Enhancing exposure-based therapy from a translational research perspective

Depressive and Anxious Symptoms, Experimentally Manipulated Acute Social-Evaluative Threat, and Cortisol Reactivity

OBJECTIVE

Exposure to social-evaluative threat (SET) can elicit greater physiological responses, including cortisol, compared to non-SET stressors. An individual's level of depressive and anxious symptoms predicts variability in cortisol responses to stressors, and other research suggests that these individual differences may predict vulnerability to social evaluation. The current study integrates both lines of research, testing if there are different relationships between depressive and/or anxious symptoms and cortisol reactivity in the presence or absence of SET.

METHODS

Healthy undergraduate students ( N = 158, 65% female) were randomly assigned to deliver a speech in the presence (SET) or absence (non-SET) of two evaluators. Salivary cortisol was collected throughout, and self-reported depressive and anxious symptoms were assessed. We hypothesized that in the SET condition, higher levels of depressive and/or anxious symptoms would predict dysregulated cortisol responses compared to lower levels of symptoms and/or assignment to the non-SET group.

RESULTS

In spite of inconclusive p values (which might be attributed to low statistical power), individuals with high depressive or high anxious symptoms appeared to have exaggerated cortisol responses in the SET condition, as indicated by more concave trajectories.

CONCLUSIONS

This study suggests that both depression and anxiety could be associated with increased cortisol reactivity to SET.

CO2 reactivity as a biomarker of exposure-based therapy non-response: study protocol

BACKGROUND

Exposure-based therapy is an effective first-line treatment for anxiety-, obsessive-compulsive, and trauma- and stressor-related disorders; however, many patients do not improve, resulting in prolonged suffering and poorly used resources. Basic research on fear extinction may inform the development of a biomarker for the selection of exposure-based therapy. Growing evidence links orexin system activity to deficits in fear extinction and we have demonstrated that reactivity to an inhaled carbon dioxide (CO₂) challenge-a safe, affordable, and easy-to-implement procedure-can serve as a proxy for orexin system activity and predicts fear extinction deficits in rodents. Building upon this basic research, the goal for the proposed study is to validate CO₂ reactivity as a biomarker of exposure-based therapy non-response.

METHODS

We will assess CO₂ reactivity in 600 adults meeting criteria for one or more fear- or anxiety-related disorders prior to providing open exposure-based therapy. By incorporating CO₂ reactivity into a multivariate model predicting treatment non-response that also includes reactivity to hyperventilation as well as a number of related predictor variables, we will establish the mechanistic specificity and the additive predictive utility of the potential CO₂ reactivity biomarker. By developing models independently within two study sites (University of Texas at Austin and Boston University) and predicting the other site's data, we will validate that the results are likely to generalize to future clinical samples.

DISCUSSION

Representing a necessary stage in translating basic research, this investigation addresses an important public health issue by testing an accessible clinical assessment strategy that may lead to a more effective treatment selection (personalized medicine) for patients with anxiety- and fear-related disorders, and enhanced understanding of the mechanisms governing exposure-based therapy.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT05467683 (20/07/2022).

Timing of vagus nerve stimulation during fear extinction determines efficacy in a rat model of PTSD

Studies have indicated that vagus nerve stimulation (VNS) enhances extinction learning in rodent models. Here, we investigated if pairing VNS with the conditioned stimulus is required for the enhancing effects of VNS. Adult Sprague-Dawley rats were exposed to intense stress followed by fear conditioning training to produce resistant fear. Rats were then implanted with a cuff electrode around the left vagus. After recovery, rats underwent extinction training paired with VNS (0.5 s, 0.8 mA, 100 µs, and 30 Hz) or with Sham VNS (0 mA). VNS rats were randomized into the following subgroups: During VNS (delivered during presentations of the conditioned stimulus, CS), Between VNS (delivered between CS presentations), Continuous VNS (delivered during the entire extinction session), and Dispersed VNS (delivered at longer inter-stimulation intervals across the extinction session). Sham VNS rats failed to extinguish the conditioned fear response over 5 days of repeated exposure to the CS. Rats that received Between or Dispersed VNS showed modest improvement in conditioned fear at the retention test. During and Continuous VNS groups displayed the greatest reduction in conditioned fear. These findings indicate that delivering VNS paired precisely with CS presentations or continuously throughout extinction promotes the maximum enhancement in extinction learning.

Intra-mPFC injection of sodium butyrate promotes BDNF expression and ameliorates extinction recall impairment in an experimental paradigm of post-traumatic stress disorder

Objectives

Therapeutic strategies that facilitate extinction are promising in the treatment of post-traumatic stress disorder (PTSD). Brain-derived neurotrophic factor (BDNF) has a crucial role in neural plasticity, a process needed for the retention of fear extinction. In this study, we investigated the effects of local administration of a histone deacetylase (HDAC) inhibitor, sodium butyrate (NaBu), on BDNF transcription and behavioral markers of extinction in the single prolonged stress (SPS) model of PTSD.

Materials and Methods

NaBu was infused into the infralimbic (IL) subregion of the medial prefrontal cortex (mPFC) of male rats. The freezing response was recorded as the criterion to assess fear strength on the day of extinction as well as 24 hr later in the retention test. Other behavioral tests were also measured to evaluate the anxiety level, locomotor activity, and working memory on the retention day. HDAC activity and BDNF mRNA expression were evaluated after the behavioral experiments.

Results

NaBu facilitated the recall of fear extinction in SPS rats (P<0.0001). SPS rats had higher HDAC activity (P<0.0001) and lower BDNF expression (P<0.05) than non-SPS animals. Also, anxiety was higher in the SPS group (P<0.0001), but locomotor activity (P=0.61) and working memory (P=0.36) were not different between SPS and Non-SPS groups.

Conclusion

Our findings provide evidence that the mechanism of action of NaBu in the improvement of extinction recall is mediated, in part, by enhancing histone acetylation and reviving BDNF expression in IL.

A Case for Translation From the Clinic to the Laboratory

Laboratory procedures have been used for decades as analogues for clinical processes with the goal of improving our understanding of psychological treatments for emotional disorders and identifying strategies to make treatments more effective. This research has often focused on translation from the laboratory to the clinic. Although this approach has notable successes, it has not been seamless. There are many examples of strategies that work in the laboratory that fail to lead to improved outcomes when applied clinically. One possible reason for this gap between experimental and clinical research is a failure to focus on translation from the clinic to the laboratory. Here, we discuss potential benefits of translation from the clinic to the laboratory and provide examples of how this might be implemented. We first consider two well-established laboratory analogues (extinction and cognitive reappraisal), identify critical aspects of the related clinical procedures (exposure and cognitive restructuring) that are missing from these analogues, and propose variations to better capture the clinical process. Second, we discuss two clinical procedures that have more recently been brought into the laboratory (eye-movement desensitization and reprocessing and imagery rescripting). We conclude by highlighting potential implications of this proposed shift in focus for translational research.

