Deactivation of the limbic system during acute psychosocial stress: evidence from positron emission tomography and functional magnetic resonance imaging studies

Stress alters personal moral decision making

While early studies of moral decision making highlighted the role of rational, conscious executive processes involving frontal lobe activation more recent work has suggested that emotions and gut reactions have a key part to play in moral reasoning. Given that stress can activate many of the same brain regions that are important for and connected to brain centres involved in emotional processing we sought to evaluate if stress could influence moral decision making. Sixty-five undergraduate volunteers were randomly assigned to control (n=33) and experimental groups (n=32). The latter underwent the Trier Social Stress Test (TSST) and induction of stress was assessed by measurement of salivary cortisol levels. Subjects were then required to provide a response to thirty moral dilemmas via a computer interface that recorded both their decision and reaction time. Three types of dilemmas were used: non-moral, impersonal moral and personal moral. Using a binary logistic model there were no significant predicators of utilitarian response in non-moral and impersonal moral dilemmas. However the stressed group and females were found to predict utilitarian responses to personal moral dilemmas. When comparing percentage utilitarian responses there were no significant differences noted for the non-moral and impersonal moral dilemmas but the stressed group showed significantly less utilitarian responses compared to control subjects. The stress response was significantly negatively correlated with utilitarian responses. Females also showed significantly less utilitarian responses than males. We conclude that activation of the stress response predisposed participants to less utilitarian responses when faced with high conflict personal moral dilemmas and suggest that this offers further support for dual process theory of moral judgment. We also conclude that females tend to make less utilitarian personal moral decisions compared to males, providing further evidence that there are gender differences in moral reasoning.

Involvement of the insular cortex in regulating glucocorticoid effects on memory consolidation of inhibitory avoidance training

Glucocorticoids are known to enhance the consolidation of memory of emotionally arousing experiences by acting upon a network of interconnected brain regions. Although animal studies typically do not consider the insular cortex (IC) to be part of this network, the present findings indicate that the IC is importantly involved in regulating glucocorticoid effects on memory consolidation of emotionally arousing inhibitory avoidance training. The specific glucocorticoid receptor (GR) agonist RU 28362 (3 or 10 ng in 0.5 μl) infused bilaterally into the IC of male Sprague-Dawley rats immediately after one-trial inhibitory avoidance training dose-dependently enhanced 48 h retention performance. Moreover, training on the inhibitory avoidance task increased neuronal activity of the IC, as assessed by an increased number of cells expressing immunoreactivity for phosphorylated extracellular signal-regulated kinase 1/2 (pERK1/2). However, systemic administration of a memory-enhancing dose of corticosterone (1 mg/kg) after inhibitory avoidance training rapidly reduced the number of pERK1/2-positive cells in the IC, suggesting that glucocorticoid administration reduces overall neuronal activity of the IC. To investigate which components of the inhibitory avoidance training experience were influenced by the intra-IC glucocorticoid administration, in the last experiment rats were trained on a modified inhibitory avoidance task in which context exposure and footshock training occur on two sequential days. RU 28362 administration into the IC enhanced later retention when infused immediately after either the context or footshock training. Thus, these findings indicate that the IC mediates glucocorticoid effects on the consolidation of memory of different components of inhibitory avoidance training and suggest that the IC might be an important element of the rodent brain network involved in emotional regulation of learning and memory.

Increased stress-induced dopamine release in psychosis

BACKGROUND

A pathologic response to common life stressors, in which a hyperresponsive dopaminergic system is thought to play a key role, is a potential etiologic factor in the triggering and relapse of psychosis. However, there is no direct evidence that brain dopaminergic response to stress is exaggerated in psychosis.

METHODS

Using the ability of endogenous dopamine (DA) to compete with [(11)C]-(+)-PHNO binding, as measured with positron emission tomography, we examined stress-induced DA release in response to a validated psychosocial stress task. We studied 12 clinical high-risk (CHR), 10 antipsychotic-naive subjects with schizophrenia (SCZ), and 12 matched healthy volunteers (HV). Stress-induced DA release was estimated as the percent change in binding potential between conditions (stress and control scan) in the striatal subdivisions: limbic striatum (LST), associative striatum (AST), and sensorimotor striatum (SMST).

RESULTS

We found a significant difference between groups in the AST (F = 8.13, df = 2,31, p = .001), and at the SMST (F = 3,64, df = 2,31, p = .03) but not in the LST (F = .43, df = 2,31, p = .40) with CHR and SCZ having larger [(11)C]-(+)-PHNO displacement in response to the stress. Bonferroni-corrected comparisons confirmed that HV displacement (-2.86%) in the AST was significantly different in CHR (6.97%) and SCZ (11.44%) (with no significant difference between CHR and SCZ).

CONCLUSIONS

This study reveals a sensitized dopaminergic response to stress in a psychiatric condition and may have important theoretical and clinical implications regarding efforts to abort or delay relapse and/or conversion to psychosis.

Stress reactivity and corticolimbic response to emotional faces in adolescents

OBJECTIVE

Adolescence is a critical period in the development of lifelong patterns of responding to stress. Understanding underpinnings of variations in stress reactivity in adolescents is important, as adolescents with altered stress reactivity are vulnerable to negative risk-taking behaviors including substance use, and have increased lifelong risk for psychopathology. Although both endocrinological and corticolimbic neural system mechanisms are implicated in the development of stress reactivity patterns, the roles of these systems and interactions between the systems in reactivity to social stimuli in adolescents are not clear. We investigated the relationship between cortisol response to a laboratory-based social stressor and regional brain responses to emotional face stimuli in adolescents.

METHOD

Changes in cortisol levels following the Trier Social Stress Test-Child version (TSST-C) were measured in 23 disadvantaged and chronically stressed adolescents who also participated in functional magnetic resonance imaging during processing of emotional faces and structural magnetic resonance imaging. The relationships between changes in cortisol following the TSST-C with regional brain activation during face processing, as well as with regional brain morphology, were assessed.

