Role of the medial prefrontal cortex in coping and resilience

The development of an fMRI protocol to investigate vmPFC network functioning underlying the generalization of behavioral control

Experiencing behavioral control over stress can have long-lasting and generalizing effects. Animal research has shown that vmPFC-subcortical interactions are critical for behavioral control; however, research in humans is sparse. Therefore a paradigm was developed in which participants (n = 18) were first assigned to a controllable or uncontrollable version of a signal detection task associated with mild shocks. Subsequently, subjects underwent an fMRI task on the anticipation of speaking in public while measuring self-reported stress, heart rate, and vmPFC network topology. The signal detection task results revealed faster responses to potential shock trials and a trend difference between the controllable and uncontrollable group. The speech anticipation procedure did not show significant between-group differences on self-reported stress or heart rate. fMRI results indicated higher vmPFC efficiency in the controllable threat group at baseline and recovery but similar to the uncontrollable group during speech anticipation. The current report establishes the feasibility of the protocol. However, to evaluate the generalization effect of controllability on the behavioral, physiological, and neural levels further, adequately-powered follow-up research is needed.

Autophagy status as a gateway for stress-induced catecholamine interplay in neurodegeneration

The catecholamine-containing brainstem nuclei locus coeruleus (LC) and ventral tegmental area (VTA) are critically involved in stress responses. Alterations of catecholamine systems during chronic stress may contribute to neurodegeneration, including cognitive decline. Stress-related catecholamine alterations, while contributing to anxiety and depression, might accelerate neuronal degeneration by increasing the formation of toxic dopamine and norepinephrine by-products. These, in turn, may impair proteostasis within a variety of cortical and subcortical areas. In particular, the molecular events governing neurotransmission, neuroplasticity, and proteostasis within LC and VTA affect a variety of brain areas. Therefore, we focus on alterations of autophagy machinery in these nuclei as a relevant trigger in this chain of events. In fact, these catecholamine-containing areas are mostly prone to autophagy-dependent neurodegeneration. Thus, we propose a dynamic hypothesis according to which stress-induced autophagy alterations within the LC-VTA network foster a cascade towards early neurodegeneration within these nuclei.

The Gender Safety Gap: Examining the Impact of Victimization History, Perceived Risk, and Personal Control

Previous research has documented that, in general, women are more concerned about their personal safety and take more safety precautions than men. However, this study looks beyond gender by examining the association of three overall factors including victimization history, perceived risk of future victimization, and personal control with worry about safety, safety responses, and bystander intervention intentions for 270 men and 821 women. There were four main findings from this study including the following: (a) The two most consistently associated factors with worry about safety, safety responses, and bystander intervention intentions were higher perceived risk of violent victimization and safety efficacy; (b) recent victimization, rather than victimization history, played an important role in safety responses particularly for women; (c) different patterns of factors are associated with different safety responses demonstrating the importance of examining a wide variety of safety responses; and (d) the pattern of factors associated with worry about safety and safety responses do differ by gender but also had some important similarities. Implications for future research and prevention as well as safety planning interventions are discussed.

Resilience to fear: The role of individual factors in amygdala response to stressors

Resilience to stress is an adaptive process that varies individually. Resilience refers to the adaptation, or the ability to maintain or regain mental health, despite being subject to adverse situation. Resilience is a dynamic concept that reflects a combination of internal individual factors, including age and gender interacting with external factors such as social, cultural and environmental factors. In the last decade, we have witnessed an increase in the prevalence of anxiety disorders, including post-traumatic stress disorder. Given that stress in unavoidable, it is of great interest to understand the neurophysiological mechanisms of resilience, the individual factors that may contribute to susceptibility and promote efficacious approaches to improve resilience. Here, we address this complex question, attempting at defining clear and operational definitions that may allow us to improve our analysis of behavior incorporating individuality. We examine how individual perception of the stressor can alter the outcome of an adverse situation using as an example, the fear-conditioning paradigm and discuss how individual differences in the reward system can contribute to resilience. Given the central role of the endocannabinoid system in regulating fear responses and anxiety, we discuss the evidence that polymorphisms in several molecules of this signaling system contribute to different anxiety phenotypes. The endocannabinoid system is highly interconnected with the serotoninergic and dopaminergic modulatory systems, contributing to individual differences in stress perception and coping mechanisms. We review how the individual variability in these modulatory systems can be used towards a multivariable assessment of stress risk. Incorporating individuality in our research will allow us to define biomarkers of anxiety disorders as well as assess prognosis, towards a personalized clinical approach to mental health.

Functional networks activated by controllable and uncontrollable stress in male and female rats

The ability of an individual to reduce the intensity, duration or frequency of a stressor is a critical determinant of the consequences of that stressor on physiology and behavior. To expand our understanding of the brain networks engaged during controllable and uncontrollable stress and to identify sex differences, we used functional connectivity analyses of the immediate early gene product Fos in male and female rats exposed to either controllable or uncontrollable tail shocks. Twenty-eight regions of interest (ROI) were selected from the structures previously evinced to be responsible for stress response, action-outcome learning, or sexual dimorphism. We found that connectivity across these structures was strongest in female rats without control while weaker connectivity was evident in male rats with control over stress. Interestingly, this pattern correlates with known behavioral sex differences where stressor controllability leads to resilience in male but not female rats. Graph theoretical analysis identified several structures important to networks under specific conditions. In sum, the findings suggest that control over stress reshapes functional connectivity.

A systems-neuroscience model of phasic dopamine

We describe a neurobiologically informed computational model of phasic dopamine signaling to account for a wide range of findings, including many considered inconsistent with the simple reward prediction error (RPE) formalism. The central feature of this PVLV framework is a distinction between a primary value (PV) system for anticipating primary rewards (Unconditioned Stimuli [USs]), and a learned value (LV) system for learning about stimuli associated with such rewards (CSs). The LV system represents the amygdala, which drives phasic bursting in midbrain dopamine areas, while the PV system represents the ventral striatum, which drives shunting inhibition of dopamine for expected USs (via direct inhibitory projections) and phasic pausing for expected USs (via the lateral habenula). Our model accounts for data supporting the separability of these systems, including individual differences in CS-based (sign-tracking) versus US-based learning (goal-tracking). Both systems use competing opponent-processing pathways representing evidence for and against specific USs, which can explain data dissociating the processes involved in acquisition versus extinction conditioning. Further, opponent processing proved critical in accounting for the full range of conditioned inhibition phenomena, and the closely related paradigm of second-order conditioning. Finally, we show how additional separable pathways representing aversive USs, largely mirroring those for appetitive USs, also have important differences from the positive valence case, allowing the model to account for several important phenomena in aversive conditioning. Overall, accounting for all of these phenomena strongly constrains the model, thus providing a well-validated framework for understanding phasic dopamine signaling. (PsycInfo Database Record (c) 2020 APA, all rights reserved).

