Avoidant symptoms in PTSD predict fear circuit activation during multimodal fear extinction

Phospholipase C beta 1 in the dentate gyrus gates fear memory formation through regulation of neuronal excitability

Memory processes rely on a molecular signaling system that balances the interplay between positive and negative modulators. Recent research has focused on identifying memory-regulating genes and their mechanisms. Phospholipase C beta 1 (PLCβ1), highly expressed in the hippocampus, reportedly serves as a convergence point for signal transduction through G protein-coupled receptors. However, the detailed role of PLCβ1 in memory function has not been elucidated. Here, we demonstrate that PLCβ1 in the dentate gyrus functions as a memory suppressor. We reveal that mice lacking PLCβ1 in the dentate gyrus exhibit a heightened fear response and impaired memory extinction, and this excessive fear response is repressed by upregulation of PLCβ1 through its overexpression or activation using a newly developed optogenetic system. Last, our results demonstrate that PLCβ1 overexpression partially inhibits exaggerated fear response caused by traumatic experience. Together, PLCβ1 is crucial in regulating contextual fear memory formation and potentially enhancing the resilience to trauma-related conditions.

Contemporaneous and temporal network analysis of complex Posttraumatic stress disorder among Chinese college students with Childhood adversity: A longitudinal study

OBJECTIVE

To enhance understanding of the longitudinal progression of complex posttraumatic stress disorder (CPTSD) symptoms, this longitudinal study examined how CPTSD symptoms interact over time in Chinese college students with childhood trauma.

METHODS

From 18,933 college students who took part in two surveys 12 months apart, 4,006 participants who reported adverse childhood experiences were screened. Cross-sectional network comparisons and cross-lagged panel network (CLPN) analysis characterized interactions among CPTSD symptoms.

RESULTS

In the cross-sectional networks, feeling like a failure and avoid activities reminiscent of the trauma were the central symptoms. Takes long time to calm down and exaggerated startle are important bridge symptoms in the two networks respectively. The comparison of cross-sectional networks indicates that the global network strength was stable. The findings of the CLPN model reveal that feel worthless and feel like a failure had the highest "out" expected influence; exaggerated startle and avoid thoughts and feelings about the trauma had the highest "in" expected influence.

CONCLUSIONS

By conducting cross-sectional network analyses, the study illuminated the attributes of CPTSD networks across various time points. Additionally, the CLPN analysis uncovered the longitudinal patterns of CPTSD symptoms.

The Impact of War Trauma and Housing Environment on Mental Wellbeing of Syrian Refugees in Jordan: A Comparison between In-Camp and Urban Populations

The aim of this study is to compare mental wellbeing and levels of post-trauma distress between Syrian refugees who live inside camps and those who live outside camps in Jordan through a survey-based cross-sectional design, where data were collected from 240 adult Syrian refugees in Jordan. The Arabic versions of the Mental Health Continuum Short Form (MHC-SF), and the Impact of Event Scale-Revised (IES-R) were used to quantitatively measure variables through descriptive statistics and multiple comparative analysis tests. Despite having no significant correlation with residence, findings of the MHC-SF showed significance for mental wellbeing with employment status and income. Whereas IES-R showed that camp refugees fared significantly better in terms of trauma effect than urban refugees. It can be concluded that Syrian refugees living inside camps were disadvantaged in terms of mental wellbeing but slightly less affected by war in comparison to those living in urban areas. Improved programs and policies are needed to uplift the mental wellbeing of Syrian refugees in Jordan and to minimize the destructive traumatic effects of the Syrian war on their wellness.

The Vestibulocerebellum and the Shattered Self: a Resting-State Functional Connectivity Study in Posttraumatic Stress Disorder and Its Dissociative Subtype

The flocculus is a region of the vestibulocerebellum dedicated to the coordination of neck, head, and eye movements for optimal posture, balance, and orienting responses. Despite growing evidence of vestibular and oculomotor impairments in the aftermath of traumatic stress, little is known about the effects of chronic psychological trauma on vestibulocerebellar functioning. Here, we investigated alterations in functional connectivity of the flocculus at rest among individuals with post-traumatic stress disorder (PTSD) and its dissociative subtype (PTSD + DS) as compared to healthy controls. Forty-four healthy controls, 57 PTSD, and 32 PTSD + DS underwent 6-min resting-state MRI scans. Seed-based functional connectivity analyses using the right and left flocculi as seeds were performed. These analyses revealed that, as compared to controls, PTSD and PTSD + DS showed decreased resting-state functional connectivity of the left flocculus with cortical regions involved in bodily self-consciousness, including the temporo-parietal junction, the supramarginal and angular gyri, and the superior parietal lobule. Moreover, as compared to controls, the PTSD + DS group showed decreased functional connectivity of the left flocculus with the medial prefrontal cortex, the precuneus, and the mid/posterior cingulum, key regions of the default mode network. Critically, when comparing PTSD + DS to PTSD, we observed increased functional connectivity of the right flocculus with the right anterior hippocampus, a region affected frequently by early life trauma. Taken together, our findings point toward the crucial role of the flocculus in the neurocircuitry underlying a coherent and embodied self, which can be compromised in PTSD and PTSD + DS.

Adverse Life Experiences and Brain Function: A Meta-Analysis of Functional Magnetic Resonance Imaging Findings

Importance

Adverse life experiences have been proposed to contribute to diverse mental health problems through an association with corticolimbic functioning. Despite compelling evidence from animal models, findings from studies in humans have been mixed; activation likelihood estimation (ALE) meta-analyses have failed to identify a consistent association of adverse events with brain function.

Objective

To investigate the association of adversity exposure with altered brain reactivity using multilevel kernel density analyses (MKDA), a meta-analytic approach considered more robust than ALE to small sample sizes and methodological differences between studies.

Data Sources

Searches were conducted using PsycInfo, Medline, EMBASE, and Web of Science from inception through May 4, 2022. The following search term combinations were used for each database: trauma, posttraumatic stress disorder (PTSD), abuse, maltreatment, poverty, adversity, or stress; and functional magnetic resonance imaging (fMRI) or neuroimaging; and emotion, emotion regulation, memory, memory processing, inhibitory control, executive functioning, reward, or reward processing.

Study Selection

Task-based fMRI studies within 4 domains (emotion processing, memory processing, inhibitory control, and reward processing) that included a measure of adverse life experiences and whole-brain coordinate results reported in Talairach or Montreal Neurological Institute space were included. Conference abstracts, books, reviews, meta-analyses, opinions, animal studies, articles not in English, and studies with fewer than 5 participants were excluded.

Data Extraction and Synthesis

Using the Preferred Reporting Items for Systematic Reviews and Meta-Analyses reporting guideline, 2 independent reviewers assessed abstracts and full-text articles for entry criteria. A third reviewer resolved conflicts and errors in data extraction. Data were pooled using a random-effects model and data analysis occurred from August to November 2022.

Main Outcomes and Measures

Peak activation x-axis (left-right), y-axis (posterior-anterior), and z-axis (inferior-superior) coordinates were extracted from all studies and submitted to MKDA meta-analyses.

Results

A total of 83 fMRI studies were included in the meta-analysis, yielding a combined sample of 5242 participants and 801 coordinates. Adversity exposure was associated with higher amygdala reactivity (familywise error rate corrected at P < .001; x-axis = 22; y-axis = -4; z-axis = -17) and lower prefrontal cortical reactivity (familywise error rate corrected at P < .001; x-axis = 10; y-axis = 60; z-axis = 10) across a range of task domains. These altered responses were only observed in studies that used adult participants and were clearest among those who had been exposed to severe threat and trauma.

