More vulnerability of left than right hippocampal damage in right-handed patients with post-traumatic stress disorder

Progress in the application of molecular imaging in psychiatric disorders

Psychiatric disorders have always attracted a lot of attention from researchers due to the difficulties in their diagnoses and treatments. Molecular imaging, as an emerging technology, has played an important role in the researchers of various diseases. In recent years, molecular imaging techniques including magnetic resonance spectroscopy, nuclear medicine imaging, and fluorescence imaging have been widely used in the study of psychiatric disorders. This review will briefly summarize the progression of molecular imaging in psychiatric disorders.

Proton Magnetic Resonance Spectroscopy in Post-Traumatic Stress Disorder-Updated Systematic Review and Meta-Analysis

A stressor-related disorder wherein traumatic experience precipitates protracted disruptions to mood and cognition, post-traumatic stress disorder (PTSD) is associated with wide-ranging abnormalities across the body. While various methods have investigated these deviations, only proton magnetic resonance spectroscopy (¹H MRS) enables noninvasive measurement of small-molecule metabolites in the living human. ¹H MRS has correspondingly been employed to test hypotheses about the composition and function of multiple brain regions putatively involved in PTSD. Here we systematically review methodological considerations and reported findings, both positive and negative, of the current ¹H-MRS literature in PTSD (N = 32 studies) to communicate the brain regional metabolite alterations heretofore observed, providing random-effects model meta-analyses for those most extensively studied. Our review suggests significant PTSD-associated decreases in N-acetyl aspartate in bilateral hippocampus and anterior cingulate cortex with less evident effect in other metabolites and regions. Model heterogeneities diverged widely by analysis (I² < 0.01% to 90.1%) and suggested regional dependence on quantification reference (creatine or otherwise). While observed variabilities in methods and reported findings suggest that ¹H-MRS explorations of PTSD could benefit from methodological standardization, informing this standardization by quantitative assessment of the existing literature is currently hampered by its small size and limited scope.

Grey Matter Volume Reductions of the Left Hippocampus and Amygdala in PTSD: A Coordinate-Based Meta-Analysis of Magnetic Resonance Imaging Studies

INTRODUCTION

In recent years, research on posttraumatic stress disorder (PTSD) focused on the description of different biological correlates of illness. Morphological changes of different brain regions were involved in PTSD neurophysiopathology, being related to trauma or considered a resilience biomarker. In this meta-analysis, we aimed to investigate the grey matter changes reported in magnetic resonance imaging (MRI) studies on patients who have developed PTSD compared to exposed subjects who did not show a clinical PTSD onset.

METHODS

We meta-analysed eight peer-reviewed MRI studies conducted on trauma-exposed patients and reported results corrected for false positives. We then conducted global and intergroup comparisons from neuroimaging data of two cohorts of included subjects. The included studies were conducted on 250 subjects, including 122 patients with PTSD and 128 non-PTSD subjects exposed to trauma.

RESULTS

Applying a family-wise error correction, PTSD subjects compared to trauma-exposed non-PTSD individuals showed a significant volume reduction of a large left-sided grey matter cluster extended from the parahippocampal gyrus to the uncus, including the amygdala.

CONCLUSIONS

These volumetric reductions are a major structural correlate of PTSD and can be related to the expression of symptoms. Future studies might consider these and other neural PTSD correlates, which may lead to the development of clinical applications for affected patients.

Does Hippocampal Volume in Patients with Posttraumatic Stress Disorder Vary by Trauma Type?

