programming of cognition, behavior and endocrine reactivity.

Hypertension and Age-Related Cognitive Impairment: Common Risk Factors and a Role for Precision Aging

Purpose of Review

Precision Aging® is a novel concept that we have recently employed to describe how the model of precision medicine can be used to understand and define the multivariate risks that drive age-related cognitive impairment (ARCI). Hypertension and cardiovascular disease are key risk factors for both brain function and cognitive aging. In this review, we will discuss the common mechanisms underlying the risk factors for both hypertension and ARCI and how the convergence of these mechanisms may be amplified in an individual to drive changes in brain health and accelerate cognitive decline.

Recent Findings

Currently, our cognitive health span does not match our life span. Age-related cognitive impairment and preventing and treating ARCI will require an in-depth understanding of the interrelated risk factors, including individual genetic profiles, that affect brain health and brain aging. Hypertension and cardiovascular disease are important risk factors for ARCI. And, many of the risk factors for developing hypertension, such as diabetes, smoking, stress, viral infection, and age, are shared with the development of ARCI. We must first understand the mechanisms common to the converging risk factors in hypertension and ARCI and then design person-specific therapies to optimize individual brain health.

Summary

The understanding of the convergence of shared risk factors between hypertension and ARCI is required to develop individualized interventions to optimize brain health across the life span. We will conclude with a discussion of possible steps that may be taken to decrease ARCI and optimize an individual’s cognitive life span.

Heat stress induced oxidative damage and perturbation in BDNF/ERK1/2/CREB axis in hippocampus impairs spatial memory

Heat exposure is an environmental stress that causes diverse heat related pathophysiological changes under extreme conditions. The brain including hippocampal region which is associated with learning and memory is significantly affected by heat stress resulting in memory impairment. However, the effect of heat on the spatial memory remains unclear. The present study aimed to explore the effect of heat stress on hippocampus and spatial memory in rats. Rat model of acute heat stress was used which was divided into two groups, viz. moderate heat stress (MHS) and severe heat stress (SHS). Redox parameters evaluation revealed that MHS and SHS exposure markedly increase the production of malondialdehyde (MDA), oxidised glutathione (GSSG), reactive oxidative species (ROS), protein oxidation level and decrease the reduced glutathione (GSH) levels in the hippocampal tissue. Furthermore, Cresyl Violet (CV) staining of hippocampal region showed higher pyknosis in rats exposed to SHS. Pronounced increase of caspase3 expression and Fluoro Jade-C (FJ-C) positive cells were observed in SHS resulting in neuronal injury and apoptosis in CA3 region of hippocampus culminating in spatial memory deficit. Our data also suggest that heat stress induces phospho Extracellular signal-regulated kinases (pERK)1/2 activation induced by Brain-derived neurotrophic factor (BDNF) leading to further activation of phospho cAMP-response element binding protein (pCREB) under MHS. However, during SHS, BDNF and pCREB expression were completely dysregulated and not sufficient to rescue cognitive decline in rats. In conclusion, SHS induces pathological alterations that include oxidative damage and apoptosis of hippocampal neurons, disturbing BDNF/ERK1/2/CREB axis that may affect spatial memory.

Differential impact of stress and environmental enrichment on corticolimbic circuits

Stress exposure can produce profound changes in physiology and behavior that can impair health and well-being. Of note, stress exposure is linked to anxiety disorders and depression in humans. The widespread impact of these disorders warrants investigation into treatments to mitigate the harmful effects of stress. Pharmacological treatments fail to help many with these disorders, so recent work has focused on non-pharmacological alternatives. One of the most promising of these alternatives is environmental enrichment (EE). In rodents, EE includes social, physical, and cognitive stimulation for the animal, in the form of larger cages, running wheels, and toys. EE successfully reduces the maladaptive effects of various stressors, both as treatment and prophylaxis. While we know that EE can have beneficial effects under stress conditions, the morphological and molecular mechanisms underlying these behavioral effects are still not well understood. EE is known to alter neurogenesis, dendrite development, and expression of neurotrophic growth factors, effects that vary by type of enrichment, age, and sex. To add to this complexity, EE has differential effects in different brain regions. Understanding how EE exerts its protective effects on morphological and molecular levels could hold the key to developing more targeted pharmacological treatments. In this review, we summarize the literature on the morphological and molecular consequences of EE and stress in key emotional regulatory pathways in the brain, the hippocampus, prefrontal cortex, and amygdala. The similarities and differences among these regions provide some insight into stress-EE interaction that may be exploited in future efforts toward prevention of, and intervention in, stress-related diseases.

