Targeting memory reconsolidation to prevent the return of fear in patients with fear of flying

BACKGROUND

When a memory is recalled, it may again exist in a labile state and stored information becomes amenable to change, a psychobiological process known as reconsolidation. Exposure therapy for anxiety disorders involves accessing a fear memory and modifying it with less fearful information. A preclinical study reported that providing a reminder of a fear memory 10 min prior to extinction training in humans decreased fear up to 1 year later (Schiller et al., 2010).

METHODS

For this pilot clinical study, we used virtual reality exposure therapy (VRE) for fear of flying (FoF) to determine if using a cue to reactivate the memory of the feared stimulus 10 min prior to exposure sessions leads to fewer anxiety-related behaviors and a more durable response compared to a neutral cue. FoF participants (N = 89) received four sessions of anxiety management training followed by four sessions of VRE. Participants were randomly assigned to receive an FoF cue (reactivation group) or a neutral cue (control group) prior to the VRE sessions. Heart rate (HR) and skin conductance levels (SCLs) were collected during posttreatment and 3-month follow-up assessments as objective markers of fear responding.

RESULTS

Treatment was effective and all clinical measures improved equally between groups at posttreatment with maintained gains through follow-ups. Significant differences were identified with regard to HR and SCL indices.

CONCLUSIONS

These results suggest that memory reactivation prior to exposure therapy did not have an impact on clinical measures but may enhance the effect of exposure therapy at the physiological level.

Baroreflex dysfunction and augmented sympathetic nerve responses during mental stress in veterans with post-traumatic stress disorder

KEY POINTS

Patients with post-traumatic stress disorder (PTSD) are at a significantly higher risk of developing hypertension and cardiovascular disease. The mechanisms underlying this increased risk are not known. Studies have suggested that PTSD patients have an overactive sympathetic nervous system (SNS) that could contribute to cardiovascular risk; however, sympathetic function has not previously been rigorously evaluated in PTSD patients. Using direct measurements of sympathetic nerve activity and pharmacological manipulation of blood pressure, we show that veterans with PTSD have augmented SNS and haemodynamic reactivity during both combat-related and non-combat related mental stress, impaired sympathetic and cardiovagal baroreflex sensitivity, and increased inflammation. Identifying the mechanisms contributing to increased cardiovascular (CV) risk in PTSD will pave the way for developing interventions to improve sympathetic function and reduce CV risk in these patients.

ABSTRACT

Post-traumatic stress disorder (PTSD) is associated with increased cardiovascular (CV) risk. We tested the hypothesis that PTSD patients have augmented sympathetic nervous system (SNS) and haemodynamic reactivity during mental stress, as well as impaired arterial baroreflex sensitivity (BRS). Fourteen otherwise healthy Veterans with combat-related PTSD were compared with 14 matched Controls without PTSD.  Muscle sympathetic nerve activity (MSNA), continuous blood pressure (BP) and electrocardiography were measured at baseline, as well as during two types of mental stress:  combat-related mental stress using virtual reality combat exposure (VRCE) and non-combat related stress using mental arithmetic (MA). A cold pressor test (CPT) was administered for comparison. BRS was tested using pharmacological manipulation of BP via the Modified Oxford technique at rest and during VRCE. Blood samples were analysed for inflammatory biomarkers. Baseline characteristics, MSNA and haemodynamics were similar between the groups. In PTSD vs. Controls, MSNA (+8.2 ± 1.0 vs. +1.2 ± 1.3 bursts min^-1 , P < 0.001) and heart rate responses (+3.2 ± 1.1 vs. -2.3 ± 1.0 beats min^-1 , P = 0.003) were significantly augmented during VRCE.  Similarly, in PTSD vs. Controls, MSNA (+21.0 ± 2.6 vs. +6.7 ± 1.5 bursts min^-1 , P < 0.001) and diastolic BP responses (+6.3 ± 1.0 vs. +3.5 ± 1.0 mmHg, P = 0.011) were significantly augmented during MA but not during CPT (P = not significant). In the PTSD group, sympathetic BRS (-1.2 ± 0.2 vs. -2.0 ± 0.3 burst incidence mmHg^-1 , P = 0.026) and cardiovagal BRS (9.5 ± 1.4 vs. 23.6 ± 4.3 ms mmHg^-1 , P = 0.008) were significantly blunted at rest. PTSD patients had significantly higher highly sensitive-C-reactive protein levels compared to Controls (2.1 ± 0.4 vs. 1.0 ± 0.3 mg L^-1 , P = 0.047). Augmented SNS and haemodynamic responses to mental stress, blunted BRS and inflammation may contribute to an increased CV risk in PTSD.