Posttraumatic stress disorder (PTSD) is a debilitating disorder that can develop after experiencing a traumatic event and is, in part, characterized by memory disturbances. Given its important role in learning and memory, the hippocampus has been studied extensively in PTSD using volumetric neuroimaging techniques. However, the results of these studies are mixed. The variability in findings across studies could arise from differences in samples with regard to trauma type, but this connection has not yet been formally assessed. To assess this question, we conducted (1) mixed-effects meta-analyses to replicate previous meta-analytic findings of significant differences in hippocampal volumes in PTSD groups versus two different types of control groups (trauma-exposed and -unexposed groups), and (2) mixed-effects subgroup and meta-regression analyses to determine whether trauma type moderated these hippocampal volume differences. Overall, the PTSD groups showed significantly smaller right hippocampal volumes than both control groups and significantly smaller left hippocampal volumes than trauma-unexposed control groups. Subgroup and meta-regression analyses revealed that trauma type did not moderate the effect seen between PTSD and trauma-exposed non-PTSD groups but did moderate the effect between the PTSD and trauma-unexposed control groups: studies that contained participants with PTSD related to combat trauma exhibited significantly smaller effect sizes for right hippocampal volumes compared to the interpersonal violence and "other" trauma-type groups with PTSD. These findings suggest that trauma type may moderate hippocampal volume in trauma-exposed individuals but not in those with PTSD.

Utility of 7,8-dihydroxyflavone in preventing astrocytic and synaptic deficits in the hippocampus elicited by PTSD

Astrocytic functions and brain-derived neurotrophic factor (BDNF)-tyrosine kinase receptor B (TrkB) signaling pathways are impaired in stress-related neuropsychiatric diseases. Previous studies have reported neuroprotective effects of 7,8-dihydroxyflavone (7,8-DHF), a TrkB activator. Here, we investigated the molecular mechanisms underlying pathogenesis of post-traumatic stress disorder (PTSD) using a modified single-prolonged stress (SPS&S) model and the potential beneficial effects of 7,8-DHF. SPS&S reduced the hippocampal expression of glial fibrillary acidic protein (GFAP), a marker of astrocytes, and induced morphological changes in astrocytes. From the perspective of synaptic function, the SPS&S model displayed reduced expression of BDNF, p-TrkB, postsynaptic density protein 95 (PSD95), AMPA receptor subunit GluR1 (GluA1), NMDA receptor subunit N2A/N2B ratio, calpain-1, phosphorylated protein kinase B (Akt) and phosphorylated mammalian target of rapamycin (mTOR) and conversely, higher phosphatase and tension homolog (PTEN) expression in the hippocampus. Acute or continuous intraperitoneal administration of 7,8-DHF (5 mg/kg) after SPS&S procedures prevented SPS&S-induced fear memory generalization and anxiety-like behaviors as well as abnormalities of hippocampal oscillations. Most importantly, 7,8-DHF attenuated SPS&S-induced abnormal BDNF-TrkB signaling and calpain-1-dependent cascade of synaptic deficits. Furthermore, treatment with a TrkB inhibitor completely blocked while an mTOR inhibitor partially blocked the effects of 7,8-DHF on behavioral changes of SPS&S model mice. Our collective findings suggest that 7,8-DHF effectively alleviates PTSD-like symptoms, including fear generalization and anxiety-like behavior, potentially by preventing astrocytic and synaptic deficits in the hippocampus through targeting of TrkB.

Larger dentate gyrus volume as predisposing resilience factor for the development of trauma-related symptoms

Early interventions to improve resilience require the identification of objective risk biomarkers for PTSD symptom development. Although altered hippocampal and amygdala volumes are consistently observed in PTSD, it remains currently unknown whether they represent a predisposing vulnerability factor for PTSD symptom development or an acquired consequence of trauma exposure and/or the disorder. We conducted a longitudinal, prospective study in 210 police recruits at high risk for trauma exposure (56 females(26.7%); mean[SD] age = 24.02[5.19]). Structural MRI scans and trauma-related symptom severity were assessed at pre-trauma baseline and at 16-month follow-up. Between assessments, police recruits were exposed to various potentially traumatic events during their police training. Police recruits reported a significant increase in police-related trauma exposure and stress-related symptoms between assessments. Smaller hippocampal left dentate gyrus (DG) volumes at baseline predicted increase in self-reported PTSD symptoms (B[SE] = -0.21[0.08], p = 0.011), stress symptoms (B[SE] = -0.16[0.07], p = 0.024) and negative affect (B[SE] = -0.21[0.07], p = 0.005) upon trauma exposure. Amount of police-related trauma exposure between assessments was positively associated with an increase in left basal amygdala nucleus volume (B[SE] = 0.11[0.05], p = 0.026). Taken together, smaller DG-volumes pre-trauma may represent a predisposing neurobiological vulnerability factor for development of trauma-related symptoms. On the other hand, amount of trauma exposure between assessments was positively associated with increased amygdala basal nucleus volume, suggesting acquired neural effects. These findings suggest that preventive interventions for PTSD aimed at improving resilience could be targeted at increasing DG-volume and potentially its functioning.