Tablet therapy as an assistive technology-based treatment for anxiety in pediatric oncology

The painful interventions and invasive procedures associated with pediatric cancer treatment can result in anxiety. Anxiety can be reduced or better controlled through distraction and thought retraining. Although art therapy, non-electronic play therapy, music therapy, and traditional counseling are often used to alleviate stress and anxiety, new technology innovations are proving to be additional options to decrease stress and anxiety through distraction and attention shifting. Tablet-based interventions are emerging as an easily available and effective means of reducing stress and fear prior to operations, and have potential applications to reduce anxiety for patients before receiving chemotherapy, during time spent in hospital rooms, and while experiencing distressing physiological symptoms. This paper reviews the research on tablet therapy and discusses the application of assistive technologies in clinical oncology settings to reduce pediatric anxiety throughout the treatment process.

The Fears of Evaluation About Performance (FEAP) Task: Inducing Anxiety-Related Responses to Direct Exposure to Negative and Positive Evaluations

Fears of negative and positive evaluation (i.e., evaluative fears) manifest within performance-based situations (e.g., public speaking, group presentations), particularly among those experiencing social anxiety. Within these performance-based situations, individuals experiencing such evaluative fears frequently display a variety of impairments (e.g., avoidance, nervousness) that might manifest within and across various settings (e.g., employment, school). How do those who experience these fears react to in-the-moment feedback about their performance? We constructed the Fear of Evaluation About Performance (FEAP) task to examine ecologically valid experiences with anxiety when reacting to positive and negative feedback. During the task, participants gave a speech, and subsequent to this and in counterbalanced order, received positive and negative feedback about their speech, with continued assessment of anxiety-related arousal throughout the task. We tested the FEAP task among 127 adults, who provided self-reports of fears of positive and negative evaluation before completing the task. Fears of positive evaluation uniquely predicted arousal following receipt of positive feedback, whereas fears of negative evaluation uniquely predicted arousal following receipt of negative feedback. Relative to participants receiving positive feedback first, those receiving negative feedback first experienced elevated post-feedback arousal, followed by a steep decline in arousal post-positive feedback. Conversely, participants receiving positive feedback first experienced a buffer effect whereby arousal post-negative feedback remained low, relative to the arousal experienced post-negative feedback among those who received negative feedback first. We expect the FEAP task to inform basic science on fears of negative and positive evaluation, as well as treatment planning in applied clinical settings.

Effects of ∆9-tetrahydrocannabinol on aversive memories and anxiety: a review from human studies

BACKGROUND

Posttraumatic stress disorder (PTSD) may stem from the formation of aberrant and enduring aversive memories. Some PTSD patients have recreationally used Cannabis, probably aiming at relieving their symptomatology. However, it is still largely unknown whether and how Cannabis or its psychotomimetic compound Δ⁹-tetrahydrocannabinol (THC) attenuates the aversive/traumatic memory outcomes. Here, we seek to review and discuss the effects of THC on aversive memory extinction and anxiety in healthy humans and PTSD patients.

METHODS

Medline, PubMed, Cochrane Library, and Central Register for Controlled Trials databases were searched to identify peer-reviewed published studies and randomized controlled trials in humans published in English between 1974 and July 2020, including those using only THC and THC combined with cannabidiol (CBD). The effect size of the experimental intervention under investigation was calculated.

RESULTS

At low doses, THC can enhance the extinction rate and reduce anxiety responses. Both effects involve the activation of cannabinoid type-1 receptors in discrete components of the corticolimbic circuitry, which could couterbalance the low "endocannabinoid tonus" reported in PTSD patients. The advantage of associating CBD with THC to attenuate anxiety while minimizing the potential psychotic or anxiogenic effect produced by high doses of THC has been reported. The effects of THC either alone or combined with CBD on aversive memory reconsolidation, however, are still unknown.

CONCLUSIONS

Current evidence from healthy humans and PTSD patients supports the THC value to suppress anxiety and aversive memory expression without producing significant adverse effects if used in low doses or when associated with CBD. Future studies are guaranteed to address open questions related to their dose ratios, administration routes, pharmacokinetic interactions, sex-dependent differences, and prolonged efficacy.

Maladaptive avoidance patterns in Parkinson's disease are exacerbated by symptoms of depression

Parkinson's disease (PD) is a chronic, progressive neurodegenerative disorder, characterized by a loss of dopaminergic neurons in the substantia nigra pars compacta. Given that dopamine is critically involved in learning and other cognitive processes, such as working memory, dopamine loss in PD has been linked both to learning abnormalities and to cognitive dysfunction more generally in the disease. It is unclear, however, whether avoidance behavior is impacted in PD. This is significant, as this type of instrumental behavior plays an important role in both decision-making and emotional (dys) function. Consequently, the aim of the present study was to examine avoidance learning and operant extinction in PD using a computer-based task. On this task, participants control a spaceship and attempt to shoot an enemy spaceship to gain points. They also learn to hide in safe areas to protect from (i.e., avoid) aversive events (on-screen explosions and point loss). The results showed that patients with PD (N = 25) acquired an avoidance response during aversive periods to the same extent as healthy age-matched controls (N = 19); however, patients demonstrated greater hiding during safe periods not associated with aversive events, which could represent maladaptive generalization of the avoidance response. Furthermore, this impairment was more pronounced during the extinction phase, and in patients who reported higher levels of depression. These results demonstrate for the first time that PD is associated with maladaptive avoidance patterns, which could possibly contribute to the emergence of depression in the disease.

Facilitative effects of environmental enrichment for cocaine relapse prevention are dependent on extinction training context and involve increased TrkB signaling in dorsal hippocampus and ventromedial prefrontal cortex

Cocaine-cue extinction training combined with brief interventions of environmental enrichment (EE) was shown previously to facilitate extinction and attenuate reacquisition of cocaine self-administration in rats. It is unknown whether or not the usefulness of this approach would be undermined if extinction training took place in a novel rather than familiar context. Drawing on previous studies involving pharmacological interventions, we hypothesized that the facilitative effects of EE for cocaine relapse prevention would be independent of the context used for extinction training. Rats trained to self-administer cocaine underwent cocaine-cue extinction training in either the familiar self-administration context or a novel context, with or without EE. Rats then were tested for reacquisition of cocaine self-administration in the familiar context. Target brain regions were lysed and probed for memory-related changes in receptors for glutamate and BDNF by western blotting. Contrary to our hypothesis, the facilitative effects of EE for cocaine relapse prevention were dependent on the context used for extinction training. While EE facilitated extinction regardless of context used, it inhibited cocaine relapse only after extinction training in the familiar context. EE was associated with increased GluA2 in nucleus accumbens, TrkB in dorsal hippocampus and activated TrkB in ventromedial prefrontal cortex. Of these, the changes in dorsal hippocampus and ventromedial prefrontal cortex mirrored outcomes of the cocaine relapse tests in that these changes were specific to rats receiving EE plus extinction training in the familiar context. These findings support a role for hippocampal-prefrontal BDNF-TrkB signaling in extinction-based relapse prevention strategies involving EE.

