The AURORA Study: a longitudinal, multimodal library of brain biology and function after traumatic stress exposure

Adverse posttraumatic neuropsychiatric sequelae (APNS) are common among civilian trauma survivors and military veterans. These APNS, as traditionally classified, include posttraumatic stress, postconcussion syndrome, depression, and regional or widespread pain. Traditional classifications have come to hamper scientific progress because they artificially fragment APNS into siloed, syndromic diagnoses unmoored to discrete components of brain functioning and studied in isolation. These limitations in classification and ontology slow the discovery of pathophysiologic mechanisms, biobehavioral markers, risk prediction tools, and preventive/treatment interventions. Progress in overcoming these limitations has been challenging because such progress would require studies that both evaluate a broad spectrum of posttraumatic sequelae (to overcome fragmentation) and also perform in-depth biobehavioral evaluation (to index sequelae to domains of brain function). This article summarizes the methods of the Advancing Understanding of RecOvery afteR traumA (AURORA) Study. AURORA conducts a large-scale (n = 5000 target sample) in-depth assessment of APNS development using a state-of-the-art battery of self-report, neurocognitive, physiologic, digital phenotyping, psychophysical, neuroimaging, and genomic assessments, beginning in the early aftermath of trauma and continuing for 1 year. The goals of AURORA are to achieve improved phenotypes, prediction tools, and understanding of molecular mechanisms to inform the future development and testing of preventive and treatment interventions.

Function and mechanisms of memory destabilization and reconsolidation after retrieval

Memory retrieval is not a passive process. When a memory is retrieved, the retrieved memory is destabilized, similar to short-term memory just after learning, and requires memory reconsolidation to re-stabilize the memory. Recent studies characterizing destabilization and reconsolidation showed that a retrieved memory is not always destabilized and that there are boundary conditions that determine the induction of destabilization and reconsolidation according to certain parameters, such as the duration of retrieval and the memory strength and age. Moreover, the reconsolidation of contextual fear memory is not independent of memory extinction; rather, these memory processes interact with each other. There is an increasing number of findings suggesting that destabilization following retrieval facilitates the modification, weakening, or strengthening of the original memory, and the resultant updated memory is stabilized through reconsolidation. Reconsolidation could be targeted therapeutically to improve emotional disorders such as post-traumatic stress disorder and phobia. Thus, this review summarizes recent findings to understand the mechanisms and function of reconsolidation.

The impact of traumatic stress on Pavlovian biases

BACKGROUND

Disturbances in Pavlovian valuation systems are reported to follow traumatic stress exposure. However, motivated decisions are also guided by instrumental mechanisms, but to date the effect of traumatic stress on these instrumental systems remain poorly investigated. Here, we examine whether a single episode of severe traumatic stress influences flexible instrumental decisions through an impact on a Pavlovian system.

METHODS

Twenty-six survivors of the 2011 Norwegian terror attack and 30 matched control subjects performed an instrumental learning task in which Pavlovian and instrumental associations promoted congruent or conflicting responses. We used reinforcement learning models to infer how traumatic stress affected learning and decision-making. Based on the importance of dorsal anterior cingulate cortex (dACC) for cognitive control, we also investigated if individual concentrations of Glx (=glutamate + glutamine) in dACC predicted the Pavlovian bias of choice.

RESULTS

Survivors of traumatic stress expressed a greater Pavlovian interference with instrumental action selection and had significantly lower levels of Glx in the dACC. Across subjects, the degree of Pavlovian interference was negatively associated with dACC Glx concentrations.

CONCLUSIONS

Experiencing traumatic stress appears to render instrumental decisions less flexible by increasing the susceptibility to Pavlovian influences. An observed association between prefrontal glutamatergic levels and this Pavlovian bias provides novel insight into the neurochemical basis of decision-making, and suggests a mechanism by which traumatic stress can impair flexible instrumental behaviours.

Traumatic Stress and Accelerated Cellular Aging: From Epigenetics to Cardiometabolic Disease

PURPOSE OF REVIEW

The aim of this paper is to review the recent literature on traumatic stress-related accelerated aging, including a focus on cellular mechanisms and biomarkers of cellular aging and on the clinical manifestations of accelerated biological aging.