Association of Prefrontal-Striatal Functional Pathology With Alcohol Abstinence Days at Treatment Initiation and Heavy Drinking After Treatment Initiation

OBJECTIVE

Alcohol use disorder (AUD) is associated with neuroadaptations in brain stress and reward circuits. It is not known whether such neuroadaptations are affected by number of days of alcohol abstinence and whether they influence heavy drinking during the early treatment phase. The authors used a novel functional MRI (fMRI) approach to assess brain responses during sustained exposure to standardized visual stimuli of stressful, alcohol cue, and neutral control images combined with prospective assessment of drinking outcomes during early outpatient treatment, in two related studies.

METHODS

In study 1, 44 treatment-entering patients with AUD and 43 demographically matched healthy control subjects participated in the fMRI experiment to identify dysfunctional responses associated with chronic alcohol abuse. In study 2, 69 treatment-entering patients with AUD were assessed for whether fMRI responses at treatment initiation were influenced by alcohol abstinence and were prospectively predictive of early heavy drinking outcomes.

RESULTS

Relative to control subjects, patients with AUD showed significant hyperreactivity in the ventromedial prefrontal cortex (vmPFC) in response to neutral images, but significant hypoactivation in the vmPFC and ventral striatum in response to stress images and to alcohol cues relative to response to neutral images. In study 2, this specific prefrontal-ventral striatal dysfunction was associated with fewer days of alcohol abstinence and also predicted greater number heavy drinking days during the subsequent 2 weeks of treatment engagement.

CONCLUSIONS

Number of days of alcohol abstinence at treatment initiation significantly affected functional disruption of the prefrontal-striatal responses to stress images and to alcohol cues in patients with AUD, and the severity of this disruption in turn predicted greater heavy drinking during early treatment. Treatments that target this functional prefrontal-striatal pathology could improve early treatment outcomes in AUD.

Chemogenetic Inhibition of Infralimbic Prefrontal Cortex GABAergic Parvalbumin Interneurons Attenuates the Impact of Chronic Stress in Male Mice

Hypofunction of the prefrontal cortex (PFC) contributes to stress-related neuropsychiatric illnesses. Mechanisms leading to prefrontal hypoactivity remain to be determined. Prior evidence suggests that chronic stress leads to an increase in activity of parvalbumin (PV) expressing GABAergic interneurons (INs) in the PFC. The purpose of the study was to determine whether reducing PV IN activity in the Infralimbic (IL) PFC would prevent stress-related phenotypes. We used a chemogenetic approach to inhibit IL PFC PV INs during stress. Mice were first tested in the tail suspension test (TST) to determine the impact of PV IN inhibition on behavioral responses to acute stress. The long-term impact of PV IN inhibition during a modified chronic variable stress (CVS) was tested in the forced swim test (FST). Acute PV IN inhibition reduced active (struggling) and increased passive coping behaviors (immobility) in the TST. In contrast, inhibition of PV INs during CVS increased active and reduced passive coping behaviors in the FST. Moreover, chronic inhibition of PV INs attenuated CVS-induced changes in Fos expression in the prelimbic cortex (PrL), basolateral amygdala (BLA), and ventrolateral periaqueductal gray (vlPAG) and also attenuated adrenal hypertrophy and body weight loss associated with chronic stress. Our results suggest differential roles of PV INs in acute versus chronic stress, indicative of distinct biological mechanisms underlying acute versus chronic stress responses. Our results also indicate a role for PV INs in driving chronic stress adaptation and support literature evidence suggesting cortical GABAergic INs as a therapeutic target in stress-related illnesses.

Involvement of P2X2 receptor in the medial prefrontal cortex in ATP modulation of the passive coping response to behavioral challenge

P2X2 and P2X3 receptors are widely expressed in both the peripheral nervous system and the central nervous system and have been proven to participate in different peripheral sensory functions, but there are few studies on the involvement of P2X2 and P2X3 receptors in animal behaviors. Here we used P2X2 and P2X3 knockout mice to address this issue. P2X2 knockout mice showed normal motor function, exploratory behavior, anxiety-like behaviors, learning and memory behaviors and passive coping response to behavioral challenge. Nevertheless, the effect of ATP infusion in the medial prefrontal cortex (mPFC) on the passive coping response was blocked by P2X2 but not P2X3 receptor deletion. Additionally, no deficits in a wide variety of behavioral tests were observed in P2X3 knockout mice. These findings demonstrate a role of P2X2 receptor in the mPFC in adenosine-5'-triphosphate modulation of the passive coping response to behavioral challenge and show that the P2X2/P2X3 receptor is dispensable for behaviors.

Brief stress impairs recognition memory through amygdalar activation in animals with medial prefrontal cortex lesions

The medial prefrontal cortex (mPFC) is thought to exert inhibitory control over stress-induced activation of the amygdala and neurocognitive effects. As evidence to support this, we examined how exposure to either a brief or prolonged stress affected on amygdalar c-Fos levels and recognition memory of animals with mPFC chemical lesions. mPFC-lesioned and sham-operated animals were subjected to either a brief 20-min restraint+20 tailshocks or a prolonged 60-min restraint+60 tailshocks. Post-stress performances in the object recognition memory and c-Fos immunoreactivity in the amygdala were then assessed. In sham-operated animals, the object recognition memory was reliably impaired following the prolonged, but not following the brief stress exposure. On the other hand, in mPFC-lesioned animals, the brief stress significantly impaired recognition memory and enhanced c-Fos expression in the amygdala. Present findings of loss of mPFC activity exacerbating stress effects provide causal evidence that the mPFC exerts inhibitory control on stress.

Activation of Infralimbic to Nucleus Accumbens Shell Pathway Suppresses Conditioned Aversion in Male But Not Female Rats

Hedonic processing plays an integral role in directing appropriate behavior, but disrupted hedonic processing is associated with psychiatric disorders such as depression. The infralimbic cortex (IL) is a key structure in affective processing in rodents and activation of its human homolog, the ventromedial prefrontal cortex, has been implicated in suppressing aversive states. Here, we tested whether optogenetic activation of glutamatergic projections from the IL to the nucleus accumbens shell (NAcSh) suppresses the aversive impact of sucrose devalued using the conditioned taste aversion paradigm in males and female rats. In naive rats, no significant differences in appetitive or aversive taste reactivity (TR) to sucrose was observed indicating that initial sucrose palatability was equivalent across sex. However, we found that optical activation of the IL-NAcSh pathway during intraoral infusion of devalued sucrose inhibited aversive TR in male but not female rats. Interestingly, when allowed to freely ingest water and sucrose in a two-bottle test both males and females with a history of IL-NAcSh stimulation exhibited greater preference for sucrose. Optical pathway activation failed to alter TR to innately bitter quinine in either sex. Finally, both sexes lever pressed to self-stimulate the IL-NAcSh pathway. These results indicate that the IL-NAcSh pathway plays an important role in suppressing learned aversive states selectively in males but spares hedonic processing of innately aversive tastants. Further, pathway activation is reinforcing in both sexes, indicating that suppression of conditioned aversive TR can be dissociable from the effects of unconditioned rewarding properties of IL-NAcSh pathway activation.SIGNIFICANCE STATEMENT Negative emotional states contribute to psychiatric disorders including depression and substance use disorders. In this study, we examined whether brain circuitry previously implicated in suppressing negative emotional states in humans can inhibit learned aversion in male and female rats. We found that optical activation of the infralimbic to nucleus accumbens shell pathway attenuates learned aversive responses in male but not female rats, indicating an important sex difference in the function of this brain pathway. Furthermore, we found that pathway stimulation was reinforcing in both sexes. Collectively, these findings support the role of the infralimbic cortex and its projection to the nucleus accumbens shell in suppressing learned negative emotional states and highlight an important sex-specific function of this pathway.