Evidenced-Based Treatment of Posttraumatic Stress Disorder: An Updated Review of Validated Psychotherapeutic and Pharmacological Approaches

LEARNING OBJECTIVES

After participating in this activity, learners should be better able to:• Evaluate psychotherapeutic and pharmacologic approaches to treating patients with posttraumatic stress disorder.

ABSTRACT

A strong evidence base exists for psychological and pharmacological interventions for the treatment of posttraumatic stress disorder (PTSD). The published literature investigating the effectiveness of these treatments in reducing the symptoms and impairments associated with PTSD has expanded substantially in recent years. This review provides a concise overview of the empirical literature examining these treatment approaches. Evidence-based, trauma-focused therapies are recommended as first-line interventions, with the most support for cognitive- and exposure-based approaches. Prolonged exposure and cognitive processing therapy are the two most cited and rigorously investigated. Various other evidence-supported protocols are discussed. Pharmacotherapies can be used when evidence-based psychotherapies are not available or are ineffective, or on the basis of patient preference. Pharmacotherapy with the most support for PTSD includes selective serotonin reuptake inhibitors and serotonin-norepinephrine reuptake inhibitors. Evidence supports the implementation of these interventions across genders, populations, and settings. Given that little research directly compares the effectiveness of different PTSD interventions and their mechanisms of action, it remains uncertain how to best select and tailor treatments to optimize individual outcomes. Future directions and novel, ongoing research are discussed.

Cannabidiol enhancement of exposure therapy in treatment refractory patients with phobias: study protocol of a randomized controlled trial

BACKGROUND

Phobic anxiety disorders are among the most prevalent psychiatric disorders and are burdensome in terms of loss of quality of life and work productivity. Evidence-based treatments are relatively successful in the majority of patients, especially exposure therapy. However, a substantial subset of patients fails to achieve or stay in remission. Preclinical and genetic research have yielded evidence that the cannabinoid system is involved in the extinction of fear, presumed to underlie the beneficial effects of exposure therapy in phobic disorders. A cannabinoid constituent that may enhance endocannabinoid signaling is cannabidiol (CBD), a non-psychoactive component of cannabis. Hence, the addition of CBD to exposure therapy is expected to strengthen effects of treatment. To determine the added benefit of CBD on exposure therapy, we conduct a randomized controlled trial, in which patients in whom previous treatment as usual has not yielded sufficient response receive either CBD or placebo preceding 8 exposure sessions in a double-blind fashion. A subsidiary aim is to explore which (combination of) clinical, behavioral and genetic profiles of patients are related to treatment response.

METHODS/DESIGN

This is an 8-week multicenter, randomized, double-blind, placebo-controlled trial. Seventy-two patients with social phobia or panic disorder with agoraphobia with incomplete response to earlier treatment will be included from outpatient clinics in the Netherlands. Patients are randomized to augmentation of exposure therapy with 300 mg CBD or placebo. The study medication is administered orally, 2 h preceding each of the eight 90 min exposure sessions. Measurements will take place at baseline, first administration of medication, every session, mid-treatment, last administration of medication, post-treatment and at 3 and 6 months' follow-up. The primary outcome measure is the score on the Fear Questionnaire (FQ). In addition, determinants of the expected treatment enhancing effect of CBD will be explored.

DISCUSSION

This is the first trial to investigate whether the addition of CBD to exposure therapy is effective in reducing phobic symptoms in treatment refractory patients with social phobia or panic disorder with agoraphobia.

TRIAL REGISTRATION

Netherlands Trial Register NTR5100 . Registered 13 March 2015. Protocol version: issue date 17 Jan 2018, protocol amendment number 7.

Discarding personal possessions increases psychophysiological activation in patients with hoarding disorder

Difficulty discarding is the core behavioral symptom of hoarding disorder (HD). Patients with HD report greater subjective distress when discarding their own possessions as compared to others' possessions. To date, no prior studies have examined psychophysiological activation, an objective measure of anxious arousal, during discarding among individuals with HD. The current study assessed psychophysiological responses during a baseline resting period and two discarding tasks, one involving personal possessions and the other involving matched control ("experimenter-owned") items in 52 patients with a primary diagnosis of HD. Results showed that, compared to discarding control items, discarding personal possessions increased skin conductance and heart rate and decreased end tidal carbon dioxide. There were no differences in heart rate variability, respiratory sinus arrhythmia, and respiration rate between the two discarding tasks. Despite the fact that discarding increased psychophysiological arousal, self-reported HD symptoms (including difficulty discarding) failed to predict psychophysiological responses during the discarding tasks. The findings suggest that there may be discordance between objective and subjective measures of hoarding-related distress, and are discussed in terms of incorporating psychophysiological measures into the assessment and treatment of HD.

Voluntary exercise or systemic propranolol ameliorates stress-related maladaptive behaviors in female rats

Many people will experience at least one traumatic event in their lifetime, with up to 20% developing Post-Traumatic Stress Disorder (PTSD) or PTSD-like symptoms. In addition, the likelihood that females will develop PTSD after trauma is more than twice that of males. Despite its prevalence, current treatment strategies for trauma victims are limited and substantial portions of affected individuals remain resistant to treatment, suggesting that additional interventions are necessary. Using an animal model of traumatic stress, the present studies tested the hypothesis that either voluntary exercise and/or administration of the adrenergic beta-receptor antagonist propranolol, would ameliorate stress-related maladaptive behaviors. In Study 1 four groups of female rats were exposed to a sequence of stressors that included anesthesia, restraint, forced swim, exposure to predator scent and fear conditioning. Rats then underwent re-exposure sessions in which stress-related conditioned stimuli were presented. In addition to re-exposure, stressed rats were treated with propranolol (10 mg/kg) and/or given the opportunity to engage in voluntary wheel running intermittently for 4 weeks. Stress-associated maladaptive behavior was assessed using the elevated plus and open field mazes and fear memory tests. Cognitive ability was assessed using a novel odor recognition task. A main effect of exercise on behaviors related to anxiety and resilience was observed, but neither a main effect of propranolol nor a synergistic effect of propranolol and exercise were observed. Neither stress induction nor treatment influenced recognition memory. In contrast, in Study 2 in which the timing and dosage of propranolol (0.25-2.0 mg/kg), and the number and timing of re-exposure sessions were adjusted, propranolol produced both a reduction in anxiety-like behaviors as well as resilience to a subsequent stressor. These results are consistent with the notion that combining re-exposure therapy with additional interventions is beneficial for female trauma victims. Furthermore, the findings support the view that in pre-clinical models, voluntary exercise, which bolsters hippocampal function and propranolol, which affects amygdala-dependent memory reconsolidation and peripheral noradrenergic signaling, can ameliorate stress-related symptoms.