Hippocampal blood-brain barrier permeability is related to the APOE4 mutation status of elderly individuals without dementia

Blood-brain barrier (BBB) disruption, modulated by APOE4 mutation, is implicated in the pathogenesis of cognitive decline. We determined whether BBB permeability differed according to cognitive functioning and APOE4 status in elderly subjects without dementia. In this prospective study, 33 subjects with mild cognitive impairment (MCI) and 33 age-matched controls (normal cognition [NC]) underwent 3 T brain magnetic resonance imaging. The Patlak model was used to calculate tissue permeability (K_trans). A region-of interest analysis of K_trans was performed to compare relevant brain regions. Effects of K_trans on cognitive functioning were evaluated with linear regression analysis adjusted for confounding factors. NC and MCI groups did not differ in terms of vascular risk factors or hippocampal K_trans, except for hippocampal volume. Hippocampal K_trans was significantly higher in APOE4 carriers than in non-carriers (p = 0.007). Factors which predicted cognitive functioning included hippocampal volume (beta=-0.445, standard error [SE]=0.137, p = 0.003) and hippocampal BBB permeability (beta = 0.142, SE = 0.050, p = 0.008) after correcting for age, education, and APOE4 status. This suggests that hippocampal BBB permeability is associated with APOE4 mutation, and may predict cognitive functioning. BBB permeability imaging represents a distinct imaging biomarker for APOE4 mutations in NC and MCI subjects and for determining the degree of APOE4-related pathology.

Early putamen hypertrophy and ongoing hippocampus atrophy predict cognitive performance in the first ten years of relapsing-remitting multiple sclerosis

BACKGROUND

The first years of relapsing-remitting multiple sclerosis (RRMS) constitute the most vulnerable phase for the progression of cognitive impairment (CImp), due to a gradual decrease of compensatory mechanisms. In the first 10 years of RRMS, the temporal volumetric changes of deep gray matter structures must be clarified, since they could constitute reliable cognitive biomarkers for diagnostic, prognostic, and therapeutic purposes.

METHODS

Forty-five cognitively asymptomatic patients with RRMS lasting ≤ 10 years, and with a brain MRI performed in a year from the neuropsychological evaluation (Te-MRI), were included. They performed the Brief International Cognitive Assessment battery for MS. Thirty-one brain MRIs performed in the year of diagnosis (Td-MRI) and 13 brain MRIs of age- and sex-matched healthy controls (HCs) were also included in the study. The relationships between clinical features, cognitive performances, and Te- and Td-MRI volumes were statistically analyzed.

RESULTS

Cognitively preserved (CP) patients had significantly increased Td-L-putamen (P = 0.035) and Td-R-putamen volume (P = 0.027) with respect to cognitively impaired (CI) ones. CI patients had significantly reduced Te-L-hippocampus (P = 0.019) and Te-R-hippocampus volume (P = 0.042) compared, respectively, with Td-L-hippocampus and Td-R-hippocampus volume. Td-L-putamen volume (P = 0.011) and Te-L-hippocampus volume (P = 0.023) were independent predictors of the Symbol Digit Modalities Test score in all patients (r2 = 0.31, F = 6.175, P = 0.001).

CONCLUSION

In the first years of RRMS, putamen hypertrophy and hippocampus atrophy could represent promising indices of cognitive performance and reserve, and become potentially useful tools for diagnostic, prognostic, and therapeutic purposes.

