Influence of trait anxiety on brain activity during the acquisition and extinction of aversive conditioning

Neural underpinnings of preferential pain learning and the modulatory role of fear

Due to its unique biological relevance, pain-related learning might differ from learning from other aversive experiences. This functional magnetic resonance imaging study compared neural mechanisms underlying the acquisition and extinction of different threats in healthy humans. We investigated whether cue-pain associations are acquired faster and extinguished slower than cue associations with an equally unpleasant tone. Additionally, we studied the modulatory role of stimulus-related fear. Therefore, we used a differential conditioning paradigm, in which somatic heat pain stimuli and unpleasantness-matched auditory stimuli served as US. Our results show stronger acquisition learning for pain- than tone-predicting cues, which was augmented in participants with relatively higher levels of fear of pain. These behavioral findings were paralleled by activation of brain regions implicated in threat processing (insula, amygdala) and personal significance (ventromedial prefrontal cortex). By contrast, extinction learning seemed to be less dependent on the threat value of the US, both on the behavioral and neural levels. Amygdala activity, however, scaled with pain-related fear during extinction learning. Our findings on faster and stronger (i.e. "preferential") pain learning and the role of fear of pain are consistent with the biological relevance of pain and may be relevant to the development or maintenance of chronic pain.

Test–retest reliability of human threat conditioning and generalization across a 1‐to‐2‐week interval

Given the increasing use of threat conditioning and generalization for clinical-translational research efforts, establishing test-retest reliability of these paradigms is necessary. Specifically, it is an empirical question whether the same participant evinces a similar generalization gradient of conditioned responses across two sessions with the identical contingencies and stimuli. Here, 46 human volunteers participated in an identical auditory threat acquisition and generalization protocol at two sessions separated by 1-to-2 weeks. Skin conductance responses (SCR) and trial-by-trial shock risk ratings served as primary measures. We used linear mixed effects modeling to test differential threat responses and generalization gradients, and Generalizability (G) theory coefficients as our primary formal assessment of test-retest reliability of intraindividual stability and change across time. Results showed largely invariant differential conditioning and generalization gradients across time. G coefficients indicated fair reliability for acquisition and generalization SCR. In contrast, risk rating reliabilities were mixed, and reliability was particularly low for acquisition risk ratings. Our findings generally support reliability of the threat conditioning and generalization paradigm for shorter test-retest intervals and highlight their utility for assessments of behavioral interventions in mental health research, but challenges remain and further work is needed. Threat conditioning and generalization tasks are increasingly used for translational efforts to improve behavioral interventions, and thus test-retest reliability for these tasks needs to be established. Our results support the test-retest reliability of threat conditioning and generalization over a relatively short (1-to-2 week) interval, but this depends on the measure used (physiological vs. self-report). Overall, these tasks could be appropriate for repeated testing over the course of a short-duration intervention study, but more research is needed, particularly in regard to longer-duration studies.

Sometimes I feel the fear of uncertainty: How intolerance of uncertainty and trait anxiety impact fear acquisition, extinction and the return of fear

It is hypothesized that the ability to discriminate between threat and safety is impaired in individuals with high dispositional negativity, resulting in maladaptive behavior. A large body of research investigated differential learning during fear conditioning and extinction protocols depending on individual differences in intolerance of uncertainty (IU) and trait anxiety (TA), two closely-related dimensions of dispositional negativity, with heterogenous results. These might be due to varying degrees of induced threat/safety uncertainty. Here, we compared two groups with high vs. low IU/TA during periods of low (instructed fear acquisition) and high levels of uncertainty (delayed non-instructed extinction training and reinstatement). Dependent variables comprised subjective (US expectancy, valence, arousal), psychophysiological (skin conductance response, SCR, and startle blink), and neural (fMRI BOLD) measures of threat responding. During fear acquisition, we found strong threat/safety discrimination for both groups. During early extinction (high uncertainty), the low IU/TA group showed an increased physiological response to the safety signal, resulting in a lack of CS discrimination. In contrast, the high IU/TA group showed strong initial threat/safety discrimination in physiology, lacking discriminative learning on startle, and reduced neural activation in regions linked to threat/safety processing throughout extinction training indicating sustained but non-adaptive and rigid responding. Similar neural patterns were found after the reinstatement test. Taken together, we provide evidence that high dispositional negativity, as indicated here by IU and TA, is associated with greater responding to threat cues during the beginning of delayed extinction, and, thus, demonstrates altered learning patterns under changing environments.