RESULTS

Cortisol change on the TSST-C showed a significant inverse relationship with left hippocampus response to fearful faces (p < .05, corrected); significant associations with volume were not observed.

CONCLUSIONS

Increased cortisol response to the Trier social stressor was associated with diminished response of the left hippocampus to faces depicting fear. This suggests that HPA-corticolimbic system mechanisms may underlie vulnerability to maladaptive responses to stress in adolescents that may contribute to development of stress-related disorders.

Stress response in postpartum women with and without obsessive-compulsive symptoms: an fMRI study

BACKGROUND

During the postpartum period, some women might be under a considerable amount of stress and at increased risk for on-set or exacerbation of obsessive-compulsive disorder (OCD). Little is known about the stress response correlates during the postpartum period and in patients with OCD. This study aimed to examine the cerebral, psychologic and endocrine correlates of the stress response in patients with OCD and during the postpartum period.

METHODS

Women with postpartum OCD, healthy postpartum women and healthy mothers past the postpartum period underwent functional magnetic resonance imaging while facing a reliable psychosocial stressor (the Montreal Imaging Stress Task). Stress-related psychologic and endocrine responses (i.e., cortisol) were obtained.

RESULTS

We enrolled 12 women with postpartum OCD, 16 healthy postpartum women and 11 healthy mothers past the postpartum period in our study. Compared with healthy postpartum counterparts, postpartum women with OCD had a heightened self-reported and endocrine stress response associated with a distinct brain activation pattern in response to psychosocial stress involving the orbitofrontal and temporal cortices. Moreover, compared with mothers assessed in a period of time beyond the postpartum period, healthy postpartum women did not differ in psychologic and cortisol response to stress, but recruited different brain regions, such as the dorsolateral prefrontal cortex and the anterior cingulate cortex, during exposure to stress.

LIMITATIONS

Potential confounding factors, such as medication use, breastfeeding, parity and personality factors, may have modulated the stress-related endocrine response and could not be assessed in this study.

CONCLUSION

Obsessive-compulsive disorder and the postpartum period differentially influence the brain circuitry underlying psychosocial stress as well as the psychologic and endocrine responses.

Cortisol awakening response and negative emotionality linked to asymmetry in major limbic fibre bundle architecture

The limbic system plays an important role in regulating the hypothalamic-pituitary-adrenal (HPA) axis as well as aspects of emotion, and both neuroendocrine disturbance and increased negative emotionality are associated with risk for developing affective disorders. However, the extent to which the architecture of connections between limbic structures may be linked to individual differences in basal HPA-axis reactivity and negative emotionality is unknown. Here we tested the hypotheses that microstructural asymmetry of the major limbic fibre bundles would be associated with cortisol awakening response (CAR) and neuroticism, a personality trait associated with the tendency to experience negative emotions. Sixty-nine healthy adults were studied with diffusion-weighted imaging, and fractional anisotropy (FA) was extracted from the cingulum and uncinate fasciculus. Higher neuroticism scores, which were associated with higher CAR, were also correlated with higher right relative to left cingulum FA. Elevated CAR was associated with the degree of FA asymmetry within both the cingulum and the uncinate fasciculus, but in opposing directions. These results suggest that the balance between left- and right-sided limbic circuits may bear an important relationship to hypothalamic-pituitary-adrenal axis reactivity, and to the tendency to experience negative emotions, and they raise important questions about the significance of limbic system architecture.

Gut memories: towards a cognitive neurobiology of irritable bowel syndrome

The brain and the gut are engaged in continual crosstalk along a number of pathways collectively termed the 'brain-gut axis'. Over recent years it has become increasingly clear that dysregulation of the axis at a number of levels can result in disorders such as irritable bowel syndrome (IBS). With recent advances in neuroimaging technologies, insights into the neurobiology of IBS are beginning to emerge. However the cognitive neurobiology of IBS has remained relatively unexplored to date. In this review we summarise the available data on cognitive function in IBS. Moreover, we specifically address three key pathophysiological factors, namely; stress, immune activation and chronic pain, together with other factors involved in the manifestation of IBS, and explore how each of these components may impact centrally, what neurobiological mechanisms might be involved, and consider the implications for cognitive functioning in IBS. We conclude that each factor addressed could significantly impinge on central nervous system function, supporting the view that future research efforts must be directed towards a detailed assessment of cognitive function in IBS.

Perception of a naturalistic stressor interacts with 5-HTTLPR/rs25531 genotype and gender to impact reward responsiveness

BACKGROUND

Stressful life experiences frequently precede the onset of major depression; however, the mechanisms that underlie this link are poorly understood. Importantly, some individuals are more susceptible to the depressogenic effects of stress than others. Carriers of the S or LG allele of the 5-HTTLPR/rs25531 polymorphisms (S' participants) have been found to be more prone to developing depression under stress relative to L or LA homozygotes (L' participants). Moreover, emerging evidence indicates that stress-induced anhedonia may be a mechanism underlying links between stress and depression. Given these findings, we hypothesized that exposure to a naturalistic stressor (school final examinations) would disrupt reward responsiveness (a key behavioral component of anhedonia), and that this effect would be strongest in S' participants.

METHODS

To objectively assess reward responsiveness, we administered a probabilistic reward task to 70 Bulgarian high school students over two sessions in the 6-month period preceding school finals. For each participant, the two sessions were designated as the 'stress' and 'control' conditions based on self-reported perceived stress.

RESULTS

A genotype×condition interaction emerged in males, with S' participants showing larger stress-related reduction in reward responsiveness relative to L' participants.

CONCLUSION

While in need of replication in a larger sample, our results indicate that stress associated with a real-life event is linked to reduced reward responsiveness, the susceptibility to which is modulated by 5-HTTLPR/rs25531 genotype. Although preliminary, these findings identify anhedonia as a promising mechanism linking 5-HTTLPR/rs25531 genotype and stress to depression.

