Spatiotemporal dynamics of hippocampal-cortical networks underlying the unique phenomenological properties of trauma-related intrusive memories.

Trauma-related intrusive memories (TR-IMs) possess unique phenomenological properties that contribute to adverse post-traumatic outcomes, positioning them as critical intervention targets. However, transdiagnostic treatments for TR-IMs are scarce, as their underlying mechanisms have been investigated separate from their unique phenomenological properties. Extant models of more general episodic memory highlight dynamic hippocampal-cortical interactions that vary along the anterior-posterior axis of the hippocampus (HPC) to support different cognitive-affective and sensory-perceptual features of memory. Extending this work into the unique properties of TR-IMs, we conducted a study of eighty-four trauma-exposed adults who completed daily ecological momentary assessments of TR-IM properties followed by resting-state functional magnetic resonance imaging (rs-fMRI). Spatiotemporal dynamics of anterior and posterior hippocampal (a/pHPC)-cortical networks were assessed using co-activation pattern analysis to investigate their associations with different properties of TR-IMs. Emotional intensity of TR-IMs was inversely associated with the frequency and persistence of an aHPC-default mode network co-activation pattern. Conversely, sensory features of TR-IMs were associated with more frequent co-activation of the HPC with sensory cortices and the ventral attention network, and the reliving of TR-IMs in the "here-and-now" was associated with more persistent co-activation of the pHPC and the visual cortex. Notably, no associations were found between HPC-cortical network dynamics and conventional symptom measures, including TR-IM frequency or retrospective recall, underscoring the utility of ecological assessments of memory properties in identifying their neural substrates. These findings provide novel insights into the neural correlates of the unique features of TR-IMs that are critical for the development of individualized, transdiagnostic treatments for this pervasive, difficult-to-treat symptom.

Reduced anhedonia following internet-based cognitive-behavioral therapy for depression is mediated by enhanced reward circuit activation.

BACKGROUND: Major depressive disorder (MDD) is a highly prevalent psychiatric condition, yet many patients do not receive adequate treatment. Novel and highly scalable interventions such as internet-based cognitive-behavioral-therapy (iCBT) may help to address this treatment gap. Anhedonia, a hallmark symptom of MDD that refers to diminished interest and ability to experience pleasure, has been associated with reduced reactivity in a neural reward circuit that includes medial prefrontal and striatal brain regions. Whether iCBT can reduce anhedonia severity in MDD patients, and whether these therapeutic effects are accompanied by enhanced reward circuit reactivity has yet to be examined. METHODS: Fifty-two MDD patients were randomly assigned to either 10-week iCBT (n = 26) or monitored attention control (MAC, n = 26) programs. All patients completed pre- and post-treatment assessments of anhedonia (Snaith-Hamilton Pleasure Scale; SHAPS) and reward circuit reactivity [monetary incentive delay (MID) task during functional magnetic resonance imaging (fMRI)]. Healthy control participants (n = 42) also underwent two fMRI scans while completing the MID task 10 weeks apart. RESULTS: Both iCBT and MAC groups exhibited a reduction in anhedonia severity post-treatment. Nevertheless, only the iCBT group exhibited enhanced nucleus accumbens (Nacc) and subgenual anterior cingulate cortex (sgACC) activation and functional connectivity from pre- to post-treatment in response to reward feedback. Enhanced Nacc and sgACC activations were associated with reduced anhedonia severity following iCBT treatment, with enhanced Nacc activation also mediating the reduction in anhedonia severity post-treatment. CONCLUSIONS: These findings suggest that increased reward circuit reactivity may contribute to a reduction in anhedonia severity following iCBT treatment for depression.

Social Anhedonia is Associated with Low Social Network Diversity in Trauma-Exposed Adults.

