Review article

Biologic models of traumatic memories and post-traumatic stress disorder: The role of neural networks

Insomnia is a risk factor for the development of posttraumatic stress disorder (PTSD) while it is also plausible that PTSD symptoms can maintain insomnia symptoms. The present study examined longitudinal bidirectional relationships between insomnia and PTSD symptoms in treatment-seeking veterans. Participants were 693 ex-serving members of the Australian Defence Force who participated in an accredited, hospital-based outpatient PTSD program. Participants completed self-reported assessments of PTSD and insomnia symptoms at four time points: intake, discharge, 3-month, and 9-months posttreatment follow-up.

Cross-lagged pathway analyses indicated significant bi-directional pathways between insomnia symptoms and PTSD symptoms at most time points. A final cross-lagged model between insomnia symptoms and the PTSD symptom clusters indicated that the PTSD symptom paths on insomnia symptoms, between intake and discharge, were attributable to reexperiencing PTSD symptoms. In contrast, across posttreatment follow-up time points there were significant paths of insomnia symptoms on all PTSD symptom clusters except from insomnia at 3-months to avoidance symptom at 9-months. PTSD symptoms and insomnia symptoms have bidirectional associations over time that may lead to the mutual maintenance or exacerbation of each condition following PTSD treatment. Where residual insomnia symptoms are present post-treatment, a sleep-focussed intervention is indicated and a sequenced approach to treatment recommended.

Post-traumatic stress disorder (PTSD) is a chronic and debilitating condition characterized by persistent intrusive memories. Although effective treatments exist for PTSD, there is a need for development of alternative treatments. Diminished ability to control proactive interference may contribute to re-experiencing symptoms and may be a novel intervention target. The present study tested an intervention designed to modify proactive interference control clinicaltrials.gov identifier: (NCT02139137). Forty-two women with PTSD were randomly assigned to a computerized cognitive training or a control condition. The impact of these programs on cognitive performance and symptoms was assessed. PTSD re-experiencing symptoms and interference control performance improved significantly more for individuals in the training group relative to those in the control group. Other PTSD and general distress symptoms improved equally over time in both groups. Cognitive training of this type may hold promise as a novel intervention for reducing PTSD symptoms, although the mechanism of action and implications for models of PTSD requires future study.

Bipolar disorder (BD) is a unique disorder that transcends domains of function since the same patient can exhibit depression or mania, states with polar opposite mood symptoms. During depression, people feel helplessness, reduced energy, and risk aversion, while with mania behaviors include grandiosity, increased energy, less sleep, and risk preference. The neural mechanism(s) underlying each state are gaining clarity, with catecholaminergic disruption seen during mania, and cholinergic dysfunction during depression. The fact that the same patient cycles/switches between these states is the defining characteristic of BD however. Of greater importance therefore, is the mechanism(s) underlying cycling from one state – and its associated neural changes – to another, considered the ‘holy grail’ of BD research. Herein, we review studies investigating triggers that induce switching to these states. By identifying such triggers, researchers can study neural mechanisms underlying each state and importantly how such mechanistic changes can occur in the same subject. Current animal models of this switch are also discussed, from submissive- and dominant-behaviors to kindling effects. Focus however, is placed on how seasonal changes can induce manic and depressive states in BD sufferers. Importantly, changing photoperiod lengths can induce local switches in neurotransmitter expression in normal animals, from increased catecholaminergic expression during periods of high activity, to increased somatostatin and corticotrophin releasing factor during periods of low activity. Identifying susceptibilities to this switch would enable the development of targeted animal models. From animal models, targeted treatments could be developed and tested that would minimize the likelihood of switching.