Psychological resilience is associated with more intact social functioning in veterans with post-traumatic stress disorder and depression

Patients with depression or post-traumatic stress disorder (PTSD), common sequelae among individuals exposed to stressful or traumatic events, often report impairment in social functioning. Resilience is a multidimensional construct that enables adaptive coping with life adversity. Relationship between resilience and social functioning among veterans with depression and PTSD is not entirely clear and is the focus of this report. Resilience was assessed in 264 veterans using the Connor-Davidson Resilience Scale, PTSD with the PTSD Symptom Scale, depression with the Beck Depression Inventory, and social functioning with the Short Form Health Survey. Higher resilience was associated with more intact social functioning after PTSD and depression severity, childhood maltreatment, physical health, gender, education, marital status, and employment were simultaneously adjusted for. Childhood maltreatment, gender, marital status, education, and employment did not predict social functioning; however, greater severity of PTSD, depression, or physical health problems was each significantly associated with more impaired social functioning. Our findings suggest that higher resilience was associated with more intact social functioning regardless of the severity of PTSD and depression. Given the importance of social functioning in depression and/or PTSD recovery, studies are needed to examine if enhancing resilience presents a complementary approach to alleviating impaired social functioning.

Fear-Potentiated Startle and Fear Extinction in a Sample of Undergraduate Women Exposed to a Campus Mass Shooting

Posttraumatic stress disorder (PTSD) is a common psychological disorder that affects a substantial minority of individuals. Previous research has suggested that PTSD can be partially explained as a disorder of impaired fear inhibition. The current study utilized a previously validated fear acquisition and extinction paradigm in a sample of 75 undergraduate women who were exposed to a campus mass shooting that occurred in 2008. We used a protocol in which conditioned fear was first acquired through the presentation of one colored shape (reinforced conditioned stimulus, CS+) that was paired with an aversive airblast to the larynx (unconditioned stimulus, US) and a different colored shape that was not paired with the airblast (non-reinforced conditioned stimulus, CS-). Fear was extinguished 10 min later through repeated presentations of the CSs without reinforcement. Number of clinically significant posttraumatic stress symptoms (PTSS) immediately following the mass shooting were positively associated with fear-potentiated startle (FPS) to the CS+ and CS- during late periods of acquisition. During early periods of fear extinction, PTSS was positively associated with FPS to the CS+. Results from the current study suggest that PTSS is related to altered fear inhibition and extinction during an FPS paradigm. In line with similar research, women with greater PTSS demonstrated a greater “fear load,” suggesting that these women experienced elevated fear to the CS+ during extinction after conditioned fear was acquired.

Prospective Associations between Emotion Dysregulation and Fear-Potentiated Startle: The Moderating Effect of Respiratory Sinus Arrhythmia

Background: Emotion dysregulation has been implicated in the negative outcomes following trauma exposure. A proposed biomarker of emotion dysregulation, respiratory sinus arrhythmia (RSA), has demonstrated associations with trauma-related phenomena, such as the fear-potentiated startle (FPS) response. The current study aimed to examine the prospective association between emotion dysregulation and RSA and FPS several years following trauma exposure.

Methods: Participants were 131 women exposed to a campus mass shooting on February 14, 2008. Pre-shooting emotion dysregulation was assessed in 2006–2008. Startle response, measured by orbicularis oculi electromyography (EMG), and RSA were gathered during an FPS paradigm conducted from 2012 to 2015.