Working Memory Performance for Differentially Conditioned Stimuli

Previous work suggests that threat-related stimuli are stored to a greater degree in working memory compared to neutral stimuli. However, most of this research has focused on stimuli with physically salient threat attributes (e.g., angry faces), failing to account for how a "neutral" stimulus that has acquired threat-related associations through differential aversive conditioning influences working memory. The current study examined how differentially conditioned safe (i.e., CS-) and threat (i.e., CS+) stimuli are stored in working memory relative to a novel, non-associated (i.e., N) stimuli. Participants (n = 69) completed a differential fear conditioning task followed by a change detection task consisting of three conditions (CS+, CS-, N) across two loads (small, large). Results revealed individuals successfully learned to distinguishing CS+ from CS- conditions during the differential aversive conditioning task. Our working memory outcomes indicated successful load manipulation effects, but no statistically significant differences in accuracy, response time (RT), or Pashler's K measures of working memory capacity between CS+, CS-, or N conditions. However, we observed significantly reduced RT difference scores for the CS+ compared to CS- condition, indicating greater RT differences between the CS+ and N condition vs. the CS- and N condition. These findings suggest that differentially conditioned stimuli have little impact on behavioral outcomes of working memory compared to novel stimuli that had not been associated with previous safe of aversive outcomes, at least in healthy populations.

Cognitive control is quickly adapted to actual task requirements despite misleading context cues-Evidence from the N2, CRN, and ERN

Cognitive control is flexibly adapted to task requirements in healthy individuals. Medio-frontal negativities in the event-related potential of the electroencephalogram can serve as indicators of cognitive control. With increasing conflict frequency, stimulus-locked control, as indexed by the N2, is increased and response-locked control, as indexed by the correct-related negativity, is reduced. On the behavioral level, this shift is associated with improved conflict resolution as evident in reduced response times and error rates in incompatible trials and a reduced response time congruency effect. Cognitive control adaptation might be implemented through experience-based task sets specifying advantageous processing strategies. Here, we investigated whether the cognitive control task set will be sustained when coupled with a contextual cue, even when the initial task requirements are no longer present. A flanker task with two conflict frequency conditions (25% incompatible and 75% incompatible trials) was presented. In the training phase, the conflict frequency conditions were paired with a distinct context cue (i.e., background color). In the test phase, the previously associated cues were again presented, but conflict frequency was identical in both conditions (50% incompatible trials). Although typical cognitive control adaptation was observed in the training phase on the behavioral and event-related potentials level, this pattern was not sustained in the test phase. Thus, the present study provides further evidence that cognitive control is flexibly adapted to task requirements even in the presence of misleading cues.

Pavlovian occasion setting in human fear and appetitive conditioning: Effects of trait anxiety and trait depression

