Chronic stress modulates neural and cardiovascular responses during reversal learning

The neural network basis of altered decision-making in patients with amyotrophic lateral sclerosis

OBJECTIVE

Amyotrophic lateral sclerosis (ALS) is a multisystem disorder associated with motor impairment and behavioral/cognitive involvement. We examined decision-making features and changes in the neural hub network in patients with ALS using a probabilistic reversal learning task and resting-state network analysis, respectively.

METHODS

Ninety ALS patients and 127 cognitively normal participants performed this task. Data from 62 ALS patients and 63 control participants were fitted to a Q-learning model.

RESULTS

ALS patients had anomalous decision-making features with little shift in choice until they thought the value of the two alternatives had become equal. The quantified parameters (Pαβ) calculated by logistic regression analysis with learning rate and inverse temperature well represented the unique choice pattern of ALS patients. Resting-state network analysis demonstrated a strong correlation between Pαβ and decreased degree centrality in the anterior cingulate gyrus and frontal pole.

INTERPRETATION

Altered decision-making in ALS patients may be related to the decreased hub function of medial prefrontal areas.

Associations of sympathetic and parasympathetic activity in job stress and burnout: A systematic review

This systematic review examines the relationship between sympathetic and parasympathetic activity on the one hand and job stress and burnout on the other, and is registered at PROSPERO under CRD42016035918. Background: Previous research has shown that prolonged job stress may lead to burnout, and that differences in heart rate variability are apparent in people who have heightened job stress. Aims: In this systematic review, the associations between job stress or burnout and heart rate (variability) or skin conductance are studied. Besides, it was investigated which–if any–guidelines are available for ambulatory assessment and reporting of the results. Methods: We extracted data from relevant databases following the PRESS checklist and contacted authors for additional resources. Participants included the employed adult population comparing validated job stress and burnout questionnaires examining heart rate and electrodermal activity. Synthesis followed the PRISMA guidelines of reporting systematic reviews. Results: The results showed a positive association between job stress and heart rate, and a negative association between job stress and heart rate variability measures. No definite conclusion could be drawn with regard to burnout and psychophysiological measures. No studies on electrodermal activity could be included based on the inclusion criteria. Conclusions: High levels of job stress are associated with an increased heart rate, and decreased heart rate variability measures. Recommendations for ambulatory assessment and reporting (STROBE) are discussed in light of the findings.

Reward-Related Neural Correlates of Antisocial Behavior and Callous-Unemotional Traits in Young Men

BACKGROUND

Individuals involved in antisocial behavior often engage in excessive reward-driven behavior even in the face of severe punishments including incarceration. However, the neural mechanisms of reward processing in antisocial behavior have not been examined while considering the heterogeneity of antisocial behavior and specific phases of reward and loss processing. In this study, we investigate the relationship between antisocial behavior, callous-unemotional traits, and neural activity during the anticipation and receipt of rewards and losses.

METHODS

A community sample of 144 low income, racially diverse, urban males at risk for antisocial behavior completed self-report measures, a clinical interview, and an fMRI scan at age 20. Neural response during the anticipation and receipt of monetary rewards and losses was linked to antisocial behavior and callous-unemotional traits using a priori ventral striatum region of interest analyses and exploratory whole brain analyses.

RESULTS

Antisocial behavior, but not callous-unemotional traits, was related to less ventral striatum response during reward anticipation. There were no significant relationships between neural reactivity and antisocial behavior or callous-unemotional traits during reward or loss outcomes. Antisocial behavior was also related to less ventrolateral prefrontal cortex reactivity during reward and loss anticipation.

CONCLUSIONS

These findings support a hypo-reactivity model of reward and loss anticipation in antisocial behavior. Lower striatal reactivity to cues of reward and lower prefrontal-regulatory recruitment during reward and loss anticipation may contribute to maladaptive reward-related behavior found in antisocial behavior.