RECENT FINDINGS

Multiple lines of research converge to suggest that PTSD is associated with accelerated aging in the epigenome, and the immune and inflammation systems, and this may be reflected in premature onset of cardiometabolic and cardiovascular disease. The current state of research paves the way for future work focused on identifying the peripheral and central biological mechanisms linking traumatic stress to accelerated biological aging and medical morbidity, with an emphasis on processes involved in inflammation, immune functioning, oxidative stress, autonomic arousal, and stress response. Ultimately, such work could help reduce the pace of biological aging and improve health and wellness.

Human and animal research into sex-specific effects of child abuse

Child abuse is the most potent experiential risk factor for developing a mood disorder later in life. The effects of child abuse are also more severe in girls and women than in men. In this review, we explore the origins of this epidemiological sex difference. We begin by offering the hypothesis that a sex-specific risk factor that influences how social cues are perceived and remembered makes girls more susceptible to the effects of child abuse. We then discuss the neural systems that mediate emotion and stress, and, how child abuse and/or mood disorders like anxiety and depression affect them. Drawing upon human and animal research, several candidates for such a risk factor are discussed. They include glucocorticoid receptor trafficking and corticotropin releasing factor receptor binding and signaling. Our own research shows that the morphometry of the prepubertal amygdala is sexually dimorphic, and could contribute to a sex difference in stimulus appraisal. We have also found that the brain of juvenile female rats is less selective than males' for threatening social stimuli. Thus, one way that women may be more vulnerable to the effects of child abuse is that they are more likely to perceive objectively benign stimuli as threatening. This bias in perception could compound with the genuinely traumatic memories caused by child abuse; the burden of traumatic memories and the increasingly reactive stress response systems could then dispose more women than men to develop depression and/or anxiety.

Minireview: Stress-related psychiatric disorders with low cortisol levels: a metabolic hypothesis

Several stress-associated neuropsychiatric disorders, notably posttraumatic stress disorder and chronic pain and fatigue syndromes, paradoxically exhibit somewhat low plasma levels of the stress hormone cortisol. The effects appear greatest in those initially traumatized in early life, implying a degree of developmental programming, perhaps of both lower cortisol and vulnerability to psychopathology. In these conditions, lowered cortisol is not due to any adrenal or pituitary insufficiency. Instead, two processes appear involved. First, there is increased target cell sensitivity to glucocorticoid action, notably negative feedback upon the hypothalamic-pituitary-adrenal (stress) axis. Altered density of the glucocorticoid receptor is inferred, squaring with much preclinical data showing early life challenges can permanently program glucocorticoid receptors in a tissue-specific manner. These effects involve epigenetic mechanisms. Second, early life trauma/starvation induces long-lasting lowering of glucocorticoid catabolism, specifically by 5α-reductase type 1 (predominantly a liver enzyme) and 11β-hydroxysteroid dehydrogenase type 2 (in kidney), an effect also seen in model systems. These changes reflect a plausible early-life adaptation to increase the persistence of active cortisol in liver (to maximize fuel output) and kidney (to increase salt retention) without elevation of circulating levels, thus avoiding their deleterious effects on brain and muscle. Modestly lowered circulating cortisol and increased vulnerability to stress-associated disorders may be the outcome. This notion implies a vulnerable early-life phenotype may be discernable and indicates potential therapy by modest glucocorticoid replacement. Indeed, early clinical trials with cortisol have shown a modicum of promise.

[Relationship between NR1 subunit of N-methyl-D-aspartate receptor and visceral hypersensitivity caused by acute restraint stress: experiment with rats]

OBJECTIVE

To investigate the response of NR1 subunit of N-methyl-D-aspartate (NMDA) receptor to restraint stress in intestinal tract.