Chronic stress and anticipatory event-related potentials: the moderating role of resilience

Chronic stress exposure is associated with impaired cognitive function; however, the underlying mechanism is not yet clear. This study investigated the association between perceived chronic stress and anticipatory processing, measured by event-related potentials, and the moderating role of resilience on this relationship in healthy adults. Fifty-nine healthy volunteers (22.52 ± 1.75 years) underwent a continuous performance test, and anticipatory processing was indexed with the contingent negative variation (CNV) of event-related potentials, the Cohen Perceived Stress Scale, and the Connor-Davidson Resilience Scale. The results showed that greater reports of perceived chronic stress were associated with more negative early CNVs; however, there was no significant relationship between perceived chronic stress and behavioral performance on the continuous performance test. More importantly, the relationship between perceived chronic stress and early CNV was moderated by resilience as the association between the Cohen Perceived Stress Scale score and early CNV amplitude was significant for low and average levels of resilience. These results not only suggest that chronic stress may lead to decreased cognitive efficiency in cortical anticipatory activity, but also underscore the role of resilience as a key protective factor in decreased cognitive efficiency.

Astrocyte-Derived Lactate Modulates the Passive Coping Response to Behavioral Challenge in Male Mice

Every organism inevitably experiences stress. In the face of acute, intense stress, for example, periods of passivity occur when an organism's actions fail to overcome the challenge. The occurrence of inactive behavior may indicate that struggling would most likely be fruitless. Repeated serious stress has been associated with mood disorders such as depression. The modulation of passive coping response patterns has been explored with a focus on the circuit level. However, the cellular and molecular mechanisms are largely uncharacterized. Here, we report that lactate is a key factor in the astrocytic modulation of the passive coping response to behavioral challenge in adult mice. We found increased extracellular lactate in the medial prefrontal cortex (mPFC) when mice experienced the forced swimming test (FST). Furthermore, we discovered that disturbing astrocytic glycogenolysis, which is a key step for lactate production in the mPFC, decreased the duration of immobility in the FST. Knocking down monocarboxylate transporter 4 (MCT4), which is expressed exclusively in astrocytes and transports lactate from astrocytes to the extracellular space, caused similar results in the FST. The behavioral effect of both the pharmacological disturbance of astrocytic glycogenolysis and viral disruption of MCT4 expression was rescued via the administration of L-lactate. Moreover, we found that both pharmacological and viral modulation of astrocyte-derived lactate in mPFC slices increased the excitability of layer V pyramidal neurons, and this enhancement was reversed by exogenous L-lactate administration. These results highlight astrocyte-derived lactate as a biological mechanism underlying the passive coping response to behavioral challenge and may provide new strategies to prevent mood disorders.

Optogenetic reactivation of prefrontal social neural ensembles mimics social buffering of fear

Social buffering occurs when the presence of a companion attenuates the physiological and/or behavioral effects of a stressful or fear-provoking event. It represents a way in which social interactions can immediately and potently modulate behavior. As such, social buffering is one mechanism by which strong social support increases resilience to mental illness. Although the behavioral and neuroendocrine impacts of social buffering are well studied in multiple species, including humans, the neuronal underpinnings of this behavioral phenomenon remain largely unexplored. Previous work has shown that the infralimbic prefrontal cortex (IL-PFC) is important for processing social information and, in separate studies, for modulating fear and anxiety. Thus, we hypothesized that socially active cells within the IL-PFC may integrate social information to modulate fear responsivity. To test this hypothesis, we employed social buffering paradigms in male and female mice. Similar to prior studies in rats, we found that the presence of a cagemate reduced freezing in fear- and anxiety-provoking contexts. In accordance with previous work, we demonstrated that interaction with a novel or familiar conspecific induces activity in the IL-PFC as evidenced by increased immediate early gene (IEG) expression. We then utilized an activity-dependent tagging murine line, the ArcCreER^T2 mice, to express channelrhodopsin (ChR2) in neurons active during the social encoding of a new cagemate. We found that optogenetic reactivation of these socially active neuronal ensembles phenocopied the effects of cagemate presence in male and female mice in learned and innate fear contexts without being inherently rewarding or altering locomotion. These data suggest that a social neural ensemble within the IL-PFC may contribute to social buffering of fear. These neurons may represent a novel therapeutic target for fear and anxiety disorders.

Exploring the bi-directional relationship between sleep and resilience in adolescence

OBJECTIVE

The study examined whether overall sleep quality and the sleep components comprising the Pittsburgh Sleep Quality Index (PSQI) have a bi-directional relationship with resilience among adolescents, after adjusting for sex, age, depression, and socioeconomic status, and investigated which sleep components have a stronger effect on resilience.

METHODS

A total of 1299 students (58% females; mean age, 15.79 years) participated at baseline, with 840 finishing all four study waves over the course of 24 months. Data were collected through questionnaires, including socio-demographics, the Pittsburgh Sleep Quality Index, Patient Health Questionnaire 9-item, and the Connor-Davidson Resilience Scale. Cross-lagged models were used to analyze the relationships between sleep and resilience.

RESULTS

Both daytime dysfunction and sleep disturbance had an independent bi-directional relationship with resilience. Higher resilience scores predicted overall better sleep quality and shorter sleep latency, but not vice versa. Sleep disturbance and daytime dysfunction had stronger effects on resilience.

CONCLUSIONS

These findings highlight the importance of future school interventions for sleep to improve students' resilience.