Functional connectivity of resting-state, working memory and inhibition networks in perceived stress

Experimental imaging studies on the effects of acute stress have revealed functional changes in the amygdalae, hippocampi and medial frontal cortices. However, much less is known about the association between perceived stress and neurological function which may have implications for the development of stress related disorders. Participants completed a working-memory task and an inhibition task whilst undergoing a functional magnetic resonance imaging (fMRI) scan. Task related and resting-state fMRI data from 22 women and 24 men were analysed to investigate changes in task activations and functional connectivity associated with perceived stress over the past month. Analyses were stratified by gender due to gender differences in the stress response. Stress was associated with faster working memory response time in women, but not men. Stress was not associated with any differences in task activations in either gender. There were many significant associations between stress and connectivity: findings in women were consistent with increased emotional regulation; men exhibited decreases in connectivity between affective processing areas during the tasks and showed no relation between perceived stress and resting-state connectivity; very few of the within gender differences were significantly different between gender. Dysregulated connectivity between areas involved in the neural stress response and self-referential thoughts (e.g. the default mode network) suggests that perceived stress may have a subtle impact on cognitive processing and neural correlates.

Perceived Occupational Stress is associated with Decreased Cortical Activity of the Prefrontal Cortex: A Multichannel Near-infrared Spectroscopy Study

Despite an increasing number of reports on the associations between chronic occupational stress and structural and functional changes of the brain, the underlying neural correlates of perceived occupational stress is still not clear. Perceived stress reflects the extents to which situations are appraised as stressful at a given point in one’s life. Using near-infrared spectroscopy, we investigated the associations between perceived occupational stress and cortical activity over the bilateral frontotemporal regions during a verbal fluency test. Sixty-eight participants (17 men, 51 women), 20–62 years of age were recruited. Perceived occupational stress was measured using the Chinese version of Job Content Questionnaire, and the Chinese version of the Copenhagen Burnout Inventory. We found statistically significant negative associations between occupational burnout and brain cortical activity over the fronto-polar and dorsolateral prefrontal cortex during the VFT (r = −0.343 to −0.464). In conclusion, our research demonstrated a possible neural basis of perceived occupational stress that are distributed across the prefrontal cortex.

Occupational status and job stress in relation to cardiovascular stress reactivity in Japanese workers

This study aimed to investigate the effects of occupational status and job stress factors on cardiovascular stress reactivity in Japanese workers. In this baseline assessment between 2001 and 2009 in Osaka, Japan, we examined 928 healthy Japanese employees (330 men, 598 women) from two occupational statuses: managers/professionals and general workers. A brief job stress questionnaire was used to evaluate job stress levels. Systolic and diastolic blood pressure (SBP, DBP), heart rate, heart rate variability (high-frequency [HF], low-frequency [LF], LF/HF], and peripheral blood flow were measured at rest and during two stressful tasks. Changes in stress reactivity were calculated as the difference between the measured variables during the tasks and the rest period. Men showed inverse associations between quantitative job overload and DBP, heart rate, and LF/HF, between physical demands and blood pressure (SBP, DBP), and between a poor physical environment and HF. Men also had positive associations between qualitative job overload and heart rate, and between physical demands and peripheral blood flow (all p < 0.05). Women showed inverse associations between qualitative job overload and SBP, and showed positive associations between qualitative job overload and peripheral blood flow, and between a poor physical environment and SBP (all p < 0.05). When stratified by occupational status, significant associations between job stress and changes in stress reactivity were observed in male managers/professionals and female general workers (p < 0.05). Job stress levels are associated with changes in cardiovascular stress reactivity in men and women. Occupational status may modify these associations.

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Job stressors are associated with changes in stress reactivity in men and women.

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Job stressors associated with stress reactivity in male managers/professionals.

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Job stressors associated with stress reactivity in female general workers.

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Occupational status and gender differences should be considered.