Social anhedonia has been proposed to contribute to social isolation in several psychiatric disorders, but it has not been examined in relation to deficits in social connection that also characterize posttraumatic stress disorder (PTSD). A growing body of evidence emphasizes the health importance of structural features of social networks, including their size and complexity. The current study examined the association between social anhedonia and social network features in a sample of trauma-exposed participants with and without PTSD as well as in non-trauma-exposed controls. Participants (N = 101; n = 37 healthy controls, n = 23 trauma-exposed without PTSD; n = 41 lifetime PTSD) completed self-report measures of social anhedonia (Revised Social Anhedonia Scale) and structural social network features, including social network size, diversity, and the number of embedded networks (Social Network Index). Relative to healthy controls, participants with PTSD reported significantly lower social network sizes and fewer embedded networks. In the combined trauma-exposed sample, higher ratings of social anhedonia were associated with lower social network diversity, r(62) = -.43, p < .001, an effect that remained statistically significant after controlling for PTSD and depression symptom severity. These results suggest that elevated social anhedonia in trauma-exposed individuals may contribute to disruptions in social network structure consistent with social isolation.

Fear Extinction Recall Modulates Human Frontomedial Theta and Amygdala Activity.

Human functional magnetic resonance imaging (fMRI) and electroencephalography (EEG) studies, as well as animal studies, indicate that the amygdala and frontomedial brain regions are critically involved in conditioned fear and that frontomedial oscillations in the theta range (4-8 Hz) may support communication between these brain regions. However, few studies have used a multimodal approach to probe interactions among these key regions in humans. Here, our goal was to bridge the gap between prior human fMRI, EEG, and animal findings. Using simultaneous EEG-fMRI recordings 24 h after fear conditioning and extinction, conditioned stimuli presented (CS+E, CS-E) and not presented during extinction (CS+N, CS-N) were compared to identify effects specific to extinction versus fear recall. Differential (CS+ vs. CS-) electrodermal, frontomedial theta (EEG) and amygdala responses (fMRI) were reduced for extinguished versus nonextinguished stimuli. Importantly, effects on theta power covaried with effects on amygdala activation. Fear and extinction recall as indicated by theta explained 60% of the variance for the analogous effect in the right amygdala. Our findings show for the first time the interplay of amygdala and frontomedial theta activity during fear and extinction recall in humans and provide insight into neural circuits consistently linked with top-down amygdala modulation in rodents.

Time-dependent differences in cortical measures and their associations with behavioral measures following mild traumatic brain injury.

There is currently a critical need to establish an improved understanding of time-dependent differences in brain structure following mild traumatic brain injury (mTBI). We compared differences in brain structure, specifically cortical thickness (CT), cortical volume (CV), and cortical surface area (CSA) in 54 individuals who sustained a recent mTBI and 33 healthy controls (HCs). Individuals with mTBI were split into three groups, depending on their time since injury. By comparing structural measures between mTBI and HC groups, differences in CT reflected cortical thickening within several areas following 0-3 (time-point, TP1) and 3-6 months (TP2) post-mTBI. Compared with the HC group, the mTBI group at TP2 showed lower CSA within several areas. Compared with the mTBI group at TP2, the mTBI group during the most chronic stage (TP3: 6-18 months post-mTBI) showed significantly higher CSA in several areas. All the above reported differences in CT and CSA were significant at a cluster-forming p < .01 (corrected for multiple comparisons). We also found that in the mTBI group at TP2, CT within two clusters (i.e., the left rostral middle frontal gyrus (L. RMFG) and the right postcentral gyrus (R. PostCG)) was negatively correlated with basic attention abilities (L. RMFG: r = -.41, p = .05 and R. PostCG: r = -.44, p = .03). Our findings suggest that alterations in CT and associated neuropsychological assessments may be more prominent during the early stages of mTBI. However, alterations in CSA may reflect compensatory structural recovery during the chronic stages of mTBI.

Disruption of white matter structural integrity and connectivity in posttraumatic stress disorder: A TBSS and tractography study.