Enhancing Endocannabinoid Neurotransmission Augments The Efficacy of Extinction Training and Ameliorates Traumatic Stress-Induced Behavioral Alterations in Rats

Exposure to a traumatic event may result in the development of post-traumatic stress disorder (PTSD). Endocannabinoids are crucial modulators of the stress response, interfere with excessive retrieval and facilitate the extinction of traumatic memories. Exposure therapy, combined with pharmacotherapy, represents a promising tool for PTSD treatment. We investigated whether pharmacological manipulations of the endocannabinoid system during extinction learning ameliorates the behavioral changes induced by trauma exposure. Rats were exposed to inescapable footshocks paired with social isolation, a risk factor for PTSD. One week after trauma, rats were subjected to three spaced extinction sessions, mimicking human exposure therapy. The anandamide hydrolysis inhibitor URB597, the 2-arachidonoylglycerol hydrolysis inhibitor JZL184 or the cannabinoid agonist WIN55,212-2 were administered before or after the extinction sessions. Rats were tested for extinction retention 16 or 36 days after trauma and 24-h later for social interaction. Extinction training alone reduced fear of the trauma-associated context but did not restore normal social interaction. Traumatized animals not exposed to extinction sessions exhibited reductions in hippocampal anandamide content with respect to home-cage controls. Noteworthy, all drugs exerted beneficial effects, but URB597 (0.1 mg/kg) induced the best improvements by enhancing extinction consolidation and restoring normal social behavior in traumatized rats through indirect activation of CB1 receptors. The ameliorating effects remained stable long after treatment and trauma exposure. Our findings suggest that drugs potentiating endocannabinoid neurotransmission may represent promising tools when combined to exposure-based psychotherapies in the treatment of PTSD.

Bridging the Gaps Between Basic Science and Cognitive-Behavioral Treatments for Anxiety Disorders in Routine Care

Abstract. As a core component of cognitive-behavioral therapies (CBT), behavioral exposure is an effective treatment for anxiety disorders. Still, recent treatment studies demonstrate relatively high rates of treatment dropout, nonresponse, and relapse, indicating a substantial need for optimizing and personalizing existing treatment procedures. In the present article, we aim to address current challenges and future demands for translational research in CBT for the anxiety disorders, including (a) a better understanding of those mechanisms conferring behavioral change, (b) identifying important sources of individual variation that may act as moderators of treatment response, and (c) targeting practical barriers for dissemination of exposure therapy to routine care. Based on a recursive process model of psychotherapy research we will describe distinct steps to systematically translate basic and clinical research “from bench to bedside” to routine care, but also vice versa. Some of these aspects may stimulate the future roadmap for evidence-based psychotherapy research in order to better target the treatment of anxiety disorders as one core health challenge of our time.

Animal to human translational paradigms relevant for approach avoidance conflict decision making

Avoidance behavior in clinical anxiety disorders is often a decision made in response to approach-avoidance conflict, resulting in a sacrifice of potential rewards to avoid potential negative affective consequences. Animal research has a long history of relying on paradigms related to approach-avoidance conflict to model anxiety-relevant behavior. This approach includes punishment-based conflict, exploratory, and social interaction tasks. There has been a recent surge of interest in the translation of paradigms from animal to human, in efforts to increase generalization of findings and support the development of more effective mental health treatments. This article briefly reviews animal tests related to approach-avoidance conflict and results from lesion and pharmacologic studies utilizing these tests. We then provide a description of translational human paradigms that have been developed to tap into related constructs, summarizing behavioral and neuroimaging findings. Similarities and differences in findings from analogous animal and human paradigms are discussed. Lastly, we highlight opportunities for future research and paradigm development that will support the clinical utility of this translational work.

Role of the dorsal anterior cingulate cortex in obsessive-compulsive disorder: converging evidence from cognitive neuroscience and psychiatric neurosurgery

OBJECTIVE Advances in understanding the neurobiological basis of psychiatric disorders will improve the ability to refine neuromodulatory procedures for treatment-refractory patients. One of the core dysfunctions in obsessive-compulsive disorder (OCD) is a deficit in cognitive control, especially involving the dorsal anterior cingulate cortex (dACC). The authors' aim was to derive a neurobiological understanding of the successful treatment of refractory OCD with psychiatric neurosurgical procedures targeting the dACC. METHODS First, the authors systematically conducted a review of the literature on the role of the dACC in OCD by using the search terms "obsessive compulsive disorder" and "anterior cingulate." The neuroscience literature on cognitive control mechanisms in the dACC was then combined with the literature on psychiatric neurosurgical procedures targeting the dACC for the treatment of refractory OCD. RESULTS The authors reviewed 89 studies covering topics that included structural and functional neuroimaging and electrophysiology. The majority of resting-state functional neuroimaging studies demonstrated dACC hyperactivity in patients with OCD relative to that in controls, while task-based studies were more variable. Electrophysiological studies showed altered dACC-related biomarkers of cognitive control, such as error-related negativity in OCD patients. These studies were combined with the cognitive control neurophysiology literature, including the recently elaborated expected value of control theory of dACC function. The authors suggest that a central feature of OCD pathophysiology involves the generation of mis-specified cognitive control signals by the dACC, and they elaborate on this theory and provide suggestions for further study. CONCLUSIONS Although abnormalities in brain structure and function in OCD are distributed across a wide network, the dACC plays a central role. The authors propose a theory of cognitive control dysfunction in OCD that attempts to explain the therapeutic efficacy of dACC neuromodulation. This theoretical framework should help to guide further research into targeted treatments of OCD and other disorders of cognitive control.

Effects of post-extinction l-DOPA administration on the spontaneous recovery and reinstatement of fear in a human fMRI study

Relapse is a pertinent problem in the treatment of anxiety disorders. In the laboratory, relapse is modeled as return of conditioned fear responses after successful fear extinction and is explained by insufficient retrieval and/or expression of the fear-inhibitory extinction memory that is generated during extinction learning. We have shown in mice and humans that return of fear can be prevented by administration of a single dose of the dopamine precursor l-3,4-dihydroxyphenylalanine (l-DOPA) immediately after extinction. In mice, this effect could be attributed to an enhancement of extinction memory consolidation. In our human study, we could not exclude that l-DOPA might have acted by interfering with the consolidation of the original fear memory. In the present study, we therefore used a combined differential cue and context conditioning paradigm where initial fear conditioning and extinction were conducted one day apart, in analogy to previous mouse studies. l-DOPA (N=21) or placebo (N=19) were administered after extinction, precluding any action on fear memory consolidation. In the return-of-fear test conducted one week later, drug effects on conditioned skin conductance responses were absent. However, we found evidence indicative of reduced neural activity, measured with functional magnetic resonance imaging (fMRI), in the l-DOPA group in areas related to conditioned fear and return of fear (amygdala, posterior hippocampus) and enhanced activity in a key area of extinction retrieval/expression (ventromedial prefrontal cortex), relative to placebo controls. These findings require further corroboration in additional experiments. Implications for further investigations on the role of the dopamine system in extinction and on the neuropharmacological augmentation of extinction-based therapies are discussed.