Conclusions and Relevance

In this meta-analysis of fMRI studies of adversity exposure and brain function, prior adversity exposure was associated with altered adult brain reactivity to diverse challenges. These results might better identify how adversity diminishes the ability to cope with later stressors and produces enduring susceptibility to mental health problems.

Enhancement of memory consolidation by an avoidance conditioned stimulus: Modulation by the D3 receptor

Conditioned stimuli (CS) paired with foot-shock can enhance memory consolidation. Because the dopamine D3R has been implicated in mediating various responses to CSs, the current study explored its potential role in modulation of memory consolidation by an avoidance CS. Male Sprague-Dawley rats trained to avoid foot-shocks in a two-way signalled active avoidance task (8 sessions, 30 trials per session, 0.8 mA foot-shock) were pre-treated with the D3R antagonist NGB-2904 (Vehicle, 0.1 or 5 mg/kg) and exposed to the CS immediately after the sample phase of an object recognition memory task. Discrimination ratios were assessed 72 h later. Immediate, but not delayed (6 h), post-sample exposure to the CS enhanced object recognition memory and this effect was dose-dependently blocked by NGB-2904. Control experiments with the beta-noradrenergic receptor antagonist propranolol (10 or 20 mg/kg) and D2R antagonist pimozide (0.2 or 0.6 mg/kg) indicated that NGB-2904 targeted post-training memory consolidation. Exploring the pharmacological selectivity of the D3R effect, it was found that: 1) 5 mg/kg NGB-2904 blocked conditioned memory modulation produced by post-sample exposure to a "weak" CS (one day of avoidance training) and concurrent stimulation of catecholamine activity by 10 mg/kg bupropion; 2) post-sample exposure to a "weak" CS and concurrent administration of the D3R agonist 7-OH-DPAT (1 mg/kg) enhanced consolidation of object memory. Finally, because 5 mg/kg NGB-2904 had no effect on modulation by avoidance training in the presence of foot-shocks, the findings herein support the hypothesis that the D3R plays an important role in modulation of memory consolidation by CSs.

Fear Extinction Learning in Posttraumatic Stress Disorder

Impairments in fear extinction processes have been implicated in the genesis and maintenance of debilitating psychopathologies, including Posttraumatic stress disorder (PTSD). PTSD, classified as a trauma- and stressor-related disorder, is characterized by four symptom clusters: intrusive recollections of trauma, avoidance of trauma-related stimuli, alterations in cognition and mood, and hyperarousal. One of the key pathological feature associated with the persistence of these symptoms is impaired fear extinction, as delineated in multiple studies employing Pavlovian fear-conditioning paradigms. These paradigms, comprising fear acquisition, extinction, extinction recall, and fear renewal phases, have illuminated the neurobiological substrates of PTSD. Dysfunctions in the neural circuits that mediate these fear learning and extinction processes can result in failure to extinguish fear responses and retain extinction memory, giving rise to enduring experience of fear and anxiety. The protective avoidance behaviors observed in individuals with PTSD further exacerbate intrusive symptoms and pose challenges to effective treatment strategies. A comprehensive analysis of fear conditioning and extinction processes, along with the underlying neurobiology, could significantly enhance our understanding of PTSD pathophysiology. This chapter delineates the role of fear extinction processes in PTSD, investigates the underlying neurobiological substrates, and underscores the therapeutic implications, while also identifying future research directions.

Potential Utility of Cannabidiol in Stress-Related Disorders

Background: The endocannabinoid (eCB) system plays an important role in homeostatic regulation of anxiety and stress responses; however, the eCB system can be disrupted following traumatic stressors. Additionally, traumatic or chronic stressors that occur during adulthood or early life can cause long-lasting disturbances in the eCB system. These alterations interfere with hypothalamic-pituitary-adrenal axis function and may be involved in lifelong increased fear and anxiety behaviors as well as increased risk for development of post-traumatic stress disorder (PTSD). Methods: This review focuses on the implications of trauma and significant stressors on eCB functionality and neural pathways, both in adolescence and into adulthood, as well as the current state of testing for CBD efficacy in treating pediatric and adult patients suffering from stress-induced eCB dysregulation. Articles were searched via Pubmed and included studies examining eCB modulation of stress-related disorders in both clinical settings and preclinical models. Conclusion: Given the potential for lifelong alterations in eCB signaling that can mediate stress responsiveness, consideration of pharmaceutical or nutraceutical agents that impact eCB targets may improve clinical outcomes in stress-related disorders. However, caution may be warranted in utilization of medicinal cannabinoid products that contain delta-9-tetrahydrocannabinol due to pronounced euphorigenic effects and potential to exacerbate stress-related behaviors. Other cannabinoid products, such as cannabidiol (CBD), have shown promise in reducing stress-related behaviors in pre-clinical models. Overall, pre-clinical evidence supports CBD as a potential treatment for stress or anxiety disorders resulting from previously stressful events, particularly by reducing fearful behavior and promoting extinction of contextual fear memories, which are hallmarks of PTSD. However, very limited clinical research has been conducted examining the potential effectiveness of CBD in this regard and should be examined further.

Reactivating hippocampal-mediated memories during reconsolidation to disrupt fear

Memories are stored in the brain as cellular ensembles activated during learning and reactivated during retrieval. Using the Tet-tag system in mice, we label dorsal dentate gyrus neurons activated by positive, neutral or negative experiences with channelrhodopsin-2. Following fear-conditioning, these cells are artificially reactivated during fear memory recall. Optical stimulation of a competing positive memory is sufficient to update the memory during reconsolidation, thereby reducing conditioned fear acutely and enduringly. Moreover, mice demonstrate operant responding for reactivation of a positive memory, confirming its rewarding properties. These results show that interference from a rewarding experience can counteract negative affective states. While memory-updating, induced by memory reactivation, involves a relatively small set of neurons, we also find that activating a large population of randomly labeled dorsal dentate gyrus neurons is effective in promoting reconsolidation. Importantly, memory-updating is specific to the fear memory. These findings implicate the dorsal dentate gyrus as a potential therapeutic node for modulating memories to suppress fear.

Divergent encoding of active avoidance behavior in corticostriatal and corticolimbic projections

Active avoidance behavior, in which an animal performs an action to avoid a stressor, is crucial for survival and may provide insight into avoidance behaviors seen in anxiety disorders. Active avoidance requires the dorsomedial prefrontal cortex (dmPFC), which is thought to regulate avoidance via downstream projections to the striatum and amygdala. However, the endogenous activity of dmPFC projections during active avoidance learning has never been recorded. Here we utilized fiber photometry to record from the dmPFC and its axonal projections to the dorsomedial striatum (DMS) and the basolateral amygdala (BLA) during active avoidance learning in both male and female mice. We examined neural activity during conditioned stimulus (CS) presentations and during clinically relevant behaviors such as active avoidance or cued freezing. Both prefrontal projections showed learning-related increases in activity during CS onset throughout active avoidance training. The dmPFC as a whole showed increased and decreased patterns of activity during avoidance and cued freezing, respectively. Finally, dmPFC-DMS and dmPFC-BLA projections show divergent encoding of active avoidance behavior, with the dmPFC-DMS projection showing increased activity and the dmPFC-BLA projection showing decreased activity during active avoidance. Our results demonstrate task-relevant encoding of active avoidance in projection-specific dmPFC subpopulations that play distinct but complementary roles in active avoidance learning.