Influences of early-life stress on frontolimbic circuitry: Harnessing a dimensional approach to elucidate the effects of heterogeneity in stress exposure

Early-life stress confers profound and lasting risk for developing cognitive, social, emotional, and physical health problems. The effects of stress on the developing brain contribute to this risk, with frontolimbic circuitry particularly susceptible to early experiences, possibly due to its innervation with glucocorticoid receptors and the timing of frontolimbic circuit maturation. To date, the majority of studies on stress and frontolimbic circuitry have employed a categorical approach, comparing stress-exposed versus non-stress-exposed youth. However, there is vast heterogeneity in the nature of stress exposure and in outcomes. Recent forays into understanding the psychobiological effects of stress have employed a dimensional approach focused on experiential, environmental, and temporal factors that influence the association between stress and subsequent vulnerability. This review highlights empirical findings that inform a dimensional approach to understanding the effects of stress on frontolimbic circuitry. We identify the timing, type, severity, controllability, and predictability of stress, and the degree to which a caregiver is involved, as specific features of stress that may play a substantial role in differential outcomes. We propose a framework for the effects of these features of stress on frontolimbic development that may partially determine how heterogeneity in stress exposure influences this circuitry and, ultimately, mental health.

Cognitive appraisal in fish: stressor predictability modulates the physiological and neurobehavioural stress response in sea bass

The role of cognitive factors in triggering the stress response is well established in humans and mammals (aka cognitive appraisal theory) but very seldom studied in other vertebrate taxa. Predictability is a key factor of the cognitive evaluation of stimuli. In this study, we tested the effects of stressor predictability on behavioral, physiological and neuromolecular responses in the European sea bass (Dicentrarchus labrax). Groups of four fish were exposed to a predictable (signalled) or unpredictable (unsignalled) stressor. Stressor predictability elicited a lower behavioural response and reduced cortisol levels. Using the expression of immediate early genes (c-fos, egr-1, bdnf and npas4) as markers of neuronal activity, we monitored the activity of three sea bass brain regions known to be implicated in stressor appraisal: the dorsomedian telencephalon, Dm (putative homologue of the pallial amygdala); and the dorsal (Dld) and ventral (Dlv) subareas of the dorsolateral telencephalon (putative homologue of the hippocampus). The activity of both the Dm and Dlv significantly responded to stressor predictability, suggesting an evolutionarily conserved role of these two brain regions in information processing related to stressor appraisal. These results indicate that stressor predictability plays a key role in the activation of the stress response in a teleost fish, hence highlighting the role of cognitive processes in fish stress.

Functional and Dysfunctional Neuroplasticity in Learning to Cope with Stress

In this brief review, we present evidence of the primary role of learning-associated plasticity in the development of either adaptive or maladaptive coping strategies. Successful interactions with novel stressors foster plasticity within the neural circuits supporting acquisition, consolidation, retrieval, and extinction of instrumental learning leading to development of a rich repertoire of flexible and context-specific adaptive coping responses, whereas prolonged or repeated exposure to inescapable/uncontrollable stressors fosters dysfunctional plasticity within the learning circuits leading to perseverant and inflexible maladaptive coping strategies. Finally, the results collected using an animal model of genotype-specific coping styles indicate the engagement of different molecular networks and the opposite direction of stress effects (reduced vs. enhanced gene expression) in stressed animals, as well as different behavioral alterations, in line with differences in the symptoms profile associated with post-traumatic stress disorder.

Longitudinal Trajectories of Post-Election Distress Track Changes in Neural and Psychological Functioning

The shift in political climate after the 2016 U.S. presidential election had a distressing effect on many individuals. To date, no research has identified how changes in societal-level distressing experiences affected ongoing neurobiological and psychological functioning. Fifty-five participants (M_age = 21.746, 37 women) were tested at two time points. fMRI and psychological measures were used to test the hypotheses that increases in distress over 1 year would relate to worsening mental health symptomology and blunted neurobiological response to reward during the same period. Because individual experiences of distress occurred within a larger macroclimate of societal attitudes, measures were standardized to reflect relative change within the sample. Distress changes over 1 year were positively associated with problematic mental health symptomology and nucleus accumbens (NAcc) response to reward, with dissociable effects for anticipation and outcome. Worsening distress was associated with increased NAcc response to reward anticipation but decreased NAcc response to reward outcome. Individuals who exhibited increased sensitivity to anticipatory reward were those who exhibited more avoidance distress symptoms, whereas intrusion and hyperarousal were associated with decreased sensitivity to reward outcome. This study highlights the importance of considering individual variation in profiles of change in response to ongoing distress, suggests that individual response styles yield differences in reward sensitivity, and extends neurobiological understanding of exposure to stressful life experiences to political events.

Monoacylglycerol lipase alpha inhibition alters prefrontal cortex excitability and blunts the consequences of traumatic stress in rat

Neural activity within the ventromedial prefrontal cortex (vmPFC) is a critical determinant of stressor-induced anxiety. Pharmacological activation of the vmPFC during stress protects against stress-induced social anxiety suggesting that altering the excitatory/inhibitory (E/I) tone in the vmPFC may promote stress resilience. E/I balance is maintained, in part, by endogenous cannabinoid (eCB) signaling with the calcium dependent retrograde release of 2-arachidonoylglycerol (2-AG) suppressing presynaptic neurotransmitter release. We hypothesized that raising 2-AG levels, via inhibition of its degradation enzyme monoacylglycerol lipase (MAGL) with KML29, would shift vmPFC E/I balance and promote resilience. In acute slice experiments, bath application of KML29 (100 nM) augmented evoked excitatory neurotransmission as evidenced by a left-shift in fEPSP I/O curve, and decreased sIPSC amplitude. In whole-cell recordings, KML29 increased resting membrane potential but reduced the after depolarization, bursting rate, membrane time constant and slow after hyperpolarization. Intra-vmPFC administration of KML29 (200ng/0.5μL/hemisphere) prior to inescapable stress (IS) exposure (25, 5s tail shocks) prevented stress induced anxiety as measured by juvenile social exploration 24 h after stressor exposure. Conversely, systemic administration of KML29 (40 mg/kg, i.p.) 2 h before IS exacerbated stress induced anxiety. MAGL inhibition in the vmPFC may promote resilience by augmenting the output of neurons that project to brainstem and limbic structures that mediate stress responses.

Corticostriatal Circuits Encode the Subjective Value of Perceived Control

The ability to perceive and exercise control over an outcome is both desirable and beneficial to our well-being. It has been shown that animals and humans alike exhibit behavioral bias towards seeking control and that such bias recruits the ventromedial prefrontal cortex (vmPFC) and striatum. Yet, this bias remains to be quantitatively captured and studied neurally. Here, we employed a behavioral task to measure the preference for control and characterize its neural underpinnings. Participants made a series of binary choices between having control and no-control over a game for monetary reward. The mere presence of the control option evoked activity in the ventral striatum. Importantly, we manipulated the expected value (EV) of each choice pair to extract the pairing where participants were equally likely to choose either option. The difference in EV between the options at this point of equivalence was inferred as the subjective value of control. Strikingly, perceiving control inflated the reward value of the associated option by 30% and this value inflation was tracked by the vmPFC. Altogether, these results capture the subjective value of perceived control inherent in decision making and highlight the role of corticostriatal circuitry in the perception of control.