Resting-state connectivity of the amygdala predicts response to cognitive behavioral therapy in obsessive compulsive disorder

BACKGROUND

Obsessive-compulsive disorder (OCD) is a psychiatric disorder which is characterized by recurrent intrusive thoughts (obsessions) and ritualized, repetitive behaviors or mental acts (compulsions). The gold standard for the treatment of OCD is cognitive behavioral therapy (CBT) with exposure and response prevention. This is the first study exploring the predictive value of resting-state functional connectivity for the outcome of CBT.

METHODS

We assessed whole-brain resting-state functional connectivity in a group of 17 un-medicated OCD inpatients prior to CBT compared to 19 healthy controls using functional magnetic resonance imaging. The graph theoretical metric degree centrality served as indicator for altered voxel-wise whole-brain functional connectivity. The relative change in the Yale-Brown Obsessive Compulsive Scale (YBOCS) score was used to evaluate treatment outcome.

RESULTS

The degree centrality of the right basolateral nuclei group of the amygdala was positively correlated with the response to subsequent CBT. OCD patients showed a lower degree centrality of the superficial amygdala (bilateral).

CONCLUSIONS

Our results suggest that two different sub-regions of the amygdala and their respective neural networks are affected in OCD: the superficial amygdala and networks related to evaluation of reinforcers and risk anticipation and the basolateral amygdala which is implicated in fear processing. The diminished CBT response in patients showing a lower degree centrality of the basolateral amygdala reflects a deficient fear circuit in these patients which may impact fear extinction as a core mechanism of exposure-based CBT.

Oxytocin facilitates the extinction of conditioned fear in humans

BACKGROUND

Current neurocircuitry models of anxiety disorders posit a lack of inhibitory tone in the amygdala during acquisition of Pavlovian fear responses and deficient encoding of extinction responses in amygdala-medial prefrontal cortex circuits. Competition between these two responses often results in a return of fear, limiting control over anxiety. However, one hypothesis holds that a pharmacologic strategy aimed at reducing amygdala activity while simultaneously augmenting medial prefrontal cortex function could facilitate the extinction of conditioned fear.

METHODS

Key among the endogenous inhibitors of amygdala activity in response to social fear signals is the hypothalamic peptide oxytocin. To address the question whether oxytocin can strengthen Pavlovian extinction beyond its role in controlling social fear, we conducted a functional magnetic resonance imaging experiment with 62 healthy male participants in a randomized, double-blind, parallel-group, placebo-controlled design. Specifically, subjects were exposed to a Pavlovian fear conditioning paradigm before receiving an intranasal dose (24 IU) of synthetic oxytocin or placebo.

RESULTS

Oxytocin, when administered intranasally after Pavlovian fear conditioning, was found to increase electrodermal responses and prefrontal cortex signals to conditioned fear in the early phase of extinction and to enhance the decline of skin conductance responses in the late phase of extinction. Oxytocin also evoked an unspecific inhibition of amygdalar responses in both phases.

CONCLUSIONS

Collectively, our findings identify oxytocin as a differentially acting modulator of neural hubs involved in Pavlovian extinction. This specific profile of oxytocin action may open up new avenues for enhancing extinction-based therapies for anxiety disorders.

HDAC inhibitors as cognitive enhancers in fear, anxiety and trauma therapy: where do we stand?

A novel strategy to treat anxiety and fear-related disorders such as phobias, panic and PTSD (post-traumatic stress disorder) is combining CBT (cognitive behavioural therapy), including extinction-based exposure therapy, with cognitive enhancers. By targeting and boosting mechanisms underlying learning, drug development in this field aims at designing CBT-augmenting compounds that help to overcome extinction learning deficits, promote long-term fear inhibition and thus support relapse prevention. Progress in revealing the role of epigenetic regulation of specific genes associated with extinction memory generation has opened new avenues in this direction. The present review examines recent evidence from pre-clinical studies showing that increasing histone acetylation, either via genetic or pharmacological inhibition of HDACs (histone deacetylases) by e.g. vorinostat/SAHA (suberoylanilide hydroxamic acid), entinostat/MS-275, sodium butyrate, TSA (trichostatin A) or VPA (valproic acid), or by targeting HATs (histone acetyltransferases), augments fear extinction and, importantly, generates a long-term extinction memory that can protect from return of fear phenomena. The molecular mechanisms and pathways involved including BDNF (brain-derived neurotrophic factor) and NMDA (N-methyl-D-aspartate) receptor signalling are just beginning to be revealed. First studies in healthy humans are in support of extinction-facilitating effects of HDAC inhibitors. Very recent evidence that HDAC inhibitors can rescue deficits in extinction-memory-impaired rodents indicates a potential clinical utility of this approach also for exposure therapy-resistant patients. Important future work includes investigation of the long-term safety aspects of HDAC inhibitor treatment, as well as design of isotype(s)-specific inhibitors. Taken together, HDAC inhibitors display promising potential as pharmacological adjuncts to augment the efficacy of exposure-based approaches in anxiety and trauma therapy.

Sleep and REM sleep disturbance in the pathophysiology of PTSD: the role of extinction memory

Post-traumatic stress disorder (PTSD) is accompanied by disturbed sleep and an impaired ability to learn and remember extinction of conditioned fear. Following a traumatic event, the full spectrum of PTSD symptoms typically requires several months to develop. During this time, sleep disturbances such as insomnia, nightmares, and fragmented rapid eye movement sleep predict later development of PTSD symptoms. Only a minority of individuals exposed to trauma go on to develop PTSD. We hypothesize that sleep disturbance resulting from an acute trauma, or predating the traumatic experience, may contribute to the etiology of PTSD. Because symptoms can worsen over time, we suggest that continued sleep disturbances can also maintain and exacerbate PTSD. Sleep disturbance may result in failure of extinction memory to persist and generalize, and we suggest that this constitutes one, non-exclusive mechanism by which poor sleep contributes to the development and perpetuation of PTSD. Also reviewed are neuroendocrine systems that show abnormalities in PTSD, and in which stress responses and sleep disturbance potentially produce synergistic effects that interfere with extinction learning and memory. Preliminary evidence that insomnia alone can disrupt sleep-dependent emotional processes including consolidation of extinction memory is also discussed. We suggest that optimizing sleep quality following trauma, and even strategically timing sleep to strengthen extinction memories therapeutically instantiated during exposure therapy, may allow sleep itself to be recruited in the treatment of PTSD and other trauma and stress-related disorders.

D-cycloserine augmentation in behavioral therapy for obsessive-compulsive disorder: a meta-analysis

OBJECTIVE

To evaluate the overall effect of D-cycloserine (DCS) augmentation on exposure and response prevention (ERP) therapy for obsessive-compulsive disorder (OCD).

METHODS

Clinical studies on the effect of DCS augmentation on ERP therapy for OCD compared to placebo were included for meta analysis. The primary outcome was the Yale-Brown Obsessive-Compulsive Scale (Y-BOCS). Meta-analyses were performed with a random-effect model or a fixed-effect model using the Cochrane Review Manager (RevMan, version 5.2) to calculate the odds ratio and the mean difference, with their corresponding 95% confidence intervals.

