At-risk individuals display altered brain activity following stress

Stress is a major risk factor for almost all psychiatric disorders, however, the underlying neurobiological mechanisms remain largely elusive. In healthy individuals, a successful stress response involves an adequate neuronal adaptation to a changing environment. This adaptive response may be dysfunctional in vulnerable individuals, potentially contributing to the development of psychopathology. In the current study, we investigated brain responses to emotional stimuli following stress in healthy controls and at-risk individuals. An fMRI study was conducted in healthy male controls (N = 39) and unaffected healthy male siblings of schizophrenia patients (N = 39) who are at increased risk for the development of a broad range of psychiatric disorders. Brain responses to pictures from the International Affective Picture System (IAPS) were measured 33 min after exposure to stress induced by the validated trier social stress test (TSST) or a control condition. Stress-induced levels of cortisol, alpha-amylase, and subjective stress were comparable in both groups. Yet, stress differentially affected brain responses of schizophrenia siblings versus controls. Specifically, control subjects, but not schizophrenia siblings, showed reduced brain activity in key nodes of the default mode network (PCC/precuneus and mPFC) and salience network (anterior insula) as well as the STG, MTG, MCC, vlPFC, precentral gyrus, and cerebellar vermis in response to all pictures following stress. These results indicate that even in the absence of a psychiatric disorder, at-risk individuals display abnormal functional activation following stress, which in turn may increase their vulnerability and risk for adverse outcomes.

Cognitive benefit and cost of acute stress is differentially modulated by individual brain state

Acute stress is associated with beneficial as well as detrimental effects on cognition in different individuals. However, it is not yet known how stress can have such opposing effects. Stroop-like tasks typically show this dissociation: stress diminishes speed, but improves accuracy. We investigated accuracy and speed during a stroop-like task of 120 healthy male subjects after an experimental stress induction or control condition in a randomized, counter-balanced cross-over design; we assessed brain–behavior associations and determined the influence of individual brain connectivity patterns on these associations, which may moderate the effect and help identify stress resilience factors. In the mean, stress was associated to increase in accuracy, but decrease in speed. Accuracy was associated to brain activation in a distributed set of brain regions overlapping with the executive control network (ECN) and speed to temporo-parietal activation. In line with a stress-related large-scale network reconfiguration, individuals showing an upregulation of the salience and down-regulation of the executive-control network under stress displayed increased speed, but decreased performance. In contrast, individuals who upregulate their ECN under stress show improved performance. Our results indicate that the individual large-scale brain network balance under acute stress moderates cognitive consequences of threat.

2D:4D and spatial abilities: From rats to humans

Variance in spatial abilities are thought to be determined by in utero levels of testosterone and oestrogen, measurable in adults by the length ratio of the 2nd and 4th digit (2D:4D). We confirmed the relationship between 2D:4D and spatial performance using rats in two different tasks (paired-associate task and watermaze) and replicated this in humans. We further clarified anatomical and functional brain correlates of the association between 2D:4D and spatial performance in humans.

Hippocampal-caudate nucleus interactions support exceptional memory performance

Participants of the annual World Memory Championships regularly demonstrate extraordinary memory feats, such as memorising the order of 52 playing cards in 20 s or 1000 binary digits in 5 min. On a cognitive level, memory athletes use well-known mnemonic strategies, such as the method of loci. However, whether these feats are enabled solely through the use of mnemonic strategies or whether they benefit additionally from optimised neural circuits is still not fully clarified. Investigating 23 leading memory athletes, we found volumes of their right hippocampus and caudate nucleus were stronger correlated with each other compared to matched controls; both these volumes positively correlated with their position in the memory sports world ranking. Furthermore, we observed larger volumes of the right anterior hippocampus in athletes. Complementing these structural findings, on a functional level, fMRI resting state connectivity of the anterior hippocampus to both the posterior hippocampus and caudate nucleus predicted the athletes rank. While a competitive interaction between hippocampus and caudate nucleus is often observed in normal memory function, our findings suggest that a hippocampal-caudate nucleus cooperation may enable exceptional memory performance. We speculate that this cooperation reflects an integration of the two memory systems at issue-enabling optimal combination of stimulus-response learning and map-based learning when using mnemonic strategies as for example the method of loci.