Sleep-Wake and Arousal Dysfunctions in Post-Traumatic Stress Disorder:Role of Orexin Systems

Post-traumatic stress disorder (PTSD) is a trauma-related condition that produces distressing fear memory intrusions, avoidance behaviors, hyperarousal/startle, stress responses and insomnia. This review focuses on the importance of the orexin neural system as a novel mechanism related to the pathophysiology of PTSD. Orexinergic neurons originate in the lateral hypothalamus and project widely to key neurotransmitter system neurons, autonomic neurons, the hypothalamic-pituitaryadrenal (HPA) axis, and fear-related neural circuits. After trauma or stress, the basolateral amygdala (BLA) transmits sensory information to the central nucleus of the amygdala (CeA) and in turn to the hypothalamus and other subcortical and brainstem regions to promote fear and threat. Orexin receptors have a prominent role in this circuit as fear conditioned orexin receptor knockout mice show decreased fear expression while dual orexin receptor antagonists (DORAs) inhibit fear acquisition and expression. Orexin activation of an infralimbic-amygdala circuit impedes fear extinction while DORA treatments enhance it. Increased orexin signaling to the amygdalocortical- hippocampal circuit promotes avoidance behaviors. Orexin has an important role in activating sympathetic nervous system (SNS) activity and the HPA axis stress responses. Blockade of orexin receptors reduces fear-conditioned startle responses. In PTSD models, individuals demonstrate sleep disturbances such as increased sleep latency and more transitions to wakefulness. Increased orexin activity impairs sleep by promoting wakefulness and reducing total sleep time while DORA treatments enhance sleep onset and maintenance. The orexinergic neural system provides important mechanisms for understanding multiple PTSD behaviors and provides new medication targets to treat this often persistent and debilitating illness.

Hippocampal activation during contextual fear inhibition related to resilience in the early aftermath of trauma

BACKGROUND

Impaired contextual fear inhibition is often associated with posttraumatic stress disorder (PTSD). Our previous work has demonstrated that more hippocampal activation during a response inhibition task after trauma exposure was related to greater resilience and fewer future PTSD symptoms. In the current study, we sought to extend our previous findings by employing a contextual fear conditioning and extinction paradigm to further determine the role of the hippocampus in resilience and PTSD in the early aftermath of trauma.

METHODS

Participants (N = 28) were recruited in the Emergency Department shortly after experiencing a traumatic event. A contextual fear inhibition task was conducted in a 3 T MRI scanner approximately two months post-trauma. Measures of resilience (CD-RISC) at time of scan and PTSD symptoms three months post-trauma were collected. The associations between hippocampal activation during fear conditioning and during the effect of context during extinction, and post-trauma resilience and PTSD symptoms at three-months were assessed.

RESULTS

During fear conditioning, activation of the bilateral hippocampal region of interest (ROI) correlated positively with resilience (r = 0.48, p = 0.01). During the effect of context during extinction, greater bilateral hippocampal activation correlated with lower PTSD symptoms three months post-trauma after controlling for baseline PTSD symptoms, age and gender (r=-0.59, p=0.009).

CONCLUSIONS

Greater hippocampal activation was related to post-trauma resilience and lower PTSD symptoms three months post-trauma. The current study supports and strengthens prior findings suggesting the importance of hippocampus-dependent context processing as a mechanism for resilience versus PTSD risk, which could be a potential mechanistic target for novel early interventions.

Posttraumatic Stress Disorder Treatment Effects on Cardiovascular Physiology: A Systematic Review and Agenda for Future Research

Posttraumatic stress disorder (PTSD) is linked to both altered physiological functioning and poorer cardiovascular health outcomes, including an increased risk for cardiovascular disease and cardiovascular-related mortality. An important question is whether interventions for PTSD might ameliorate the risk for poorer health by improving cardiovascular physiological intermediaries. To begin to characterize the literature addressing this question, we conducted a systematic review of empirical studies examining the impact of PTSD interventions on cardiovascular physiological intermediaries, including blood pressure (BP), heart rate (HR), cardiac impedance, and subclinical atherosclerosis. Outcomes included both tonic (i.e., resting) cardiovascular functioning and cardiovascular reactivity (CVR). A total of 44 studies met the inclusion criteria. There was mixed evidence regarding whether PTSD treatment improved tonic cardiovascular functioning. There was stronger evidence that PTSD treatments reduced CVR to trauma-related stressors, particularly for higher-quality studies of cognitive behavioral interventions. No studies examined cardiac impedance or subclinical atherosclerosis. The studies had a high degree of heterogeneity in the populations sampled and interventions tested. Moreover, they generally included small sample sizes and lacked control conditions. Interventions for PTSD may improve cardiovascular physiological outcomes, particularly CVR to trauma cues, although additional methodologically rigorous studies are needed. We outline changes to future research that would improve the literature regarding this important question, including the more frequent use of control groups and larger sample sizes.

Roles for the Dorsal Striatum in Aversive Behavior

The ability to identify and avoid environmental stimuli that signal danger is essential to survival. Our understanding of how the brain encodes aversive behaviors has been primarily focused on roles for the amygdala, hippocampus (HIPP), prefrontal cortex, ventral midbrain, and ventral striatum. Relatively little attention has been paid to contributions from the dorsal striatum (DS) to aversive learning, despite its well-established role in stimulus-response learning. Here, we review studies exploring the role of DS in aversive learning, including different roles for the dorsomedial and dorsolateral striatum in Pavlovian fear conditioning as well as innate and inhibitory avoidance (IA) behaviors. We outline how future investigation might determine specific contributions from DS subregions, cell types, and connections that contribute to aversive behavior.

Fear-induced brain activations distinguish anxious and trauma-exposed brains

Translational models of fear conditioning and extinction have elucidated a core neural network involved in the learning, consolidation, and expression of conditioned fear and its extinction. Anxious or trauma-exposed brains are characterized by dysregulated neural activations within regions of this fear network. In this study, we examined how the functional MRI activations of 10 brain regions commonly activated during fear conditioning and extinction might distinguish anxious or trauma-exposed brains from controls. To achieve this, activations during four phases of a fear conditioning and extinction paradigm in 304 participants with or without a psychiatric diagnosis were studied. By training convolutional neural networks (CNNs) using task-specific brain activations, we reliably distinguished the anxious and trauma-exposed brains from controls. The performance of models decreased significantly when we trained our CNN using activations from task-irrelevant brain regions or from a brain network that is irrelevant to fear. Our results suggest that neuroimaging data analytics of task-induced brain activations within the fear network might provide novel prospects for development of brain-based psychiatric diagnosis.