RESULTS

A total of six studies was included in the current meta-analyses, and their data were extracted. Among them, four were for analyses of DCS and Y-BOCS at midtreatment, six for analysis at posttreatment, and four at 3-month follow-up. Besides, three of the six eligible studies were included in the meta-analysis of the DCS and Clinical Global Impression-Severity Scale at posttreatment, and three in the meta-analysis of DCS and proportions of treatment responders and of subjects attaining clinical remission status criteria at posttreatment. Our meta-analyses do not reveal a significant effect of DCS augmentation in ERP therapy for OCD patients, except when measured at midtreatment. Compared to the placebo group, DCS augmentation did show a trend toward significantly lower/decreased Y-BOCS; when measured at posttreatment and in the subpopulation of DCS taken before some of the ERP sessions, DCS augmentation showed a trend toward significantly lower/decreased Y-BOCS.

CONCLUSION

Our result suggested that with the careful optimization of DCS-augmented ERP therapy by fine-tuning timing and dosing of DCS administration and number and frequency of ERP sessions, DCS may enhance the efficacy of ERP therapy in reducing the symptomatic severity of OCD patients, especially at early stage of the treatment; therefore, DCS augmentation could possibly reduce treatment cost, reduce treatment drop and refusal rate, and help to improve access to the limited number of experienced therapists.

D-cycloserine to enhance extinction of cue-elicited craving for alcohol: a translational approach

Cue-elicited craving for alcohol is well established but extinction-based treatment to extinguish this response has generated only modest positive outcomes in clinical trials. Basic and clinical research suggests that D-cycloserine (DCS) enhances extinction to fear cues under certain conditions. However, it remains unclear whether DCS would also accelerate extinction of cue-elicited craving for alcohol. The goal of the current study was to examine whether, compared with placebo (PBO), DCS enhanced extinction of cue-elicited craving among treatment-seeking individuals with alcohol use disorders (AUDs). Participants were administered DCS (50 mg) or PBO 1 h before an alcohol extinction paradigm in a simulated bar environment on two occasions. The extinction procedures occurred 1 week apart and were fully integrated into outpatient treatment. Subjective craving for alcohol was the primary variable of interest. Follow-up cue reactivity sessions were conducted 1 week and 3 weeks later to ascertain persisting DCS effects. Drinking outcomes and tolerability were also examined. DCS was associated with augmented reductions in alcohol craving to alcohol cues during the first extinction session and these effects persisted through all subsequent sessions, suggesting facilitation of extinction. Participants in the DCS condition reported significant short-term reductions in drinking, although these did not persist to follow-up, and found the medication highly tolerable. These findings provide evidence that DCS enhances extinction of cue-elicited craving for alcohol in individuals with AUDs in the context of outpatient treatment. The potential clinical utility of DCS is discussed, including methodological considerations and context-dependent learning.

Relapse of extinguished fear after exposure to a dangerous context is mitigated by testing in a safe context

Aversive events can trigger relapse of extinguished fear memories, presenting a major challenge to the long-term efficacy of therapeutic interventions. Here, we examined factors regulating the relapse of extinguished fear after exposure of rats to a dangerous context. Rats received unsignaled shock in a distinct context ("dangerous" context) 24 h prior to auditory fear conditioning in another context. Fear to the auditory conditioned stimulus (CS) was subsequently extinguished either in the conditioning context ("ambiguous" context) or in a third novel context ("safe" context). Exposure to the dangerous context 30 min before a CS retention test caused relapse to the CS in the ambiguous and safe test contexts relative to nonextinguished controls. When rats were tested 24 h later (with or without short-term testing), rats tested in the ambiguous context continued to exhibit relapse, whereas rats tested in the safe context did not. Additionally, exposure of rats to the conditioning context--in place of the unsignaled shock context--did not result in relapse of fear to the CS in the safe testing context. Our work highlights the vulnerabilities of extinction recall to interference, and demonstrates the importance of context associations in the relapse of fear after extinction.

The role of stress and fear in the development of mental disorders

The most common pathologic manifestation of fear is posttraumatic stress disorder (PTSD). Developing PTSD is closely related with predisposing factors such as genes and early traumatic experiences. In PTSD, enhanced fear learning and poor extinction are common. Fear is manifested through autonomic responses and persistent memories of the traumatic event. These manifestations are related to stress responses modulated by the hypothalamic-pituitary-adrenal axis. This article evaluates the role of fear and stress in the course of PTSD. Findings on fear learning and extinction are presented in order to guide future treatments of patients with PTSD.

Brain regions related to fear extinction in obsessive-compulsive disorder and its relation to exposure therapy outcome: a morphometric study

BACKGROUND

The size of particular sub-regions within the ventromedial prefrontal cortex (vmPFC) has been associated with fear extinction in humans. Exposure therapy is a form of extinction learning widely used in the treatment of obsessive-compulsive disorder (OCD). Here we investigated the relationship between morphometric measurements of different sub-regions of the vmPFC and exposure therapy outcome in OCD.

METHOD

A total of 74 OCD patients and 86 healthy controls underwent magnetic resonance imaging (MRI). Cortical thickness and volumetric measurements were obtained for the rostral anterior cingulate cortex (rACC), the medial orbital frontal cortex and the subcallosal cortex. After MRI acquisition, patients were enrolled in an exposure therapy protocol, and we assessed the relationship between MRI-derived measurements and treatment outcome. Baseline between-group differences for such measurements were also assessed.

RESULTS

Compared with healthy controls, OCD patients showed a thinner left rACC (p = 0.008). Also, left rACC thickness was inversely associated with exposure therapy outcome (r - 0.32, p = 0.008), and this region was significantly thinner in OCD patients who responded to exposure therapy than in those who did not (p = 0.006). Analyses based on regional volumetry did not yield any significant results.

CONCLUSIONS

OCD patients showed cortical thickness reductions in the left rACC, and these alterations were related to exposure therapy outcome. The precise characterization of neuroimaging predictors of treatment response derived from the study of the brain areas involved in fear extinction may optimize exposure therapy planning in OCD and other anxiety disorders.

Improving Outcome of Psychosocial Treatments by Enhancing Memory and Learning

Mental disorders are prevalent and can lead to significant impairment. Some progress has been made toward establishing treatments; however, effect sizes are small to moderate, gains may not persist, and many patients derive no benefit. Our goal is to highlight the potential for empirically supported psychosocial treatments to be improved by incorporating insights from cognitive psychology and research on education. Our central question is: If it were possible to improve memory for the content of sessions of psychosocial treatments, would outcome substantially improve? We leverage insights from scientific knowledge on learning and memory to derive strategies for transdiagnostic and transtreatment cognitive support interventions. These strategies can be applied within and between sessions and to interventions delivered via computer, the Internet, and text message. Additional novel pathways to improving memory include improving sleep, engaging in exercise, and using imagery. Given that memory processes change across the lifespan, services to children and older adults may benefit from different types and amounts of cognitive support.