Knockdown of CLC-3 in the hippocampal CA1 impairs contextual fear memory

Previous studies support a critical role of hippocampus in contextual fear memory. Structural and functional alterations of hippocampus occur frequently in posttraumatic stress disorders (PTSD). Recent reports reveal that knockout of CLC-3, a member of the CLC family of anion channels and transporters, leads to neuronal degeneration and loss of hippocampus. However, the role of CLC-3 in contextual fear memory remains unknown. Using adenovirus and adeno-associated virus gene transfer to knockdown CLC-3 in hippocampal CA1, we investigate the role of CLC-3 in contextual fear memory. CLC-3 expression is increased in hippocampal CA1 after formation of long-term contextual fear memory. Knockdown of CLC-3 by adenovirus infusion in hippocampal CA1 significantly attenuates the contextual fear memory, reduces spine density, induces defects of excitatory synaptic ultrastructure showed by the decreased PSD length, PSD thickness and active zone length, and impairs L-LTP induction and maintenance. Knockdown of CLC-3 also induces the synaptic NMDAR subunit composition to an increased GluN2A/GluN2B ratio pattern and reduces the activity of CaMKII-α. Furthermore, selectively knockdown of CLC-3 in excitatory neurons by adeno-associated virus driven from CaMKII-α promoter is sufficient to impair long-term contextual fear memory. These findings highlight that CLC-3 in hippocampal CA1 is necessary for contextual fear memory.

Oxidative Stress, Inflammation, and Neuroprogression in Chronic PTSD

Posttraumatic stress disorder is a serious and often disabling syndrome that develops in response to a traumatic event. Many individuals who initially develop the disorder go on to experience a chronic form of the condition that in some cases can last for many years. Among these patients, psychiatric and medical comorbidities are common, including early onset of age-related conditions such as chronic pain, cardiometabolic disease, neurocognitive disorders, and dementia. The hallmark symptoms of posttraumatic stress-recurrent sensory-memory reexperiencing of the trauma(s)-are associated with concomitant activations of threat- and stress-related neurobiological pathways that occur against a tonic backdrop of sleep disturbance and heightened physiological arousal. Emerging evidence suggests that the molecular consequences of this stress-perpetuating syndrome include elevated systemic levels of oxidative stress and inflammation. In this article we review evidence for the involvement of oxidative stress and inflammation in chronic PTSD and the neurobiological consequences of these processes, including accelerated cellular aging and neuroprogression. Our aim is to update and expand upon previous reviews of this rapidly developing literature and to discuss magnetic resonance spectroscopy as an imaging technology uniquely suited to measuring oxidative stress and inflammatory markers in vivo. Finally, we highlight future directions for research and avenues for the development of novel therapeutics targeting oxidative stress and inflammation in patients with PTSD.

Systematic review of in-vivo neuro magnetic resonance spectroscopy for the assessment of posttraumatic stress disorder

Posttraumatic stress disorder (PTSD) is a trauma and stressor-related disorder that results in complex somatic, cognitive, affective and behavioural effects, after exposure to traumatic event(s). Conventional imaging (T1 and T2 weighted magnetic resonance imaging) has little to offer in the way of diagnosis of mental health conditions such as PTSD and there is currently no objective diagnostic test available. Magnetic resonance spectroscopy (MRS) allows for non-invasive measurement of metabolites and neurochemicals in the brain using a conventional MRI scanner and offers the potential to predict, diagnose and monitor PTSD. This systematic review summarises the results of 24 MRS studies, performed between 1998 and 2017, to measure neurochemical differences, occurring as a consequence of PTSD. The most consistent finding in subjects with PTSD is lower N-acetylaspartate levels in the hippocampus and anterior cingulate cortex, with and without atrophic change. More recent studies, using more advanced techniques and modern hardware, have shown evidence of glutamatergic dysfunction and differences in gamma-aminobutyric acid levels in the brain of patients with PTSD. Conflicting results have been reported in choline-containing metabolites and there is emerging evidence of glutathione being affected. Myo-inositol and creatine are unchanged in the majority of studies.

Posttraumatic stress disorder symptom severity is associated with left hippocampal volume reduction: a meta-analytic study

OBJECTIVE

Many studies have reported hippocampal volume reductions associated with posttraumatic stress disorder (PTSD), while others have not. Here we provide an updated meta-analysis of such reductions associated with PTSD and evaluate the association between symptom severity and hippocampal volume.

