A review of neuroimaging studies in PTSD: heterogeneity of response to symptom provocation

Functional neuroimaging of reward circuitry responsivity to monetary gains and losses in posttraumatic stress disorder

BACKGROUND

Clinical impressions and preclinical work suggest that posttraumatic stress disorder (PTSD) might be associated with dysfunctional reward processing. To pursue this issue, we administered a validated passive-viewing monetary reward task during functional magnetic resonance imaging (fMRI) to subjects with chronic PTSD and to mentally healthy individuals.

METHODS

The protocol evaluated fMRI signal changes that anticipated or accompanied monetary gains and losses under varying conditions of controlled expectation. The "expectancy phase" entailed presentation of a promising, unpromising, or intermediate Wheel of Fortune-type spinner, whereas the "outcome phase" was defined by the arrow landing on one of three sectors of that spinner, thereby determining the subjects' gain or loss for that trial.

RESULTS

Neuroimaging data from 20 PTSD and 26 healthy subjects withstood quality control procedures and were included. In voxelwise and anatomically defined region-of-interest analyses, when gains were contrasted to losses, between-group comparison revealed smaller bilateral striatal activations in the PTSD subjects. In the PTSD group, less striatal activation to gains versus losses was associated with more self-reported motivational and social deficits.

CONCLUSIONS

The present data support the hypothesis that PTSD is associated with abnormal processing of monetary outcomes and that this alteration might be related to some aspects of emotional numbing.

Post-traumatic amnesia and the nature of post-traumatic stress disorder after mild traumatic brain injury

The prevalence and nature of post-traumatic stress disorder (PTSD) following mild traumatic brain injury (MTBI) is controversial because of the apparent paradox of suffering PTSD with impaired memory for the traumatic event. In this study, 1167 survivors of traumatic injury (MTBI: 459, No TBI: 708) were assessed for PTSD symptoms and post-traumatic amnesia during hospitalization, and were subsequently assessed for PTSD 3 months later (N = 920). At the follow-up assessment, 90 (9.4%) patients met criteria for PTSD (MTBI: 50, 11.8%; No-TBI: 40, 7.5%); MTBI patients were more likely to develop PTSD than no-TBI patients, after controlling for injury severity (adjusted odds ratio: 1.86; 95% confidence interval, 1.78-2.94). Longer post-traumatic amnesia was associated with less severe intrusive memories at the acute assessment. These findings indicate that PTSD may be more likely following MTBI, however, longer post-traumatic amnesia appears to be protective against selected re-experiencing symptoms.

Functional connectivity reveals inefficient working memory systems in post-traumatic stress disorder

We applied a covariance-based multivariate analysis to functional magnetic resonance imaging (fMRI) data to investigate abnormalities in working memory (WM) systems in patients with post-traumatic stress disorder (PTSD). Patients (n=13) and matched controls (n=12) were scanned with fMRI while updating or maintaining trauma-neutral verbal stimuli in WM. A multivariate statistical analysis was used to investigate large-scale brain networks associated with these experimental tasks. For the control group, the first network reflected brain activity associated with WM updating and principally involved bilateral prefrontal and bilateral parietal cortex. Controls' second network was associated with WM maintenance and involved regions typically activated during storage and rehearsal of verbal material, including lateral premotor and inferior parietal cortex. In contrast, PTSD patients appeared to activate a single fronto-parietal network for both updating and maintenance tasks. This is indicative of abnormally elevated activity during WM maintenance and suggests inefficient allocation of resources for differential task demands. A second network in PTSD, which was not activated in controls, showed regions differentially activated between WM tasks, including the anterior cingulate, medial prefrontal cortex, fusiform and supplementary motor area. These activations may be linked to hyperarousal and abnormal reactivity, which are characteristic of PTSD.

One-year functional magnetic resonance imaging follow-up study of neural activation during the recall of unresolved negative life events in borderline personality disorder

BACKGROUND

Recall of adverse life events under brain imaging conditions has been shown to coincide with activation of limbic and prefrontal brain areas in borderline personality disorder (BPD). We investigate changes of functional magnetic resonance imaging (fMRI) activation patterns during the recall of unresolved adverse life events (ULE) over 1 year.