METHODS

Thirty Sprague-Dawley rats were randomly divided into 3 equal groups: acute stress group undergoing intraperitoneal injection of normal saline (NS), acute stress + MK-801 group, undergoing intraperitoneal injection of MK-801, a NMDA receptor inhibitor, and then acute restraint for 1 h, 30 min after the injection. Control group underwent intraperitoneal injection of NS without acute restraint to be used as. Then all rats underwent colorectal distension (CRD) at the pressure levels of 20, 40, 60, and 80 mm Hg respectively for 10 s 3 times with an interval of 40 s so as to establish visceral hypersensitivity models. Electromyography was performed at the external oblique muscle of abdomen to record the frequency of discharge to evaluate the visceral sensitivity. Then the rats were killed and specimens of ileocecum and the proximal and distal ends of colon were obtained. RT-PCR and Western blotting were used to detect the mRNA and protein expression of NMDA receptor NR1 subunit in intestinal tract.

RESULTS

(1) The frequencies of discharge of external oblique muscle of abdomen responding to CRD of the acute stress group at the pressure levels of 40, 60, and 80 mm Hg were 925 +/- 217, 1480 +/- 347, and 1732 +/- 344 respectively, all significantly higher than those of the control group (188 +/- 31, 510 +/- 68, and 765 +/- 103, all P < 0.01) and the acute stress + MK-801 group (210 +/- 47, 525 +/- 97, 841 +/- 156, all P < 0.05). But no significantly different from the acute stress + MK-801 group and the control group (all P > 0.05). (2) The A values of the mRNA expression of NR1 in the ileocecal junction, proximal colon end, and distal colon end of the acute stress group were 1.57 +/- 0.20, 2.00 +/- 0.20, and 1.36 +/- 0.17 respectively, all significantly higher than those of the control group (0.68 +/- 0.10, 0.87 +/- 0.19, and 0.74 +/- 0.15, all P < 0.01) and the acute stress + MK-801 group (0.84 +/- 0.13, 0.91 +/- 0.16, 0.79 +/- 0.13, all P < 0.05). But no significantly different from the acute stress + MK-801 group and the control group (all P > 0.05). (3) The A values of the protein expression of NR1 in the ileocecal junction, proximal colon end, and distal colon end of the acute stress group were 1.69 +/- 0.20, 1.41 +/- 0.12, and 1.63 +/- 0.15 respectively, all significantly higher than those of the control group (0.54 +/- 0.11, 0.71 +/- 0.06, 0.71 +/- 0.07, all P = 0.000) and the acute + MK-801 group (0.75 +/- 0.09, 0.70 +/- 0.11, 0.63 +/- 0.11, all P = 0.000). But no significantly different from the acute stress + MK-801 group and the control group (all P > 0.05).

CONCLUSION

NMDA receptor plays an important role in the visceral sensitivity induced by acute restraint stress.

Prolonged expression of c-Fos protein in the lateral habenular nucleus of the Japanese monkey (Macaca fuscata) after eye enucleation

To elucidate the effect of traumatic stress on the lateral habenular nucleus, we investigated the time course of the expression of c-Fos protein in this nucleus of the Japanese monkey (Macaca fuscata) after enucleation of one eye using c-Fos protein immunocytochemistry. c-Fos protein-like immunoreactive neurons were significantly increased; the increase started 1 h after the enucleation and remained high for 3-9 h in the lateral habenular nucleus on both sides. These results suggest that the prolonged expression of c-Fos protein occurred in the lateral habenular nucleus after traumatic stress through multiple transsynaptic activations.

Genomic regions controlling corticosterone levels in rats

BACKGROUND

The identification of genetic factors controlling stress-responsiveness should advance the understanding of susceptibility to psychiatric illness.

METHODS

Rat strains, F344/NHsd and LEW/NHsd, which differ in measures of stress-responsiveness and behaviors modeling psychiatric disorders, were bred to generate F2 progeny that were used in a quantitative trait loci (QTL) analysis to identify genomic regions influencing late-afternoon corticosterone levels.

RESULTS

Regions on chromosomes 4 and 10 previously identified as influencing autoimmune phenomena were the most significant QTL observed, reaching suggestive significance at the genome-wide level. Congenic animals targeting these regions with F344/NHsd deoxyribonucleic acid on a DA/Bkl genomic background demonstrated corticosterone levels approximating those of F344/NHsd rats and differing significantly from DA/Bkl rats.

CONCLUSIONS

Specific genomic regions influence both corticosterone levels and stress-related disease susceptibility. These findings not only represent the first identification of QTL controlling corticosterone levels but also suggest a mechanism underlying genetic differences in stress-responsiveness.