A Key Role for Prefrontocortical Small Conductance Calcium-Activated Potassium Channels in Stress Adaptation and Rapid Antidepressant Response

The muscarinic acetylcholine receptor antagonist scopolamine elicits rapid antidepressant activity, but its underlying mechanism is not fully understood. In a chronic stress model, a single low-dose administration of scopolamine reversed depressive-like reactivity. This antidepressant-like effect was mediated via a muscarinic M1 receptor–SKC pathway because it was mimicked by intra-medial prefrontal cortex (intra-mPFC) infusions of scopolamine, of the M1 antagonist pirenzepine or of the SKC antagonist apamin, but not by the selective serotonin reuptake inhibitor (SSRI) antidepressant fluoxetine. Extracellular and whole-cell recordings revealed that scopolamine and ketamine attenuate the SKC-mediated action potential hyperpolarization current and rapidly enhance mPFC neuronal excitability within the therapeutically relevant time window. The SKC agonist 1-EBIO abrogated scopolamine-induced antidepressant activity at a dose that completely suppressed burst firing activity. Scopolamine also induced a slow-onset activation of raphe serotonergic neurons, which in turn was dependent on mPFC-induced neuroplasticity or excitatory input, since mPFC transection abolished this effect. These early behavioral and mPFC activational effects of scopolamine did not appear to depend on prefrontocortical brain-derived neurotrophic factor and serotonin-1A activity, classically linked to SSRIs, and suggest a novel mechanism associated with antidepressant response onset through SKC-mediated regulation of activity-dependent plasticity.

Susceptibility and Resilience to PTSD-Like Symptoms in Mice Are Associated with Opposite Dendritic Changes in the Prelimbic and Infralimbic Cortices Following Trauma

Post-traumatic stress disorder (PTSD) is triggered by exposure to traumatic events, but not everyone who experiences trauma develops this disorder. Like humans, PTSD-like symptoms develop in some laboratory rodents (susceptible individuals), while others express less or no symptoms (resilient individuals). Here, considering (i) the putative causal role of fear conditioning in PTSD development and (ii) the involvement of the medial prefrontal cortex (mPFC) in the regulation of conditioned fear response, we tested whether trauma-associated changes in the mPFC may discriminate stress-resilient from stress-susceptible mice. From data on avoidance behavior (as a major symptom), we found that trauma-exposed mice displayed a bimodal distribution in their step-through latency, with low avoider (stress-resilient) individuals and high avoider (stress-susceptible) individuals. Dendrites of Golgi-Cox-stained neurons were analyzed in two parts of the mPFC: the prelimbic (PrL) and infralimbic (IL) areas. In the resilient phenotype, the total number of dendrites decreased in the PrL and increased in the IL; however, it decreased only in the IL in the susceptible phenotype compared to controls. These findings demonstrate that the type of post-trauma morphological changes in the mPFC is associated with susceptibility or resilience to trauma-related symptoms.

Impaired Motor Learning Following a Pain Episode in Intact Rats

Motor learning and pain are important factors influencing rehabilitation. Despite being mostly studied independently from each other, important interactions exist between them in the context of spinal cord injury, whether to the spinal cord or the body. Ongoing or recent past episodes of nociceptive activity can prevent motor learning in spinalized rats. In intact animals, it has been proposed that supraspinal activity could counter the repressive effect of nociception on motor system plasticity, but this has not yet been verified in behavioral conditions. The aim of this study was to test whether a recent episode of nociception affects subsequent motor learning in intact animals. We trained rodents to walk on a custom-made horizontal ladder. After initial training, the rats underwent a week-long rest, during which they were randomly assigned to a control group, or one out of two pain conditions. Nociceptive stimuli of different durations were induced through capsaicin or Complete Freund's Adjuvant injections and timed so that the mechanical hypersensitivity had entirely subsided by the end of the resting period. Training then resumed on a modified version of the horizontal ladder. We evaluated the animals' ability to adapt to the modified task by measuring their transit time and paw misplacements over 4 days. Our results show that prior pain episodes do affect motor learning in neurologically intact rats. Motor learning deficits also seem to be influenced by the duration of the pain episode. Rats receiving a subcutaneous injection of capsaicin displayed immediate signs of mechanical hypersensitivity, which subsided rapidly. Nonetheless, they still showed learning deficits 24 h after injection. Rats who received a Complete Freund's Adjuvant injection displayed mechanical hypersensitivity for up to 7 days during the resting period. When trained on the modified ladder task upon returning to normal sensitivity levels, these rats exhibited more prolonged motor learning deficits, extending over 3 days. Our results suggest that prior pain episodes can negatively influence motor learning, and that the duration of the impairment relates to the duration of the pain episode. Our results highlight the importance of addressing pain together with motor training after injury.

Loss of control over mild aversive events produces significant helplessness in mice

Most of the pathophysiology of depression are still unknown because of its numerous disease states of distinct etiology and pathogenesis. Stressful rodent models have been used to test a number of hypotheses regarding the etiology of depression. The learned helplessness rodent model demonstrates that having no control at all over aversive events produces helplessness and depression, but the role of loss of control over aversive events in helplessness is still not reliably modelled or deeply investigated. A rodent model of helplessness produced by loss of control is closer to human conditions and is therefore more useful for novel mechanistic and pre-clinic studies. The present work proposed a triadic experimental design in which a Loss Of Control (LOC) group of mice was firstly exposed to escapable mild footshocks to acquire control, and then to inescapable shocks to lose control, with a yoked (L-Yoked) group receiving identical but always uncontrollable shocks. Although both the LOC and the L-Yoked groups developed helplessness, as compared with the naive control group, the helplessness exhibited in the LOC group was significantly more serious than that in the L-Yoked group. The difference in severity between the LOC and the L-Yoked groups demonstrates the effects of loss of control over aversive events, in addition to the effects of the aversive events per se. The LOC paradigm can be used to reproduce pathology of depression induced by loss of control over aversive life events, with a good constructive validity.

Sex- and Stress-Dependent Effects on Dendritic Morphology and Spine Densities in Putative Orexin Neurons

We recently found that non-stressed female rats have higher basal prepro-orexin expression and activation of orexinergic neurons compared to non-stressed males, which lead to impaired habituation to repeated restraint stress at the behavioral, neural, and endocrine level. Here, we extended our study of sex differences in the orexin system by examining spine densities and dendritic morphology in putative orexin neurons in adult male and female rats that were exposed to 5 consecutive days of 30-min restraint. Analysis of spine distribution and density indicated that putative orexinergic neurons in control non-stressed females had significantly more dendritic spines than those in control males, and the majority of these were mushroom spines. This morphological finding may suggest more excitatory input onto orexin neurons in female rats. As orexin neurons are known to promote the hypothalamic-pituitary-adrenal response, this morphological change in orexin neurons could underlie the impaired habituation to repeated stress in female rats. Dendritic complexity did not differ between non-stressed males and females, however repeated restraint stress decreased total dendritic length, nodes, and branching primarily in males. Thus, reduced dendritic complexity of putative orexinergic neurons is observed in males but not in females after 5days of repeated restraint stress. This morphological change might be reflective of decreased orexin system function, which may allow males to habituate more fully to repeated restraint than females. These results extend our understanding of the role of orexin neurons in regulating habituation and demonstrate changes in putative orexin cell morphology and spines that may underlie sex differences in habituation.