BACKGROUND: Most studies of brain white matter (WM) in posttraumatic stress disorder (PTSD) have focused on combat trauma, and often were confounded by neurological and substance dependence comorbidity. This study used tract-based spatial statistics (TBSS) and probabilistic tractography to characterize WM microstructure in a mixed-sex community sample of PTSD patients exposed to diverse and multiple traumas, and in trauma-exposed normal comparison (TENC) subjects. METHODS: TBSS compared diffusion measures between 20 adults with DSM-IV PTSD and 17 TENC, using a whole-brain voxel-wise approach. Probabilistic tractography using Freesurfer's TRACULA was employed to measure diffusion tensor imaging (DTI) metrics within anatomically defined pathways. DTI metrics were compared between groups and correlated with PTSD symptom severity and trauma load. RESULTS: Controlling for age, sex, and motion, PTSD subjects had significantly reduced fractional anisotropy (FA) in a left frontal lobe cluster compared with TENC, at p < .05, family-wise error corrected. Tractography identified significant group differences in the inferior longitudinal fasciculus (ILF), including lower FA and higher radial diffusivity in PTSD compared with TENC. Within the PTSD group, FA values were not correlated with symptom severity or trauma load. Results remained significant after removing participants using psychotropic medication or those with comorbid major depression. CONCLUSIONS: PTSD patients had reduced WM integrity in left hemisphere frontal WM and temporal-occipital WM tracts, compared to trauma-exposed controls. Reduced frontal FA is consistent with compromised top-down attentional control and emotion regulation in PTSD, while reduced ILF FA may be related to sensory processing and gating abnormalities in this disorder.

Internet-based cognitive behavior therapy for major depressive disorder: A randomized controlled trial.

BACKGROUND: Prior research has shown that the Sadness Program, a technician-assisted Internet-based cognitive behavioral therapy (iCBT) intervention developed in Australia, is effective for treating major depressive disorder (MDD). The current study aimed to expand this work by adapting the protocol for an American population and testing the Sadness Program with an attention control group. METHODS: In this parallel-group, randomized controlled trial, adult MDD participants (18-45 years) were randomized to a 10-week period of iCBT (n = 37) or monitored attention control (MAC; n = 40). Participants in the iCBT group completed six online therapy lessons, which included access to content summaries and homework assignments. During the 10-week trial, iCBT and MAC participants logged into the web-based system six times to complete self-report symptom scales, and a nonclinician technician contacted participants weekly to provide encouragement and support. The primary outcome was the Hamilton Rating Scale for Depression (HRSD), and the secondary outcomes were the Patient Health Questionnaire-9 and Kessler-10. RESULTS: Intent-to-treat analyses revealed significantly greater reductions in depressive symptoms in iCBT compared with MAC participants, using both the self-report measures and the clinician-rated HRSD (d = -0.80). Importantly, iCBT participants also showed significantly higher rates of clinical response and remission. Exploratory analyses did not support illness severity as a moderator of treatment outcome. CONCLUSIONS: The Sadness Program led to significant reductions in depression and distress symptoms. With its potential to be delivered in a scalable, cost-efficient manner, iCBT is a promising strategy to enhance access to effective care.

Microstructure of frontoparietal connections predicts individual resistance to sleep deprivation.

Sleep deprivation (SD) can degrade cognitive functioning, but growing evidence suggests that there are large individual differences in the vulnerability to this effect. Some evidence suggests that baseline differences in the responsiveness of a fronto-parietal attention system that is activated during working memory (WM) tasks may be associated with the ability to sustain vigilance during sleep deprivation. However, the neurocircuitry underlying this network remains virtually unexplored. In this study, we employed diffusion tensor imaging (DTI) to investigate the association between the microstructure of the axonal pathway connecting the frontal and parietal regions--i.e., the superior longitudinal fasciculus (SLF)--and individual resistance to SD. Thirty healthy participants (15 males) aged 20-43 years underwent functional magnetic resonance imaging (fMRI) and diffusion tensor imaging (DTI) at rested wakefulness prior to a 28-hour period of SD. Task-related fronto-parietal fMRI activation clusters during a Sternberg WM Task were localized and used as seed regions for probabilistic fiber tractography. DTI metrics, including fractional anisotropy, mean diffusivity, axial and radial diffusivity were measured in the SLF. The psychomotor vigilance test (PVT) was used to evaluate resistance to SD. We found that activation in the left inferior parietal lobule (IPL) and dorsolateral prefrontal cortex (DLPFC) positively correlated with resistance. Higher fractional anisotropy of the left SLF comprising the primary axons connecting IPL and DLPFC was also associated with better resistance. These findings suggest that individual differences in resistance to SD are associated with the functional responsiveness of a fronto-parietal attention system and the microstructural properties of the axonal interconnections.