METHOD

Thirteen female BPD patients participated in the study. During fMRI measurement subjects recalled ULE and negative but resolved life events (RLE) after individual cue words to stimulate autobiographical memory retrieval. Subjective intensity of emotional and sensoric experiences during recall was assessed as well as standardized measures of psychopathology.

RESULTS

A 2x2 factorial analysis of fMRI data (Deltat1/t2xDeltaULE/RLE) revealed major right more than left differences of activation (i.e. t1>t2) of the posterior more than anterior cingulate, superior temporal lobes, insula, and right middle and superior frontal lobes (second-level analysis, t=3.0, puncorrected=0.003). The opposite contrast (Deltat2/t1xDeltaULE/RLE) did not reveal any differences. We did not find changes of emotional or sensoric qualities during recall (ULE versus RLE) or of psychopathology measures over the 1-year period.

CONCLUSIONS

Although subjective and clinical data did not change within 1 year, we observed a substantial decrease of temporo-frontal activation during the recall of ULE from t1 to t2. If future research confirms these findings, the question arises whether the decrease of neural activation precedes clinical improvement in BPD.

Imaging stress effects on memory: a review of neuroimaging studies

OBJECTIVE

To review and give an overview of neuroimaging studies that look at the role of stress (hormones) on memory.

METHOD

An overview will be given of imaging studies that looked at the role of stress (hormones) on memory. Stress is here defined as the acute provocation of the sympathetic adrenal medullar system and the hypothalamic-pituitary-adrenal axis in experimental designs. Stress hormone levels can be raised endogenously in response to stimulus material (for example, pictures and films) or social evaluative threat situations (stress tasks). Other studies use the exogenous application of drugs to enhance or decrease stress hormone levels. Finally, we review studies on chronic stress and memory.

RESULTS

Stress or emotional arousal, leading to increased noradrenaline or cortisol levels, led to better memory performance when it is applied during perception or encoding. Brain regions involved in this process were medial temporal lobe regions such as amygdala and hippocampus, and several parts of the prefrontal cortex (PFC). High stress levels accompanied by high cortisol levels during retrieval led to impaired memory performance. Sex effects on memory as well as lateralization effects on brain activation were found.

CONCLUSION

High stress levels during encoding and consolidation of emotional material involve increased amygdala and hippocampus activation. The role of the anterior cingulate cortex and other parts of the PFC during perception and encoding of arousing material appears to be a modulating one. However, additional research is needed to shed more light on the nature of the brain changes during stress, especially during retrieval.

Dissociative responses to conscious and non-conscious fear impact underlying brain function in post-traumatic stress disorder

BACKGROUND

Dissociative reactions in post-traumatic stress disorder (PTSD) have been regarded as strategic responses that limit arousal. Neuroimaging studies suggest distinct prefrontal responses in individuals displaying dissociative and hyperarousal responses to threat in PTSD. Increased prefrontal activity may reflect enhanced regulation of limbic arousal networks in dissociation. If dissociation is a higher-order regulatory response to threat, there may be differential responses to conscious and automatic processing of threat stimuli. This study addresses this question by examining the impact of dissociation on fear processing at different levels of awareness.

METHOD

Functional magnetic resonance imaging (fMRI) with a 1.5-T scanner was used to examine activation to fearful (versus neutral) facial expressions during consciously attended and non-conscious (using backward masking) conditions in 23 individuals with PTSD. Activation in 11 individuals displaying non-dissociative reactions was compared to activation in 12 displaying dissociative reactions to consciously and non-consciously perceived fear stimuli.

RESULTS

Dissociative PTSD was associated with enhanced activation in the ventral prefrontal cortex for conscious fear, and in the bilateral amygdala, insula and left thalamus for non-conscious fear compared to non-dissociative PTSD. Comparatively reduced activation in the dissociative group was apparent in dorsomedial prefrontal regions for conscious fear faces.

CONCLUSIONS

These findings confirm our hypotheses of enhanced prefrontal activity to conscious fear and enhanced activity in limbic networks to non-conscious fear in dissociative PTSD. This supports the theory that dissociation is a regulatory strategy invoked to cope with extreme arousal in PTSD, but this strategy appears to function only during conscious processing of threat.