Effects of Ethanol Exposure and Withdrawal on Neuronal Morphology in the Agranular Insular and Prelimbic Cortices: Relationship with Withdrawal-Related Structural Plasticity in the Nucleus Accumbens

The present study investigated the effects of chronic intermittent ethanol exposure and withdrawal on dendritic morphology and spine density in the agranular insular and prelimbic cortices. Adult male Sprague–Dawley rats were passively exposed to vaporized ethanol (~37 mg/L; 12 h/day) or air (control) for ten consecutive days. Dendritic length, branching, and spine density were quantified in layer II/III pyramidal neurons 24 hours or seven days following the final ethanol exposure. Compared to unexposed control animals there were structural alterations on neurons in the prelimbic cortex, and to a lesser extent the agranular insular cortex. The most prominent ethanol-related differences were the transient increases in dendritic length and branching in prelimbic neurons at 24 h post-cessation, and increased mushroom-shaped spines at seven days post-cessation. The results obtained in the prelimbic cortex are the opposite of those previously reported in the nucleus accumbens core (Peterson, et al. 2015), suggesting that these regions undergo distinct functional adaptations following ethanol exposure and withdrawal.

Sex differences in neural stress responses and correlation with subjective stress and stress regulation

Emotional stress responses, encompassing both stress reactivity and regulation, have been shown to differ between men and women, but the neural networks supporting these processes remain unclear. The current study used functional neuroimaging (fMRI) to investigate sex differences in neural responses during stress and the sex-specific relationships between these responses and emotional stress responses for men and women. A significant sex by condition interaction revealed that men showed greater stress responses in prefrontal cortex (PFC) regions, whereas women had stronger responses in limbic/striatal regions. Although men and women did not significantly differ in emotional stress reactivity or subjective reports of stress regulation, these responses were associated with distinct neural networks. Higher dorsomedial PFC responses were associated with lower stress reactivity in men, but higher stress reactivity in women. In contrast, while higher ventromedial PFC stress responses were associated with worse stress regulation in men (but better regulation in women), dynamic increases in vmPFC responses during stress were associated with lower stress reactivity in men. Finally, stress-induced hippocampal responses were more adaptive for women: for men, high and dynamically increasing responses in left hippocampus were associated with high stress reactivity, and dynamic increases in the left (but not right) hippocampus were associated with worse stress regulation. Together, these results reveal that men and women engage distinct neural networks during stress, and sex-specific neural stress responses facilitate optimal emotional stress responses.

Neuronal Dynamics Regulating Brain and Behavioral State Transitions

Prolonged behavioral challenges can cause animals to switch from active to passive coping strategies to manage effort-expenditure during stress; such normally adaptive behavioral state transitions can become maladaptive in psychiatric disorders such as depression. The underlying neuronal dynamics and brainwide interactions important for passive coping have remained unclear. Here, we develop a paradigm to study these behavioral state transitions at cellular-resolution across the entire vertebrate brain. Using brainwide imaging in zebrafish, we observed that the transition to passive coping is manifested by progressive activation of neurons in the ventral (lateral) habenula. Activation of these ventral-habenula neurons suppressed downstream neurons in the serotonergic raphe nucleus and caused behavioral passivity, whereas inhibition of these neurons prevented passivity. Data-driven recurrent neural network modeling pointed to altered intra-habenula interactions as a contributory mechanism. These results demonstrate ongoing encoding of experience features in the habenula, which guides recruitment of downstream networks and imposes a passive coping behavioral strategy.

Naltrexone Acutely Enhances Connectivity Between the Ventromedial Prefrontal Cortex and a Left Frontoparietal Network

BACKGROUND

Naltrexone, an opioid receptor antagonist that is Food and Drug Administration approved for treating alcohol use disorder (AUD), reduces alcohol craving and intake. Despite known pharmacological properties, little is known regarding the effects of naltrexone on neural circuit function. Thus, a data-driven examination of the neural effects of naltrexone in human subjects may offer novel insight into its treatment mechanisms.

METHODS

Twenty-one alcohol using males (22 to 39) participated in a double-blind, placebo-controlled crossover study of the effects of naltrexone on brain voxel-wise functional connectivity (FC) using intersubject FC correlation mapping. We first cross-correlated the time series from each gray matter voxel to produce a 6,356 × 6,356 FC matrix for each subject and session. We then subtracted the placebo FC matrix from the naltrexone FC matrix. To identify brain regions demonstrating significant reconfiguration of whole-brain FC patterns following naltrexone treatment, we statistically quantified the consistency of patterns of voxel FC changes across subjects. Permutation testing identified significant clusters of voxels undergoing significant reconfiguration. Using the identified clusters in a seed-based FC analysis, we then compared the FC patterns of affected brain areas on placebo versus naltrexone in a paired t-test. Ridge regression analyses identified self-report measures, including substance use, that significantly predicted individual differences in FC among naltrexone-modulated regions.

RESULTS

Two clusters in the rostral anterior cingulate cortex (rACC)/ventromedial prefrontal cortex (vmPFC) demonstrated significant modulation of FC by naltrexone. Using these 2 proximal clusters as a single seed, specific FC changes were identified in regions associated with a left frontoparietal network (increasing), as well as visual and motor regions (decreasing). Stronger FC between the rACC/vmPFC and this set of regions on placebo was associated with more external locus of control, whereas weaker connectivity was associated with greater substance use problems. Naltrexone strengthened these connections most among individuals who reported greater drinking to cope.

CONCLUSIONS

Enhancing connectivity between the rACC/vmPFC, implicated in alcohol craving, and components of a left frontoparietal network involved in executive control may represent an effective strategy for the treatment of AUD.

Top-down and bottom-up control of stress-coping

In this 30th anniversary issue review, we focus on the glucocorticoid modulation of limbic-prefrontocortical circuitry during stress-coping. This action of the stress hormone is mediated by mineralocorticoid receptors (MRs) and glucocorticoid receptors (GRs) that are co-expressed abundantly in these higher brain regions. Via both receptor types, the glucocorticoids demonstrate, in various contexts, rapid nongenomic and slower genomic actions that coordinate consecutive stages of information processing. MR-mediated action optimises stress-coping, whereas, in a complementary fashion, the memory storage of the selected coping strategy is promoted via GR. We highlight the involvement of adipose tissue in the allocation of energy resources to central regulation of stress reactions, point to still poorly understood neuronal ensembles in the prefrontal cortex that underlie cognitive flexibility critical for effective coping, and evaluate the role of cortisol as a pleiotropic regulator in vulnerability to, and treatment of, trauma-related psychiatric disorders.