Animal models of fear relapse

Whereas fear memories are rapidly acquired and enduring over time, extinction memories are slow to form and are susceptible to disruption. Consequently, behavioral therapies that involve extinction learning (e.g., exposure therapy) often produce only temporary suppression of fear and anxiety. This review focuses on the factors that are known to influence the relapse of extinguished fear. Several phenomena associated with the return of fear after extinction are discussed, including renewal, spontaneous recovery, reacquisition, and reinstatement. Additionally, this review describes recent work, which has focused on the role of psychological stress in the relapse of extinguished fear. Recent developments in behavioral and pharmacological research are examined in light of treatment of pathological fear in humans.

Generating new neurons to circumvent your fears: the role of IGF signaling

Extinction of fear memory is a particular form of cognitive function that is of special interest because of its involvement in the treatment of anxiety and mood disorders. Based on recent literature and our previous findings (EMBO J 30(19):4071-4083, 2011), we propose a new hypothesis that implies a tight relationship among IGF signaling, adult hippocampal neurogenesis and fear extinction. Our proposed model suggests that fear extinction-induced IGF2/IGFBP7 signaling promotes the survival of neurons at 2-4 weeks old that would participate in the discrimination between the original fear memory trace and the new safety memory generated during fear extinction. This is also called "pattern separation", or the ability to distinguish similar but different cues (e.g., context). To understand the molecular mechanisms underlying fear extinction is therefore of great clinical importance.

Bridging the theory-practice gap by getting even bolder with the Boulder model

Cognitive behavioral therapy is an effective treatment for virtually all psychiatric disorders. However, very few patients have access to it and few therapists are trained in the theory and practice of cognitive behavioral therapy. Based on the existing evidence and the articles of this series, the following recommendations are made: (a) all mental health care providers (including Psy.D. and social workers) need to be trained in the practice and theories of empirically supported treatments, specifically cognitive behavioral therapy; (b) clinical practice also needs to be based on theory, not just treatment manuals; and (c) psychological treatments have to move beyond the DSM boundaries.

Cannabinoid modulation of prefrontal-limbic activation during fear extinction learning and recall in humans

Pre-extinction administration of Δ9-tetrahydrocannibinol (THC) facilitates recall of extinction in healthy humans, and evidence from animal studies suggest that this likely occurs via enhancement of the cannabinoid system within the ventromedial prefrontal cortex (vmPFC) and hippocampus (HIPP), brain structures critical to fear extinction. However, the effect of cannabinoids on the underlying neural circuitry of extinction memory recall in humans has not been demonstrated. We conducted a functional magnetic resonance imaging (fMRI) study using a randomized, double-blind, placebo-controlled, between-subjects design (N=14/group) coupled with a standard Pavlovian fear extinction paradigm and an acute pharmacological challenge with oral dronabinol (synthetic THC) in healthy adult volunteers. We examined the effects of THC on vmPFC and HIPP activation when tested for recall of extinction learning 24 h after extinction learning. Compared to subjects who received placebo, participants who received THC showed increased vmPFC and HIPP activation to a previously extinguished conditioned stimulus (CS+E) during extinction memory recall. This study provides the first evidence that pre-extinction administration of THC modulates prefrontal-limbic circuits during fear extinction in humans and prompts future investigation to test if cannabinoid agonists can rescue or correct the impaired behavioral and neural function during extinction recall in patients with PTSD. Ultimately, the cannabinoid system may serve as a promising target for innovative intervention strategies (e.g. pharmacological enhancement of exposure-based therapy) in PTSD and other fear learning-related disorders.

Enhancing exposure therapy for PTSD with yohimbine HCL: protocol for a double-blind, randomized controlled study implementing subjective and objective measures of treatment outcome

Prolonged exposure (PE) therapy is considered a gold standard protocol for the treatment of PTSD, and it is associated with large treatment effect sizes in combat veteran samples. However, considering high rates of PTSD in the present veteran population, ongoing research work is important toward improving treatment efficiency by decreasing time to symptom amelioration and increasing the amount of symptom amelioration. The proposed research aims to enhance exposure therapy outcomes for veterans with PTSD via combination treatment with PE and yohimbine hydrochloride (HCL), an alpha-2 adrenergic receptor antagonist. The proposed investigation entails a randomized, placebo-controlled trial investigating the effect of a single administration of yohimbine HCL (paired with the first session of imaginal exposure) on outcome of PE in 40 veterans with PTSD. An additional goal is to establish a pragmatic method of tracking psychophysiological measures over the course of therapy for incorporation into future clinical psychotherapy trials. Thus, in addition to traditional self- and clinician-reported psychological outcomes, heart rate and skin conductance reactivity will be measured during a standard trauma-specific imagery task before, during, and after PE treatment. We will further investigate whether changes in psychophysiological measures predict changes in patient- and clinician-reported outcome measures.

D-Cycloserine as an augmentation strategy for cognitive behavioral therapy of anxiety disorders

The goal of this review is to examine the clinical studies on d-cycloserine, a partial glutamatergic N-methyl-D-aspartate agonist, as an augmentation strategy for exposure procedures during cognitive behavioral therapy for anxiety disorders. Although cognitive behavioral therapy and anxiolytic medications are more effective than placebo for treating anxiety disorders, there is still considerable room for further improvement. Traditional combination strategies typically yield disappointing results. However, recent studies based on translational research have shown promise to augment the neural circuitry underlying fear extinction with pharmacological means. We discuss the current state of the literature, including inconsistencies of findings and issues concerning the drug mechanism, dosing, and dose timing. D-cycloserine is a promising combination strategy for cognitive behavioral therapy of anxiety disorders by augmenting extinction learning. However, there is also evidence to suggest that d-cycloserine can facilitate reconsolidation of fear memory when exposure procedures are unsuccessful.

The science of cognitive therapy

Cognitive therapy (CT) refers to a family of interventions and a general scientific approach to psychological disorders. This family has evolved from a specific treatment model into a scientific approach that incorporates a wide variety of disorder-specific interventions and treatment techniques. The goal of this article is to describe the scientific approach of CT, review the efficacy and validity of the CT model, and exemplify important differences and commonalities of the CT approaches based on two specific disorders, posttraumatic stress disorder and health anxiety.

Glycine transporter-1 inhibition preceding extinction training inhibits reacquisition of cocaine seeking

Cognitive enhancers that act by increasing glycine transmission might be useful adjuncts to cocaine-cue extinction training to deter relapse. The study investigated the effects of combining treatments of the glycine transporter-1 (GlyT-1) inhibitor, Org24598, with extinction training on the subsequent reacquisition of cocaine self-administration. Squirrel monkeys and rats were trained to self-administer cocaine under a second-order schedule of intravenous drug injection in which responding was maintained by cocaine injections and a cocaine-paired visual stimulus. During three weekly extinction sessions, saline was substituted for cocaine but responding still produced the cocaine-paired stimulus. Subjects were treated with Org24598 or vehicle, either before or after each extinction session. One week later, cocaine injections were restored, and reacquisition of cocaine self-administration was evaluated over 15 sessions. Compared with vehicle, administration of Org24598 (1.0 mg/kg in monkeys; 3.0 or 7.5 mg/kg in rats) before each extinction session significantly inhibited reacquisition of cocaine self-administration in each species. In contrast, administration of Org24598 (1.0 mg/kg in monkeys) following, rather than preceding, each extinction session did not affect reacquisition compared with vehicle. When extinction training was replaced by cocaine self-administration or abstinence control conditions, treatment with the same doses of Org24598 resulted in reacquisition that was significantly more rapid than the reacquisition observed when Org24598 was administered before extinction training sessions. The results support the potential clinical utility of GlyT-1 inhibitor pretreatments combined with cocaine-cue extinction training to inhibit relapse.