Cognitive control mechanisms, emotion and memory: a neural perspective with implications for psychopathology

In this paper we provide a focused review of the literature examining neural mechanisms involved in cognitive control over memory processes that can influence, and in turn are influenced by, emotional processes. The review is divided into two parts, the first focusing on working memory and the second on long-term memory. With regard to working memory, we discuss the neural bases of (1) control mechanisms that can select against distracting emotional information, (2) mechanisms that can regulate emotional reactions or responses, (3) how mood state influences cognitive control, and (4) individual differences in control mechanisms. For long-term memory, we briefly review (1) the neural substrates of emotional memory, (2) the cognitive and neural mechanisms that are involved in controlling emotional memories and (3) how these systems are altered in post-traumatic stress disorder. Finally, we consider tentative generalizations that can be drawn from this relatively unexplored conjunction of research endeavors.

Amygdala and hippocampal volumes and cognition in adult survivors of childhood abuse with dissociative disorders

OBJECTIVE

Trauma-exposed individuals with post-traumatic stress disorder (PTSD) display reduced amygdala and hippocampal size and impaired cognition. However, studies on trauma-exposed individuals with dissociative amnesia (DA) or dissociative identity disorder (DID) are lacking.

METHOD

Twenty-three young women who had experienced severe childhood sexual/physical abuse, diagnosed with DA/DID or PTSD, and 25 healthy control subjects were subjected to 3D structural magnetic resonance imaging of amygdala and hippocampus and a clinical and neuropsychological investigation.

RESULTS

Compared with controls, trauma-exposed subjects with PTSD (n = 10) displayed significantly reduced amygdala and hippocampal size and significantly impaired cognition. By contrast, trauma-exposed subjects with DA or DID (n = 13) displayed normal amygdala and hippocampal size and normal cognition.

CONCLUSION

We report for the first time volumetric results in subjects with DA/DID without PTSD as comorbid diagnosis. Our results indicate preserved amygdala and hippocampal size and preserved cognition in subjects with these disorders.

[Psychopathology of Ganser's syndrome. Literature review and case report]

The key feature of Ganser's syndrome includes approximate answers to simple questions. The cause of this rare syndrome remains uncertain. Current classification systems categorise it as a dissociative disorder, the symptoms of which are judged as psychogenic in origin. Our review of the literature (n=151) demonstrates however that Ganser's syndrome is frequently associated with brain injury, although detailed imaging, neuropsychological, and neurological data of this for the most part do not exist. We describe a right-handed patient with Ganser's syndrome after a large left-hemispheric middle cerebral artery infarction. Detailed neuropsychological examination showed atypical lateralisation of cognitive functions with so-called crossed nonaphasia and pronounced frontal-executive dysfunctions. Regarding both psychiatric and neuropsychological aspects, we discuss how the key feature of approximate answers may be associated with frontal-executive cerebral dysfunctions.

Making sense of neuroimaging in psychiatry

OBJECTIVE

Neuroimaging of psychiatric disorders has increased exponentially in the last decade; however, much of the uptake thus far has been in the realm of research. We anticipate that clinical use of neuroimaging modalities in psychiatry will increase dramatically in the near future and suggest that clinicians need to be aware of the potential applications.

METHOD

The authors conducted an extensive MEDLINE, EMBASE, PubMED and PsychInfo search of the published literature (1965-2007) using a variety of search terms to find relevant articles. Bibliographies of retrieved papers were further scrutinised for publications of interest, as were indices of books. Articles that reported clinically significant findings and research reports conducted using pertinent neuroimaging modalities were reviewed in detail.

RESULTS

The review suggests that exciting neuroimaging advances are being made that have relevance to psychiatry. Novel neuroimaging applications with potential clinical utility are rapidly emerging and the accessibility and use of these technologies will increase in coming years. Clinically meaningful findings have begun to emerge in mood disorders, post-traumatic stress disorder, schizophrenia and dementia. Coupling multimodal imaging with genetics and pharmacotherapeutic studies will further assist in understanding the pathophysiology of neuropsychiatric disorders.

CONCLUSION

It is important that clinicians understand the benefits and limitations of modern neuroimaging techniques and are also suitably equipped to appraise future developments. The use of neuroimaging in evaluating psychopathology is likely to impact upon the future nosology of psychiatric disorders, and assist in diagnosis and clinical management. The integrated use of neuroimaging in conjunction with clinical assessments promises to improve clinical care and markedly alter psychiatric practice.