Results: No significant associations among emotion dysregulation, RSA, and FPS emerged among the full sample. However, emotion dysregulation predicted FPS during both acquisition (r = 0.40, p < 0.05) and extinction (r = 0.57, p < 0.01) among individuals with high resting RSA.

Conclusions: Findings suggest that pre-shooting emotion dysregulation is a potent predictor of FPS several years following potential trauma exposure, and this association varies by RSA level. Results emphasize the importance of examining autonomic regulation in the association between emotion dysregulation and recovery from trauma exposure.

Dexamethasone Treatment Leads to Enhanced Fear Extinction and Dynamic Fkbp5 Regulation in Amygdala

Posttraumatic stress disorder (PTSD) is both a prevalent and debilitating trauma-related disorder associated with dysregulated fear learning at the core of many of its signs and symptoms. Improvements in the currently available psychological and pharmacological treatments are needed in order to improve PTSD treatment outcomes and to prevent symptom relapse. In the present study, we used a putative animal model of PTSD that included presentation of immobilization stress (IMO) followed by fear conditioning (FC) a week later. We then investigated the acute effects of GR receptor activation on the extinction (EXT) of conditioned freezing, using dexamethasone administered systemically which is known to result in suppression of the HPA axis. In our previous work, IMO followed by tone-shock-mediated FC was associated with impaired fear EXT. In this study, we administered dexamethasone 4 h before EXT training and then examined EXT retention (RET) 24 h later to determine whether dexamethasone suppression rescued EXT deficits. Dexamethasone treatment produced dose-dependent enhancement of both EXT and RET. Dexamethasone was also associated with reduced amygdala Fkbp5 mRNA expression following EXT and after RET. Moreover, DNA methylation of the Fkbp5 gene occurred in a dose-dependent and time course-dependent manner within the amygdala. Additionally, we found dynamic changes in epigenetic regulation, including Dnmt and Tet gene pathways, as a function of both fear EXT and dexamethasone suppression of the HPA axis. Together, these data suggest that dexamethasone may serve to enhance EXT by altering Fkbp5-mediated glucocorticoid sensitivity via epigenetic regulation of Fkbp5 expression.

Biomarkers of post-deployment resilience among military service members

The development of PTSD after military deployment is influenced by a combination of biopsychosocial risk and resilience factors. In particular, physiological factors may mark risk for symptom progression or resiliency. Research in civilian populations suggests elevated catecholamines after trauma are associated with PTSD months following the trauma. However, less is known regarding physiological markers of PTSD resilience among post-deployment service members (SM). We therefore assessed whether catecholamines obtained shortly after deployment were associated with combat-related PTSD symptoms three months later. Eighty-seven SMs completed the Clinician-Administered PTSD Scale for DSM-IV and blood draws within two months after return from deployment to Iraq or Afghanistan ("Time 1" or "T1") and three months later ("Time 2" or "T2"). Linear regression analyses demonstrated that lower norepinephrine at T1 was associated with lower PTSD symptoms at T2. In particular, T1 norepinephrine was positively associated with T2 symptom intensity and avoidance symptoms. The present findings represent a biologically-informed method of assessing PTSD resilience after deployment, which may aid clinicians in providing tailored treatments for those in the greatest need. Further research is needed to validate these findings and incorporate physiological measures within an assessment battery.

An investigation of outcome expectancies as a predictor of treatment response for combat veterans with PTSD: comparison of clinician, self-report, and biological measures

BACKGROUND

Outcome expectancy, or the degree to which a client believes that therapy will result in improvement, is related to improved treatment outcomes for multiple disorders. There is a paucity of research investigating this relation in regards to posttraumatic stress disorder (PTSD). Additionally, the bulk of the research on outcome expectancy and treatment outcomes has relied mostly on self-report outcome measures.

METHODS

The relation between outcome expectancy on self-report measures, clinician-rated measures, and two biological indices (fear-potentiated startle and cortisol reactivity) of PTSD symptoms was explored. The sample included combat veterans (N = 116) treated with virtual reality exposure therapy for PTSD.