Contexts and discrete stimuli often hierarchically influence the association between a stimulus and outcome. This phenomenon, called occasion setting, is central to modulation-based Pavlovian learning. We conducted two experiments with humans in fear and appetitive conditioning paradigms, training stimuli in differential conditioning, feature-positive discriminations, and feature-negative discriminations. We also investigated the effects of trait anxiety and trait depression on these forms of learning. Results from both experiments showed that participants were able to successfully learn which stimuli predicted the electric shock and monetary reward outcomes. Additionally, as hypothesized, the stimuli trained as occasion setters had little-to-no effect on simple reinforced or non-reinforced stimuli, suggesting the former were indeed occasion setters. Lastly, in fear conditioning, trait anxiety was associated with increases in fear of occasion setter/conditional stimulus compounds; in appetitive conditioning, trait depression was associated with lower expectations of monetary reward for the trained negative occasion setting compound and transfer of the negative occasion setter to the simple reinforced stimulus. These results suggest that clinically anxious individuals may have enhanced fear of occasion setting compounds, and clinically depressed individuals may expect less reward with compounds involving the negative occasion setter.

Gut microbiome diversity mediates the association between right dorsolateral prefrontal cortex and anxiety level

Despite the fast growing interest in the impact of microbiome-gut-brain interaction on regulating emotional behavior in animals, the underlying mechanisms on how brain anatomy together with gut microbiotic condition jointly influence emotional state in healthy human volunteers remain largely unknown and hypothetic. Here, high-resolution structural magnetic resonance imaging data, stool samples, and psychological assessment results on anxiety level were collected from 61 healthy adults. Voxel-based morphometry was used to assess gray matter (GM) volumes, whereas 16s rRNA gene sequencing was used for bacterial classification. Correlation and mediation analysis were conducted to quantify the relationships among regional GM volume, gut microbiome diversity, and anxiety level. We observed that anxiety level was negatively correlated with GM volume in the right dorsolateral prefrontal cortex and alpha diversity index of gut microbiome. Additional mediation analysis revealed the indirect effect of dorsolateral prefrontal cortex GM volume on anxiety level via gut microbiome diversity. Our findings provide potential evidence of the microbiome-gut-brain interactions and their association with anxiety, highlighting gut microbiome diversity as a mediator that influences the relationship between brain morphometry and anxiety level.

Oxytocin and Fear Memory Extinction: Possible Implications for the Therapy of Fear Disorders?

Several psychiatric conditions such as phobias, generalized anxiety, and post-traumatic stress disorder (PTSD) are characterized by pathological fear and anxiety. The main therapeutic approach used in the management of these disorders is exposure-based therapy, which is conceptually based upon fear extinction with the formation of a new safe memory association, allowing the reduction in behavioral conditioned fear responses. Nevertheless, this approach is only partially resolutive, since many patients have difficulty following the demanding and long process, and relapses are frequently observed over time. One strategy to improve the efficacy of the cognitive therapy is the combination with pharmacological agents. Therefore, the identification of compounds able to strengthen the formation and persistence of the inhibitory associations is a key goal. Recently, growing interest has been aroused by the neuropeptide oxytocin (OXT), which has been shown to have anxiolytic effects. Furthermore, OXT receptors and binding sites have been found in the critical brain structures involved in fear extinction. In this review, the recent literature addressing the complex effects of OXT on fear extinction at preclinical and clinical levels is discussed. These studies suggest that the OXT roles in fear behavior are due to its local effects in several brain regions, most notably, distinct amygdaloid regions.

Trait anxiety predicts amygdalar responses during direct processing of threat-related pictures

Previous studies on the associations between trait anxiety and amygdalar responses to threat stimuli have resulted in mixed findings, possibly due to sample characteristics, specific tasks, and analytical methods. The present functional magnetic resonance imaging (fMRI) study aimed to investigate linear or non-linear associations between trait anxiety and amygdalar responses in a sample of participants with low, medium, and high trait anxiety scores. During scanning, participants were presented with threat-related or neutral pictures and had either to solve an emotional task or an emotional-unrelated distraction task. Results showed that only during the explicit task trait anxiety was associated with right amygdalar responses to threat-related pictures as compared to neutral pictures. The best model was a cubic model with increased amygdala responses for very low and medium trait anxiety values but decreased amygdala activation for very high trait anxiety values. The findings imply a non-linear relation between trait anxiety and amygdala activation depending on task conditions.