Effects of chronic stress on reinstatement of palatable food seeking: Sex differences and relationship to trait anxiety

Previous research in our lab has established a causal role for chronic stress exposure in subsequent increases in relapse-like behaviors in male rats with a history of palatable food self-administration. Given that many of the neurobehavioral consequences of stress are sex dependent, we aimed to determine whether sex differences exist with regard to the effects of chronic stress on relapse. Additionally, because high trait anxiety confers vulnerability to stress-related disorders, we examined whether individual differences in trait anxiety were related to differences in relapse-like behavior after chronic stress exposure. Following elevated plus maze testing for classification into high- or low-anxiety phenotypes, male and female rats responded for highly palatable food pellets. During subsequent extinction training, stress was manipulated (0 or 90 min restraint/day for 7 days). Rats were then tested for cue- and pellet priming-induced reinstatement of palatable food seeking. Results showed that female rats displayed higher levels of responding during cue-induced reinstatement tests compared to males, and that a history of chronic stress caused an attenuation of cue-induced reinstatement in female, but not male, rats. Regarding pellet priming-induced reinstatement, there was a three-way interaction such that neither stress history nor anxiety phenotype was related to reinstatement in females, but a history of stress in males caused increased and decreased responding in low- and high-anxiety rats, respectively. These results suggest that biological sex and trait anxiety level may help to explain differences in vulnerability to relapse among individuals exposed to chronic stress. Such information may be useful in designing more personalized and effective treatments for obesity and eating disorders.

Stress hypothesis overload: 131 hypotheses exploring the role of stress in tradeoffs, transitions, and health

Stress is ubiquitous and thus, not surprisingly, many hypotheses and models have been created to better study the role stress plays in life. Stress spans fields and is found in the literature of biology, psychology, psychophysiology, sociology, economics, and medicine, just to name a few. Stress, and the hypothalamic-pituitaryadrenal/interrenal (HPA/I) axis and sympathetic nervous system (SNS), are involved in a multitude of behaviors and physiological processes, including life-history and ecological tradeoffs, developmental transitions, health, and survival. The goal of this review is to highlight and summarize the large number of available hypotheses and models, to aid in comparative and interdisciplinary thinking, and to increase reproducibility by a) discouraging hypothesizing after results are known (HARKing) and b) encouraging a priori hypothesis testing. For this review I collected 214 published hypotheses or models dealing broadly with stress. In the main paper, I summarized and categorized 131 of those hypotheses and models which made direct connections among stress and/or HPA/I and SNS, tradeoffs, transitions, and health. Of those 131, the majority made predictions about reproduction (n = 43), the transition from health to disease (n = 38), development (n = 23), and stress coping (n = 18). Additional hypotheses were classified as stage-spanning or models (n = 37). The additional 83 hypotheses found during searches were tangentially related, or pertained to immune function or oxidative stress, and these are listed separately. Many of the hypotheses share underlying rationale and suggest similar, if not identical, predictions, and are thus not mutually exclusive; some hypotheses spanned classification categories. Some of the hypotheses have been tested multiple times, whereas others have only been examined a few times. It is the hope that multi-disciplinary stress researchers will begin to harmonize their naming of hypotheses in the literature so as to build a clearer picture of how stress impacts various outcomes across fields. The paper concludes with some considerations and recommendations for robust testing of stress hypotheses.

Experimental Effects of Acute High-Intensity Resistance Exercise on Episodic Memory Function: Consideration for Post-Exercise Recovery Period

Background

The present experiments evaluated the effects of acute high-intensity resistance exercise on episodic memory.

Methods

Two experiments were conducted. For Experiment 1, participants (N = 40; M_age = 21.0 years) were randomized into one of two groups, including an experimental exercise group and a control group (seated for 20 min). The experimental group engaged in an acute bout of resistance exercises (circuit style exercises) for 15 minutes, followed by a 5-min recovery period. Memory function was subsequently assessed using a multiple trial (immediate and delay), word-list episodic memory task (Rey Auditory Verbal Learning Test, RAVLT), and then followed by a comprehensive, computerized assessment of episodic memory (Treasure Hunt task, THT). The THT involved a spatio-temporal assessment of what, where, and when components of episodic memory. Experiment 2 evaluated if altering the recovery period would influence the potential negative effects of high-intensity resistance exercise on episodic memory function. For Experiment 2, participants (N = 51) were randomized into the same acute resistance exercise protocol but either with a 10-min recovery period, 20-min recovery period, or a control group.