ADULT ANXIETY DISORDERS IN RELATION TO TRAIT ANXIETY AND PERCEIVED STRESS IN CHILDHOOD.

It is well established that objective early life stressors increase risk for anxiety disorders and that environmental stressors interact with dispositional factors such as trait anxiety. There is less information on how subjective perception of stress during childhood relates to later clinical anxiety. This study tested whether childhood perceived stress and trait anxiety were independently and interactively associated with adult anxiety disorders. Forty-seven adults diagnosed with anxiety disorders (M age = 34 yr., SD = 11) and 29 healthy participants (M = 33 yr., SD = 13) completed the adult Perceived Stress Scale, the State-Trait Anxiety Inventory, and the Global Perceived Early Life Events Scale as a measure of perceived stress during childhood. In a logistic regression model, high childhood perceived stress (ß = 0.64) and trait anxiety (ß = 0.11) were associated with significantly greater odds of adult anxiety disorder. The association between childhood perceived stress and adult anxiety remained significant when controlling for adult perceived stress. These findings suggest that children's perception of stress in their daily lives may be an important target of intervention to prevent the progression of stress into clinically significant anxiety.

Altered anterior cingulate neurochemistry in emerging adult binge drinkers with a history of alcohol-induced blackouts.

BACKGROUND: Binge alcohol consumption is associated with multiple neurobiological consequences, including altered neurophysiology, brain structure, and functional activation. Magnetic resonance spectroscopy (MRS) studies have demonstrated neurochemical alterations in the frontal lobe of alcohol users, although most studies focused on older, alcohol-dependent subjects. METHODS: In this study, neurochemical data were acquired using MRS at 4.0 Tesla from emerging adults (18 to 24 years old) who were binge alcohol drinkers (BD, n = 23) or light drinkers (LD, n = 31). Since binge drinking is also associated with increased prevalence of experiencing an alcohol-induced blackout, BD were stratified into alcohol-induced blackout (BDBO) and non-blackout (BDN) groups. RESULTS: Overall, BD had significantly lower gamma amino-butyric acid (GABA) and N-acetyl-aspartate (NAA) in the anterior cingulate cortex (ACC) than LD. When stratified by blackout history, BDBO also had lower ACC glutamate (Glu) than LD. No group differences in MRS metabolites were observed in the parietal-occipital cortex. Lower ACC GABA and Glu remained significant after accounting for lower gray matter content in BD, however, NAA differences were no longer evident. In addition, low ACC GABA levels were associated with greater alcohol use consequences, and worse response inhibition and attention/mental flexibility in BD. CONCLUSIONS: These data indicate that binge drinking affects frontal lobe neurochemistry, more so in those who had experienced an alcohol-induced blackout. Characterization of the neurochemical profiles associated with binge alcohol consumption and blackout history may help identify unique risk factors for the later manifestation of alcohol abuse and dependence, in young individuals who are heavy, frequent drinkers, but who do not meet the criteria for alcohol abuse disorders.

Peril and pleasure: an rdoc-inspired examination of threat responses and reward processing in anxiety and depression.