METHODS

A total of 37 studies met the criteria for inclusion in the meta-analysis. Mean effect sizes (Hedges' g) and 95% confidence intervals (CI 95%) were computed for each study and then averaged to obtain an overall mean effect size across studies. Meta-regression was employed to examine the relationship between PTSD symptom severity and hippocampal volume.

RESULTS

Results showed that PTSD is associated with significant bilateral reduction of the hippocampus (left hippocampus effect size=-0.400, p<0.001, 5.24% reduction; right hippocampus effect size=-0.462, p<0.001, 5.23% reduction). Symptom severity, as measured by the Clinician-Administered PTSD Scale (CAPS), was significantly associated with decreased left, but not right, hippocampal volume.

CONCLUSIONS

PTSD was associated with significant bilateral volume reduction of the hippocampus. Increased symptom severity was significantly associated with reduced left hippocampal volume. This finding is consistent with the hypothesis that PTSD is more neurotoxic to the left hippocampus than to the right. However, whether the association between PTSD and lower hippocampal volume reflects a consequence of or a predisposition to PTSD remains unclear. More prospective studies are needed in this area.

Hippocampus Glutamate and N-Acetyl Aspartate Markers of Excitotoxic Neuronal Compromise in Posttraumatic Stress Disorder

Hippocampus atrophy is implicated in posttraumatic stress disorder (PTSD), and may partly reflect stress-induced glutamate excitotoxicity that culminates in neuron injury and manifests as re-experiencing symptoms and other memory abnormalities. This study used high-field proton magnetic resonance spectroscopy (MRS) to determine whether PTSD is associated with lower hippocampus levels of the neuron marker N-acetyl aspartate (NAA), along with higher levels of glutamate (Glu) and Glu/NAA. We also predicted that metabolite levels would correlate with re-experiencing symptoms and lifetime trauma load. Twenty-four adult PTSD patients and 23 trauma-exposed normal controls (TENC) underwent 4T MRS of the left and right hippocampus. Participants received psychiatric interviews, and completed the Traumatic Life Events Questionnaire to define lifetime trauma load. Relative to TENC participants, PTSD patients exhibited significantly lower NAA in right and left hippocampi, and significantly higher Glu and Glu/NAA in the right hippocampus. Re-experiencing symptoms were negatively correlated with left and right NAA, and positively correlated with right Glu and right Glu/NAA. Trauma load was positively correlated with right Glu/NAA in PTSD patients. When re-experiencing symptoms and trauma load were examined together in relation to right Glu/NAA, only re-experiencing symptoms remained a significant correlate. This represents the first report that PTSD is associated with MRS markers of hippocampus Glu excess, together with indices of compromised neuron integrity. Their robust associations with re-experiencing symptoms affirm that MRS indices of hippocampus neuron integrity and glutamate metabolism may reflect biomarkers of clinically significant disease variation in PTSD.

Molecular Neuroimaging in Posttraumatic Stress Disorder

Over the past decade, an increasing number of neuroimaging studies have provided insight into the neurobiological mechanisms of posttraumatic stress disorder (PSTD). In particular, molecular neuroimaging techniques have been employed in examining metabolic and neurochemical processes in PTSD. This article reviews molecular neuroimaging studies in PTSD and focuses on findings using three imaging modalities including positron emission tomography (PET), single photon emission computed tomography (SPECT), and magnetic resonance spectroscopy (MRS). Although there were some inconsistences in the findings, patients with PTSD showed altered cerebral metabolism and perfusion, receptor bindings, and metabolite profiles in the limbic regions, medial prefrontal cortex, and temporal cortex. Studies that have investigated brain correlates of treatment response are also reviewed. Lastly, the limitations of the molecular neuroimaging studies and potential future research directions are discussed.