Bridging "Office-Based Care" With the "Virtual Practice Care Model": Evolving Care for Chronic Kidney Disease Patients in the COVID-19 Pandemic-And Beyond

Since the outbreak of the coronavirus epidemic, the “virtual” telemedicine has become a critical substitute for patient-provider interactions. However, virtual encounters often face challenges in the care of patients in high-risk categories such as chronic kidney disease (CKD) patients. In this study, we explore the patient's satisfaction and the practical effects of a newly established telemedicine program on CKD patients' care during the COVID-19 pandemic. Based on a prior version of an online patient care platform established in 2017, we developed a customized and improved online telemedicine program designed to specifically address the challenges emerging from the pandemic. This included an online, smart phone-based strategy for triage and medical care delivery and psychological support. We invited a total of 278 CKD patients to join the new platform during the pandemic. The subjects in group A were patients utilizing our old online CKD system and were historical users registered at least 3 months before the pandemic. A pilot survey interrogating medical and psychological conditions was conducted. Feedback on the program as well as a psychological assessment were collected after 1 month. In total, 181 patients showed active responses to the program, with 289 person-time medical consultations occurring during the study. The virtual care program provided a rapid triage for 17% (30 out of 181) patients, with timely referral to in-patient medical encounters for their worsening medical conditions or severe psychological problems. Nearly all patients (97.4%) believed the program was helpful. The number of symptoms (OR 1.309, 95%CI 1.113–1.541; P = 0.001) and being enrolled during the pandemic (OR 3.939, 95% CI 1.174–13.221; P = 0.026) were associated with high stress. During the follow-up, the high-stress CKD group at baseline showed a significant decrease in avoidance score (6.9 ± 4.7 vs. 9.8 ± 1.9, P = 0.015). In conclusion, during the pandemic, we established an online telemedicine care program for CKD patients that provides a rapid triage function, effective CKD disease management, and potentially essential psychological support.

Alterations in fear extinction neural circuitry and fear-related behavior linked to trauma exposure in children

Exposure to childhood trauma is extremely common (>60 %) and is a leading risk factor for fear-based disorders, including anxiety and posttraumatic stress disorder. These disorders are characterized by deficits in fear extinction and dysfunction in underlying neural circuitry. Given the strong and pervasive link between childhood trauma and the development of psychopathology, fear extinction may be a key mechanism. The present study tests the impact of childhood trauma exposure on fear extinction and underlying neural circuitry. Children (N = 44, 45 % trauma-exposed; 6-11 yrs) completed a novel two-day virtual reality fear extinction experiment. On day one, participants underwent fear conditioning and extinction. Twenty-four hours later, participants completed a test of extinction recall during fMRI. Conditioned fear was measured throughout the experiment using skin conductance and fear-related behavior, and activation in fear-related brain regions was estimated during recall. There were no group differences in conditioned fear during fear conditioning or extinction learning. During extinction recall, however, trauma-exposed children kept more distance from both the previously extinguished and the safety cue, suggesting poor differentiation between threat and safety cues. Trauma-exposed youth also failed to approach the previously extinguished cue over the course of extinction recall. The effects on fear-related behavior during extinction recall were accompanied by higher activation to the previously extinguished cue in fear-relevant brain regions, including the dorsal anterior cingulate cortex and anterior insula, in trauma-exposed relative to control children. Alterations in fear-related brain regions and fear-related behavior may be a core mechanism through which childhood trauma confers heightened vulnerability to psychopathology.

Acute and Post-Traumatic Stress Disorders: A biased nervous system

Acute stress disorder and post-traumatic stress disorder are generally triggered by an exceptionally intense threat. The consequences of this traumatogenic situation are explored here in chronological order, from exposure to the threat to development of symptoms. Such a situation may disrupt the equilibrium between two fundamental brain circuits, referred to as the "defensive" and "cognitive". The defensive circuit triggers the stress response as well as the formation of implicit memory. The cognitive circuit triggers the voluntary response and the formation of explicit autobiographical memory. During a traumatogenic situation, the defensive circuit could be over-activated while cognitive circuit is under-activated. In the most severe cases, overactivation of the defensive circuit may cause its brutal deactivation, resulting in dissociation. Here, we address the underlying neurobiological mechanisms at every scale: from neurons to behaviors, providing a detailed explanatory model of trauma.

An integrated model of chronic trauma-induced insomnia

Insomnia is the most commonly reported symptom of posttraumatic stress disorder (PTSD), with at least 70% of patients with PTSD reporting disturbed sleep. Although posttraumatic insomnia has traditionally been conceptualized as a consequence of PTSD, it is the most likely symptom to not remit following otherwise successful PTSD treatment. This suggests that the relationship between PTSD and insomnia is more complex, such that they likely share underlying pathological mechanisms and that factors non-specific to PTSD maintain chronic trauma-induced insomnia. Although several theories and hypotheses have been presented to explain the relationship between PTSD and insomnia, neurobiological and psychological models have not been integrated, thereby limiting their comprehensiveness and abilities to inform effective intervention. Further, existing models have not addressed how acute trauma-induced insomnia becomes chronic. The present review examined models of PTSD and insomnia separately, as well as existing theorized mechanisms of their co-morbidity. The distinct characteristics of trauma-induced insomnia were also reviewed and presented to describe the unique clinical presentation of trauma-induced insomnia. Review and integration of the literature were used to propose an integrated model of chronic trauma-induced insomnia informed by a neuropsychobiological framework. Clinical implications and future research directions are presented and discussed.

Neural signatures of conditioning, extinction learning, and extinction recall in posttraumatic stress disorder: a meta-analysis of functional magnetic resonance imaging studies

BACKGROUND

Establishing neurobiological markers of posttraumatic stress disorder (PTSD) is essential to aid in diagnosis and treatment development. Fear processing deficits are central to PTSD, and their neural signatures may be used as such markers.

METHODS

Here, we conducted a meta-analysis of seven Pavlovian fear conditioning fMRI studies comparing 156 patients with PTSD and 148 trauma-exposed healthy controls (TEHC) using seed-based d-mapping, to contrast neural correlates of experimental phases, namely conditioning, extinction learning, and extinction recall.

RESULTS

Patients with PTSD, as compared to TEHCs, exhibited increased activation in the anterior hippocampus (extending to the amygdala) and medial prefrontal cortex during conditioning; in the anterior hippocampus-amygdala regions during extinction learning; and in the anterior hippocampus-amygdala and medial prefrontal areas during extinction recall. Yet, patients with PTSD have shown an overall decreased activation in the thalamus during all phases in this meta-analysis.

CONCLUSION

Findings from this metanalysis suggest that PTSD is characterized by increased activation in areas related to salience and threat, and lower activation in the thalamus, a key relay hub between subcortical areas. If replicated, these fear network alterations may serve as objective diagnostic markers for PTSD, and potential targets for novel treatment development, including pharmacological and brain stimulation interventions. Future longitudinal studies are needed to examine whether these observed network alteration in PTSD are the cause or the consequence of PTSD.

The Hidden Burden of Mental Health Outcomes Following Firearm-related Injures

OBJECTIVES

Examine the effect of different types of firearms on readmission due to acute stress disorder (ASD) and/or post-traumatic stress disorder (PTSD) in firearm-injury victims.

BACKGROUND

Survivors of firearm-related injuries suffer long-term sequelae such as disability, work loss, and deterioration in the quality of life. There is a paucity of data describing the long-term mental health outcomes in these patients.

METHODS

We performed a 5-year (2011-2015) analysis of the Nationwide Readmission Database. All adult patients with firearm injuries were stratified into 3 groups by firearm type: handgun, shotgun, and semiautomatic rifle. Outcome measures were the incidence and predictors of ASD/PTSD.