As a step toward addressing limitations in the current psychiatric diagnostic system, the National Institute of Mental Health recently developed the Research Domain Criteria (RDoC) to stimulate integrative research-spanning self-report, behavior, neural circuitry, and molecular/genetic mechanisms-on core psychological processes implicated in mental illness. Here, we use the RDoC conceptualization to review research on threat responses, reward processing, and their interaction. The first section of the manuscript highlights the pivotal role of exaggerated threat responses-mediated by circuits connecting the frontal cortex, amygdala, and midbrain-in anxiety, and reviews data indicating that genotypic variation in the serotonin system is associated with hyperactivity in this circuitry, which elevates the risk for anxiety and mood disorders. In the second section, we describe mounting evidence linking anhedonic behavior to deficits in psychological functions that rely heavily on dopamine signaling, especially cost/benefit decision making and reward learning. The third section covers recent studies that document negative effects of acute threats and chronic stress on reward responses in humans. The mechanisms underlying such effects are unclear, but the fourth section reviews new optogenetic data in rodents indicating that GABAergic inhibition of midbrain dopamine neurons, driven by activation of the habenula, may play a fundamental role in stress-induced anhedonia. In addition to its basic scientific value, a better understanding of interactions between the neural systems that mediate threat and reward responses may offer relief from the burdensome condition of anxious depression.

Insula and anterior cingulate GABA levels in posttraumatic stress disorder: preliminary findings using magnetic resonance spectroscopy.

BACKGROUND: Increased reactivity of the insular cortex and decreased activity of the dorsal anterior cingulate cortex (ACC) are seen in functional imaging studies of posttraumatic stress disorder (PTSD), and may partly explain the persistent fear and anxiety proneness that characterize the disorder. A possible neurochemical correlate is altered function of the inhibitory neurotransmitter gamma-aminobutyric acid (GABA). We report results from what we believe is the first study applying proton magnetic resonance spectroscopy ((1) H-MRS) to measure brain GABA in PTSD. METHODS: Thirteen adults with DSM-IV PTSD and 13 matched healthy control subjects underwent single voxel (1) H-MRS at 4 Tesla. GABA was measured in the right anterior insula and dorsal ACC, using Mescher-Garwood Point-Resolved Echo Spectroscopy Sequence (MEGAPRESS) spectral editing. Subjects were interviewed with the Structured Clinical Interview for DSM-IV and the Clinician Administered PTSD Scale, and also completed the State and Trait Anxiety Inventory. RESULTS: Insula GABA was significantly lower in PTSD subjects than in controls, and dorsal ACC GABA did not differ significantly between the groups. Insula GABA was not significantly associated with severity of PTSD symptoms. However, lower insula GABA was associated with significantly higher state and trait anxiety in the subject sample as a whole. CONCLUSIONS: PTSD is associated with reduced GABA in the right anterior insula. This preliminary evidence of the (1) H-MRS GABA metabolite as a possible biomarker of PTSD encourages replication in larger samples and examination of relations with symptom dimensions. Future studies also should examine whether insula GABA is a marker of anxiety proneness, cutting across clinical diagnostic categories.

Cortico-limbic responses to masked affective faces across ptsd, panic disorder, and specific phobia.

BACKGROUND: Exaggerated amygdala and reduced ventromedial prefrontal cortex (vmPFC) responsiveness during emotional processing have been reported in studies examining individual anxiety disorders. Studies are needed, however, which directly compare activation of amygdalo-cortical circuitry across multiple anxiety disorders within the same study. Here we compared cortico-limbic neurocircuitry across three different anxiety disorders using a well-validated emotional probe task. METHODS: Sixty-five adult volunteers, including 22 healthy controls (HC) and participants meeting DSM-IV criteria for either posttraumatic stress disorder (14 PTSD), panic disorder (14 PD), or specific animal phobia (15 SP), underwent functional magnetic resonance imaging (fMRI) at 3 T while passively viewing backward-masked images of faces expressing fear, happy, and neutral emotions. RESULTS: A group comprising all three anxiety disorders showed greater activation within the left amygdala and reduced activation within the vmPFC compared to the HC group during the masked fear versus neutral condition. Pairwise group comparisons showed that amygdala activation only reached significance for the PTSD versus HCs, whereas decreased vmPFC was only evident for SP and PD groups versus the HC group. Furthermore, activation did not differ among the anxiety groups when contrasted directly with one another. A similar pattern was observed for masked happy versus neutral faces. CONCLUSIONS: Exclusive of specific diagnostic category, anxiety disorders were generally associated with increased activation of the amygdala and reduced activation within vmPFC. Categorical distinctions were generally weak or not observed and suggest that functional differences may reflect the magnitude of responses within a common neurocircuitry across disorders rather than activation of distinct systems.