Neural correlates of levels of emotional awareness during trauma script-imagery in posttraumatic stress disorder

OBJECTIVE

To examine individual differences in levels of emotional awareness as a predictor of the blood oxygenation level dependent (BOLD) response to trauma script-driven imagery in trauma-exposed individuals with (n = 25) and without (n = 16) posttraumatic stress disorder (PTSD).

METHODS

Participants completed the Levels of Emotional Awareness Scale (LEAS) and a functional magnetic resonance imaging trauma script-driven imagery paradigm.

RESULTS

Patients with PTSD exhibited lower LEAS scores in comparison with the control group. LEAS scores correlated positively with BOLD activity during trauma script-imagery in the ventral anterior cingulate cortex (vACC) in healthy controls, whereas LEAS scores correlated negatively with activation of vACC in individuals with PTSD.

CONCLUSION

Patients with PTSD exhibit lower than average levels of emotional awareness. Levels of emotional awareness are differentially associated with vACC response during trauma script-driven imagery in healthy controls versus individuals with PTSD.

Functional neuroimaging of anxiety: a meta-analysis of emotional processing in PTSD, social anxiety disorder, and specific phobia

OBJECTIVE

The study of human anxiety disorders has benefited greatly from functional neuroimaging approaches. Individual studies, however, vary greatly in their findings. The authors searched for common and disorder-specific functional neurobiological deficits in several anxiety disorders. The authors also compared these deficits to the neural systems engaged during anticipatory anxiety in healthy subjects.

METHOD

Functional magnetic resonance imaging and positron emission tomography studies of posttraumatic stress disorder (PTSD), social anxiety disorder, specific phobia, and fear conditioning in healthy individuals were compared by quantitative meta-analysis. Included studies compared negative emotional processing to baseline, neutral, or positive emotion conditions.

RESULTS

Patients with any of the three disorders consistently showed greater activity than matched comparison subjects in the amygdala and insula, structures linked to negative emotional responses. A similar pattern was observed during fear conditioning in healthy subjects. Hyperactivation in the amygdala and insula were, of interest, more frequently observed in social anxiety disorder and specific phobia than in PTSD. By contrast, only patients with PTSD showed hypoactivation in the dorsal and rostral anterior cingulate cortices and the ventromedial prefrontal cortex-structures linked to the experience and regulation of emotion.

CONCLUSIONS

This meta-analysis allowed us to synthesize often disparate findings from individual studies and thereby provide neuroimaging evidence for common brain mechanisms in anxiety disorders and normal fear. Effects unique to PTSD furthermore suggested a mechanism for the emotional dysregulation symptoms in PTSD that extend beyond an exaggerated fear response. Therefore, these findings help refine our understanding of anxiety disorders and their interrelationships.

Neurobiological alterations associated with traumatic stress

PURPOSE

The purpose of this article is to describe the effects of traumatic stress on brain structure and function, and the relationship of these neurobiological changes to symptoms experienced after trauma.

CONCLUSIONS

Exposure to traumatic stress is associated with changes in the limbic system, the hypothalamic-pituitary-adrenal axis, and key monoamine neurotransmitters. Different neurobiological alterations can be linked to specific symptoms of hyperarousal, dissociation/numbing, and reexperiencing of the trauma.

PRACTICE IMPLICATIONS

Understanding what is happening in the brain can inform more targeted treatment for various symptoms that the individual may be experiencing.

The neural basis of narrative imagery: emotion and action

It has been proposed that narrative emotional imagery activates an associative network of stimulus, semantic, and response (procedural) information. In previous research, predicted response components have been demonstrated through psychophysiological methods in peripheral nervous system. Here we investigate central nervous system concomitants of pleasant, neutral, and unpleasant narrative imagery with functional magnetic resonance imaging. Subjects were presented with brief narrative scripts over headphones, and then imagined themselves engaged in the described events. During script perception, auditory association cortex showed enhanced activation during affectively arousing (pleasant and unpleasant), relative to neutral imagery. Structures involved in language processing (left middle frontal gyrus) and spatial navigation (retrosplenium) were also active during script presentation. At the onset of narrative imagery, supplementary motor area, lateral cerebellum, and left inferior frontal gyrus were initiated, showing enhanced signal change during affectively arousing (pleasant and unpleasant), relative to neutral scripts. These data are consistent with a bioinformational model of emotion that considers response mobilization as the measurable output of narrative imagery.