Autoradiographic Evaluation of [(18)F]FECUMI-101, a High Affinity 5-HT1AR Ligand in Human Brain

[(18)F]FECUMI-101 ([(18)F]1) is a 5HT1AR ligand demonstrating specific binding in brain regions corresponding to the distribution of 5-HT1AR in baboons. However, we detected moderate uptake of [(18)F]1 in baboon thalamus, a brain region lacking 5-HT1AR. We sought to investigate the relative binding of [(18)F]1 to 5-HT1AR, α1R, and 5-HT7R in vitro. Using autoradiography in human brain sections, specific binding of [(18)F]1 to 5-HT1AR was confirmed. However, [(18)F]1 also showed 26% binding to α1R in PFC. The hippocampal formation exhibited 51% and 92% binding of [(18)F]1 to α1R and 5-HT1AR, respectively. Thalamus and cerebellum showed very little binding. There is no measurable specific binding of [(18)F]1 to 5-HT7R and no effect of temperature on [(18)F]1 specific binding to 5-HT1AR or α1R. These results indicate that, while [(18)F]FECUMI-101 is not a completely selective 5-HT1AR ligand for receptor quantification, it may be useful for occupancy measurements of drugs acting at 5-HT1AR in vivo.

Ginseng and Ginkgo Biloba Effects on Cognition as Modulated by Cardiovascular Reactivity: A Randomised Trial

Background

There is some evidence to suggest that ginseng and Ginkgo biloba can improve cognitive performance, however, very little is known about the mechanisms associated with such improvement. Here, we tested whether cardiovascular reactivity to a task is associated with cognitive improvement.

Methodology/Principal findings

Using a double-blind, placebo controlled, crossover design, participants (N = 24) received two doses of Panax Ginseng (500, 1000 mg) or Ginkgo Biloba (120, 240 mg) (N = 24), and underwent a series of cognitive tests while systolic, diastolic, and heart rate readings were taken. Ginkgo Biloba improved aspects of executive functioning (Stroop and Berg tasks) in females but not in males. Ginseng had no effect on cognition. Ginkgo biloba in females reversed the initial (i.e. placebo) increase in cardiovascular reactivity (systolic and diastolic readings increased compared to baseline) to cognitive tasks. This effect (reversal) was most notable after those tasks (Stroop and Iowa) that elicited the greatest cardiovascular reactivity during placebo. In males, although ginkgo also decreased cardiovascular readings, it did so from an initial (placebo) blunted response (i.e. decrease or no change from baseline) to cognitive tasks. Ginseng, on the contrary, increased cardiovascular readings compared to placebo.

Conclusions/Significance

These results suggest that cardiovascular reactivity may be a mechanism by which ginkgo but not ginseng, in females is associated with certain forms of cognitive improvement.

Trial Registration

ClinicalTrials.gov NCT02386852

Chronic Stress Alters Spatial Representation and Bursting Patterns of Place Cells in Behaving Mice

Chronic uncontrollable stress has been shown to produce various physiological alterations and impair mnemonic functions in the rodent hippocampus. Impacts on neuronal activities, however, have not been well investigated. The present study examined dorsal CA1 place cells to elucidate the computational changes associated with chronic stress effects on cognitive behaviors. After administering chronic restraint stress (CRS; 6 hours/day for ≥21 consecutive days) to adult male mice, several hippocampal characteristics were examined; i.e., spatial learning, in vitro synaptic plasticity, in vivo place cell recording, and western blot analysis to determine protein levels related to learning and memory. Behaviorally, CRS significantly impeded spatial learning but enhanced non-spatial cue learning on the Morris water maze. Physiologically, CRS reduced long-term potentiation (LTP) of Schaffer collateral/commisural-CA1 pathway, phospho-αCaMKII (alpha Ca2(+)/calmodulin-dependent protein kinase II) level in the hippocampus, and stability of spatial representation and the mean firing rates (FRs) of place cells. Moreover, the local cue-dependency of place fields was increased, and the intra-burst interval (IntraBI) between consecutive spikes within a burst was prolonged following CRS. These results extend the previous findings of stress impairing LTP and spatial learning to CRS modifying physical properties of spiking in place cells that contribute to changes in navigation and synaptic plasticity.