Evaluation of Rhodosporidium fluviale as biocontrol agent against Botrytis cinerea on apple fruit

The aim of the present work was to evaluate the ability of the native yeast Rhodosporidium fluviale to control Botrytis cinerea on apple fruit and to study the possible mechanisms of action with the goal of improving the control of gray mold. For this, the influence of application time of the yeast was studied simulating preventive and curative effects. Also, the effect of nonviable cells of the yeast in the biocontrol was assessed. According to the results obtained, the following mechanisms of action of R. fluviale could be proposed: 1- competition for space, 2- direct interaction between antagonist and pathogen, 3- induction of β-1,3-glucanase in apple tissue, 4- Probable production of glucanase in the apple wounds and 5- antifungal action of cellular components, probably chitin, present in the wall of yeast cells that could be the explanation for the activity of nonviable cells.

SIGNIFICANCE AND IMPACT OF THE STUDY

Significance and Impact of the Study: Botrytis cinerea Pers: Fr, which causes gray mold of fruits and vegetables around the world, is difficult to control successfully because it is genetically variable and rapidly develops resistance to the chemicals commonly used for its control. This study is a contribution to the biocontrol of this phytopathogen fungus. The evaluation of the native yeast Rhodosporidium fluviale as biocontrol agent and the elucidation of possible mechanisms of action, including the participation of nonviable cells of this yeast, have not been reported up to date.

The increase in medial prefrontal glutamate/glutamine concentration during memory encoding is associated with better memory performance and stronger functional connectivity in the human medial prefrontal-thalamus-hippocampus network

The classical model of the declarative memory system describes the hippocampus and its interactions with representational brain areas in posterior neocortex as being essential for the formation of long‐term episodic memories. However, new evidence suggests an extension of this classical model by assigning the medial prefrontal cortex (mPFC) a specific, yet not fully defined role in episodic memory. In this study, we utilized 1H magnetic resonance spectroscopy (MRS) and psychophysiological interaction (PPI) analysis to lend further support for the idea of a mnemonic role of the mPFC in humans. By using MRS, we measured mPFC γ‐aminobutyric acid (GABA) and glutamate/glutamine (GLx) concentrations before and after volunteers memorized face–name association. We demonstrate that mPFC GLx but not GABA levels increased during the memory task, which appeared to be related to memory performance. Regarding functional connectivity, we used the subsequent memory paradigm and found that the GLx increase was associated with stronger mPFC connectivity to thalamus and hippocampus for associations subsequently recognized with high confidence as opposed to subsequently recognized with low confidence/forgotten. Taken together, we provide new evidence for an mPFC involvement in episodic memory by showing a memory‐related increase in mPFC excitatory neurotransmitter levels that was associated with better memory and stronger memory‐related functional connectivity in a medial prefrontal–thalamus–hippocampus network.

Persistence of Amygdala-Hippocampal Connectivity and Multi-Voxel Correlation Structures During Awake Rest After Fear Learning Predicts Long-Term Expression of Fear

After encoding, memories undergo a process of consolidation that determines long-term retention. For conditioned fear, animal models postulate that consolidation involves reactivations of neuronal assemblies supporting fear learning during postlearning "offline" periods. However, no human studies to date have investigated such processes, particularly in relation to long-term expression of fear. We tested 24 participants using functional MRI on 2 consecutive days in a fear conditioning paradigm involving 1 habituation block, 2 acquisition blocks, and 2 extinction blocks on day 1, and 2 re-extinction blocks on day 2. Conditioning blocks were preceded and followed by 4.5-min rest blocks. Strength of spontaneous recovery of fear on day 2 served as a measure of long-term expression of fear. Amygdala connectivity primarily with hippocampus increased progressively during postacquisition and postextinction rest on day 1. Intraregional multi-voxel correlation structures within amygdala and hippocampus sampled during a block of differential fear conditioning furthermore persisted after fear learning. Critically, both these main findings were stronger in participants who exhibited spontaneous recovery 24 h later. Our findings indicate that neural circuits activated during fear conditioning exhibit persistent postlearning activity that may be functionally relevant in promoting consolidation of the fear memory.

[Perception of Primary Care physicians on the integration with cardiology through continuity of healthcare programs in secondary prevention]

OBJECTIVE

To determine the perception of Primary Care (PC) physicians on the integration with cardiology (CA) through continuity of healthcare programs.

MATERIAL AND METHODS

A cross-sectional and multicentre study was conducted, in which a total of 200 PC physicians from all over Spain completed a qualitative survey that evaluated the level of integration with CA in secondary prevention. Physicians were grouped according to the level of PC-CA integration.