Neural correlates of hypothalamic-pituitary-adrenal regulation of mothers with their infants

BACKGROUND

Neural correlates of stress regulation via the hypothalamic-pituitary-adrenal (HPA) axis have been identified, but little is known about how these apply to real-world interpersonal stress contexts such as mother-infant interaction. We extended stress regulation research by examining maternal neural activation to infant cry related to HPA regulation with their infants.

METHODS

Twenty-two primiparous mothers listened to the cry sounds of their own 18-month-old infant and an unfamiliar infant and a control sound during functional magnetic resonance imaging scanning. Salivary cortisol was collected at four timepoints in a separate session involving the Strange Situation stressor. Cortisol trajectories were modeled with hierarchical linear modeling, and trajectory terms were used to predict neural response to own infant cry.

RESULTS

Mothers who showed less HPA reactivity-indexed by trajectory curvature rather than level-showed increased activation to the cry of their infant relative to control sound across limbic/paralimbic and prefrontal circuits. These included periaqueductal gray, right insula, and bilateral orbitofrontal cortex as well as anterior cingulate-medial prefrontal cortex. Activations overlapped to some extent with previous HPA regulation findings and converged more extensively with circuits identified in other maternal response paradigms.

CONCLUSIONS

Maternal stress regulation involves both circuits found across stressor types (i.e., prefrontal) and areas unique to the mother-infant relationship (i.e., limbic/paralimbic). The shape of the HPA response trajectory of mothers was more important than the level of such response in defining stress-related neural correlates. Future research should consider dimensions of the stress context and of physiological trajectories to define stress-regulatory circuits.

Circadian cortisol, depressive symptoms and neurological impairment in early multiple sclerosis

OBJECTIVE

There is evidence for the existence of a hyperactive hypothalamus-pituitary-adrenal (HPA) axis and its potential role in disease progression in multiple sclerosis (MS). Depressive symptoms are also common in MS. At the same time, depressive symptoms are often associated with an elevated circadian cortisol secretion. So far, little is known about the interplay between depressive symptoms and circadian HPA axis abnormalities in MS.

METHODS

Here we investigated depressive symptoms, circadian HPA axis function, cortisol awakening response (CAR) and neurological impairment in 32 early stage relapsing-remitting MS (RRMS) patients and 16 age- and sex-matched controls. Saliva cortisol samples were collected in patients' home environment. Depressive symptoms were assessed by self-report measures. Neurological impairment was assessed by the Kurtzke Expanded Disability Status Scale (EDSS).

RESULTS

RRMS patients expressed a significantly higher CAR when compared to healthy controls. After patients were divided into two groups based on their depressive symptom load (Beck Depression Inventory (BDI); median-split), only RRMS patients with moderately elevated depression scores (BDI high) statistically differed in their cortisol release when compared to healthy controls. RRMS patients with low depression scores (BDI low) expressed similar circadian patterns as healthy controls. Neurological impairment (EDSS) was more pronounced in the BDI high group than in the BDI low group.

CONCLUSION

In summary, there is evidence, that a hyperactive HPA axis is primarily present in MS patients expressing moderately elevated depressive symptoms. MS patients with only few depressive symptoms do not significantly differ in CAR when compared to healthy controls. To the best of our knowledge, this is the first study showing that in early stage MS, a hyperactive HPA axis is primarily present in patients who express moderate depressive symptoms.

Phasic deactivation of the medial temporal lobe enables working memory processing under stress

Demanding cognitive tasks are sometimes carried out under stressful conditions. Several studies indicate that whereas severe stress impairs performance, moderate stress can enhance cognitive performance. In this study, we investigated how moderate stress influences the neural systems supporting working memory. We embedded an N-back working memory task in a moderately stressful context, as indicated by our physiological stress measures, and probed phasic and tonic human brain activity using two fMRI-techniques: conventional blood oxygen level dependent fMRI and arterial spin labeling (ASL). The results showed that the stress induction, as compared to the neutral control condition, led to slightly faster reaction times without changes in accuracy. In general, working memory processing was associated with increased activity in a frontoparietal network and reduced activity in the medial temporal lobe (MTL). The stress induction led to enhanced reduction of phasic MTL responses, specifically the hippocampus and amygdala. In addition, ASL showed that stress increased tonic amygdala activity, while tonic hippocampal activity was unaffected. These findings suggest that the influence of stress on MTL deactivation during working memory processing is task-related rather than a general consequence of the stressful state. The temporal suspension of hippocampal processing in favor of more task relevant processes may allow subjects to maintain normal performance levels under moderate stress.

Limbic response to psychosocial stress in schizotypy: a functional magnetic resonance imaging study

Psychological stress causes dopamine release in the striatum and is thought to play a role in susceptibility to psychotic illness. Previous work suggests that an elevated dopaminergic response to stress may index vulnerability to psychosis in certain individuals. With functional magnetic resonance imaging, we measured stress-induced changes in brain activity in healthy individuals at elevated risk of developing psychosis. Participants were 15 controls and 25 psychometric schizotypes: 12 with positive symptom schizotypy (perceptual aberrations) and 13 with negative symptom schizotypy (physical anhedonia), as determined by questionnaires (Chapman et al., 1976; Chapman and Chapman, 1978). In the scanner, participants performed the Montreal Imaging Stress Task and a matched sensory-motor control task. Measures of self-reported stress and salivary cortisol levels were taken throughout the experiment. All three groups showed significant increases in self-reported stress and significant fMRI signal change in the striatal, limbic and cortical regions. However, the Physical Anhedonia group showed greater stress-induced striatal and limbic deactivation than the other two groups. Deactivation in the striatum was significantly correlated with Physical Anhedonia score across all subjects. Our findings suggest the presence of abnormalities in striatal response to stress in negative symptom schizotypy.