Anhedonia and Delay Discounting: Differing Patterns of Brain-Behavior Relationships in Healthy Control Participants Versus Individuals With Posttraumatic Stress Disorder.

BACKGROUND: Anhedonia may contribute to individual differences in delay discounting (DD). In prior work, we found that higher anhedonia was associated with shallower DD in healthy control (HC) participants but steeper DD in individuals with posttraumatic stress disorder (PTSD). In this study, we aimed to directly compare the relationship between anhedonia and DD across groups and to identify functional brain correlates of this interaction. METHODS: Participants (HC group: n = 23, DSM-5 PTSD group: n = 23) completed a questionnaire assessing anhedonia (Snaith-Hamilton Pleasure Scale [SHAPS]), task-based functional magnetic resonance imaging of decision making including DD, and resting-state functional magnetic resonance imaging. Task-based activity and resting-state functional connectivity were evaluated in reward-related regions that have also been implicated in PTSD (nucleus accumbens [NAcc], right anterior insula). RESULTS: Higher SHAPS scores were associated with steeper DD in PTSD, but there was no relationship between DD and SHAPS in the HC group. There was a significant group-by-SHAPS interaction for NAcc activity, t31 = 2.92, p = .007: Greater NAcc activity when immediate rewards were chosen was associated with higher SHAPS in the PTSD group but lower SHAPS in the HC group. In resting-state functional connectivity, there was a group-by-SHAPS interaction between the NAcc seed and right parietal and frontal pole clusters. CONCLUSIONS: These results extend prior findings that anhedonia is associated with steeper DD in PTSD and demonstrate that this behavioral finding occurs in the context of NAcc hyperactivity to immediate rewards and hyperconnectivity in anhedonic individuals with PTSD.

Unconditioned response to a naturally aversive stimulus is associated with sensitized defensive responding and self-reported fearful traits in a PTSD sample.

Unconditioned responding (UCR) to a naturally aversive stimulus is associated with defensive responding to a conditioned threat cue (CS+) and a conditioned safety cue (CS-) in trauma-exposed individuals during fear acquisition. However, the relationships of UCR with defensive responses during extinction training, posttraumatic stress disorder (PTSD) symptom severity, and fearful traits in trauma-exposed individuals are not known. In a sample of 100 trauma-exposed adults with a continuum of PTSD severity, we recorded startle responses and skin conductance responses (SCR) during fear acquisition and extinction training using a 140 psi, 250-ms air blast to the larynx as the unconditioned stimulus. We explored dimensional associations of two different measures of UCR (unconditioned startle and unconditioned SCR) with conditioned defensive responding to CS+ and CS-, conditioned fear (CS+ minus CS-), PTSD symptom severity, and a measure of fearful traits (composite of fear survey schedule, anxiety sensitivity index, and Connor-Davidson resilience scale). Unconditioned startle was positively associated with startle potentiation to the threat cue and the safety cue across both learning phases (CS+ Acquisition, CS- Acquisition, CS+ Extinction Training, CS- Extinction Training) and with fearful traits. Unconditioned SCR was positively associated with SCR to the CS+ and CS- and SCR difference score during Acquisition. Neither type of UCR was associated with PTSD symptom severity. Our findings suggest that UCR, particularly unconditioned startle to a naturally aversive stimulus, may inform research on biomarkers and treatment targets for symptoms of pervasive and persistent fear in trauma-exposed individuals.

Ecological Momentary Assessments of Trauma-Related Intrusive Memories: Potential Clinical Utility.