Decreased left hippocampal volumes in parents with or without posttraumatic stress disorder who lost their only child in China

BACKGROUND

Limbic structural changes have been found in people with post-traumatic stress disorder (PTSD). However, the results were controversial, and no study has examined the hippocampal and amygdala volume changes in parents with or without PTSD who had lost their only child and could no longer conceive in China.

METHODS

Hippocampal and amygdala volumes of 57 parents with PTSD (PTSD+), 11 trauma-exposed parents without PTSD (PTSD-) and 39 non-traumatized controls were examined using magnetic resonance imaging. Correlations of the volumes with the time since trauma, Clinician-Administered PTSD Scale (CAPS) scores, age, gender and intracranial volume (ICV) were investigated in the PTSD+ group.

RESULTS

left hippocampal volumes were significantly smaller in the PTSD+ and PTSD- groups than in the controls, but there were no significant differences between the PTSD+ and PTSD- groups. Furthermore, there was no significant difference in the right hippocampus or bilateral amygdala volumes. Additionally, the hippocampal and amygdala volumes showed no correlation with the time since trauma, CAPS score and gender, whereas the left hippocampal volumes were correlated with ICV, and the bilateral amygdala volumes were correlated with ICV and age in the PTSD+ group.

LIMITATIONS

The PTSD- group included only 11 participants.

CONCLUSIONS

left hippocampal volumes decreased in parents who lost their only child, with or without PTSD. Our results suggest a potentially unique role of the trauma of losing an only child, which is extremely painful and may induce a decrease in the left hippocampal volume independent of PTSD effects.

Subcortical neuromorphometry in schizophrenia spectrum and bipolar disorders

Background

Disorders within the schizophrenia spectrum genetically overlap with bipolar disorder, yet questions remain about shared biological phenotypes. Investigation of brain structure in disease has been enhanced by developments in shape analysis methods that can identify subtle regional surface deformations. Our study aimed to identify brain structure surface deformations that were common across related psychiatric disorders, and characterize differences.

Methods

Using the automated FreeSurfer-initiated Large Deformation Diffeomorphic Metric Mapping, we examined volumes and shapes of seven brain structures: hippocampus, amygdala, caudate, nucleus accumbens, putamen, globus pallidus and thalamus. We compared findings in controls (CON; n = 40), and those with schizophrenia (SCZ; n = 52), schizotypal personality disorder (STP; n = 12), psychotic bipolar disorder (P-BP; n = 49) and nonpsychotic bipolar disorder (N-BP; n = 24), aged 15–35. Relationships between morphometric measures and positive, disorganized and negative symptoms were also investigated.

Results

Inward deformation was present in the posterior thalamus in SCZ, P-BP and N-BP; and in the subiculum of the hippocampus in SCZ and STP. Most brain structures however showed unique shape deformations across groups. Correcting for intracranial size resulted in volumetric group differences for caudate (p < 0.001), putamen (p < 0.01) and globus pallidus (p < 0.001). Shape analysis showed dispersed patterns of expansion on the basal ganglia in SCZ. Significant clinical relationships with hippocampal, amygdalar and thalamic volumes were observed.

Conclusions

Few similarities in surface deformation patterns were seen across groups, which may reflect differing neuropathologies. Posterior thalamic contraction in SCZ and BP suggest common genetic or environmental antecedents. Surface deformities in SCZ basal ganglia may have been due to antipsychotic drug effects.

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Shape analysis identified structural abnormalities in psychiatric disorders, where volume analysis did not

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Few similarities in surface deformation patterns were seen across diagnostic groups

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Posterior thalamic contraction was seen in both schizophrenia and bipolar patients

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Expansion of basal ganglia regions were seen in schizophrenia patients

Proton magnetic resonance spectroscopy revealed differences in the glutamate + glutamine/creatine ratio of the anterior cingulate cortex between healthy and pediatric post-traumatic stress disorder patients diagnosed after 2008 Wenchuan earthquake

AIMS

Earthquakes always leave many surviving teenagers suffering from various mental problems, such as post-traumatic stress disorder (PTSD). We studied the metabolites in current and remitted pediatric PTSD patients and healthy controls after an earthquake, aiming to find the neurochemistry differences in these teenagers.