RESULTS

A total of 100,704 victims of firearm-related injuries were identified, of which 13.3% (n = 13,393) were readmitted within 6 months of index hospitalization, 6.7% (n = 8970) of these due to ASD/PTSD. Mean age was 34 ± 14 years, 88% were men. Of those readmitted due to ASD/PTSD, 24% (n = 2153) sustained a handgun-related injury on index hospitalization, 12% (n = 1076) shotgun, and 64% (n = 5741) semiautomatic gun (P = 0.039). On regression analysis, semiautomatic gun and shotgun victims had higher odds of developing ASD/PTSD upon readmission [odds ratio (OR): 2.05 (1.10-4.12) and OR: 1.41 (1.08-2.11)] compared to handgun. Female sex [OR: 1.79 (1.05-3.05)] and younger age representing those younger than 25 years [OR: 4.66 (1.12-6.74)] were also independently associated with higher odds of ASD/PTSD.

CONCLUSIONS

Apart from the lives lost, survivors of semiautomatic rifle- and shotgun-related injuries suffer long-term mental health sequalae. These secondary and debilitating mental health outcomes are important considerations for capturing the overall burden of the disease.

The predator odor avoidance model of post-traumatic stress disorder in rats

Individuals with post-traumatic stress disorder avoid trauma-related stimuli and exhibit blunted hypothalamic-pituitary-adrenal axis response at the time of trauma. Our laboratory uses predator odor (i.e. bobcat urine) stress to divide adult Wistar rats into groups that exhibit high (avoiders) or low (nonavoiders) avoidance of a predator odor-paired context, modeling the fact that not all humans exposed to traumatic events develop psychiatric conditions. Male avoiders exhibit lower body weight gain after stress, as well as extinction-resistant avoidance that persists after a second stress exposure. These animals also show attenuated hypothalamic-pituitary-adrenal axis response to predator odor that predicts subsequent avoidance of the odor-paired context. Avoiders exhibit unique brain activation profiles relative to nonavoiders and controls (as measured by Fos immunoreactivity), and higher corticotropin-releasing factor levels in multiple brain regions. Furthermore, avoider rats exhibit escalated and compulsive-like alcohol self-administration after traumatic stress. Here, we review the predator odor avoidance model of post-traumatic stress disorder and its utility for tracking behavior and measuring biological outcomes predicted by avoidance. The major strengths of this model are (i) etiological validity with exposure to a single intense stressor, (ii) established approach distinguishing individual differences in stress reactivity, and (iii) robust behavioral and biological phenotypes during and after trauma.

Reduced electrophysiological habituation to novelty after trauma reflects heightened salience network detection

BACKGROUND

Event-Related Potential (ERP) studies of PTSD have reported enhanced P3 amplitudes in response to trauma-related stimuli that are less likely to habituate over time.

METHODS

In the present study, we compared ERPs to the first and last half of an auditory novelty oddball task using neutral (trauma-unrelated) stimuli. Participants were 59 young students who were: trauma-exposed with "Probable PTSD", trauma-exposed without PTSD, or non-traumatized controls.

RESULTS

Reduced P3 amplitudes were observed for the last half of the trials for the entire sample, but this habituation was less profound for both trauma-exposed groups, demonstrating reduced habituation over time. Arousal symptom severity and trauma history negatively correlated with P3 amplitude habituation across the entire sample. Reduced N1 amplitudes for the last half of the trials were found in both trauma-exposed groups, but not among controls.

CONCLUSIONS

Our findings suggest that trauma-exposed individuals exhibit information processing alterations in response to neutral environmental stimuli that may be related to a general pattern of heightened activity of the Salience Network. Implications for the neurobiological model of PTSD and PTSD psychotherapy are discussed.

Therapeutic Challenges of Post-traumatic Stress Disorder: Focus on the Dopaminergic System

Post-traumatic stress disorder (PTSD) is a mental illness developed by vulnerable individuals exposed to life-threatening events. The pharmacological unresponsiveness displayed by the vast majority of PTSD patients has raised considerable interest in understanding the poorly known pathophysiological mechanisms underlying this disorder. Most studies in the field focused, so far, on noradrenergic mechanisms, because of their well-established role in either tuning arousal or in encoding emotional memories. However, less attention has been paid to other neural systems. Manipulations of the dopaminergic system alter behavioral responses to stressful situations and recent findings suggest that dopaminergic dysfunction might play an overriding role in the pathophysiology of PTSD. In the present review, dopaminergic mechanisms relevant for the pathogenesis of PTSD, as well as potential dopaminergic-based pharmacotherapies are discussed in the context of addressing the unmet medical need for new and effective drugs for treatment of PTSD.

Impaired inhibition as an intermediate phenotype for PTSD risk and treatment response

Inhibition of fear involves learning and then appropriately responding to safety signals, and has been shown to be impaired in PTSD patients. Response inhibition refers to cognitive control and likely uses the same prefrontal cortex circuits as fear inhibition, and has also been implicated in PTSD. Impaired inhibition can serve as an intermediate phenotype for PTSD and can be measured with neuroimaging and psychophysiological tools. We first review the neurobiological mechanisms of fear and response inhibition. Next, we summarize the functional magnetic resonance imaging (fMRI) and psychophysiological studies using fear and response inhibition paradigms in PTSD patients. Finally, we evaluate the theranostic role of impaired inhibition in PTSD risk and treatment response.

A review of hippocampal activation in post-traumatic stress disorder

Post-traumatic stress disorder (PTSD) is often characterized by deficits in memory encoding and retrieval and aberrant fear and extinction learning. The hippocampus plays a critical role in memory and contextual processing and has been implicated in intrinsic functional connectivity networks involved in self-referential thought and memory-related processes. This review focuses on hippocampal activation findings during memory and fear and extinction learning tasks, as well as resting state hippocampal connectivity in individuals with PTSD. A preponderance of functional neuroimaging studies to date, using memory, fear learning, and extinction tasks, report decreased or "controls comparable" hippocampal activation in individuals with PTSD, which is usually associated with poorer performance on the task imaged. Existing evidence thus raises the possibility that greater hippocampal recruitment in PTSD participants may be required for similar performance levels. Studies of resting state functional connectivity in PTSD predominantly report reduced within-network connectivity in the default mode network (DMN), as well as greater coupling between the DMN and salience network (SN) via the hippocampus. Together, these findings suggest that deficient hippocampal activation in PTSD may be associated with poorer performance during memory, extinction recall, and fear renewal tasks. Furthermore, studies of resting state connectivity implicate the hippocampus in decreased within-network DMN connectivity and greater coupling with SN regions characteristic of PTSD.

A neurobehavioral account for decentering as the salve for the distressed mind

Distress is commonly characterized by prolonged internal suffering that can range from self-focused processing of negative emotions and stressors, to highly intensely aversive and prolonged emotional states, thereby, worsening or complicating emotional and physical conditions. Decentering represents a metacognitive capacity thought to reflect three interrelated processes: meta-awareness, disidentification from internal experience, and reduced reactivity to thought content-which is reliably increased with mindfulness-based interventions. In this essay, we seek to link the clinical presentation of distress disorders to known or hypothesized disruptions in neural networks that underlie emotion, cognition, and goal directed behavior, and offer a neurobehavioral account for how and why treatments imbued with mindfulness meditation might ameliorate these conditions, in part through increases in decentering.