As the global prevalence of trauma rises, there is a growing need for accessible and scalable treatments for trauma-related disorders like posttraumatic stress disorder (PTSD). Trauma-related intrusive memories (TR-IMs) are a central PTSD symptom and a target of exposure-based therapies, gold-standard treatments that are effective but resource-intensive. This study examined whether a brief ecological momentary assessment (EMA) protocol assessing the phenomenology of TR-IMs could reduce intrusion symptoms in trauma-exposed adults. Participants (N=131) experiencing at least 2 TR-IMs per week related to a DSM-5 criterion A trauma completed a 2-week EMA protocol during which they reported on TR-IM properties three times per day, and on posttraumatic stress symptoms at the end of each day. Longitudinal symptom measurements were entered into linear mixed-effects models to test the effect of Time on TR-IMs. Over the 2-week EMA protocol, intrusion symptom severity (cluster B scores) significantly declined (t = -2.78, p = 0.006), while other symptom cluster scores did not significantly change. Follow-up analyses demonstrated that this effect was specific to TR-IMs (t = -4.02, p < 0.001), and was not moderated by survey completion rate, total PTSD symptom severity, or ongoing treatment. Our findings indicate that implementing an EMA protocol assessing intrusive memories could be an effective trauma intervention. Despite study limitations like its quasi-experimental design and absence of a control group, the specificity of findings to intrusive memories argues against a mere regression to the mean. Overall, an EMA approach could provide a cost-effective and scalable treatment option targeting intrusive memory symptoms.

Intrinsic functional connectivity of right dorsolateral prefrontal cortex and hippocampus subregions relates to emotional and sensory-perceptual properties of intrusive trauma memories.

BACKGROUND: Trauma-related intrusive memories (TR-IMs), unwanted and vivid, are core symptoms of posttraumatic stress disorder (PTSD). Prior research links voluntary TR-IM suppression to inhibitory control of the right dorsolateral prefrontal cortex (dlPFC) over the hippocampus (HPC). However, the potential relevance of tonic resting-state inhibition has not been examined, nor has the functional differentiation of the anterior and posterior hippocampus (aHPC/HPC). This study examined relationships of TR-IM frequency and properties with resting-state negative coupling between the right dlPFC and right aHPC/pHPC in trauma-exposed individuals with PTSD symptoms. METHODS: Participants (N=109; 88 female) completed two weeks of ecological momentary assessments capturing TR-IM frequency and properties (intrusiveness, emotional intensity, vividness, visual properties, and reliving). Using 3T resting-state magnetic resonance imaging, participant-specific 4-mm spheres were placed at the right dlPFC voxel most anticorrelated with the right aHPC and pHPC. Quasi-Poisson and linear mixed-effects models assessed relationships of TR-IM frequency and properties with right dlPFC-right aHPC and pHPC anticorrelation. RESULTS: TR-IM emotional intensity was positively associated with right dlPFC-aHPC connectivity, while vividness and visual properties were linked to right dlPFC-pHPC connectivity. No significant associations were found between TR-IM frequency, intrusiveness, or reliving, and anticorrelation with either HPC subregion. CONCLUSIONS: This study provides novel insights into the neural correlates of TR-IMs, highlighting the relevance of intrinsic negative coupling between the right dlPFC and aHPC/pHPC to their emotional impact and perceptual properties. Further research on inhibitory mechanisms in this circuit could improve understanding of component processes of intrusive reexperiencing, a severe and treatment-refractory PTSD symptom.

Affective Visual Circuit Dysfunction in Trauma and Stress-Related Disorders.

Posttraumatic stress disorder (PTSD) is widely recognized as involving disruption of core neurocircuitry that underlies processing, regulation, and response to threat. In particular, the prefrontal cortex-hippocampal-amygdala circuit is a major contributor to posttraumatic dysfunction. However, the functioning of core threat neurocircuitry is partially dependent on sensorial inputs, and previous research has demonstrated that dense, reciprocal connections exist between threat circuits and the ventral visual stream. Furthermore, emergent evidence suggests that trauma exposure and resultant PTSD symptoms are associated with altered structure and function of the ventral visual stream. In the current review, we discuss evidence that both threat and visual circuitry together are an integral part of PTSD pathogenesis. An overview of the relevance of visual processing to PTSD is discussed in the context of both basic and translational research, highlighting the impact of stress on affective visual circuitry. This review further synthesizes emergent literature to suggest potential timing-dependent effects of traumatic stress on threat and visual circuits that may contribute to PTSD development. We conclude with recommendations for future research to move the field toward a more complete understanding of PTSD neurobiology.