METHODS

Proton magnetic resonance spectroscopy ((1) H-MRS) was performed in the anterior cingulate cortex (ACC) of 21 healthy, 10 PTSD and 23 remitted subjects.

RESULTS

Significantly lower glutamate + glutamine/creatine (Glx/Cr) levels in the ACC (1.15 ± 0.14 vs 1.37 ± 0.08, P = 0.047) were found in PTSD subjects relative to remitted subjects; and significantly lower Glx/Cr levels in the ACC (1.37 ± 0.08 vs 1.59 ± 0.10, P = 0.045) were found in remitted subjects relative to healthy controls.

CONCLUSIONS

Our findings imply that the Glx/Cr ratio in the ACC can be used to differentiate not only between healthy and pediatric PTSD patients, but also between the current and remitted phases of pediatric PTSD. The changes in the Glx/Cr ratio may be caused by brain dysfunction in the current phase and recovery in the remitted phase.

A systematic review and meta-analysis of magnetic resonance imaging measurement of structural volumes in posttraumatic stress disorder

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.

Stress- and PTSD-associated obesity and metabolic dysfunction: a growing problem requiring further research and novel treatments

Posttraumatic stress disorder (PTSD) is a growing public health concern. More recently, evidence has indicated that PTSD leads to obesity and associated metabolic dysfunction. Possible mechanisms of this link are through dysfunction of the hypothalamic-pituitary-adrenal axis and related moderation of appetite hormones and neural activity, leading to changes in consumptive behaviors. Although research has been examining associations between PTSD and obesity, diabetes, cardiovascular disease, and metabolic syndrome, future research should delineate potential mechanisms for these associations and develop targeted treatments to reduce these metabolic outcomes.

Structural impairments of hippocampus in coal mine gas explosion-related posttraumatic stress disorder

Investigations on hippocampal and amygdalar volume have revealed inconsistent results in patients with posttraumatic stress disorder (PTSD). Little is known about the structural covariance alterations between the hippocampus and amygdala in PTSD. In this study, we evaluated the alteration in the hippocampal and amygdalar volume and their structural covariance in the coal mine gas explosion related PTSD. High resolution T1-weighted magnetic resonance imaging (MRI) was performed on coal mine gas explosion related PTSD male patients (n = 14) and non-traumatized coalminers without PTSD (n = 25). The voxel-based morphometry (VBM) method was used to test the inter-group differences in hippocampal and amygdalar volume as well as the inter-group differences in structural covariance between the ipsilateral hippocampus and amygdala. PTSD patients exhibited decreased gray matter volume (GMV) in the bilateral hippocampi compared to controls (p<0.05, FDR corrected). GMV covariances between the ipsilateral hippocampus and amygdala were significantly reduced in PTSD patients compared with controls (p<0.05, FDR corrected). The coalminers with gas explosion related PTSD had decreased hippocampal volume and structural covariance with the ipsilateral amygdala, suggesting that the structural impairment of the hippocampus may implicate in the pathophysiology of PTSD.

A pilot study evaluating presurgery neuroanatomical biomarkers for postoperative cognitive decline after total knee arthroplasty in older adults

BACKGROUND

Total knee arthroplasty improves quality of life but is associated with postoperative cognitive dysfunction in older adults. This prospective longitudinal pilot study with a parallel control group tested the hypotheses that (1) nondemented adults would exhibit primary memory and executive difficulties after total knee arthroplasty, and (2) reduced preoperative hippocampus/entorhinal volume would predict postoperative memory change, whereas preoperative leukoaraiosis and lacunae volumes would predict postoperative executive dysfunction.

METHODS

Surgery (n = 40) and age-education-matched controls with osteoarthritis (n = 15) completed pre- and postoperative (3 weeks, 3 months, and 1 yr) memory and cognitive testing. Hypothesized brain regions of interest were measured in patients completing preoperative magnetic resonance scans (surgery, n = 31; control, n = 12). Analyses used reliable change methods to identify the frequency of cognitive change at each time point.