RESULTS

Results supported a negative association between outcome expectancy and both self-report and clinician-rated symptoms at the conclusion of treatment, but outcome expectancy was related to the magnitude of change during treatment for self-report measures only. Outcome expectancy was unrelated to biological measures of treatment response.

CONCLUSIONS

These findings suggest that outcome expectancy may be related to patient and clinician perceptions of outcomes, but not biological indices of outcome for PTSD.

Fear conditioned responses and PTSD symptoms in children: Sex differences in fear-related symptoms

Fear conditioning studies in adults have found that posttraumatic stress disorder (PTSD) is associated with heightened fear responses and impaired discrimination. The objective of the current study was to examine the association between PTSD symptoms and fear conditioned responses in children from a highly traumatized urban population. Children between 8 and 13 years old participated in a fear conditioning study in addition to providing information about their trauma history and PTSD symptoms. Results showed that females showed less discrimination between danger and safety signals during conditioning compared to age-matched males. In boys, intrusive symptoms were predictive of fear responses, even after controlling for trauma exposure. However, in girls, conditioned fear to the danger cue was predictive of self-blame and fear of repeated trauma. This study suggests there are early sex differences in the patterns of fear conditioning and that these sex differences may translate to differential risk for trauma-related psychopathology.

Catecholamine responses to virtual combat: implications for post-traumatic stress and dimensions of functioning

Posttraumatic stress disorder (PTSD) symptoms can result in functional impairment among service members (SMs), even in those without a clinical diagnosis. The variability in outcomes may be related to underlying catecholamine mechanisms. Individuals with PTSD tend to have elevated basal catecholamine levels, though less is known regarding catecholamine responses to trauma-related stimuli. We assessed whether catecholamine responses to a virtual combat environment impact the relationship between PTSD symptom clusters and elements of functioning. Eighty-seven clinically healthy SMs, within 2 months after deployment to Iraq or Afghanistan, completed self-report measures, viewed virtual-reality (VR) combat sequences, and had sequential blood draws. Norepinephrine responses to VR combat exposure moderated the relationship between avoidance symptoms and scales of functioning including physical functioning, physical-role functioning, and vitality. Among those with high levels of avoidance, norepinephrine change was inversely associated with functional status, whereas a positive correlation was observed for those with low levels of avoidance. Our findings represent a novel use of a virtual environment to display combat-related stimuli to returning SMs to elucidate mind-body connections inherent in their responses. The insight gained improves our understanding of post-deployment symptoms and quality of life in SMs and may facilitate enhancements in treatment. Further research is needed to validate these findings in other populations and to define the implications for treatment effectiveness.

Fear-potentiated startle during extinction is associated with white matter microstructure and functional connectivity

BACKGROUND

Extinction of conditioned fear is an associative learning process that involves communication among the hippocampus, medial prefrontal cortex, and amygdala. Strength of connectivity between the hippocampus and the anterior cingulate cortex (ACC), and between the amygdala and ventromedial prefrontal cortex (vmPFC), may influence fear-potentiated startle (FPS) responses during extinction. Specific white matter tracts, the cingulum and uncinate fasciculus (UF), serve as primary routes of communication for these areas. Our objective was to investigate associations between FPS during extinction and cingulum and UF connectivity.

METHOD

Diffusion tensor imaging (DTI) and probabilistic tractography analyses were used to examine cingulum and UF structural connectivity in 40 female African-Americans with psychological trauma exposure. FPS responses during fear conditioning and extinction were assessed via electromyography (EMG) of the right orbicularis oculi muscle. Secondarily, functional connectivity analyses were performed with the seed regions of interest (ROIs) used for tractography.

RESULTS

A significant negative association between cingulum microstructure and FPS during early extinction (r = -.42, p = .01) and late extinction (r = -.36, p = .03) was observed after accounting for the effects of age, trauma exposure, and psychopathology (post-traumatic stress disorder symptoms); this pattern was similar for early extinction and functional connectivity between these regions (p < .05(corrected)). No significant correlations were observed between FPS and UF microstructure.