RESULTS

The integration between CA and PC was good, but it was better in those centres with a higher integration (74.0% vs. 60.0%; p=.02) and in general, physicians considered that integration had improved (92.0% vs. 73.0%; p<.001). Almost all PC physicians received the hospital discharge report. The majority of the hospital discharge reports included recommendations about the CA and PC follow-up, control of risk factors, as well as the duration of secondary prevention treatment, with not significant differences according to the level of integration. In 55.8%, 63.6%, and 51.3% of hospital discharge reports, indications were given on when to perform the follow-up blood analysis, as well as information about returning to working life and sexual activity, respectively. The most common communication method was the paper-based report (75 vs. 84%; p=NS). The communication between healthcare levels was greater in those Primary Care centres with a higher level of integration, as well as periodicity of the communication and the satisfaction of physicians (80.0% vs. 63.0%; p=.005).

CONCLUSIONS

The level of integration between PC and CA is, in general, satisfactory, but those centres with a higher level of integration benefit more from a greater communication and satisfaction.

How acute stress may enhance subsequent memory for threat stimuli outside the focus of attention: DLPFC-amygdala decoupling

Stress-related disorders, e.g., anxiety and depression, are characterized by decreased top-down control for distracting information, as well as a memory bias for threatening information. However, it is unclear how acute stress biases mnemonic encoding and leads to prioritized storage of threat-related information even if outside the focus of attention. In the current study, healthy adults (N = 53, all male) were randomly assigned to stress induction using the socially evaluated cold-pressor test (SECPT) or a control condition. Participants performed a task in which they were required to identify a target letter within a string of letters that were either identical to the target and thereby facilitating detection (low distractor load) or mixed with other letters to complicate the search (high load). Either a fearful or neutral face was presented on the background, outside the focus of attention. Twenty-four hours later, participants were asked to perform a surprise recognition memory test for those background faces. Stress induction resulted in increased cortisol and negative subjective mood ratings. Stress did not affect visual search performance, however, participants in the stress group showed stronger memory compared to the control group for fearful faces in the low attentional load condition. Critically, the stress induced memory bias was accompanied by decoupling between amygdala and DLFPC during encoding, which may represent a mechanism for decreased ability to filter task-irrelevant threatening background information. The current study provides a potential neural account for how stress can produce a negative memory bias for threatening information even if presented outside the focus of attention. Despite of an adaptive advantage for survival, such tendencies may ultimately also lead to generalized fear, a possibility requiring additional investigation.

Physical neglect during childhood alters white matter connectivity in healthy young males

BACKGROUND

Childhood adversity (CA) leads to greater vulnerability for psychopathology by causing structural as well as functional brain abnormalities. Recent findings on gray matter effects point towards the importance of identifying CA outcome as a function of different CA types, varying in the dimensions of threat and deprivation. Using diffusion tensor imaging, we investigate whether different forms of CA impact differently on white matter connectivity in a healthy cohort not confounded by other aspects of disease.

METHODS

In 120 healthy young males, we assessed different forms of maltreatment during childhood with the Childhood Trauma Questionnaire (CTQ). Fractional anisotropy (FA) and mean diffusivity (MD) images were generated and projected onto a white matter skeleton using tract-based spatial statistics. Correlational analysis between FA, MD, and CTQ subscores was then performed using voxelwise statistics.

RESULTS

Of all CTQ-subscores, only physical neglect (PN) predicted a decrease of FA but not MD in the bilateral anterior thalamic radiation around the middle frontal gyrus and the right inferior fronto-occipital fasciculus, the inferior longitudinal fasciculus, the cingulum and precuneus. Reduced FA in the posterior cingulum was related to the effects of PN during childhood on anxiety levels at trend level.

CONCLUSIONS

PN may have severe consequences and should be considered equally important to more active forms of abuse. FA changes, particularly in the cingulum, actually appear to a functional consequence and are linked to trait anxiety, a personality dimension that is suggested to be a transdiagnostic risk factor of affective disorders. Potentially this reveals a mechanistic chain that forms one pathyway from CA to disease.

Stress leads to aberrant hippocampal involvement when processing schema-related information

Prior knowledge, represented as a mental schema, has critical impact on how we organize, interpret, and process incoming information. Recent findings indicate that the use of an existing schema is coordinated by the medial prefrontal cortex (mPFC), communicating with parietal areas. The hippocampus, however, is crucial for encoding schema-unrelated information but not for schema-related information. A recent study indicated that stress mediators may affect schema-related memory, but the underlying neural mechanisms are currently unknown. Here, we thus tested the impact of acute stress on neural processing of schema-related information. We exposed healthy participants to a stress or control manipulation before they processed, in the MRI scanner, words related or unrelated to a preexisting schema activated by a specific cue. Participants’ memory for the presented material was tested 3–5 d after encoding. Overall, the processing of schema-related information activated the mPFC, the precuneus, and the angular gyrus. Stress resulted in aberrant hippocampal activity and connectivity while participants processed schema-related information. This aberrant engagement of the hippocampus was linked to altered subsequent memory. These findings suggest that stress may interfere with the efficient use of prior knowledge during encoding and may have important practical implications, in particular for educational settings.