RESULTS

The incidence of postoperative memory difficulties was shown with delay test indices (i.e., story memory test: 3 weeks = 17%, 3 months = 25%, 1 yr = 9%). Postoperative executive difficulty with measures of inhibitory function (i.e., Stroop Color Word: 3 weeks = 21%, 3 months = 22%, 1 yr = 9%). Hierarchical regression analysis assessing the predictive interaction of group (surgery, control) and preoperative neuroanatomical structures on decline showed that greater preoperative volumes of leukoaraiosis/lacunae were significantly contributed to postoperative executive (inhibitory) declines.

CONCLUSIONS

This pilot study suggests that executive and memory declines occur in nondemented adults undergoing orthopedic surgery. Severity of preoperative cerebrovascular disease may be relevant for understanding executive decline, in particular.

Intranasal oxytocin as strategy for medication-enhanced psychotherapy of PTSD: salience processing and fear inhibition processes

About ten percent of people experiencing a traumatic event will subsequently develop post-traumatic stress disorder (PTSD). PTSD is characterized by an exaggerated fear response which fails to extinguish over time and cannot be inhibited in safe contexts. The neurobiological correlates of PTSD involve enhanced salience processing (i.e. amygdala, dorsal anterior cingulate cortex (dACC) and anterior insula (AI) hyperactivity), and reduced top-down inhibitory control over this fear response (i.e. dorsal and ventromedial prefrontal cortex (vmPFC) hypoactivity and diminished structural and functional connectivity between the vmPFC, hippocampus and amygdala). Therefore, dampening the exaggerated fear response (i.e. by reducing amygdala hyperactivity) and enhancing top-down inhibitory control (i.e. by promoting prefrontal control over the amygdala) during psychotherapy is an important target for medication-enhanced psychotherapy (MEP) in PTSD patients. Since the neuropeptide oxytocin (OT) has been found to act on these two processes, we propose that OT is a promising pharmacological agent to boost treatment response in PTSD. Human fMRI studies indicate that intranasal OT attenuates amygdala (hyper)activity and enhances connectivity of the amygdala with the vmPFC and hippocampus, resulting in increased top-down control over the fear response. In addition, intranasal OT was found to attenuate amygdala-brainstem connectivity and to change activity and connectivity in nodes of the salience network (i.e. AI and dACC). Furthermore, OT administration may modulate hypothalamus-pituitary-adrenal (HPA) axis and autonomic nervous system (ANS) function and may enhance social behaviour, which could be beneficial in the therapeutic alliance. We also discuss contextual and interindividual factors (e.g. gender and social context) which may influence the effectiveness of OT in MEP. In all, we propose that intranasal OT given prior to each psychotherapy session may be an effective additive treatment to boost treatment response in PTSD.

Co-activation of NR2A and NR2B subunits induces resistance to fear extinction

Unpredictable stress is known to profoundly enhance susceptibility to fear and anxiety while reducing the ability to extinguish fear when threat is no longer present. Accordingly, partial aversive reinforcement, via random exposure to footshocks, induces fear that is resistant to extinction. Here we sought to determine the hippocampal mechanisms underlying susceptibility versus resistance to context fear extinction as a result of continuous (CR) and partial (PR) reinforcement, respectively. We focused on N-methyl-D-aspartate receptor (NMDAR) subunits 2A and B (NR2A and NR2B) as well as their downstream signaling effector, extracellular signal-regulated kinase (ERK), based on their critical role in the acquisition and extinction of fear. Pharmacological inactivation of NR2A, but not NR2B, blocked extinction after CR, whereas inactivation of NR2A, NR2B, or both subunits facilitated extinction after PR. The latter finding suggests that co-activation of NR2A and NR2B contributes to persistent fear following PR. In contrast to CR, PR increased membrane levels of ERK and NR2 subunits after the conditioning and extinction sessions, respectively. In parallel, nuclear activation of ERK was significantly reduced after the extinction session. Thus, co-activation and increased surface expression of NR2A and NR2B, possibly mediated by ERK, may cause persistent fear. These findings suggest that patients with post-traumatic stress disorder (PTSD) may benefit from antagonism of specific NR2 subunits.