CONCLUSIONS

These data indicate that structural integrity of the cingulum is directly associated with extinction learning and appears to influence functional connectivity between these regions. Decrements in cingulum microstructure may interfere with extinction learning, thereby increasing risk for the development of pathological anxiety.

A randomized, double-blind evaluation of D-cycloserine or alprazolam combined with virtual reality exposure therapy for posttraumatic stress disorder in Iraq and Afghanistan War veterans

OBJECTIVE

The authors examined the effectiveness of virtual reality exposure augmented with D-cycloserine or alprazolam, compared with placebo, in reducing posttraumatic stress disorder (PTSD) due to military trauma.

METHOD

After an introductory session, five sessions of virtual reality exposure were augmented with D-cycloserine (50 mg) or alprazolam (0.25 mg) in a double-blind, placebo-controlled randomized clinical trial for 156 Iraq and Afghanistan war veterans with PTSD.

RESULTS

PTSD symptoms significantly improved from pre- to posttreatment across all conditions and were maintained at 3, 6, and 12 months. There were no overall differences in symptoms between D-cycloserine and placebo at any time. Alprazolam and placebo differed significantly on the Clinician-Administered PTSD Scale score at posttreatment and PTSD diagnosis at 3 months posttreatment; the alprazolam group showed a higher rate of PTSD (82.8%) than the placebo group (47.8%). Between-session extinction learning was a treatment-specific enhancer of outcome for the D-cycloserine group only. At posttreatment, the D-cycloserine group had the lowest cortisol reactivity and smallest startle response during virtual reality scenes.

CONCLUSIONS

A six-session virtual reality treatment was associated with reduction in PTSD diagnoses and symptoms in Iraq and Afghanistan veterans, although there was no control condition for the virtual reality exposure. There was no advantage of D-cycloserine for PTSD symptoms in primary analyses. In secondary analyses, alprazolam impaired recovery and D-cycloserine enhanced virtual reality outcome in patients who demonstrated within-session learning. D-cycloserine augmentation reduced cortisol and startle reactivity more than did alprazolam or placebo, findings that are consistent with those in the animal literature.

Changes in trauma-potentiated startle with treatment of posttraumatic stress disorder in combat Veterans

Emotional Processing Theory proposes that habituation to trauma-related stimuli is an essential component of PTSD treatment. However, the mechanisms underlying treatment-related habituation are not well understood. We examined one psychophysiological measure that holds potential for elucidating the biological processes involved in treatment response: trauma-potentiated startle response. Seventeen OEF/OIF combat Veterans participated in the study and completed three assessments using a trauma-potentiated startle paradigm over PTSD treatment. Results revealed different patterns of trauma-potentiated startle across treatment for responders and nonresponders, but no differences in within task habituation. Responders showed an increase followed by a decrease in trauma-potentiated startle, whereas nonresponders showed a relatively flat response profile. Results suggested that PTSD patients who engage with emotional content as demonstrated by greater startle reactivity may be more likely to respond to PTSD treatment. Furthermore, trauma-potentiated startle shows promise as an objective measure of psychophysiological responses involved in PTSD recovery.

Inhibition of fear is differentially associated with cycling estrogen levels in women

BACKGROUND

Although the prevalence of posttraumatic stress disorder (PTSD) is twice as high in women as it is in men, the role of estrogen in the risk for PTSD is not well understood. Deficits in fear inhibition and impaired safety signal learning may be biomarkers for PTSD. We examined menstrual cycle phase and serum estradiol levels in naturally cycling women while they were undergoing a novel conditioned inhibition procedure that measured their ability to discriminate between cues representing danger versus safety and to inhibit fear in the presence of safety cues.

METHODS

Sample 1 included healthy participants in whom we compared inhibition of fearpotentiated startle during the follicular (lower estrogen) and luteal (higher estrogen) phases of the menstrual cycle. We used the same paradigm in a traumatized clinical population (sample 2) in whom we compared low versus high estradiol levels.