Results

For Experiment 1, for RAVLT, the exercise group performed worse (F_{group × time} = 3.7, p = .001, η ²p = .09). Across nearly all THT outcomes, the exercise group had worse spatio-temporal memory than the control group. These results suggest that high-intensity resistance exercise (with a 5-min recovery) may have a detrimental effect on episodic memory function. For Experiment 2, for RAVLT, the exercise with 10-min recovery group performed better (F_{group × time} = 3.1, p = .04, η ²p = .11). Unlike Experiment 1, exercise did not impair spatio-temporal memory, with the 20-min exercise recovery group having the best "where" component of episodic memory.

Conclusion

Collectively, the results from these two experiments suggest that acute high-intensity resistance exercise may impair episodic memory when a short exercise recovery period (e.g., 5-min) is employed, but with a longer recovery period (10+ min), acute high-intensity resistance exercise may, potentially, enhance episodic memory.

An investigation to ascertain whether or not time pressure influences the accuracy of final year student radiographers in abnormality detection when interpreting conventional appendicular trauma radiographs: A pilot study

INTRODUCTION

There is an increasing demand on diagnostic imaging departments, a shortage of radiologists, and a backlog of images requiring a report across several trusts in the UK. A negative impact on performance can result in significant outcomes for the patient. The aim of this study is to ascertain whether decisions made under time pressure will affect the accuracy of the interpretation of conventional radiographs.

METHODS

Final year undergraduate diagnostic radiography students were recruited [n = 21] and separated into three groups of seven at random, assigning time limits per image for a set of normal and abnormal conventional appendicular radiographs; 15 s (high pressure), 30 s (moderate pressure) and unlimited time (low pressure). Each image was assessed, and answers were recorded as normal or abnormal with an approximate location of the pathology.

RESULTS

The ANOVA test revealed no statistical significance amongst results. The mean accuracy was highest in the 15 s group (82.86%) and lowest in the unlimited time group (74.52%). The results also demonstrated a decrease in accuracy with increased image review times within the unlimited time group; with the quickest participant achieving 88.33% and the slowest, 56.67%.

CONCLUSION

The results demonstrated no statistical significance. However, it is recommended to conduct a similar study using sufficient reporting practitioners to enable direct parallels to be drawn with statistical significance.

IMPLICATIONS FOR PRACTICE

The results signify an importance for imaging departments to manage the number of staff and their workload. Subsequently, this aims to ensure reporting practitioners work at their optimum stress level for efficient work performance.

Constitutive differences in glucocorticoid responsiveness are related to divergent spatial information processing abilities

The stress response facilitates survival through adaptation and is intimately related to cognitive processes. The Morris water maze task probes spatial learning and memory in rodents and glucocorticoids (i.e. corticosterone (CORT) in rats) have been suggested to elicit a facilitating action on memory formation. Moreover, the early aging period (around 16-18 months of age) is susceptible to stress- and glucocorticoid-mediated acceleration of cognitive decline. In this study, we tested three lines of rats selectively bred according to their individual differences in CORT responsiveness to repeated stress exposure during juvenility. We investigated whether endogenous differences in glucocorticoid responses influenced spatial learning, long-term memory, and reversal learning abilities in a Morris water maze task at early aging. Additionally, we assessed the quality of the different swimming strategies of the rats. Our results indicate that rats with differential CORT responsiveness exhibit similar spatial learning abilities but different long-term memory retention and reversal learning. Specifically, the high CORT responding line had a better long-term spatial memory, while the low CORT responding line was impaired for both long-term retention and reversal learning. Our modeling analysis of performance strategies revealed further important line-related differences. Therefore, our findings support the view that individuals with high CORT responsiveness would form stronger long-term memories to navigate in stressful environments. Conversely, individuals with low CORT responsiveness would be impaired at different phases of spatial learning and memory.

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.

The Impact of Acute Stress Physiology on Skilled Motor Performance: Implications for Policing

Investigations of police performance during acutely stressful situations have primarily focused on higher-order cognitive processes like attention, affect or emotion and decision-making, and the behavioral outcomes of these processes, such as errors in lethal force. However, behavioral outcomes in policing must be understood as a combination of both higher-order processes and the physical execution of motor skills. What is missing from extant police literature is an understanding of how physiological responses to acute stress contribute to observed decrements in skilled motor performance at the neuromuscular level. The purpose of the current paper is to fill this knowledge gap in the following ways: (1) review scientific evidence for the physiological (i.e., autonomic, endocrine, and musculoskeletal) responses to acutely stressful exposures and their influence on skilled motor performance in both human and animal models, (2) review applied evidence on occupationally relevant stress physiology and observed motor decrements in performance among police, and (3) discuss the implications of stress physiology for police training and identify future directions for applied researchers. Evidence is compelling that skill decay is inevitable under high levels of acute stress; however, robust evidence-informed training practices can help mitigate this decay and contribute to officer safety.