Modulation of neuroplasticity-related targets following stress-induced acute escape deficit

Understanding resilience is a major challenge to improve current pharmacological therapies aimed at complementing psychological-based approaches of stress-related disorders. In particular, resilience is a multi-factorial construct where the complex network of molecular events that drive the process still needs to be resolved. Here, we exploit the acute escape deficit model, an animal model based on exposure to acute unavoidable stress followed by an escape test, to define vulnerable and resilient phenotypes in rats. Hippocampus and prefrontal cortex (PFC), two of the brain areas most involved in the stress response, were analysed for gene expression at two different time points (3 and 24 h) after the escape test. Total Brain-Derived Neurotrophic Factor (BDNF) was highly responsive in the PFC at 24-h after the escape test, while expression of BDNF transcript IV increased in the hippocampus of resistant animals 3 h post-test. Expression of memory enhancers like Neuronal PAS Domain Protein 4 (Npas4) and Activity-regulated cytoskeleton-associated protein (Arc) decreased in a time- and region-dependent fashion in both behavioural phenotypes. Also, the memory inhibitor Protein Phosphatase 1 (Ppp1ca) was increased in the hippocampus of resilient rats at 3 h post-test. Given the importance of neurotrophic factors and synaptic plasticity-related genes for the development of appropriate coping strategies, our data contribute to an additional step forward in the comprehension of the psychobiology of stress and resiliency.

Development of social play in hamsters: Sex differences and their possible functions

In several rodent species social play appears to be necessary for proper deployment of species-specific patterns of aggressive and reproductive behavior. Specifically, in male Syrian hamsters (Mesocricetus auratus), play has been linked to the development of adult aggression. We quantified several types of social play behavior in same-sex peer groups of Syrian hamsters three times per week for three consecutive weeks after weaning, which included postnatal days 22-42 (PD22 to PD42). Male hamsters increased playful contact during PD36-PD42, whereas females showed peak playful contact during PD29-PD35. These findings suggest that the motivation for social play increases during mid-adolescence in males, but dissipates in females. To investigate the effects of social play deprivation, one hamster per litter remained pair-housed with its mother forthree weeks after weaning its littermates. In adulthood, both play-deprived and play-exposed animals received acute social defeat stress followed by social interaction testing. Play deprivation led to increased defeat-induced social avoidance in both males and females. In males, play deprivation increased fighting back during social defeat stress, whereas in females it reduced aggressive behavior during conditioned defeat testing. We suggest that social play deprivation disrupts neural circuits regulating aggression in a sex-specific manner, perhaps related to sex differences in territorial defense, but has similar effects on neural circuits regulating stress responsivity. Overall, these findings suggest that juvenile social play functions to promote coping with stress and appropriate social behavior in adulthood.

Prefrontal-Bed Nucleus Circuit Modulation of a Passive Coping Response Set

One of the challenges facing neuroscience entails localization of circuits and mechanisms accounting for how multiple features of stress responses are organized to promote survival during adverse experiences. The rodent medial prefrontal cortex (mPFC) is generally regarded as a key site for cognitive and affective information processing, and the anteroventral bed nuclei of the stria terminalis (avBST) integrates homeostatic information from a variety of sources, including the mPFC. Thus, we proposed that the mPFC is capable of generating multiple features (endocrine, behavioral) of adaptive responses via its influence over the avBST. To address this possibility, we first optogenetically inhibited input to avBST from the rostral prelimbic cortical region of mPFC and observed concurrent increases in immobility and hypothalamo-pituitary-adrenal (HPA) output in male rats during tail suspension, whereas photostimulation of this pathway decreased immobility during the same challenge. Anatomical tracing experiments confirmed projections from the rostral prelimbic subfield to separate populations of avBST neurons, and from these to HPA effector neurons in the paraventricular hypothalamic nucleus, and to aspects of the midbrain periaqueductal gray that coordinate passive defensive behaviors. Finally, stimulation and inhibition of the prelimbic-avBST pathway, respectively, decreased and increased passive coping in the shock-probe defensive burying test, without having any direct effect on active coping (burying) behavior. These results define a new neural substrate in the coordination of a response set that involves the gating of passive, rather than active, coping behaviors while restraining neuroendocrine activation to optimize adaptation during threat exposure.SIGNIFICANCE STATEMENT The circuits and mechanisms accounting for how multiple features of responses are organized to promote adaptation have yet to be elucidated. Our report identifies a prefrontal-bed nucleus pathway that organizes a response set capable of gating passive coping behaviors while concurrently restraining neuroendocrine activation during exposure to inescapable stressors. These data provide insight into the central organization of how multiple features of responses are integrated to promote adaptation during adverse experiences, and how disruption in one neural pathway may underlie a broad array of maladaptive responses in stress-related psychiatric disorders.

Behavioral and neural mechanisms underlying habitual and compulsive drug seeking

Addiction is characterized by compulsive drug use despite negative consequences. Here we review studies that indicate that compulsive drug use, and in particular punishment resistance in animal models of addiction, is related to impaired cortical control over habitual behavior. In humans and animals, instrumental behavior is supported by goal-directed and habitual systems that rely on distinct corticostriatal networks. Chronic exposure to addictive drugs or stress has been shown to bias instrumental response strategies toward habit learning, and impair prefrontal cortical (PFC) control over responding. Moreover, recent work has implicated prelimbic PFC hypofunction in the punishment resistance that has been observed in a subset of animals with an extended history of cocaine self-administration. This may be related to a broader role for prelimbic PFC in mediating adaptive responding and behavioral flexibility, including exerting goal-directed control over behavior. We hypothesize that impaired cortical control and reduced flexibility between habitual and goal-directed systems may be critically involved in the development of maladaptive, compulsive drug use.

Recover from the adversity: functional connectivity basis of psychological resilience

Psychological resilience refers to the ability that individuals can positively adapt and respond to stress and adversity. It is important for mental health and well-being. However, there was few study examined the functional connectivity basis of psychological resilience. The present study used resting-state seed-based functional connectivity to explore the neural basis of psychological resilience and its association with positive affect in a big healthy sample. Results showed that resilience is associated with functional connectivity between regions involved in emotional flexibility, coping ability, and inhibitory control. Specifically, resilience is positively correlated with the strength of the left insula and the right parahippocampus connectivity which is involved in the self-evaluation process. It is also positively correlated with the strength of the left orbitofrontal gyrus (OFC) and the left inferior frontal gyrus (IFG) connectivity which is associated with the flexible use of emotional resources and flexible control in processing affective information. Additionally, resilience is negatively correlated with the strength of the left OFC and the right precuneus connectivity which is implicated in the rumination in negatively self-related thoughts. Crucially, the left OFC-IFG connectivity mediated the effect of positive affect on resilience, supporting the opinion that positive affect facilitates resilience by broadening one's attention and promoting flexible thinking and coping abilities. In summary, these findings extend previous studies by revealing the functional connectivity basis of psychological resilience and highlighting the left OFC-IFG connectivity as a neural substrate linking positive affect and psychological resilience.