RESULTS

In both samples, we found that lower estrogen in cycling women was associated with impaired fear inhibition.

LIMITATIONS

In the clinical sample, the low estradiol group was on average older than the high estradiol group owing to the random recruitment approach; we did not exclude participants based on hormonal status or menopause.

CONCLUSION

Our results suggest that the lower estrogen state during normal menstrual cycling may contribute to risk for anxiety disorders through dysregulated fear responses.

Reduced neural activation during an inhibition task is associated with impaired fear inhibition in a traumatized civilian sample

INTRODUCTION

Impaired inhibition of fear in the presence of safety cues and a deficiency in the extinction of fear cues are increasingly thought to be important biological markers of Posttraumatic stress disorder (PTSD). Other studies have suggested that there may be altered neural activation during behavioral inhibition tasks in subjects with PTSD. The current study aimed to see whether neural activation during inhibition was reduced in a highly traumatized civilian population, and whether atypical activation was associated with impaired fear inhibition.

METHODS

The participants were 41 traumatized women (20 PTSD+, 21 PTSD-) recruited from Grady Memorial Hospital in Atlanta, GA. We used a Go/NoGo procedure with functional magnetic resonance imaging (fMRI) in a high-resolution 3T scanner. Participants were instructed to press a button whenever an "X" or "O" appeared on the screen, but not if a red square appeared behind the letter. Participants were assessed for trauma history and PTSD diagnosis, and completed a fear-potentiated startle and extinction paradigm.

RESULTS

We found stronger activation in the ventromedial prefrontal cortex (vmPFC) in traumatized subjects without PTSD compared to those with PTSD in the NoGo greater than Go contrast condition. Activation in the vmPFC was negatively correlated with fear-potentiated startle responses during safety signal learning (p = .02) and fear extinction (p = .0002).

CONCLUSIONS

These results contribute to understanding of how the neural circuitry involved in inhibitory processes may be deficient in PTSD. Furthermore, the same circuits involved in behavioral inhibition appear to be involved in fear inhibition processes during differential fear conditioning and extinction.

Acute stress disorder versus chronic posttraumatic stress disorder: inhibition of fear as a function of time since trauma

BACKGROUND

Previous work has shown that inhibition of fear is impaired in posttraumatic stress disorder (PTSD) resulting from both civilian and combat trauma. The purpose of the present study was to investigate the inhibition of learned fear in traumatized individuals diagnosed with either acute stress disorder (ASD) or PTSD. This is the first study to use a conditioned inhibition paradigm with traumatized individuals within a month of trauma exposure. We hypothesized that impaired fear inhibition would be evident in PTSD, but not ASD.

METHOD

Using established translational, psychophysiological methods including fear-potentiated startle, and skin conductance, we examined fear acquisition, stimulus discrimination, and the transfer of learned safety in a Croatian population with ASD or PTSD. This cross-sectional study included three age-matched groups: healthy nontrauma controls (n = 27), a group with chronic PTSD (10 or more years since trauma exposure, n = 24), and a group with ASD (30 days or less since trauma exposure, n = 27).

RESULTS

The presence of trauma-related psychopathology, whether acute or chronic, was associated with an impaired ability to transfer learned safety based on fear-potentiated startle measures, while healthy control subjects showed significant fear inhibition in the presence of the safety cue compared to the danger cue, F(1,26) = 12.64, P = .001.

CONCLUSIONS

These data expand our previously observed findings of PTSD-associated fear inhibition deficits by demonstrating that trauma-related impairments in safety learning are evident within 30 days of trauma exposure.

Heart rate response to fear conditioning and virtual reality in subthreshold PTSD

Posttraumatic stress disorder (PTSD) is a significant health concern for U.S. military service members (SMs) returning from Afghanistan and Iraq. Early intervention to prevent chronic disability requires greater understanding of subthreshold PTSD symptoms, which are associated with impaired physical health, mental health, and risk for delayed onset PTSD. We report a comparison of physiologic responses for recently deployed SMs with high and low subthreshold PTSD symptoms, respectively, to a fear conditioning task and novel virtual reality paradigm (Virtual Iraq). The high symptom group demonstrated elevated heart rate (HR) response during fear conditioning. Virtual reality sequences evoked significant HR responses which predicted variance of the PTSD Checklist-Military Version self-report. Our results support the value of physiologic assessment during fear conditioning and combat-related virtual reality exposure as complementary tools in detecting subthreshold PTSD symptoms in Veterans.