Neural and sympathetic activity associated with exploration in decision-making: further evidence for involvement of insula

We previously reported that sympathetic activity was associated with exploration in decision-making indexed by entropy, which is a concept in information theory and indexes randomness of choices or the degree of deviation from sticking to recent experiences of gains and losses, and that activation of the anterior insula mediated this association. The current study aims to replicate and to expand these findings in a situation where contingency between options and outcomes is manipulated. Sixteen participants performed a stochastic decision-making task in which we manipulated a condition with low uncertainty of gain/loss (contingent-reward condition) and a condition with high uncertainty of gain/loss (random-reward condition). Regional cerebral blood flow was measured by (15)O-water positron emission tomography (PET), and cardiovascular parameters and catecholamine in the peripheral blood were measured, during the task. In the contingent-reward condition, norepinephrine as an index of sympathetic activity was positively correlated with entropy indicating exploration in decision-making. Norepinephrine was negatively correlated with neural activity in the right posterior insula, rostral anterior cingulate cortex, and dorsal pons, suggesting neural bases for detecting changes of bodily states. Furthermore, right anterior insular activity was negatively correlated with entropy, suggesting influences on exploration in decision-making. By contrast, in the random-reward condition, entropy correlated with activity in the dorsolateral prefrontal and parietal cortices but not with sympathetic activity. These findings suggest that influences of sympathetic activity on exploration in decision-making and its underlying neural mechanisms might be dependent on the degree of uncertainty of situations.

Age-associated epigenetic upregulation of the FKBP5 gene selectively impairs stress resiliency

Single nucleotide polymorphisms (SNPs) in the FK506 binding protein 5 (FKBP5) gene combine with traumatic events to increase risk for post-traumatic stress and major depressive disorders (PTSD and MDD). These SNPs increase FKBP51 protein expression through a mechanism involving demethylation of the gene and altered glucocorticoid signaling. Aged animals also display elevated FKBP51 levels, which contribute to impaired resiliency to depressive-like behaviors through impaired glucocorticoid signaling, a phenotype that is abrogated in FKBP5^−/− mice. But the age of onset and progressive stability of these phenotypes remain unknown. Moreover, it is unclear how FKBP5 deletion affects other glucocorticoid-dependent processes or if age-associated increases in FKBP51 expression are mediated through a similar epigenetic process caused by SNPs in the FKBP5 gene. Here, we show that FKBP51-mediated impairment in stress resiliency and glucocorticoid signaling occurs by 10 months of age and this increased over their lifespan. Surprisingly, despite these progressive changes in glucocorticoid responsiveness, FKBP5^−/− mice displayed normal longevity, glucose tolerance, blood composition and cytokine profiles across lifespan, phenotypes normally associated with glucocorticoid signaling. We also found that methylation of Fkbp5 decreased with age in mice, a process that likely explains the age-associated increases in FKBP51 levels. Thus, epigenetic upregulation of FKBP51 with age can selectively impair psychological stress-resiliency, but does not affect other glucocorticoid-mediated physiological processes. This makes FKBP51 a unique and attractive therapeutic target to treat PTSD and MDD. In addition, aged wild-type mice may be a useful model for investigating the mechanisms of FKBP5 SNPs associated with these disorders.

Dual learning processes underlying human decision-making in reversal learning tasks: functional significance and evidence from the model fit to human behavior

Humans are capable of correcting their actions based on actions performed in the past, and this ability enables them to adapt to a changing environment. The computational field of reinforcement learning (RL) has provided a powerful explanation for understanding such processes. Recently, the dual learning system, modeled as a hybrid model that incorporates value update based on reward-prediction error and learning rate modulation based on the surprise signal, has gained attention as a model for explaining various neural signals. However, the functional significance of the hybrid model has not been established. In the present study, we used computer simulation in a reversal learning task to address functional significance in a probabilistic reversal learning task. The hybrid model was found to perform better than the standard RL model in a large parameter setting. These results suggest that the hybrid model is more robust against the mistuning of parameters compared with the standard RL model when decision-makers continue to learn stimulus-reward contingencies, which can create abrupt changes. The parameter fitting results also indicated that the hybrid model fit better than the standard RL model for more than 50% of the participants, which suggests that the hybrid model has more explanatory power for the behavioral data than the standard RL model.