Impact of chronic hypercortisolemia on affective processing

Cushing syndrome (CS) is the classic condition of cortisol dysregulation, and cortisol dysregulation is the prototypic finding in Major Depressive Disorder (MDD). We hypothesized that subjects with active CS would show dysfunction in frontal and limbic structures relevant to affective networks, and also manifest poorer facial affect identification accuracy, a finding reported in MDD. Twenty-one patients with confirmed CS (20 ACTH-dependent and 1 ACTH-independent) were compared to 21 healthy control subjects. Identification of affective facial expressions (Facial Emotion Perception Test) was conducted in a 3 Tesla GE fMRI scanner using BOLD fMRI signal. The impact of disease (illness duration, current hormone elevation and degree of disruption of circadian rhythm), performance, and comorbid conditions secondary to hypercortisolemia were evaluated. CS patients made more errors in categorizing facial expressions and had less activation in left anterior superior temporal gyrus, a region important in emotion processing. CS patients showed higher activation in frontal, medial, and subcortical regions relative to controls. Two regions of elevated activation in CS, left middle frontal and lateral posterior/pulvinar areas, were positively correlated with accuracy in emotion identification in the CS group, reflecting compensatory recruitment. In addition, within the CS group, greater activation in left dorsal anterior cingulate was related to greater severity of hormone dysregulation. In conclusion, cortisol dysregulation in CS patients is associated with problems in accuracy of affective discrimination and altered activation of brain structures relevant to emotion perception, processing and regulation, similar to the performance decrements and brain regions shown to be dysfunctional in MDD. This article is part of a Special Issue entitled 'Anxiety and Depression'.

Psychosocial stress is associated with in vivo dopamine release in human ventromedial prefrontal cortex: a positron emission tomography study using [¹⁸F]fallypride

Rodent studies suggest that prefrontal dopamine neurotransmission plays an important role in the neural processing of psychosocial stress. Human studies investigating stress-induced changes in dopamine levels, however, have focused solely on striatal dopamine transmission. The aim of this study was to investigate in vivo dopamine release in the human prefrontal cortex in response to a psychosocial stress challenge, using the highly selective dopamine D₂/₃ PET radioligand [¹⁸F]fallypride in healthy subjects. Twelve healthy subjects (age (y): 39.8; SD=15.8) underwent a single dynamic Positron Emission Tomography (PET) scanning session after intravenous administration of 185.2 (SD=10.2) MBq [¹⁸F]fallypride. Psychosocial stress was initiated at 100 min postinjection. PET data were analyzed using the linearized simplified reference region model (LSRRM), which accounts for time-dependent changes in [¹⁸F]fallypride displacement. Voxel-based statistical maps, representing specific D₂/₃ binding changes, were computed to localize areas with increased ligand displacement after task initiation, reflecting dopamine release. The psychosocial stress challenge induced detectable amounts of dopamine release throughout the prefrontal cortex, with dopaminergic activity in bilateral ventromedial prefrontal cortex being associated with subjectively rated experiences of psychosocial stress. The novel finding that a mild psychosocial stress in humans induces increased levels of endogenous dopamine in the PFC indicates that the dynamics of the dopamine-related stress response cannot be interpreted by focusing on mesolimbic brain regions alone.

Attachment figures activate a safety signal-related neural region and reduce pain experience

Although it has long been hypothesized that attachment figures provide individuals with a sense of safety and security, the neural mechanisms underlying attachment-induced safety have not been explored. Here, we investigated whether an attachment figure acts as a safety signal by exploring whether viewing an attachment figure during a threatening experience (physical pain) led to increased activity in a neural region associated with safety signaling, the ventromedial prefrontal cortex (VMPFC), and corresponding reductions in pain. Female participants in long-term romantic relationships were scanned as they received painful stimuli while viewing pictures of their partner and control images (stranger, object). Consistent with the idea that the attachment figure may signal safety, results revealed that viewing partner pictures while receiving painful stimulation led to reductions in self-reported pain ratings, reductions in pain-related neural activity (dorsal anterior cingulate cortex, anterior insula), and increased activity in the VMPFC. Moreover, greater VMPFC activity in response to partner pictures was associated with longer relationship lengths and greater perceived partner support, further highlighting a role for the VMPFC in responding to the safety value of the partner. Last, greater VMPFC activity while viewing partner pictures was associated with reduced pain ratings and reduced pain-related neural activity. An implication of these findings is that, in the same way that stimuli that historically have threatened survival (e.g., snakes, spiders) are considered to be prepared fear stimuli, attachment figures, who have historically benefited survival, may serve as prepared safety stimuli, reducing threat- or distress-related responding in their presence.

Association between Cold Face Test-induced vagal inhibition and cortisol response to acute stress

Low vagal function is related to several disorders. One possible underlying mechanism linking the vagus nerve and disorders is the HPA axis. Thirty-three healthy male subjects participated in a stress task, while heart rate (HR), respiratory sinus arrhythmia (RSA), salivary cortisol, and mood were assessed. Vagal function was determined using baseline, stress-induced inhibition, and Cold Face Test (CFT)-induced stimulation. The stress task induced a significant increase in cortisol and HR, a decrease in RSA, and a worsening of mood. A linear regression model with the time from CFT onset until maximum bradycardia as the independent variable explained 17.9% of the total variance in cortisol in response to the stressor (mood: 36.5%). The results indicate that a faster CFT response is associated with reduced cortisol increase and enhanced mood after acute stress. Our data support an inverse relationship between vagal function and the HPA axis.

Predicting cortisol stress responses in older individuals: influence of serotonin receptor 1A gene (HTR1A) and stressful life events

Considerable variability in the activity of the hypothalamus-pituitary-adrenal (HPA) axis in response to stress has been found in quantitative genetic studies investigating healthy individuals suggesting that at least part of this variance is due to genetic factors. Since the HPA axis is regulated by a neuronal network including amygdala, hippocampus, prefrontal cortex as well as brainstem circuits, the investigation of candidate genes that impact neurotransmitter systems related to these brain regions might further elucidate the genetic underpinnings of the stress response. However, aside from genetic risk factors, past stressful life events might also result in long-term adjustments of HPA axis reactivity. Here, we investigated the effects of the -1019 G/C polymorphism in the HTR1A gene encoding the serotonin (5-HT) receptor 1A (5-HT(1A)) and stressful life events experienced during childhood and adolescence on changes in cortisol levels in response to the Trier Social Stress Test (TSST) in a sample of healthy older adults (N=97). Regression analyses revealed a significant effect of HTR1A genotype with the G allele being associated with a less pronounced stress response. In addition, an inverse relationship between past stressful life events and cortisol release but no gene × environment interaction was detected. The results further underscore the crucial role of functional serotonergic genetic variation as well as stressful events during critical stages of development on the acute stress response later in life.