Estrogen levels are associated with extinction deficits in women with posttraumatic stress disorder

BACKGROUND

Women are twice as likely to develop posttraumatic stress disorder (PTSD) than men. As shown in our previous work, the inability to suppress fear responses in safe conditions may be a biomarker for PTSD. Low estrogen in naturally cycling women is associated with deficits in fear extinction. On the basis of these findings, we have now examined the influence of estrogen levels on fear extinction in women with and without PTSD.

METHODS

We measured fear-potentiated startle during fear conditioning and extinction in women. The study sample (N = 81) was recruited from an urban, highly traumatized civilian population at Grady Memorial Hospital in Atlanta, Georgia. We assayed serum estrogen levels and used a median split to divide the sample into high and low estradiol (E(2)) groups. Seventeen of 41 women (41.5%) in the low E(2) group and 15 of 40 women (37.5%) met criteria for PTSD in the high E(2) group.

RESULTS

The results showed that all groups had equivalent levels of fear conditioning. However, we found significant interaction effects between high versus low E(2) groups and PTSD diagnosis [F(1,71) = 4.55, p < .05] on extinction. Among women with low estrogen levels, fear-potentiated startle was higher during extinction in the PTSD group compared with traumatized control women [F(1,38) = 5.04, p < .05]. This effect was absent in the High E(2) group.

CONCLUSION

This study suggests that low estrogen may be a vulnerability factor for development of PTSD in women with trauma histories. Research on the role of estrogen in fear regulation may provide insight into novel treatment strategies for PTSD.

Attention bias toward threat is associated with exaggerated fear expression and impaired extinction in PTSD

BACKGROUND

Post-traumatic stress disorder (PTSD) develops in a minority of traumatized individuals. Attention biases to threat and abnormalities in fear learning and extinction are processes likely to play a critical role in the creation and/or maintenance of PTSD symptomatology. However, the relationship between these processes has not been established, particularly in highly traumatized populations; understanding their interaction can help inform neural network models and treatments for PTSD.

METHOD

Attention biases were measured using a dot probe task modified for use with our population; task stimuli included photographs of angry facial expressions, which are emotionally salient threat signals. A fear-potentiated startle paradigm was employed to measure atypical physiological response during acquisition and extinction phases of fear learning. These measures were administered to a sample of 64 minority (largely African American), highly traumatized individuals with and without PTSD.

RESULTS

Participants with PTSD demonstrated attention biases toward threat; this attentional style was associated with exaggerated startle response during fear learning and early and middle phases of extinction, even after accounting for the effects of trauma exposure.

CONCLUSIONS

Our findings indicate that an attentional bias toward threat is associated with abnormalities in 'fear load' in PTSD, providing seminal evidence for an interaction between these two processes. Future research combining these behavioral and psychophysiological techniques with neuroimaging will be useful toward addressing how one process may modulate the other and understanding whether these phenomena are manifestations of dysfunction within a shared neural network. Ultimately, this may serve to inform PTSD treatments specifically designed to correct these atypical processes.

Tools for translational neuroscience: PTSD is associated with heightened fear responses using acoustic startle but not skin conductance measures

BACKGROUND

Posttraumatic stress disorder (PTSD) patients show heightened fear responses to trauma reminders and an inability to inhibit fear in the presence of safety reminders. Brain imaging studies suggest that this is in part due to amygdala over-reactivity as well as deficient top-down cortical inhibition of the amygdala. Consistent with these findings, previous studies, using fear-potentiated startle (FPS), have shown exaggerated startle and deficits in fear inhibition in PTSD participants. However, many PTSD studies using the skin conductance response (SCR) report no group differences in fear acquisition.