Prefrontal endocannabinoids, stress controllability and resilience: A hypothesis

Stressor exposure is a predisposing risk factor for many psychiatric conditions such as PTSD and depression. However, stressors do not influence all individuals equally and in response to an identical stressor some individuals may be vulnerable while others are resilient. While various biological and behavioral factors contribute to vulnerability versus resilience, an individual's degree of control over the stressor is among the most potent. Even with only one experience with control over stress, behavioral control has been shown to have acute and long-lasting stress-mitigating effects. This suggests that control both blunts the response to acute stress and prepares the subject to be resilient to future stressors. In this review, we first summarize the evidence which suggests the ventromedial prefrontal cortex (vmPFC) is a critical component of stressor controllability circuits and a locus of neuroplasticity supporting the acute and long-lasting consequences of control. We next review the central endocannabinoid (eCB) system as a possible mediator of short and long-term synaptic transmission in the vmPFC, and offer a hypothesis whereby eCBs regulate vmPFC circuits engaged when a subject has control over stress and may contribute to the encoding of acute stress coping into long lasting stressor resilience.

Interpersonal dysfunction in borderline personality: a decision neuroscience perspective

Borderline personality disorder (BPD) is characterized by disadvantageous decisions that are often expressed in close relationships and associated with intense negative emotions. Although functional neuroimaging studies of BPD have described regions associated with altered social cognition and emotion processing, these correlates do not inform an understanding of how brain activity leads to maladaptive choices. Drawing on recent research, we argue that formal models of decision-making are crucial to elaborating theories of BPD that bridge psychological constructs, behavior, and neural systems. We propose that maladaptive interactions between Pavlovian and instrumental influences play a crucial role in the expression of interpersonal problems. Finally, we articulate specific hypotheses about how clinical features of BPD may map onto neural systems that implement separable decision processes.

Anteroventral bed nuclei of the stria terminalis neurocircuitry: Towards an integration of HPA axis modulation with coping behaviors - Curt Richter Award Paper 2017

A network of interconnected cell groups in the limbic forebrain regulates hypothalamic-pituitary-adrenal (HPA) axis activation and behavioral responses to emotionally stressful experiences, and chronic disruption of these systems chronically is implicated in the pathogenesis of psychiatric illnesses. A significant challenge has been to unravel the circuitry and mechanisms providing for regulation of HPA activity, as these limbic forebrain regions do not provide any direct innervation of HPA effector cell groups in the paraventricular hypothalamus (PVH). Moreover, information regarding how endocrine and behavioral responses are integrated has remained obscure. Here we summarize work from our laboratory showing that anteroventral (av) bed nuclei of the stria terminalis (BST) acts as a point of convergence between the limbic forebrain and PVH, receiving and coordinating upstream influences, and restraining HPA axis output in response to inescapable stressors. Recent studies highlight a more expansive modulatory role for avBST as one that coordinates HPA-inhibitory influences while concurrently suppressing passive behavioral responses via divergent pathways. avBST is uniquely positioned to convey endocrine and behavioral alterations resulting from chronic stress exposure, such as HPA axis hyperactivity and increased passive coping strategies, that may result from synaptic reorganization in upstream limbic cortical regions. We discuss how these studies give new insights into understanding the systems-level organization of stress response circuitry, the neurobiology of coping styles, and BST circuit dysfunction in stress-related psychiatric disorders.

Inhibition of a Descending Prefrontal Circuit Prevents Ketamine-Induced Stress Resilience in Females

Stress is a potent etiological factor in the onset of major depressive disorder and posttraumatic stress disorder (PTSD). Therefore, significant efforts have been made to identify factors that produce resilience to the outcomes of a later stressor, in hopes of preventing untoward clinical outcomes. The NMDA receptor antagonist ketamine has recently emerged as a prophylactic capable of preventing neurochemical and behavioral outcomes of a future stressor. Despite promising results of preclinical studies performed in male rats, the effects of proactive ketamine in female rats remains unknown. This is alarming given that stress-related disorders affect females at nearly twice the rate of males. Here we explore the prophylactic effects of ketamine on stress-induced anxiety-like behavior and the neural circuit-level processes that mediate these effects in female rats. Ketamine given one week prior to an uncontrollable stressor (inescapable tailshock; IS) reduced typical stress-induced activation of the serotonergic (5-HT) dorsal raphe nucleus (DRN) and eliminated DRN-dependent juvenile social exploration (JSE) deficits 24 h after the stressor. Proactive ketamine altered prelimbic cortex (PL) neural ensembles so that a later experience with IS now activated these cells, which it ordinarily would not. Ketamine acutely activated a PL to DRN (PL-DRN) circuit and inhibition of this circuit with Designer Receptors Exclusively Activated by Designer Drugs (DREADDs) at the time of IS one week later prevented stress prophylaxis, suggesting that persistent changes in PL-DRN circuit activity are responsible, at least in part, for mediating long-term effects associated with ketamine.

Coping with Childbirth: Brain Structural Associations of Personal Growth Initiative

Major life events require psychological adaptations and can be accompanied by brain structural and functional changes. The goal of the current study was to investigate the association of personal growth initiative (PGI) as a form of proactive coping strategy before childbirth, with gray matter volume after delivery. Childbirth is one of the few predictable major life events, which, while being one of the most positive experiences for many, is also accompanied by multidimensional stress for the mother. Previous research has shown that high stress is associated with reductions in gray matter volume in limbic cortices as well as the prefrontal cortex (PFC). We hypothesized that PGI before childbirth is positively related to gray matter volume after delivery, especially in the ventromedial PFC (vmPFC). In a prospective study, 22 first-time mothers answered questionnaires about their PGI level 1 month before birth (T1) and 1 month after delivery (T2). Four months after giving birth, a follow-up assessment was applied with 16 of these mothers (T3). Structural brain data were acquired at both postpartal measurement occasions. Voxel-based morphometry was used to correlate prenatal PGI levels with postpartal gray matter volume. Higher PGI levels before delivery were positively associated with larger gray matter volume in the vmPFC directly after childbirth. Previous structural neuroimaging research in the context of major life events focused primarily on pathological reactions to stress (e.g., post-traumatic stress disorder; PTSD). The current study gives initial indications that proactive coping may be positively associated with gray matter volume in the vmPFC, a brain region which shows volumetric reductions in PTSD patients.