D-cycloserine in the basolateral amygdala prevents extinction and enhances reconsolidation of odor-reward associative learning in rats

It is well established that D-cycloserine (DCS), a partial agonist of the NMDA receptor glycine site, enhances learning and memory processes. Although the effects of DCS have been especially elucidated in the extinction and reconsolidation of aversive behavioral paradigms or drug-related behaviors, they have not been clearly determined in appetitive tasks using natural reinforcers. The current study examined the effects of pre-retrieval intra-basolateral amygdala (BLA) infusions of DCS on the extinction and reconsolidation of an appetitive odor discrimination task. Rats were trained to discriminate between three odors, one of which was associated with a palatable food reward, and, 20 min prior to extinction learning (experiment 1) or reactivation (experiment 2), they received bilateral intra-BLA infusions of DCS or vehicle. In experiment 1, DCS infusion reduced the rate of extinction learning, weakened extinction retention in a post-extinction test and enhanced reacquisition of the ODT task. In experiment 2, DCS improved subsequent memory expression in the reconsolidation test performed one day after the reactivation session. Such results indicate the involvement of BLA NMDA receptors in odor-food reward associative memory and suggest that DCS may potentiate the persistence or strength of the original memory trace.

The effect of D-cycloserine on subliminal cue exposure in spider fearful individuals

Research on D-cycloserine (DCS) has demonstrated a significant effect on symptom reduction in human studies that utilized conventional exposure-based approaches. Recent studies have offered promising results for targeting fears through subliminal paradigms. In this double-blind, randomized placebo-controlled study, 45 spider fearful individuals received DCS or placebo pills prior to completing a subliminal cue exposure task to images of spiders. Participants completed self-report questionnaires and a behavioral approach task to a live caged tarantula. After repeated exposure to subliminal spider cues, participants in the DCS group reported a greater reduction in disgust than individuals in the placebo group. No difference was observed in fear ratings. These findings suggest that DCS augments the reduction in disgust in spider fearful subjects after subliminal exposure to spider cues.

A randomized placebo-controlled trial of D-cycloserine and exposure therapy for posttraumatic stress disorder

D-Cycloserine (DCS) is a partial NMDA receptor agonist that has been shown to enhance therapeutic response to exposure-based treatments for anxiety disorders, but has not been tested in the treatment of combat-related posttraumatic stress disorder (PTSD). The aim of this randomized, double-blind, placebo-controlled trial was to determine whether DCS augments exposure therapy for PTSD in veterans returning from Iraq and Afghanistan and to test whether a brief six-session course of exposure therapy could effectively reduce PTSD symptoms in returning veterans. In contrast to previous trials using DCS to enhance exposure therapy, results indicated that veterans in the exposure therapy plus DCS condition experienced significantly less symptom reduction than those in the exposure therapy plus placebo condition over the course of the treatment. Possible reasons for why DCS was associated with poorer outcome are discussed. Clinicaltrials.gov Registry #: NCT00371176; A Placebo-Controlled Trail of D-Cycloserine and Exposure Therapy for Combat-PTSD; www.clinicaltrials.gov/ct2/results?term=NCT00371176.

Failure to extinguish fear and genetic variability in the human cannabinoid receptor 1

Failure to extinguish fear can lead to persevering anxiety and has been postulated as an important mechanism in the pathogenesis of human anxiety disorders. In animals, it is well documented that the endogenous cannabinoid system has a pivotal role in the successful extinction of fear, most importantly through the cannabinoid receptor 1. However, no human studies have reported a translation of this preclinical evidence yet. Healthy medication-free human subjects (N=150) underwent a fear conditioning and extinction procedure in a virtual reality environment. Fear potentiation of the eyeblink startle reflex was measured to assess fear-conditioned responding, and subjective fear ratings were collected. Participants were genotyped for two polymorphisms located within the promoter region (rs2180619) and the coding region (rs1049353) of cannabinoid receptor 1. As predicted from the preclinical literature, acquisition and expression of conditioned fear did not differ between genotypes. Crucially, whereas both homozygote (G/G, N=23) and heterozygote (A/G, N=68) G-allele carriers of rs2180619 displayed robust extinction of fear, extinction of fear-potentiated startle was absent in A/A homozygotes (N=51). Additionally, this resistance to extinguish fear left A/A carriers of rs2180619 with significantly higher levels of fear-potentiated startle at the end of the extinction training. No effects of rs1049353 genotype were observed regarding fear acquisition and extinction. These results suggest for the first time involvement of the human endocannabinoid system in fear extinction. Implications are that genetic variability in this system may underlie individual differences in anxiety, rendering cannabinoid receptor 1 a potential target for novel pharmacological treatments of anxiety disorders.

Glucocorticoid receptors and extinction retention deficits in the single prolonged stress model

Single prolonged stress (SPS) is a rodent model of post traumatic stress disorder that is comprised of serial application of restraint (r), forced swim (fs), and ether (eth) followed by a 7-day quiescent period. SPS induces extinction retention deficits and it is believed that these deficits are caused by the combined stressful effect of serial exposure to r, fs, and eth. However, this hypothesis remains untested. Neurobiological mechanisms by which SPS induces extinction retention deficits are unknown, but SPS enhances glucocorticoid receptor (GR) expression in the hippocampus, which is critical for contextual modulation of extinction retrieval. Upregulation of GRs in extinction circuits may be a mechanism by which SPS induces extinction retention deficits, but this hypothesis has not been examined. In this study, we systematically altered the stressors that constitute SPS (i.e. r, fs, eth), generating a number of partial SPS (p-SPS) groups, and observed the effects SPS and p-SPSs had on extinction retention and GR levels in the hippocampus and prefrontal cortex (PFC). PFC GRs were assayed, because regions of the PFC are critical for maintaining extinction. We predicted that only exposure to full SPS would result in extinction retention deficits and enhance hippocampal and PFC GR levels. Only exposure to full SPS induced extinction retention deficits. Hippocampal and PFC GR expression was enhanced by SPS and most p-SPSs, however hippocampal GR expression was significantly larger following the full SPS exposure than all other conditions. Our findings suggest that the combined stressful effect of serial exposure to r, fs, and eth results in extinction retention deficits. The results also suggest that simple enhancements in GR expression in the hippocampus and PFC are insufficient to result in extinction retention deficits, but raise the possibility that a threshold-enhancement in hippocampal GR expression contributes to SPS-induced extinction retention deficits.