Altered frontolimbic activity during virtual reality-based contextual fear learning in patients with posttraumatic stress disorder

BACKGROUND

Deficiency in contextual and enhanced responding in cued fear learning may contribute to the development of posttraumatic stress disorder (PTSD). We examined the responses to aversive Pavlovian conditioning with an unpredictable spatial context as conditioned stimulus compared to a predictable context. We hypothesized that the PTSD group would demonstrate less hippocampal and ventromedial prefrontal cortex (vmPFC) activation during acquisition and extinction of unpredictable contexts and an over-reactive amygdala response in the predictable contexts compared to controls.

METHODS

A novel combined differential cue-context conditioning paradigm was applied using virtual reality with spatial contexts that required configural and cue processing. We assessed 20 patients with PTSD, 21 healthy trauma-exposed (TC) and 22 non-trauma-exposed (HC) participants using functional magnetic resonance imaging, skin conductance responses, and self-report measures.

RESULTS

During fear acquisition, patients with PTSD compared to TC showed lower activity in the hippocampi in the unpredictable and higher activity in the amygdalae in the predictable context. During fear extinction, TC compared to patients and HC showed higher brain activity in the vmPFC in the predictable context. There were no significant differences in self-report or skin conductance responses.

CONCLUSIONS

Our results suggest that patients with PTSD differ in brain activation from controls in regions such as the hippocampus, the amygdala, and the vmPFC in the processing of unpredictable and predictable contexts. Deficient encoding of more complex configurations might lead to a preponderance of cue-based predictions in PTSD. Exposure-based treatments need to focus on improving predictability of contextual processing and reducing enhanced cue reactivity.

Structural white and gray matter differences in a large sample of patients with Posttraumatic Stress Disorder and a healthy and trauma-exposed control group: Diffusion tensor imaging and region-based morphometry

Differences in structural white and gray matter in survivors of traumatic experiences have been related to the development and maintenance of Posttraumatic Stress Disorder (PTSD). However, there are very few studies on diffusion tensor imaging and region based morphometry comparing patients with PTSD to two control groups, namely healthy individuals with or without trauma experience. It is also unknown if differences in white and gray matter are associated. In this cross-sectional study, we examined white- and gray matter differences between 44 patients with PTSD, 49 trauma control and 61 healthy control subjects. We compared the groups applying Tract-Based Spatial Statistics (TBSS) for a whole brain white matter analysis as well as region of interest analyses for white and gray matter. First, trauma control subjects in comparison to patients with PTSD and healthy control subjects showed significantly a) higher fractional anisotropy (FA) in the left corticospinal tract and inferior fronto-occipital fasciculus than patients with PTSD, b) higher FA in the left inferior fronto-occipital-, right inferior- and right superior longitudinal fasciculi, c) higher FA in the forceps minor and d) higher volume of the left and right anterior insulae. Second, we show significant correlations between the FA in the forceps minor and the gray matter volume in the left and right anterior insulae. Third, the mean FA value in the forceps minor correlated negatively with symptom severity of PTSD and depression as well as trait anxiety, whereas the gray matter volume in the left anterior insula correlated negatively with symptom severity in PTSD. Our findings underline the importance of brain structures critically involved in emotion regulation and salience mapping. While previous studies associated these processes primarily to functional and task-based differences in brain activity, we argue that morphometrical white and gray matter differences could serve as targets in neuroscientifically-informed prevention and treatment interventions for PTSD.

EMDR Therapy's Efficacy in the Treatment of Pain

Chronic pain is the most common global cause of functional and quality of life limitations. Although there are many effective therapies for the treatment of acute pain, chronic pain is often unsatisfactory. Against this background, there is currently an urgent need to develop innovative therapies that enable more efficient pain relief. Psychosocial factors play an important role in the development and persistence of chronic pain. Especially in patients with high levels of emotional stress, significant anxiety, or relevant psychological comorbidity, classical pain therapy approaches often fail. This is in line with the results of recent pain research, which has shown that dysfunctions in emotion processing have a significant influence on the persistence of pain symptoms. The recognition that pain can become chronic through maladaptive emotional processing forms the pathophysiological basis for the application of eye movement desensitization and reprocessing (EMDR) in the treatment of chronic pain. In this sense, EMDR can be used as an established method for desensitizing and processing of emotional distress from trauma therapy specifically for processing emotional stress in patients with chronic pain. Against this background, it is not surprising that the implementation of EMDR for patients with chronic pain is expanding. However, the increasing clinical use of EMDR in the treatment of chronic pain has also led to a reputation to test the efficacy of EMDR in pain management through randomized clinical trials. In addition to numerous case control studies, there are now also six randomized controlled clinical trials available that demonstrate the efficacy and safety of EMDR in the treatment of different pain conditions. However, in order to overcome several methodological limitations, large multicenter studies are needed to confirm the results.

[EMDR as a psychotherapeutic approach in the treatment of chronic pain : Is Eye Movement Desensitization and Reprocessing an effective therapy for patients with chronic pain who do not suffer from posttraumatic stress disorder?]