Posttraumatic stress disorder (PTSD) is a debilitating condition associated with mild to moderate cognitive impairment and with a prevalence rate of up to 22% in veterans. This systematic review and quantitative meta-analysis explore volumetric differences of three key structural brain regions (hippocampus, amygdala and anterior cingulate cortex (ACC)), all of which have been implicated in dysfunction of both salience network (SN) and default mode network (DMN) in PTSD sufferers. A literature search was conducted in Embase, Medline, PubMed and PsycINFO in May 2013. Fifty-nine volumetric analyses from 44 articles were examined and included (36 hippocampus, 14 amygdala and nine ACC) with n=846 PTSD participants, n=520 healthy controls (HCs) and n=624 traumatised controls (TCs). Nine statistical tests were performed for each of the three regions of interest (ROIs), measuring volume differences in PTSD subjects, healthy and traumatised controls. Hippocampal volume was reduced in subjects with PTSD, with a greater reduction in the left hippocampus. A medium effect size reduction was found in bilateral amygdala volume when compared with findings in healthy controls; however, no significant differences in amygdala volume between PTSD subjects and trauma-exposed controls were found. Significant volume reductions were found bilaterally in the ACC. While often well matched with their respective control groups, the samples of PTSD subjects composed from the source studies used in the meta-analyses are limited in their homogeneity. The current findings of reduced hippocampal volume in subjects with PTSD are consistent with the existing literature. Amygdala volumes did not show significant reductions in PTSD subjects when compared with volumes in trauma-exposed controls—congruous with reported symptoms of hypervigilance and increased propensity in acquisition of conditioned fear memories—but a significant reduction was found in the combined left and right hemisphere volume analysis when compared with healthy controls. Bilateral volume reductions in the ACC may underpin the attentional deficits and inabilities to modulate emotions that are characteristically associated with PTSD patients.

Crime is now a top-priority public-health issue in many urban areas. Sao Paulo’s state police force was the target of gunfire attack on an unprecedented scale. Several officers were killed or wounded, and many more were affected by psychological trauma. We investigated the brain activity underlying trauma, the coping effect of psychotherapy, and resilience in a highly homogenous sample that experienced the same traumatic event. The design applied was a between-group comparison of cerebral blood-oxygenation-level-dependent signals and symptom scores of police officers with and without partial Posttraumatic Stress Disorder (pPTSD).

We used functional magnetic resonance imaging (fMRI) to investigate the retrieval of traumatic memories of 36 volunteers divided in three groups: (1) pPTSD policemen submitted to psychotherapy; (2) pPTSD policemen on the wait list; and (3) symptom-free (resilient) policemen. All participants were given a baseline fMRI scan and a follow-up scan some 40 days later. Not given psychotherapy, groups 2 and 3 were controls.

Group 1 showed 37% fewer PTSD symptoms post-psychotherapy and their scores and neural expressions were comparable to Group 3 resilient policemen. A marked increased in medial prefrontal cortex (mPFC) activity was concomitant with decreased amygdala activity during traumatic memory retrieval in both resilient and pPTSD participants (after psychotherapy) and these findings were associated with symptom attenuation.

Our results provide neurophysiological evidence of resilience in a high-risk group for PTSD. Psychotherapy may help to build narratives and resilient integrated translations of fragmented traumatic memories via mPFC, and thus weaken their sensory content while strengthening them cognitively.

The aims of this study were to examine the factor structure, reliability and validity of the Taiwanese version of the Multidimensional Anxiety Scale for Children (MASC-T) in a group of adolescents in mountainous regions worst affected by Typhoon Morakot-associated mudslides. In total, 271 adolescents in grades 7–9 completed the MASC-T and the Chinese version of the Impact of Events Scale-Revised (C-IES-R). They also received a diagnostic interview to determine whether they had post-traumatic stress disorder (PTSD). We examined adequacy of the original four-factor structure of the MASC-T using confirmatory factor analysis, as well as its internal reliability, discriminant and predictive validities for PTSD, and convergent validity with the C-IES-R. Results support adequacy of the four-factor structure and internal reliability of the MASC-T in adolescents affected by Typhoon Morakot. Scores for the total MASC-T and subscales significantly discriminated adolescents with PTSD from those without PTSD. However, levels of predictive values for PTSD and the convergent validity with the C-IES-R differed among the MASC-T subscales and the total scale. The physical symptoms and harm avoidance subscales had the highest and lowest predictive accuracies for presence of PTSD, respectively. The MASC-T combined with diagnostic interviews for PTSD and self-report measures for assessing PTSD-specific symptoms can be used to evaluate a broad range of anxiety symptoms.