Augmentation of Extinction and Inhibitory Learning in Anxiety and Trauma-Related Disorders

Although the fear response is an adaptive response to threatening situations, a number of psychiatric disorders feature prominent fear-related symptoms caused, in part, by failures of extinction and inhibitory learning. The translational nature of fear conditioning paradigms has enabled us to develop a nuanced understanding of extinction and inhibitory learning based on the molecular substrates to systems neural circuitry and psychological mechanisms. This knowledge has facilitated the development of novel interventions that may augment extinction and inhibitory learning. These interventions include nonpharmacological techniques, such as behavioral methods to implement during psychotherapy, as well as device-based stimulation techniques that enhance or reduce activity in different regions of the brain. There is also emerging support for a number of psychopharmacological interventions that may augment extinction and inhibitory learning specifically if administered in conjunction with exposure-based psychotherapy. This growing body of research may offer promising novel techniques to address debilitating transdiagnostic fear-related symptoms.

The clinical applications and practical relevance of human conditioning paradigms for posttraumatic stress disorder

The classical conditioning paradigm of fear learning has spawned a number of experimental variations for the explanation of posttraumatic stress disorder (PTSD) etiology. These paradigms include extinction learning and recall, fear inhibition, fear generalization, and conditioned avoidance. As such, each of these paradigms have significant applications for understanding the development, maintenance, treatment, and relapse of the fear-related features of PTSD. In the present review, we describe each of these conditioning-based paradigms with reference to the clinical applications, and supported by case examples from patients with severe PTSD symptoms. We also review the neurobiological models of conditioning and extinction in animals, psychiatrically healthy humans, and PTSD patients, and discuss the current balance of evidence suggesting a number of biological, behavioral, and cognitive mechanisms/moderators of the conditioning and extinction process in experimental and clinical contexts.

Alteration of BDNF in the medial prefrontal cortex and the ventral hippocampus impairs extinction of avoidance

Brain-derived neurotrophic factor (BDNF) is critical for establishing activity-related neural plasticity. There is increasing interest in the mechanisms of active avoidance and its extinction, but little is known about the role of BDNF in these processes. Using the platform-mediated avoidance task combined with local infusions of an antibody against BDNF, we show that blocking BDNF in either prelimbic (PL) or infralimbic (IL) medial prefrontal cortex during extinction training impairs subsequent recall of extinction of avoidance, differing from extinction of conditioned freezing. By combining retrograde tracers with BDNF immunohistochemistry, we show that extinction of avoidance increases BDNF expression in ventral hippocampal (vHPC) neurons, but not amygdala neurons, projecting to PL and IL. Using the CRISPR/Cas9 system, we further show that reducing BDNF production in vHPC neurons impairs recall of avoidance extinction. Thus, the vHPC may mediate behavioral flexibility in avoidance by driving extinction-related plasticity via BDNFergic projections to both PL and IL. These findings add to the growing body of knowledge implicating the hippocampal-prefrontal pathway in anxiety-related disorders and extinction-based therapies.

Neuroscience Informed Prolonged Exposure Practice: Increasing Efficiency and Efficacy Through Mechanisms

Prolonged exposure (PE) is an empirically supported efficacious treatment for posttraumatic stress disorder (PTSD). In this focused review, we briefly review the neurobiological networks in PTSD relevant to PE, discuss the theoretical basis of PE, review the neurobiological mechanisms underlying the effectiveness of PE and identify the enhancements that can be applied to increase treatment response and retention. Based on the reviewed studies, it is clear that PTSD results in disrupted network of interconnected regions, and PE has been shown to increase the connectivity within and between these regions. Successful extinction recall in PE is related to increased functional coherence between the ventromedial prefrontal cortex (vmPFC), amygdala and the hippocampus. Increased connectivity within the dorsolateral PFC (dlPFC) following PE is associated with more effective downregulation of emotional responses in stressful situations. Pre-existing neural connectivity also in some cases predicts response to exposure treatment. We consider various enhancements that have been used with PE, including serotonin reuptake inhibitors (SSRIs), D-cycloserine (DCS), allopregnanolone (ALLO) and propranolol, repetitive transcranial magnetic stimulation (rTMS), oxytocin and MDMA. Given that neural connectivity appears to be crucial in mechanisms of action of PE, rTMS is a logical target for further research as an enhancement of PE. Additionally, exploring the effectiveness and mechanisms of action of oxytocin and MDMA in conjunction with PE may lead to improvement in treatment engagement and retention.

Altered cerebral benzodiazepine receptor binding in post-traumatic stress disorder

Agonists of the γ-aminobutyric acid (GABA) type A benzodiazepine (BZD) receptor exert anxiolytic effects in anxiety disorders, raising the possibility that altered GABA-ergic function may play a role in the pathophysiology of anxiety disorders, such as post-traumatic stress disorder (PTSD). However, few neuroimaging studies have assessed the function or binding potential of the central GABA_A BZD receptor system in PTSD. Therefore, our aim was to compare the BZD receptor binding potential between PTSD patients and healthy controls. Twelve medication-free participants with a current diagnosis of PTSD and 15 matched healthy controls underwent positron emission tomography (PET) imaging using [¹¹C] flumazenil. Structural magnetic resonance imaging (MRI) scans were obtained and co-registered to the PET images to permit co-location of neuroanatomical structures in the lower resolution PET image data. Compared to healthy controls, PTSD patients exhibited increased BZD binding in the caudal anterior cingulate cortex and precuneus (p's < 0.05). Severity of PTSD symptoms positively correlated with BZD binding in the left mid- and anterior insular cortices. This study extends previous findings by suggesting that central BZD receptor system involvement in PTSD includes portions of the default mode and salience networks, along with insular regions that support interoception and autonomic arousal.

Brain circuit dysfunction in post-traumatic stress disorder: from mouse to man

Post-traumatic stress disorder (PTSD) is a prevalent, debilitating and sometimes deadly consequence of exposure to severe psychological trauma. Although effective treatments exist for some individuals, they are limited. New approaches to intervention, treatment and prevention are therefore much needed. In the past few years, the field has rapidly developed a greater understanding of the dysfunctional brain circuits underlying PTSD, a shift in understanding that has been made possible by technological revolutions that have allowed the observation and perturbation of the macrocircuits and microcircuits thought to underlie PTSD-related symptoms. These advances have allowed us to gain a more translational knowledge of PTSD, have provided further insights into the mechanisms of risk and resilience and offer promising avenues for therapeutic discovery.

Serine Racemase and D-serine in the Amygdala Are Dynamically Involved in Fear Learning

BACKGROUND

The amygdala is a central component of the neural circuitry that underlies fear learning. N-methyl-D-aspartate receptor-dependent plasticity in the amygdala is required for pavlovian fear conditioning and extinction. N-methyl-D-aspartate receptor activation requires the binding of a coagonist, D-serine, which is synthesized from L-serine by the neuronal enzyme serine racemase (SR). However, little is known about SR and D-serine function in the amygdala.

METHODS

We used immunohistochemical methods to characterize the cellular localization of SR and D-serine in the mouse and human amygdala. Using biochemical and molecular techniques, we determined whether trace fear conditioning and extinction engages the SR/D-serine system in the brain. D-serine was administered systemically to mice to evaluate its effect on fear extinction. Finally, we investigated whether the functional single nucleotide polymorphism rs4523957, which is an expression quantitative trait locus of the human serine racemase (SRR) gene, was associated with fear-related phenotypes in a highly traumatized human cohort.

RESULTS

We demonstrate that approximately half of the neurons in the amygdala express SR, including both excitatory and inhibitory neurons. We find that the acquisition and extinction of fear memory engages the SR/D-serine system in the mouse amygdala and that D-serine administration facilitates fear extinction. We also demonstrate that the SRR single nucleotide polymorphism, rs4523957, is associated with posttraumatic stress disorder in humans, consistent with the facilitatory effect of D-serine on fear extinction.