Trauma-related intrusive memories and anterior hippocampus structural covariance: an ecological momentary assessment study in posttraumatic stress disorder.

Trauma-related intrusive memories (TR-IMs) are hallmark symptoms of posttraumatic stress disorder (PTSD), but their neural correlates remain partly unknown. Given its role in autobiographical memory, the hippocampus may play a critical role in TR-IM neurophysiology. The anterior and posterior hippocampi are known to have partially distinct functions, including during retrieval of autobiographical memories. This study aimed to investigate the relationship between TR-IM frequency and the anterior and posterior hippocampi morphology in PTSD. Ninety-three trauma-exposed adults completed daily ecological momentary assessments for fourteen days to capture their TR-IM frequency. Participants then underwent anatomical magnetic resonance imaging to obtain measures of anterior and posterior hippocampal volumes. Partial least squares analysis was applied to identify a structural covariance network that differentiated the anterior and posterior hippocampi. Poisson regression models examined the relationship of TR-IM frequency with anterior and posterior hippocampal volumes and the resulting structural covariance network. Results revealed no significant relationship of TR-IM frequency with hippocampal volumes. However, TR-IM frequency was significantly negatively correlated with the expression of a structural covariance pattern specifically associated with the anterior hippocampus volume. This association remained significant after accounting for the severity of PTSD symptoms other than intrusion symptoms. The network included the bilateral inferior temporal gyri, superior frontal gyri, precuneus, and fusiform gyri. These novel findings indicate that higher TR-IM frequency in individuals with PTSD is associated with lower structural covariance between the anterior hippocampus and other brain regions involved in autobiographical memory, shedding light on the neural correlates underlying this core symptom of PTSD.

Circulating PACAP levels are associated with altered imaging measures of entorhinal cortex neurite density in posttraumatic stress disorder.

Introduction: Pituitary adenylate cyclase-activating polypeptide (PACAP) regulates plasticity in brain systems underlying arousal and memory and is associated with posttraumatic stress disorder (PTSD). Research in animal models suggests that PACAP modulates entorhinal cortex (EC) input to the hippocampus, contributing to impaired contextual fear conditioning. In PTSD, PACAP is associated with higher activity of the amygdala to threat stimuli and lower functional connectivity of the amygdala and hippocampus. However, PACAP-affiliated structural alterations of these regions have not been investigated in PTSD. Here, we examined whether peripheral PACAP levels were associated with neuronal morphology of the amygdala and hippocampus (primary analyses), and EC (secondary) using Neurite Orientation Dispersion and Density Imaging.Methods: Sixty-four (44 female) adults (19 to 54 years old) with DSM-5 Criterion A trauma exposure completed the Clinician-Administered PTSD Scale (CAPS-5), a blood draw, and magnetic resonance imaging. PACAP38 radioimmunoassay was performed and T1-weighted and multi-shell diffusion-weighted images were acquired. Neurite Density Index (NDI) and Orientation Dispersion Index (ODI) were quantified in the amygdala, hippocampus, and EC. CAPS-5 total score and anxious arousal score were used to test for clinical associations with brain structure.Results: Higher PACAP levels were associated with greater EC NDI (ß = 0.0099, q = 0.032) and lower EC ODI (ß = -0.0073, q = 0.047), and not hippocampal or amygdala measures. Neither EC NDI nor ODI was associated with clinical measures.Conclusions: Circulating PACAP levels were associated with altered neuronal density of the EC but not the hippocampus or amygdala. These findings strengthen evidence that PACAP may impact arousal-associated memory circuits in PTSD.

PACAP was associated with altered entorhinal cortex neurite density in PTSD.PACAP was not associated with altered neurite density in amygdala or hippocampus.PACAP may impact arousal-associated memory circuits.