Neural mechanisms mediating association of sympathetic activity and exploration in decision-making

The somatic marker hypothesis asserts that decision-making can be guided by feedback of bodily states to the brain. In line with this hypothesis, the present study tested whether sympathetic activity shows an association with a tonic dimension of decision-making, exploratory tendency represented by entropy in information theory, and further examined the neural mechanisms of the association. Twenty participants performed a stochastic reversal learning task that required decision-making in an unstable and uncertain situation. Regional cerebral blood flow was evaluated using (15)O-water positron emission tomography (PET), and cardiovascular indices and concentrations of catecholamine in peripheral blood were also measured, during the task. In reversal learning, increased epinephrine during the task positively correlated with larger entropy, indicating a greater tendency for exploration in decision-making. The increase of epinephrine also correlated with brain activity revealed by PET in the somatosensory cortices, anterior insula, dorsal anterior cingulate cortex, and the dorsal pons. This result is consistent with previously reported brain matrixes of representation of bodily states and interoception. In addition, activity of the anterior insula specifically correlated with entropy, suggesting possible mediation of this brain region between peripheral sympathetic arousal and exploration in decision-making. These findings shed a new light about a role of bodily states in decision-making and underlying neural mechanisms.

Autoradiographic evaluation of [3H]CUMI-101, a novel, selective 5-HT1AR ligand in human and baboon brain

[11C]CUMI-101 is the first selective serotonin receptor (5-HT1AR) partial agonist radiotracer for positron emission tomography (PET) tested in vivo in nonhuman primates and humans. We evaluated specific binding of [3H]CUMI-101 by quantitative autoradiography studies in postmortem baboon and human brain sections using the 5-HT1AR antagonist WAY-100635 as a displacer. The regional and laminar distributions of [3H]CUMI-101 binding in baboon and human brain sections matched the known distribution of [3H]8-OH-DPAT and [3H]WAY-100635. Prazosin did not measurably displace [3H]CUMI-101 binding in baboon or human brain sections, thereby ruling out [3H]CUMI-101 binding to α1-adrenergic receptors. This study demonstrates that [11C]CUMI-101 is a selective 5-HT1AR ligand for in vivo and in vitro studies in baboon and human brain.

HPA axis genes may modulate the effect of childhood adversities on decision-making in suicide attempters

Decision-making impairment is found in several neuropsychiatric disorders, including suicidal behavior, and has been shown to be modulated by genes. On the other hand, early trauma have/has been associated with poor mental health outcome in adulthood, in interaction with genetic factors, possibly through sustained alterations in the hypothalamic-pituitary-adrenal axis (HPA axis). Here, we aimed to investigate the effect of childhood trauma and its interaction with HPA-axis related genes on decision-making abilities in adulthood among a sample of suicide attempters. The Iowa Gambling Task (IGT) was used to assess decision-making in 218 patients with a history of suicide attempt. Participant fulfilled the Childhood Trauma Questionnaire to report traumatic childhood experiences. Patients were genotyped for single-nucleotide polymorphisms within CRHR1 and CRHR2 genes. Patients with a history of sexual abuse had significantly lower IGT scores than non-sexually abused individuals. Polymorphisms within CRHR1 and CRHR2 genes interacted with both childhood sexual abuse and emotional neglect to influence IGT performance. In conclusion, childhood sexual abuse and emotional neglect may have long-term effects on decision-making through an interaction with key HPA axis genes. Even if these results need to be replicated in other sample, impaired decision-making may thus be the dimension through which child maltreatment, in interaction with HPA axis related genes, may have a sustained negative impact on adult mental health.