The mesoaccumbens dopamine in coping with stress

Mesoaccumbens dopamine (DA) is involved in the stress response. Although neural mechanisms involved in stress are of paramount importance for both clinical and preclinical research, the results of studies on the stress response by mesoaccumbens DA have received little attention. Therefore, we aimed to review these results and propose a role for mesoaccumbens DA in coping with stress. The data reviewed support the view that fluctuations of tonic levels characterize the mesoaccumbens DA stress response. Stress-induced increase of tonic DA levels in nucleus accumbens (NAc) supports expression of responses aimed at removing and avoiding the stressor through activation of DA D2 receptors, whereas inhibition of DA is associated with cessation of active defensive responses. In novel unescapable/uncontrollable stressful conditions tonic levels of DA in NAc show an initial increase followed by a decrease below pre-stress levels that lasts as long as the stressful situation. This biphasic response fits with the dynamics of the primary and secondary appraisal of a stressor that cannot be removed, escaped or controlled by the organism. In fact, NAc DA fluctuations are controlled by the medial pre-frontal cortex, which is involved in stress appraisal. We propose that enhanced mesoaccumbens DA supports expression of active coping strategies against an event appraised as a stressor and that inhibition of DA is required for passive coping with stressful situations appraised as unescapable/uncontrollable.

Hippocampal regulation of aversive memories

For many years, the hippocampal formation has been implicated in the regulation of negative emotion, yet the nature of this link has remained elusive. Recent studies have made important links between the hippocampus and regulation of stress hormones that affect aversive memory. Additional studies have shown that the hippocampus regulates the gating of fear by contextual information. An emerging literature also links the hippocampus to prediction errors during fear learning and extinction. The mechanisms by which the hippocampus regulates negative emotion are clearly complicated, but suggest that interventions aimed at restoring normal hippocampal function may help with disorders of negative affect, such as depression or post-traumatic stress disorder and depression.

Mood disorders and their pharmacological treatment during pregnancy: is the future child affected?

Nearly half the US population will meet criteria for a neuropsychiatric disorder at some point in their lives, and 1 in 17 has a seriously debilitating illness. Although not all affected adults had an identified disorder as a child, increasingly these psychopathologies are conceptualized as the late-stage culmination of aberrant developmental processes shaped by a complex interplay of genes and experience, including experiences in utero. Decades of studies with pregnant animals demonstrate that stress-elicited perturbations in maternal biology affect offspring neurodevelopment. Studies of stress in pregnant women largely mirror these findings. Pregnant women with anxiety and/or depression experience greater life stress, and illness-related alterations in their neurobiology, with a potential to impact fetal neurobehavioral development via associated changes in the intrauterine environment and/or pharmacologic interventions. This article critically reviews findings on child development (including fetal neurobehavior) related to maternal depression, anxiety, and pharmacological treatments, primarily selective serotonin reuptake inhibitors (SSRIs). The hypothesis under review is that, in addition to genetics and characteristics of the postnatal environment, the familial transmission of risk for neuropsychiatric disorders involves a "third path"-prenatal exposure to psychiatric illness and its treatment.

Emotional reactivity in chronic schizophrenia: structural and functional brain correlates and the influence of adverse childhood experiences

BACKGROUND

Despite behavioural signs of flattened affect, patients affected by schizophrenia show enhanced sensitivity to negative stimuli. The current literature concerning neural circuitry for emotions supports dysregulations of cortico-limbic networks, but gives contrasting results. Adverse childhood experiences (ACEs) could persistently influence emotional regulation and neural correlates of response to emotional stimuli in healthy humans. This study evaluated the effect of ACEs and chronic undifferentiated schizophrenia on neural responses to emotional stimuli (negative facial expression).

METHOD

Brain blood-oxygen-level-dependent functional magnetic resonance imaging neural responses to a face-matching paradigm, and regional grey matter (GM) volumes were studied at 3.0 T in the amygdala, hippocampus, anterior cingulated cortex (ACC) and prefrontal cortex (PFC). The severity of ACEs was assessed. Participants included 20 consecutively admitted in-patients affected by chronic undifferentiated schizophrenia, and 20 unrelated healthy volunteers from the general population.

RESULTS

Patients reported higher ACEs than controls. Worse ACEs proportionally led to decreasing responses in the amygdala and hippocampus, and to increasing responses in the PFC and ACC in all participants. Patients showed higher activations in the amygdala and hippocampus, and lower activations in the PFC and ACC. Higher ACEs were associated with higher GM volumes in the PFC and ACC, and schizophrenia was associated with GM reduction in all studied regions.

CONCLUSIONS

Structural and functional brain correlates of emotional reactivity are influenced by both current chronic undifferentiated schizophrenia and the severity of past ACEs.

Acute psycho-social stress does not disrupt item-method directed forgetting, emotional stimulus content does

It has been shown that stress affects episodic memory in general, but knowledge about stress effects on memory control processes such as directed forgetting is sparse. Whereas in previous studies item-method directed forgetting was found to be altered in post-traumatic stress disorder patients and abolished for highly arousing negative pictorial stimuli in students, no study so far has investigated the effects of experimentally induced psycho-social stress on this task or examined the role of positive picture stimuli. In the present study, 41 participants performed an item-method directed forgetting experiment while being exposed either to a psychosocial laboratory stressor, the Trier Social Stress Test (TSST), or a cognitively challenging but non-stressful control condition. Neutral and positive pictures were presented as stimuli. As predicted, salivary cortisol level as a biological marker of the human stress response increased only in the TSST group. Still, both groups showed directed forgetting. However, emotional content of the employed stimuli affected memory control: Directed forgetting was intact for neutral pictures whereas it was attenuated for positive ones. This attenuation was primarily due to selective rehearsal improving discrimination accuracy for neutral, but not positive, to-be-remembered items. Results suggest that acute experimentally induced stress does not alter item-method directed forgetting while emotional stimulus content does.

