Zoning out: Automatic and conscious attention biases are differentially related to dissociative and post-traumatic symptoms

Time course of attentional bias and its relationship with PTSD symptoms in bereaved Chinese parents who have lost their only child

Background: The death of a child is a highly traumatic event for parents and often leads to posttraumatic stress disorder (PTSD). Attentional bias has been demonstrated in the onset and maintenance of PTSD symptoms.Objective: This study aimed to investigate the time course of attentional bias among bereaved Chinese parents who have lost their only child (Shidu parents), and to examine its relationship with PTSD symptoms and symptom clusters.Methods: Shidu parents (n = 38; 50-72 years of age) completed a dot-probe task with negative (trauma-related), positive, and neutral images at four stimulus presentation times (250, 500, 750, and 1250 ms). PTSD symptoms were measured by the PTSD Checklist for DSM-5 (PCL-5).Results: We observed difficulty in disengaging from both negative and positive stimuli at 750 ms and attentional bias away from negative stimuli at 1250 ms. At 1250 ms, attentional avoidance of trauma-related stimuli was positively correlated with PCL-5 total and intrusion scores. Difficulty in disengaging from positive stimuli was negatively correlated with PCL-5 total and intrusion scores as well as negative alterations in cogniti and mood scores.Conclusions: These findings enhance our understanding of attentional bias and cognitive-affective processing in PTSD. This study provides evidence that attentional bias (difficulty in disengaging from positive stimuli and bias away from negative stimuli) are correlated with PTSD symptoms and certain symptom clusters.

Contrasting Associations Between Heart Rate Variability and Brainstem-Limbic Connectivity in Posttraumatic Stress Disorder and Its Dissociative Subtype: A Pilot Study

Background

Increasing evidence points toward the need to extend the neurobiological conceptualization of posttraumatic stress disorder (PTSD) to include evolutionarily conserved neurocircuitries centered on the brainstem and the midbrain. The reticular activating system (RAS) helps to shape the arousal state of the brain, acting as a bridge between brain and body. To modulate arousal, the RAS is closely tied to the autonomic nervous system (ANS). Individuals with PTSD often reveal altered arousal patterns, ranging from hyper- to blunted arousal states, as well as altered functional connectivity profiles of key arousal-related brain structures that receive direct projections from the RAS. Accordingly, the present study aims to explore resting state functional connectivity of the RAS and its interaction with the ANS in participants with PTSD and its dissociative subtype.

Methods

Individuals with PTSD (n = 57), its dissociative subtype (PTSD + DS, n = 32) and healthy controls (n = 40) underwent a 6-min resting functional magnetic resonance imaging and pulse data recording. Resting state functional connectivity (rsFC) of a central node of the RAS – the pedunculopontine nuclei (PPN) – was investigated along with its relation to ANS functioning as indexed by heart rate variability (HRV). HRV is a prominent marker indexing the flexibility of an organism to react adaptively to environmental needs, with higher HRV representing greater effective adaptation.

Results

Both PTSD and PTSD + DS demonstrated reduced HRV as compared to controls. HRV measures were then correlated with rsFC of the PPN. Critically, participants with PTSD and participants with PTSD + DS displayed inverse correlations between HRV and rsFC between the PPN and key limbic structures, including the amygdala. Whereas participants with PTSD displayed a positive relationship between HRV and PPN rsFC with the amygdala, participants with PTSD + DS demonstrated a negative relationship between HRV and PPN rsFC with the amygdala.

Conclusion

The present exploratory investigation reveals contrasting patterns of arousal-related circuitry among participants with PTSD and PTSD + DS, providing a neurobiological lens to interpret hyper- and more blunted arousal states in PTSD and PTSD + DS, respectively.

Attentional Bias Toward Threat in Sexually Victimized Hispanic Women: A Dot Probe Study

The current study examined attentional bias toward threat in Hispanic college women exposed to lifetime sexual victimization in childhood, adulthood, and both childhood and adulthood. Response latencies and attention bias scores were compared between victimized and non-victimized individuals. Participants were 20 women exposed to adulthood sexual victimization (AS group), 15 exposed to childhood sexual victimization (CS group), 8 exposed to both childhood and adulthood sexual assault (revictimization: RV group), and 20 not endorsing sexual victimization (NS group). They were asked to complete the dot-probe task. The CS group and RV group were combined to create the CS-RV group. Among the AS and CS-RV groups, response latencies were faster when attention was engaged to threat than when attention was engaged to non-threat. The NS group did not demonstrate such differences. When response latencies were compared among the three groups, the CS-RV group had slower response latencies than the NS group. The CS-RV and AS groups revealed similarly significantly elevated bias scores toward threat words than the NS group. Hispanic college women exposed to lifetime sexual victimization display elevated levels of attention bias compared to non-victimized women. Further, the current findings align with an integrative cognitive model for explaining maladaptive informational processing in trauma victims.