The efficacy of Eye Movement Desensitization and Reprocessing (EMDR) has been demonstrated for posttraumatic stress disorder. Despite promising research, it is still not clear if EMDR is a similarly effective treatment for chronic pain. Controlled trials are lacking and whether specific mechanisms underlie the effects remains unknown. The treatment of chronic pain aims at a reduction of subjective pain sensations. To achieve this goal without the usage of pain medications, i. e. through psychotherapy, is desirable for many reasons (e. g. reduction of treatment costs and side effects). Whether or not EMDR is an effective intervention for all chronic pain patients (or just a specific subgroup) constitutes an important question for psychological pain research.

Deficient fear extinction memory in posttraumatic stress disorder

BACKGROUND

Posttraumatic stress disorder (PTSD) might be maintained by deficient extinction memory. We used a cued fear conditioning design with extinction and a post-extinction phase to provoke the return of fear and examined the role of the interplay of amygdala, hippocampus and prefrontal regions.

METHODS

We compared 18 PTSD patients with two healthy control groups: 18 trauma-exposed subjects without PTSD (nonPTSD) and 18 healthy controls (HC) without trauma experience. They underwent a three-day ABC-conditioning procedure in a functional magnetic resonance imaging scanner. Two geometric shapes that served as conditioned stimuli (CS) were presented in the context of virtual reality scenes. Electric painful stimuli were delivered after one of the two shapes (CS+) during acquisition (in context A), while the other (CS-) was never paired with pain. Extinction was performed in context B and extinction memory was tested in a novel context C.

RESULTS

The PTSD patients showed significantly higher differential skin conductance responses than the non-PTSD and HC and higher differential amygdala and hippocampus activity than the HC in context C. In addition, elevated arousal to the CS+ during extinction and to the CS- throughout the experiment was present in the PTSD patients but self-reported differential valence or contingency were not different. During extinction recall, differential amygdala activity correlated positively with the intensity of numbing and ventromedial prefrontal cortex activity correlated positively with behavioral avoidance.

CONCLUSIONS

PTSD patients show heightened return of fear in neural and peripheral measures. In addition, self-reported arousal was high to both danger (CS+) and safety (CS-) cues. These results suggest that a deficient maintenance of extinction and a failure to identify safety signals might contribute to PTSD symptoms, whereas non-PTSD subjects seem to show normal responses.

Vascular Risk Factors and Diseases Modulate Deficits of Reward-Based Reversal Learning in Acute Basal Ganglia Stroke

BACKGROUND

Besides motor function, the basal ganglia have been implicated in feedback learning. In patients with chronic basal ganglia infarcts, deficits in reward-based reversal learning have previously been described.

METHODS

We re-examined the acquisition and reversal of stimulus-stimulus-reward associations and acquired equivalence in eleven patients with acute basal ganglia stroke (8 men, 3 women; 57.8±13.3 years), whose performance was compared eleven healthy subjects of comparable age, sex distribution and education, who were recruited outside the hospital. Eleven hospitalized patients with a similar vascular risk profile as the stroke patients but without stroke history served as clinical control group.

RESULTS

In a neuropsychological assessment 7±3 days post-stroke, verbal and spatial short-term and working memory and inhibition control did not differ between groups. Compared with healthy subjects, control patients with vascular risk factors exhibited significantly reduced performance in the reversal phase (F[2,30] = 3.47; p = 0.044; post-hoc comparison between risk factor controls and healthy controls: p = 0.030), but not the acquisition phase (F[2,30] = 1.01; p = 0.376) and the acquired equivalence (F[2,30] = 1.04; p = 0.367) tasks. In all tasks, the performance of vascular risk factor patients closely resembled that of basal ganglia stroke patients. Correlation studies revealed a significant association of the number of vascular risk factors with reversal learning (r = -0.33, p = 0.012), but not acquisition learning (r = -0.20, p = 0.121) or acquired equivalence (r = -0.22, p = 0.096).

CONCLUSIONS

The previously reported impairment of reward-based learning may be attributed to vascular risk factors and associated diseases, which are enriched in stroke patients. This study emphasizes the necessity of appropriate control subjects in cognition studies.

Neuropsychological measures of hippocampal function

The role of the medial temporal lobe, specifically the hippocampus, in learning and memory has been consistently demonstrated over the past years and has led to the identification of the hippocampus as a target imaging marker for several neurological and psychiatric disorders. Hippocampal dysfunctions and smaller hippocampal volumes have been reported as characteristic for these disorders, and hippocampal asymmetry has been shown to be associated with memory deficits in older adults. These findings underline the importance of screenings for memory functions using neuropsychological cognitive test batteries within the clinical context. To the best of our knowledge, there has been no comprehensive review that has presented neuropsychological tests related to the hippocampus in detail. However, we did not aim to provide a complete overview of neuropsychological tests related to hippocampal function, which would fail in the light of the widespread area. This chapter focuses on neuropsychological tests that assess cognitive functions that depend on the hippocampus in a state-of-the-art fashion and additionally provide the link to several disorders for which hippocampal abnormalities are a common characteristic.