Does stress alter everyday moral decision-making?

Recent studies in the field of neuropsychological decision-making as well as moral psychology emphasize the role of emotions in decision-making. The current study examines whether stress affects moral decision-making. We induced stress in 20 participants with the Trier Social Stress Test (TSST) and also examined 20 participants in a control condition (Placebo TSST). The level of stress was assessed with questionnaires and endocrine markers (salivary cortisol and alpha-amylase). All participants performed a moral decision-making task in which everyday moral dilemmas were described. Dilemmas varied in emotional intensity and each offered a rather egoistic and a rather altruistic option. Results show that groups did not differ significantly in everyday moral decision-making. However, cortisol responses and egoistic decision-making in emotional dilemmas were positively correlated. Our results indicate that stress per se does not cause more egoistic decision-making in the current setting but suggest an association between the individual's cortisol stress response and egoistic decision-making in high-emotional situations.

Existential neuroscience: a functional magnetic resonance imaging investigation of neural responses to reminders of one's mortality

A considerable body of evidence derived from terror management theory indicates that the awareness of mortality represents a potent psychological threat engendering various forms of psychological defense. However, extant research has yet to examine the neurological correlates of cognitions about one's inevitable death. The present study thus investigated in 17 male participants patterns of neural activation elicited by mortality threat. To induce mortality threat, participants answered questions arranged in trial blocks that referred to fear of death and dying. In the control condition participants answered questions about fear of dental pain. Neural responses to mortality threat were greater than to pain threat in right amygdala, left rostral anterior cingulate cortex, and right caudate nucleus. We discuss implications of these findings for stimulating further research into the neurological correlates of managing existential fear.

Effects of acute psychosocial stress on working memory related brain activity in men

Acute psychosocial stress in humans triggers the release of glucocorticoids (GCs) and influences performance in declarative and working memory (WM) tasks. These memory systems rely on the hippocampus and prefrontal cortex (PFC), where GC-binding receptors are present. Previous studies revealed contradictory results regarding effects of acute stress on WM-related brain activity. We combined functional magnetic resonance imaging with a standardized psychosocial stress protocol to investigate the effects of acute mental stress on brain activity during encoding, maintenance, and retrieval of WM. Participants (41 healthy young men) underwent either a stress or a control procedure before performing a WM task. Stress increased salivary cortisol levels and tended to increase WM accuracy. Neurally, stress-induced increases in cortical activity were evident in PFC and posterior parietal cortex (PPC) during WM maintenance. Furthermore, hippocampal activity was modulated by stress during encoding and retrieval with increases in the right anterior hippocampus during WM encoding and decreases in the left posterior hippocampus during retrieval. Our study demonstrates that stress increases activity in PFC and PPC specifically during maintenance of items in WM, whereas effects on hippocampal activity are restricted to encoding and retrieval. The finding that psychosocial stress can increase and decrease activity in two different hippocampal areas may be relevant for understanding the often-reported phase-dependent opposing behavioral effects of stress on long-term memory.

Central role of the brain in stress and adaptation: links to socioeconomic status, health, and disease

The brain is the key organ of stress reactivity, coping, and recovery processes. Within the brain, a distributed neural circuitry determines what is threatening and thus stressful to the individual. Instrumental brain systems of this circuitry include the hippocampus, amygdala, and areas of the prefrontal cortex. Together, these systems regulate physiological and behavioral stress processes, which can be adaptive in the short-term and maladaptive in the long-term. Importantly, such stress processes arise from bidirectional patterns of communication between the brain and the autonomic, cardiovascular, and immune systems via neural and endocrine mechanisms underpinning cognition, experience, and behavior. In one respect, these bidirectional stress mechanisms are protective in that they promote short-term adaptation (allostasis). In another respect, however, these stress mechanisms can lead to a long-term dysregulation of allostasis in that they promote maladaptive wear-and-tear on the body and brain under chronically stressful conditions (allostatic load), compromising stress resiliency and health. This review focuses specifically on the links between stress-related processes embedded within the social environment and embodied within the brain, which is viewed as the central mediator and target of allostasis and allostatic load.

Glucocorticoids, stress and obesity

Obesity and the associated metabolic syndrome have been suggested to be the consequence of a maladaptation to chronic stress exposure mediated by a dysregulation of neuroendocrine axes. The hypothalamic-pituitary-adrenal (HPA) axis represents the major hormone system responsible for maintenance of the homeostatic balance in response to stress. The brainstem nuclei and the limbic regions are strongly involved in stressor neural processing and represent a regulatory network for the HPA axis. Moreover, the same neuroendocrine stress centers are involved in the regulation of feeding behavior following acute and chronic stress exposure. Studies performed in experimental animals suggest that consumption of so-called comfort foods, while favoring an adaptation to the detrimental impact of chronic stress on the reward system, may, in turn, lead to the rapid development of obesity. Available data also indicate that the endocannabinoid system modulates the HPA axis and that its type 1 receptors, which are extensively localized in the hypothalamus and in limbic structures, are involved in the regulation of the stress response and the reward mechanisms. Based on extensive clinical experience and studies performed in experimental animals, we developed the concept that there is a specific phenotype of individuals who may become obese as a result of exposure to major stressful events.

Anterior cingulate pyramidal neurons display altered dendritic branching in depressed suicides

BACKGROUND

It is hypothesized that mood disorders are accompanied by altered wiring and plasticity in key limbic brain regions such as the anterior cingulate cortex (ACC). To test this hypothesis at the cellular level, we analyzed basilar dendritic arborizations extended by layer VI pyramidal neurons in silver-impregnated postmortem ACC samples from well-characterized depressed suicide subjects (n=12) and matched sudden-death controls (n=7).