CONCLUSIONS

These new findings have important implications for understanding D-serine-mediated N-methyl-D-aspartate receptor plasticity in the amygdala and how this system could contribute to disorders with maladaptive fear circuitry.

Diagnostic potential of multimodal neuroimaging in posttraumatic stress disorder

Despite accumulating evidence of physiological abnormalities related to posttraumatic stress disorder (PTSD), the current diagnostic criteria for PTSD still rely on clinical interviews. In this study, we investigated the diagnostic potential of multimodal neuroimaging for identifying posttraumatic symptom trajectory after trauma exposure. Thirty trauma-exposed individuals and 29 trauma-unexposed healthy individuals were followed up over a 5-year period. Three waves of assessments using multimodal neuroimaging, including structural magnetic resonance imaging (MRI) and diffusion-weighted MRI, were performed. Based on previous findings that the structural features of the fear circuitry-related brain regions may dynamically change during recovery from the trauma, we employed a machine learning approach to determine whether local, connectivity, and network features of brain regions of the fear circuitry including the amygdala, orbitofrontal and ventromedial prefrontal cortex (OMPFC), hippocampus, insula, and thalamus could distinguish trauma-exposed individuals from trauma-unexposed individuals at each recovery stage. Significant improvement in PTSD symptoms was observed in 23%, 52%, and 88% of trauma-exposed individuals at 1.43, 2.68, and 3.91 years after the trauma, respectively. The structural features of the amygdala were found as major classifiers for discriminating trauma-exposed individuals from trauma-unexposed individuals at 1.43 years after the trauma, but these features were nearly normalized at later phases when most of the trauma-exposed individuals showed clinical improvement in PTSD symptoms. Additionally, the structural features of the OMPFC showed consistent predictive values throughout the recovery period. In conclusion, the current study provides a promising step forward in the development of a clinically applicable predictive model for diagnosing PTSD and predicting recovery from PTSD.

Abnormal fear circuitry in Attention Deficit Hyperactivity Disorder: A controlled magnetic resonance imaging study

We examined whether non-traumatized subjects with Attention Deficit Hyperactivity Disorder (ADHD) have dysfunctional activation in brain structures mediating fear extinction, possibly explaining the statistical association between ADHD and other disorders characterized by aberrant fear processing such as PTSD. Medication naïve, non-traumatized young adult subjects with (N=27) and without (N=20) ADHD underwent a 2-day fear conditioning and extinction protocol in a 3T functional magnetic resonance imaging (fMRI) scanner. Skin conductance response (SCR) was recorded as a measure of conditioned response. Compared to healthy controls, ADHD subjects had significantly greater insular cortex activation during early extinction, lesser dorsal anterior cingulate cortex (dACC) activation during late extinction, lesser ventromedial prefrontal cortex (vmPFC) activation during late extinction learning and extinction recall, and greater hippocampal activation during extinction recall. Hippocampal and vmPFC deficits were similar to those documented in PTSD subjects compared to traumatized controls without PTSD. Non-traumatized, medication naive adults with ADHD had abnormalities in fear circuits during extinction learning and extinction recall, and some findings were consistent with those previously documented in subjects with PTSD compared to traumatized controls without PTSD. These findings could explain the significant association between ADHD and PTSD as well as impaired emotion regulation in ADHD.

The utility of hair cortisol concentrations in the prediction of PTSD symptoms following traumatic physical injury

RATIONALE

Although cortisol alterations have been associated with posttraumatic stress disorder (PTSD) and PTSD symptoms (PTSS), the direction of association is mixed. Cortisol which is measured in blood, saliva, or urine is subject to transient factors that may confound results. Recent advances in cortisol sampling techniques provide novel opportunities to address these inconsistencies. Hair cortisol sampling is a non-invasive method for the retrospective assessment of long-term integrated cortisol, yet its utility at predicting PTSS has not been assessed in acute injury victims.

OBJECTIVE

The aim of this prospective study was to examine whether higher levels of hair cortisol concentrations (HCC) were associated with increases in PTSS following traumatic physical injury.

METHOD

From January 2012 to May 2013, injury victims admitted to a level-1 Midwestern trauma center were recruited during their routine trauma clinic appointment within 30-days post-injury. Thirty participants had sufficient hair length to obtain 3-cm hair samples for cortisol assay. These participants completed PTSS assessments in relation to their recent injury at both the baseline and follow-up assessments (within 30- and 60-days post-injury, respectively).

RESULTS

Hierarchical regression analyses - which controlled for baseline PTSS, age, and sex - revealed that higher HCC predicted significant increases in overall PTSS at follow-up. Higher HCC also predicted increases in the avoidance/numbing subscale symptoms of PTSS. Dividing the avoidance symptoms and numbing symptoms into two separate clusters (consistent with the 4-factor DSM-5 model of PTSD) revealed that HCC was only marginally associated with numbing, but not with avoidance symptoms.

CONCLUSION

Hair sampling is a feasible method for assessing integrated cortisol levels soon after traumatic physical injury. This study suggests that elevated HCC may serve as a biomarker of risk for the development of posttraumatic symptomatology, and identifies specific symptoms that may be targeted for intervention in those with high HCC in the aftermath of injury.

Interoceptive dimensions across cardiac and respiratory axes

Interoception refers to the sensing of signals concerning the internal state of the body. Individual differences in interoceptive sensitivity are proposed to account for differences in affective processing, including the expression of anxiety. The majority of investigations of interoceptive accuracy focus on cardiac signals, typically using heartbeat detection tests and self-report measures. Consequently, little is known about how different organ-specific axes of interoception relate to each other or to symptoms of anxiety. Here, we compare interoception for cardiac and respiratory signals. We demonstrate a dissociation between cardiac and respiratory measures of interoceptive accuracy (i.e. task performance), yet a positive relationship between cardiac and respiratory measures of interoceptive awareness (i.e. metacognitive insight into own interoceptive ability). Neither interoceptive accuracy nor metacognitive awareness for cardiac and respiratory measures was related to touch acuity, an exteroceptive sense. Specific measures of interoception were found to be predictive of anxiety symptoms. Poor respiratory accuracy was associated with heightened anxiety score, while good metacognitive awareness for cardiac interoception was associated with reduced anxiety. These findings highlight that detection accuracies across different sensory modalities are dissociable and future work can better delineate their relationship to affective and cognitive constructs.This article is part of the themed issue 'Interoception beyond homeostasis: affect, cognition and mental health'.

The centrality of fear extinction in linking risk factors to PTSD: A narrative review

Recent prospective studies in emergency services have identified impaired fear extinction learning and memory to be a significant predictor of Posttraumatic Stress Disorder (PTSD), complementing a wealth of cross-sectional evidence of extinction deficits associated with the disorder. Additional fields of research show specific risk factors and biomarkers of the disorder, including candidate genotypes, stress and sex hormones, cognitive factors, and sleep disturbances. Studies in mostly nonclinical populations also reveal that the aforementioned factors are involved in fear extinction learning and memory. Here, we provide a comprehensive narrative review of the literature linking PTSD to these risk factors, and linking these risk factors to impaired fear extinction. On balance, the evidence suggests that fear extinction may play a role in the relationship between risk factors and PTSD. Should this notion hold true, this review carries important implications for the improvement of exposure-based treatments, as well as strategies for the implementation of treatment.