Emotion and sex of facial stimuli modulate conditional automaticity in behavioral and neuronal interference in healthy men

Our surrounding provides a host of sensory input, which we cannot fully process without streamlining and automatic processing. Levels of automaticity differ for different cognitive and affective processes. Situational and contextual interactions between cognitive and affective processes in turn influence the level of automaticity. Automaticity can be measured by interference in Stroop tasks. We applied an emotional version of the Stroop task to investigate how stress as a contextual factor influences the affective valence-dependent level of automaticity. 120 young, healthy men were investigated for behavioral and brain interference following a stress induction or control procedure in a counter-balanced cross-over-design. Although Stroop interference was always observed, sex and emotion of the face strongly modulated interference, which was larger for fearful and male faces. These effects suggest higher automaticity when processing happy and also female faces. Supporting behavioral patterns, brain data show lower interference related brain activity in executive control related regions in response to happy and female faces. In the absence of behavioral stress effects, congruent compared to incongruent trials (reverse interference) showed little to no deactivation under stress in response to happy female and fearful male trials. These congruency effects are potentially based on altered context- stress-related facial processing that interact with sex-emotion stereotypes. Results indicate that sex and facial emotion modulate Stroop interference in brain and behavior. These effects can be explained by altered response difficulty as a consequence of the contextual and stereotype related modulation of automaticity.

How the brain connects in response to acute stress: A review at the human brain systems level

The brain's response to stress is a matter of extensive neurocognitive research in an attempt to unravel the mechanistic underpinnings of neural adaptation. In line with the broadly defined concept of acute stress, a wide variety of induction procedures are used to mimic stress experimentally. We set out to review commonalities and diversities of the stress-related functional activity and connectivity changes of functional brain networks in healthy adults across procedures. The acute stress response is consistently associated with both increased activity and connectivity in the salience network (SN) and surprisingly also with increased activity in the default mode network (DMN), while most studies show no changes in the central executive network. These results confirm earlier findings of an essential, coordinating role of the SN in the acute stress response and indicate a dynamic role of the DMN whose function is less clear. Moreover, paradigm specific brain responses have to be taken into account when investigating the role and the within and between network connectivity of these three networks.

Human subcortical brain asymmetries in 15,847 people worldwide reveal effects of age and sex

The two hemispheres of the human brain differ functionally and structurally. Despite over a century of research, the extent to which brain asymmetry is influenced by sex, handedness, age, and genetic factors is still controversial. Here we present the largest ever analysis of subcortical brain asymmetries, in a harmonized multi-site study using meta-analysis methods. Volumetric asymmetry of seven subcortical structures was assessed in 15,847 MRI scans from 52 datasets worldwide. There were sex differences in the asymmetry of the globus pallidus and putamen. Heritability estimates, derived from 1170 subjects belonging to 71 extended pedigrees, revealed that additive genetic factors influenced the asymmetry of these two structures and that of the hippocampus and thalamus. Handedness had no detectable effect on subcortical asymmetries, even in this unprecedented sample size, but the asymmetry of the putamen varied with age. Genetic drivers of asymmetry in the hippocampus, thalamus and basal ganglia may affect variability in human cognition, including susceptibility to psychiatric disorders.

Mnemonic Training Reshapes Brain Networks to Support Superior Memory

Memory skills strongly differ across the general population; however, little is known about the brain characteristics supporting superior memory performance. Here we assess functional brain network organization of 23 of the world's most successful memory athletes and matched controls with fMRI during both task-free resting state baseline and active memory encoding. We demonstrate that, in a group of naive controls, functional connectivity changes induced by 6 weeks of mnemonic training were correlated with the network organization that distinguishes athletes from controls. During rest, this effect was mainly driven by connections between rather than within the visual, medial temporal lobe and default mode networks, whereas during task it was driven by connectivity within these networks. Similarity with memory athlete connectivity patterns predicted memory improvements up to 4 months after training. In conclusion, mnemonic training drives distributed rather than regional changes, reorganizing the brain's functional network organization to enable superior memory performance.