METHODS

One cm(3) tissue blocks were stained using a Golgi preparation, cut on a microtome, and mounted on slides. Basilar dendritic arbors from 195 neurons were reconstructed, and the number, length, and diameter of branches were determined at each branch order. The size and number of spines borne by these branches were also assessed.

RESULTS

Third-order branches were significantly reduced in number (24% fewer; p=0.00262) in depressed suicides compared to controls. The size and average length of these branches, as well as their number of spines/length were unaltered. On average, for each pyramidal neuron analyzed in depressed subjects, the fewer third-order branches resulted in a significant reduction in branch length (28% shorter; p=0.00976) at this branch order.

CONCLUSIONS

These results provide the first evidence of altered cortical dendritic branching in mood disorders. Given that proximal dendritic branches grow during perinatal development, and that they are generally less plastic at maturity than distal segments, we speculate that these differences in dendritic branching may reflect a biological predisposition to depression and suicide.

Hippocampal activation during a cognitive task is associated with subsequent neuroendocrine and cognitive responses to psychological stress

Increased activation of the hypothalamus pituitary adrenal (HPA) axis, marked by increased secretion of cortisol, is a biological marker of psychological stress. It is well established that the hippocampus plays an important role in the regulation of HPA axis activity. The relationship between cortisol (stress-related elevation or exogenous administration) and the hippocampal-related cognitive function is often examined. However, few human studies to date have examined the effect of stress on hippocampal activity and the interactions between stress-induced activation of the HPA axis and hippocampal function during different phases of cognitive function. On the basis of our previous work, we hypothesized that group differences in stress-sensitivity relate to differences in hippocampal-related stress-integration. To test this hypothesis, we conducted a functional MRI study using tasks known to involve the hippocampal formation: novel-picture encoding, psychological stress, and paired-picture recognition. On the basis of their cortisol responses to stress, we divided subjects into stress-responders (increase in cortisol, n = 9) and nonresponders (decrease in cortisol, n = 10). Responders showed higher hippocampal deactivation during the stress task and lower recognition scores due to a larger number of misses. Intriguingly, stress-responders showed significant differences in hippocampal activation already prior to stress, with higher levels of hippocampal activity during the picture encoding. Although effects of both cortisol and hippocampal activation on recognition were present in responders, similar effects were absent in the nonresponder group. Our results indicate that hippocampus plays an important role in adaptive behavioral responses. We hypothesize that states of hippocampal activation prior to stress might reflect states of vigilance or anxiety, which might be important for determining interindividual differences in subsequent stress response and cognitive performance.

Investigating the impact of sex and cortisol on implicit fear conditioning with fMRI

Fear conditioning is influenced by stress but opposing effects in males and females have often been reported. In a previous human functional magnetic resonance imaging (fMRI) study, we observed acute effects of the stress hormone cortisol on prefrontal structures. Men showed evidence for impaired fear conditioning after cortisol treatment, while the opposite pattern was found for women. In the current experiment, we tested whether similar sex-dependent effects would occur on the neural level if contingency awareness was prevented experimentally to investigate implicit learning processes. A differential fear conditioning experiment with transcutaneous electrical stimulation as unconditioned stimulus and geometric figures as conditioned stimuli (CS) was conducted. One figure was always paired (CS+), whereas the other (CS-) was never paired with the UCS. Thirty-nine (19 female) subjects participated in this fMRI study, receiving either placebo or 30 mg cortisol (hydrocortisone) before conditioning. Dependent variables were skin conductance responses (SCRs) and neural activity (BOLD signal). In line with prior findings in unaware participants, no differential learning could be observed for the SCRs. However, a sex x cortisol interaction was detected with a reduced mean response to the CS after cortisol treatment in men, while the opposite pattern was observed in women (enhanced mean SCR under cortisol). In the contrast CS+ minus CS-, neural activity showed a sex x cortisol interaction in the insula and further trends in the hippocampus and the thalamus. In these regions, cortisol reduced the CS+/CS- differentiation in men but enhanced it in women. In contrast to these sex specific effects, differential amygdala activation was found in the placebo group but not in the cortisol group, irrespective of sex. Further, differential neural activity in the amygdala and thalamus were positively correlated with the SCRs in the placebo group only. The present study in contingency unaware participants illustrates that cortisol has in some brain regions sex specific effects on neural correlates of emotional learning. These effects might translate into a different vulnerability of the two sexes for anxiety disorders.

Stress regulation in the central nervous system: evidence from structural and functional neuroimaging studies in human populations - 2008 Curt Richter Award Winner

The metabolic effects of stress are known to have significant health effects in both humans and animals. Most of these effects are mediated by the major stress hormonal axis in the body, the hypothalamic-pituitary-adrenal (HPA) axis. Within the central nervous system (CNS), the hippocampus, the amygdala and the prefrontal cortex as part of the limbic system are believed to play important roles in the regulation of the HPA axis. With the advent of structural and functional neuroimaging techniques, the role of different CNS structures in the regulation of the HPA axis can be investigated more directly. In the current paper, we summarize the findings obtained in our laboratory in the context of stress and HPA axis regulation. Our laboratory has developed and contributed to the development of manual and automated segmentation protocols from structural magnetic resonance imaging (MRI) scans for assessment of hippocampus, amygdala, medial temporal lobe and frontal lobe structures. Employing these protocols, we could show significant age-related changes in HC volumes, which were different between men and women, with pre-menopausal women showing smaller age-related volume decline compared to men. We could recently extent these findings by showing how estrogen therapy after menopause leads to higher volumes in the HC. Investigating possible neurotoxicity effects of steroids, we showed effects of long-term steroid exposure on HC volumes, and investigated variability of HC volumes in relation to HPA axis regulation in young and elderly populations. Here, we were able to follow-up from non-imaging studies showing that subjects low in self-esteem have higher cortisol stress responses, and the HC emerged as the critical link between these variables. Recently, we have made two more important discoveries with regard to HC volume: we could show that HC volume is as variable in young as it is in older adults, in subjects ranging in age from 18 to 80 years. Also, we have linked birth weight and maternal care to HC volumes in young adults, demonstrating the effects of variations in maternal care on the integrity of the CNS. Besides structural assessments, there is increasing interest in functional techniques to investigate possible links between CNS activity and HPA axis regulation. These two approaches complement each other; some aspects of HPA axis regulation might be linked to the integrity of a specific CNS structure, while other aspects might be linked to the function of a specific structure with no involvement of CNS morphology. Thus, we have developed a mental arithmetic stress task that can be employed in functional neuroimaging studies, and have used it in a number of functional neuroimaging studies. Employing positron emission tomography (PET), we were able to demonstrate that stress causes dopamine release if subjects reported low maternal care early in life. Finally, employing the task in functional magnetic resonance imaging (fMRI), we could show how exposure to stress and activation of the HPA axis are associated with decreased activity in major portions of the limbic system, a result that allows to speculate on the effects of stress on cognitive and emotional regulation in the brain. Taken together, the use of neuroimaging techniques in Psychoneuroendocrinology opens exciting new possibilities for the investigation of stress effects in the central nervous system.