METHOD

The study included 41 participants with PTSD and 70 without PTSD. The fear conditioning session included a reinforced conditioned stimulus (CS+, danger cue) paired with an aversive airblast, and a nonreinforced conditioned stimulus (CS-, safety cue). Acoustic startle responses and SCR were acquired during the presentation of each CS.

RESULTS

The results showed that fear conditioned responses were captured in both the FPS and SCR measures. Furthermore, PTSD participants had higher FPS to the danger cue and safety cue compared to trauma controls. However, SCR did not differ between groups. Finally, we found that FPS to the danger cue predicted re-experiencing symptoms, whereas FPS to the safety cue predicted hyper-arousal symptoms. However, SCR did not contribute to PTSD symptom variance.

CONCLUSIONS

Replicating earlier studies, we showed increased FPS in PTSD participants. However, although SCR was a good measure of differential conditioning, it did not differentiate between PTSD groups. These data suggest that FPS may be a useful tool for translational research.

Versatility of fear-potentiated startle paradigms for assessing human conditioned fear extinction and return of fear

Fear conditioning methodologies have often been employed as testable models for assessing learned fear responses in individuals with anxiety disorders such as post-traumatic stress disorder (PTSD) and specific phobia. One frequently used paradigm is measurement of the acoustic startle reflex under conditions that mimic anxiogenic and fear-related conditions. For example, fear-potentiated startle is the relative increase in the frequency or magnitude of the acoustic startle reflex in the presence of a previously neutral cue (e.g., colored shape; termed the conditioned stimulus or CS+) that has been repeatedly paired with an aversive unconditioned stimulus (e.g., airblast to the larynx). Our group has recently used fear-potentiated startle paradigms to demonstrate impaired fear extinction in civilian and combat populations with PTSD. In the current study, we examined the use of either auditory or visual CSs in a fear extinction protocol that we have validated and applied to human clinical conditions. This represents an important translational bridge in that numerous animal studies of fear extinction, upon which much of the human work is based, have employed the use of auditory CSs as opposed to visual CSs. Participants in both the auditory and visual groups displayed robust fear-potentiated startle to the CS+, clear discrimination between the reinforced CS+ and non-reinforced CS−, significant extinction to the previously reinforced CS+, and marked spontaneous recovery. We discuss the current results as they relate to future investigations of PTSD-related impairments in fear processing in populations with diverse medical and psychiatric histories.

Cortisol suppression by dexamethasone reduces exaggerated fear responses in posttraumatic stress disorder

PTSD symptoms are associated with heightened fear responses in laboratory fear conditioning paradigms. This study examined the effects of dexamethasone administration on hypothalamic-pituitary-adrenal (HPA) function and fear-potentiated startle (FPS) in trauma-exposed individuals with and without PTSD. We used an established fear discrimination procedure, in which one visual stimulus (CS+, danger cue) was paired with aversive airblasts to the throat (unconditioned stimulus, US), and another stimulus (CS-, safety cue) was presented without airblasts. In addition to FPS, the dexamethasone suppression test (DST) was performed. The study sample (N=100) was recruited from a highly traumatized civilian population in Atlanta, GA. Half of the subjects (n=54, 16 PTSD, 38 controls) underwent conditioning at baseline and the other half (n=46, 17 PTSD, 29 controls) after DST, in a cross-sectional design. We found a significant interaction effect of diagnostic group and dexamethasone treatment. Under baseline conditions, subjects with PTSD showed more than twice as much fear-potentiated startle to the danger cue compared to traumatized controls, F(1,53)=8.08, p=0.006. However, there was no group difference in subjects tested after dexamethasone suppression. Furthermore, there was a significant treatment effect in PTSD subjects but not in controls, with dexamethasone reducing fear-potentiated startle to the CS+, F(1,32)=4.00, p=0.05. There was also a positive correlation between PTSD subjects' FPS and cortisol levels, r=0.46, p=0.01. These results suggest that transient suppression of HPA function via dexamethasone suppression may reduce exaggerated fear in patients with PTSD.