Alpha oscillation neurofeedback modulates amygdala complex connectivity and arousal in posttraumatic stress disorder

OBJECTIVE

Electroencephalogram (EEG) neurofeedback aimed at reducing the amplitude of the alpha-rhythm has been shown to alter neural networks associated with posttraumatic stress disorder (PTSD), leading to symptom alleviation. Critically, the amygdala is thought to be one of the central brain regions mediating PTSD symptoms. In the current study, we compare directly patterns of amygdala complex connectivity using fMRI, before and after EEG neurofeedback, in order to observe subcortical mechanisms associated with behavioural and alpha oscillatory changes among patients.

METHOD

We examined basolateral (BLA), centromedial (CMA), and superficial (SFA) amygdala complex resting-state functional connectivity using a seed-based approach via SPM Anatomy Toolbox. Amygdala complex connectivity was measured in twenty-one individuals with PTSD, before and after a 30-minute session of EEG neurofeedback targeting alpha desynchronization.

RESULTS

EEG neurofeedback was associated with a shift in amygdala complex connectivity from areas implicated in defensive, emotional, and fear processing/memory retrieval (left BLA and left SFA to the periaqueductal gray, and left SFA to the left hippocampus) to prefrontal areas implicated in emotion regulation/modulation (right CMA to the medial prefrontal cortex). This shift in amygdala complex connectivity was associated with reduced arousal, greater resting alpha synchronization, and was negatively correlated to PTSD symptom severity.

CONCLUSION

These findings have significant implications for developing targeted non-invasive treatment interventions for PTSD patients that utilize alpha oscillatory neurofeedback, showing evidence of neuronal reconfiguration between areas highly implicated in the disorder, in addition to acute symptom alleviation.

Unique insula subregion resting-state functional connectivity with amygdala complexes in posttraumatic stress disorder and its dissociative subtype

The insula and amygdala are implicated in the pathophysiology of posttraumatic stress disorder (PTSD), where both have been shown to be hyper/hypoactive in non-dissociative (PTSD-DS) and dissociative subtype (PTSD+DS) PTSD patients, respectively, during symptom provocation. However, the functional connectivity between individual insula subregions and the amygdala has not been investigated in persons with PTSD, with or without the dissociative subtype. We examined insula subregion (anterior, mid, and posterior) functional connectivity with the bilateral amygdala using a region-of-interest seed-based approach via PickAtlas and SPM8. Resting-state fMRI was conducted with (n=61) PTSD patients (n=44 PTSD-DS; n=17 PTSD+DS), and (n=40) age-matched healthy controls. When compared to controls, the PTSD-DS group displayed increased insula connectivity (bilateral anterior, bilateral mid, and left posterior) to basolateral amygdala clusters in both hemispheres, and the PTSD+DS group displayed increased insula connectivity (bilateral anterior, left mid, and left posterior) to the left basolateral amygdala complex. Moreover, as compared to PTSD-DS, increased insula subregion connectivity (bilateral anterior, left mid, and right posterior) to the left basolateral amygdala was found in PTSD+DS. Depersonalization/derealization symptoms and PTSD symptom severity correlated with insula subregion connectivity to the basolateral amygdala within PTSD patients. This study is an important first step in elucidating patterns of neural connectivity associated with unique symptoms of arousal/interoception, emotional processing, and awareness of bodily states, in PTSD and its dissociative subtype.

Does Cannabis Cause, Exacerbate or Ameliorate Psychiatric Disorders? An Oversimplified Debate Discussed

There have been extensive policy shifts in the legality of recreational and therapeutic use of cannabis in the United States, as well as a steady increase in the number of people using the drug on a regular basis. Given these rapid societal changes, defining what is known scientifically about the consequences of cannabis use on mental health takes on added public health significance. The purpose of this circumspectives piece is to discuss evidence of cannabis' effects on two psychiatric conditions: post-traumatic stress disorder and psychotic disorders. Dr Haney and Dr Evins will discuss two viewpoints regarding the benefit and harm of cannabis use for these conditions, while outlining what remains unproven and requires further testing to move the field forward.

Neuroimaging of Fear-Associated Learning

Fear conditioning has been commonly used as a model of emotional learning in animals and, with the introduction of functional neuroimaging techniques, has proven useful in establishing the neurocircuitry of emotional learning in humans. Studies of fear acquisition suggest that regions such as amygdala, insula, anterior cingulate cortex, and hippocampus play an important role in acquisition of fear, whereas studies of fear extinction suggest that the amygdala is also crucial for safety learning. Extinction retention testing points to the ventromedial prefrontal cortex as an essential region in the recall of the safety trace, and explicit learning of fear and safety associations recruits additional cortical and subcortical regions. Importantly, many of these findings have implications in our understanding of the pathophysiology of psychiatric disease. Recent studies using clinical populations have lent insight into the changes in regional activity in specific disorders, and treatment studies have shown how pharmaceutical and other therapeutic interventions modulate brain activation during emotional learning. Finally, research investigating individual differences in neurotransmitter receptor genotypes has highlighted the contribution of these systems in fear-associated learning.

Evidence for disrupted gray matter structural connectivity in posttraumatic stress disorder

Posttraumatic stress disorder (PTSD) is characterized by atrophy within the prefrontal-limbic network. Graph analysis was used to investigate to what degree atrophy in PTSD is associated with impaired structural connectivity within prefrontal limbic network (restricted) and how this affects the integration of the prefrontal limbic network with the rest of the brain (whole-brain). 85 male veterans (45 PTSD neg, 40 PTSD pos) underwent volumetric MRI on a 3T MR. Subfield volumes were obtained using a manual labeling scheme and cortical thickness measurements and subcortical volumes from FreeSurfer. Regression analysis was used to identify regions with volume loss. Graph analytical Toolbox (GAT) was used for graph-analysis. PTSD pos had a thinner rostral anterior cingulate and insular cortex but no hippocampal volume loss. PTSD was characterized by decreased nodal degree (orbitofrontal, anterior cingulate) and clustering coefficients (thalamus) but increased nodal betweenness (insula, orbitofrontal) and a reduced small world index in the whole brain analysis and by orbitofrontal and insular nodes with increased nodal degree, clustering coefficient and nodal betweenness in the restricted analysis. PTSD associated atrophy in the prefrontal-limbic network results in an increased structural connectivity within that network that negatively affected its integration with the rest of the brain.

Persistent active avoidance correlates with activity in prelimbic cortex and ventral striatum

Persistent avoidance is a prominent symptom of anxiety disorders and is often resistant to extinction-based therapies. Little is known about the circuitry mediating persistent avoidance. Using a recently described platform-mediated active avoidance task, we assessed activity in several structures with c-Fos immuno-labeling. In Task 1, rats were conditioned to avoid a tone-signaled shock by moving to a safe platform, and then were extinguished over two days. One day later, failure to retrieve extinction correlated with increased activity in the prelimbic prefrontal cortex (PL), ventral striatum (VS), and basal amygdala (BA), and decreased activity in infralimbic prefrontal cortex (IL), consistent with pharmacological inactivation studies. In Task 2, the platform was removed during extinction training and fear (suppression of bar pressing) was extinguished to criterion over 3–5 days. The platform was then returned in a post-extinction test. Under these conditions, avoidance levels were equivalent to Experiment 1 and correlated with increased activity in PL and VS, but there was no correlation with activity in IL or BA. Thus, persistent avoidance can occur independently of deficits in fear extinction and its associated structures.