Allostasis and the human brain: Integrating models of stress from the social and life sciences

We draw on the theory of allostasis to develop an integrative model of the current stress process that highlights the brain as a dynamically adapting interface between the changing environment and the biological self. We review evidence that the core emotional regions of the brain constitute the primary mediator of the well-established association between stress and health, as well as the neural focus of wear and tear due to ongoing adaptation. This mediation, in turn, allows us to model the interplay over time between context, current stressor exposure, internal regulation of bodily processes, and health outcomes. We illustrate how this approach facilitates the integration of current findings in human neuroscience and genetics with key constructs from stress models from the social and life sciences, with implications for future research and the design of interventions targeting individuals at risk.

Medial prefrontal cortex damage affects physiological and psychological stress responses differently in men and women

The ability to produce appropriate physiological and psychological responses to stressful situations depends on accurate recognition and appraisal of such situations. Such ability is also important for proper emotion regulation. A number of studies have suggested that the medial prefrontal cortex (mPFC) plays a significant role in emotion regulation, as well as in the control of physiological endpoints of emotion regulation such as the hypothalamic-pituitary-adrenal (HPA) axis and autonomic nervous system (ANS). Further, recent work has suggested that men and women may differ in these mechanisms of neural control of emotion regulation. Here, we examined the role of the human mPFC in self-report, ANS, and HPA stress reactivity by testing a group of participants with damage to this region (9 women and 9 men), a brain damaged comparison group (6 women and 6 men), and healthy comparison participants (27 women and 27 men) on an orthostatic challenge and the Trier Social Stress Test (TSST). The mPFC participants showed heightened self-reported stress in response to the TSST. In women, mPFC damage led to an increased cortisol response to the TSST. By contrast, in men, greater volume of mPFC damage was correlated with a decreased cortisol response. Finally, men with mPFC damage showed altered autonomic control of the heart (higher heart rate and lower high frequency heart rate variability) during an orthostatic challenge. These findings support the idea that the mPFC is involved in the regulation of physiological and psychological responses to stress and that this regulation may differ between men and women.

High pregnancy anxiety during mid-gestation is associated with decreased gray matter density in 6-9-year-old children

Because the brain undergoes dramatic changes during fetal development it is vulnerable to environmental insults. There is evidence that maternal stress and anxiety during pregnancy influences birth outcome but there are no studies that have evaluated the influence of stress during human pregnancy on brain morphology. In the current prospective longitudinal study we included 35 women for whom serial data on pregnancy anxiety was available at 19 (+/-0.83), 25 (+/-0.9) and 31 (+/-0.9) weeks gestation. When the offspring from the target pregnancy were between 6 and 9 years of age, their neurodevelopmental stage was assessed by a structural MRI scan. With the application of voxel-based morphometry, we found regional reductions in gray matter density in association with pregnancy anxiety after controlling for total gray matter volume, age, gestational age at birth, handedness and postpartum perceived stress. Specifically, independent of postnatal stress, pregnancy anxiety at 19 weeks gestation was associated with gray matter volume reductions in the prefrontal cortex, the premotor cortex, the medial temporal lobe, the lateral temporal cortex, the postcentral gyrus as well as the cerebellum extending to the middle occipital gyrus and the fusiform gyrus. High pregnancy anxiety at 25 and 31 weeks gestation was not significantly associated with local reductions in gray matter volume.This is the first prospective study to show that a specific temporal pattern of pregnancy anxiety is related to specific changes in brain morphology. Altered gray matter volume in brain regions affected by prenatal maternal anxiety may render the developing individual more vulnerable to neurodevelopmental and psychiatric disorders as well as cognitive and intellectual impairment.

Polymorphism of the serotonin transporter gene modulates brain and physiological responses to acute stress in Japanese men

A short (S) variant, compared to a long (L) variant, of the promoter region of the serotonin transporter gene-linked polymorphic region (5HTTLPR) has been related to emotional hyper-reactivity. We tested whether the 5HTTLPR could modulate acute stress responses in the brain and, the cardiovascular and neuroendocrine systems. Ten Japanese male participants carrying double copies of the S alleles and 10 Japanese males carrying S and L alleles conducted a mental arithmetic task, and their regional cerebral blood flow by (15)O positron emission tomography and cardiovascular and neuroendocrine parameters were measured. During the acute stress task, the participants with the SS alleles showed stronger reactivity in blood pressure and secretion of epinephrine, compared to the participants with the SL and LL alleles. Furthermore, the SS carriers showed greater activation in stress-related brain regions such as the hypothalamus, cerebellum, midbrain, and pulvinar compared to the SL and LL carriers during the acute stress task. The present findings indicated that the S allele of the 5HTTLPR is associated with greater brain and physiological reactivity to acute stress in Japanese men.