A reciprocal inhibition model of alternations between under-/overemotional modulatory states in patients with PTSD

Patients with posttraumatic stress disorder (PTSD) appear to manifest two opposing tendencies in their attentional biases and symptoms. However, whether common neural mechanisms account for their opposing attentional biases and symptoms remains unknown. We here propose a model in which reciprocal inhibition between the amygdala and ventromedial prefrontal cortex (vmPFC) predicts synchronized alternations between emotional under- and overmodulatory states at the neural, behavioral, and symptom levels within the same patients. This reciprocal inhibition model predicts that when the amygdala is dominant, patients enter an emotional undermodulatory state where they show attentional bias toward threat and manifest re-experiencing symptoms. In contrast, when the vmPFC is dominant, patients are predicted to enter an emotional overmodulatory state where they show attentional bias away from threat and avoidance symptoms. To test the model, we performed a behavioral meta-analysis (total N = 491), analyses of own behavioral study (N = 20), and a neuroimaging meta-analysis (total N = 316). Supporting the model, we found the distributions of behavioral attentional measurements to be bimodal, suggesting alternations between the states within patients. Moreover, attentional bias toward threat was related to re-experiencing symptoms, whereas attentional bias away from threat was related with avoidance symptoms. We also found that the increase and decrease of activity in the left amygdala activity was related with re-experiencing and avoidance symptoms, respectively. Our model may help elucidate the neural mechanisms differentiating nondissociative and dissociative subtypes of PTSD, which usually show differential emotional modulatory levels. It may thus provide a new venue for therapies targeting each subtype.

Dissociative Symptoms in a Nationally Representative Sample of Trauma-Exposed U.S. Military Veterans: Prevalence, Comorbidities, and Suicidality

BACKGROUND

Dissociative symptoms have been documented in diverse clinical and non-clinical populations, and are associated with poor mental health outcomes. Yet, research on dissociative symptoms is frequently limited to PTSD samples, and therefore little is known about the prevalence, clinical correlates, and risk factors related to dissociative symptoms in broader, representative trauma-exposed populations.

METHODS

The current study assessed dissociative symptoms in a contemporary, nationally representative sample of trauma-exposed U.S. veterans irrespective of PTSD diagnostic status. We then compared sociodemographic, military, and psychiatric characteristics, trauma histories, level of functioning, and quality of life in veterans with dissociative symptoms to those without dissociative symptoms; and determined the incremental association between dissociative symptoms, and suicidality, functioning, and quality of life, independent of comorbidities.

RESULTS

A total 20.8% of U.S. veterans reported experiencing mild-to-severe dissociative symptoms. Compared to veterans without dissociative symptoms, veterans with dissociative symptoms were younger, and more likely to be non-white, unmarried/partnered and unemployed, had lower education and income, and were more likely to have been combat-exposed and use the VA are their primary source of healthcare. They also had elevated rates of psychiatric comorbidities, lower functioning and quality of life, and a 5-fold greater likelihood of current suicidal ideation and 4-fold greater likelihood of lifetime suicide attempt history.

LIMITATIONS

Cross-sectional data limit inference of the directionality of findings, and results may not generalize to non-veteran populations.

CONCLUSIONS

Dissociative symptoms are prevalent in U.S. veterans and may be an important transdiagnostic marker of heightened risk for suicidality and psychiatric comorbidities. These results underscore the importance of assessing, monitoring, and treating dissociative symptoms in this population.

Back to the Basics: Resting State Functional Connectivity of the Reticular Activation System in PTSD and its Dissociative Subtype

BACKGROUND

Brainstem and midbrain neuronal circuits that control innate, reflexive responses and arousal are increasingly recognized as central to the neurobiological framework of post-traumatic stress disorder (PTSD). The reticular activation system represents a fundamental neuronal circuit that plays a critical role not only in generating arousal but also in coordinating innate, reflexive responding. Accordingly, the present investigation aims to characterize the resting state functional connectivity of the reticular activation system in PTSD and its dissociative subtype.

METHODS

We investigated patterns of resting state functional connectivity of a central node of the reticular activation system, namely, the pedunculopontine nuclei, among individuals with PTSD (n = 77), its dissociative subtype (PTSD+DS; n = 48), and healthy controls (n = 51).

RESULTS

Participants with PTSD and PTSD+DS were characterized by within-group pedunculopontine nuclei resting state functional connectivity to brain regions involved in innate threat processing and arousal modulation (i.e., midbrain, amygdala, ventromedial prefrontal cortex). Critically, this pattern was most pronounced in individuals with PTSD+DS, as compared to both control and PTSD groups. As compared to participants with PTSD and controls, individuals with PTSD+DS showed enhanced pedunculopontine nuclei resting state functional connectivity to the amygdala and the parahippocampal gyrus as well as to the anterior cingulate and the ventromedial prefrontal cortex. No group differences emerged between PTSD and control groups. In individuals with PTSD+DS, state derealization/depersonalization was associated with reduced resting state functional connectivity between the left pedunculopontine nuclei and the anterior nucleus of the thalamus. Altered connectivity in these regions may restrict the thalamo-cortical transmission necessary to integrate internal and external signals at a cortical level and underlie, in part, experiences of depersonalization and derealization.

CONCLUSIONS

The present findings extend the current neurobiological model of PTSD and provide emerging evidence for the need to incorporate brainstem structures, including the reticular activation system, into current conceptualizations of PTSD and its dissociative subtype.