Error consciousness predicts physiological response to an acute psychosocial stressor in men

There are substantial individual differences in the response towards acute stressor. The aim of the current study was to examine how the neural activity after an error response during a non-stressful state, prospectively predicts the magnitude of physiological stress response (e.g., cortisol response and heart rate) and negative affect elicited by a laboratory stress induction procedure in nonclinical participants. Thirty-seven healthy young male adults came to the laboratory for the baseline neurocognitive measurement on the first day during which they performed a Go/Nogo task with their electroencephalogram recorded. On the second day, they came again to be tested on their stress response using an acute psychosocial stress procedure (i.e., the Trier Social Stress Test, the TSST). Results showed that the amplitude of error positivity (Pe) significantly predicted both the heart rate and cortisol response towards the TSST. Our results suggested that baseline cognitive neural activity reflecting error consciousness could be used as a biological predictor of physiological response to an acute psychological stressor in men.

Acute Stress Enhances Emotional Face Processing in the Aging Brain

BACKGROUND

Healthy aging has been associated with stable emotional well-being and attenuated brain responses to negative stimuli. At the same time, depressive symptoms are common in older adults. The neural mechanisms behind this paradox remain to be clarified. We hypothesized that acute stress could alter emotion processing in healthy aging brain and constitute a pathway to vulnerability.

METHODS

Using a randomized, controlled crossover design, we explored the influence of acute stress on brain responses to happy and fearful facial expressions in 25 older adults (60-75 years of age) and 25 young (18-30 years of age) control subjects. Groups were matched on trait anxiety and education. Subjects underwent two separate functional magnetic resonance imaging sessions involving acute stress or a control procedure.

RESULTS

Affective and physiological responses to the stressor were similar between the two age groups. On a whole-brain level, we revealed a significant age by stress interaction in the fusiform gyrus, indicating a selective enhancement of neural activity with stress in elderly subjects only. When specifically aiming analysis at the amygdala, we found the same stress-related increase in activity in elderly subjects only. Modulation of amygdala reactivity due to stress correlated with trait conscientiousness in elderly subjects exclusively.

CONCLUSIONS

Compared with younger adults, healthy older adults showed increased responsivity of brain regions involved in face and emotion processing while stressed. These findings suggest that increased reactivity of this neural circuitry after acute stress may constitute one mechanism by which emotional well-being during healthy aging could rapidly change into heightened vulnerability for affective disorders.

Distribution of Aleutian mink disease virus contamination in the environment of infected mink farms

Control and eradication of Aleutian Mink Disease Virus (AMDV) are a major concern for fur-bearing animal production. Despite notably reducing disease prevalence, current control programs are unable to prevent the reinfection of farms, and environmental AMDV persistence seems to play a major role regarding this issue. In this study 114 samples from different areas and elements of seven infected mink farms were analyzed by qPCR in order to evaluate the environmental distribution of AMDV load. Samples were classified into nine categories, depending on the type of sample and degree of proximity to the animals, the main source of infection. Two different commercial DNA extraction kits were employed in parallel for all samples. qPCR analysis showed 69.3% positive samples with one kit and 81.6% with the other, and significant differences between the two DNA extraction methods were found regarding AMDV DNA recovery. Regarding sample categorization, all categories showed a high percentage of AMDV positive samples (31%-100%). Quantification of positive samples showed a decrease in AMDV load from animal barns to the periphery of the farm. In addition, those elements in direct contact with animals, the street clothes and vehicles of farm workers and personal protective equipment used for sampling showed a high viral load, and statistical analysis revealed significant differences in AMDV load between the first and last categories. These results indicate high environmental contamination of positive farms, which is helpful for future considerations about cleaning and disinfection procedures and biosecurity protocols.

Transient medial prefrontal perturbation reduces false memory formation

Knowledge extracted across previous experiences, or schemas, benefit encoding and retention of congruent information. However, they can also reduce specificity and augment memory for semantically related, but false information. A demonstration of the latter is given by the Deese-Roediger-McDermott (DRM) paradigm, where the studying of words that fit a common semantic schema are found to induce false memories for words that are congruent with the given schema, but were not studied. The medial prefrontal cortex (mPFC) has been ascribed the function of leveraging prior knowledge to influence encoding and retrieval, based on imaging and patient studies. Here, we used transcranial magnetic stimulation (TMS) to transiently perturb ongoing mPFC processing immediately before participants performed the DRM-task. We observed the predicted reduction in false recall of critical lures after mPFC perturbation, compared to two control groups, whereas veridical recall and recognition memory performance remained similar across groups. These data provide initial causal evidence for a role of the mPFC in biasing the assimilation of new memories and their consolidation as a function of prior knowledge.