Intolerance of uncertainty, and not social anxiety, is associated with compromised extinction of social threat

Extinction-resistant threat is regarded as a central hallmark of pathological anxiety. However, it remains relatively under-studied in social anxiety. Here we sought to determine whether self-reported trait social anxiety is associated with compromised threat extinction learning and retention. We tested this hypothesis within two separate, socially relevant conditioning studies. In the first experiment, a Selective Extinction Through Cognitive Evaluation (SECE) paradigm was used, which included a cognitive component during the extinction phase, while experiment 2 used a traditional threat extinction paradigm. Skin conductance responses and subjective ratings of anxiety (experiment 1 and 2) and expectancy (experiment 2) were collected across both experiments. The findings of both studies demonstrated no effect of social anxiety on extinction learning or retention. Instead, results from experiment 1 indicated that individual differences in Intolerance of Uncertainty (IU) were associated with the ability to use contextual cues to decrease a conditioned response during SECE. However, during extinction retention, high IU predicted greater generalisation across context cues. Findings of experiment 2 revealed that higher IU was associated with impaired extinction learning and retention. The results from both studies suggest that compromised threat extinction is likely to be a characteristic of high levels of IU and not social anxiety.

Trait anxiety is associated with reduced typicality asymmetry in fear generalization

In fear conditioning, training with typical category exemplars has been shown to promote fear generalization to novel exemplars of the same category, whereas training with atypical category exemplars supports limited if any generalization to other category members, amounting to a typicality asymmetry in fear generalization. The present study sought to examine how trait anxiety bears on typicality asymmetry in fear generalization. Participants in one condition were presented with typical exemplars during fear acquisition and atypical exemplars of the same category in the subsequent generalization test (typical condition), whereas in the other group, atypical and typical exemplars were presented during fear acquisition and generalization test, respectively (atypical condition). We observed a typicality asymmetry in fear generalization in self-reported expectancy ratings in low trait anxious individuals only. High trait anxious individuals showed a similar degree of fear generalization in both conditions. The current results help illuminate why some individuals are at risk for exhibiting broad fear generalization after exposure to an aversive event.

Individual differences in fear acquisition: multivariate analyses of different emotional negativity scales, physiological responding, subjective measures, and neural activation

Negative emotionality is a well-established and stable risk factor for affective disorders. Individual differences in negative emotionality have been linked to associative learning processes which can be captured experimentally by computing CS-discrimination values in fear conditioning paradigms. Literature suffers from underpowered samples, suboptimal methods, and an isolated focus on single questionnaires and single outcome measures. First, the specific and shared variance across three commonly employed questionnaires [STAI-T, NEO-FFI-Neuroticism, Intolerance of Uncertainty (IU) Scale] in relation to CS-discrimination during fear-acquisition in multiple analysis units (ratings, skin conductance, startle) is addressed (NStudy1 = 356). A specific significant negative association between STAI-T and CS-discrimination in SCRs and between IU and CS-discrimination in startle responding was identified in multimodal and dimensional analyses, but also between latent factors negative emotionality and fear learning, which capture shared variance across questionnaires/scales and across outcome measures. Second, STAI-T was positively associated with CS-discrimination in a number of brain areas linked to conditioned fear (amygdala, putamen, thalamus), but not to SCRs or ratings (NStudy2 = 113). Importantly, we replicate potential sampling biases between fMRI and behavioral studies regarding anxiety levels. Future studies are needed to target wide sampling distributions for STAI-T and verify whether current findings are generalizable to other samples.

Fear conditioning and extinction in anxious youth, offspring at-risk for anxiety and healthy comparisons: An fMRI study

Dysfunctions in fronto-amygdala circuitry have been linked to anxiety. Questions remain regarding the impact of familial-risk and ongoing anxiety on such circuitry function, especially in youth. Using fMRI fear conditioning and extinction paradigms, we examined these relationships in 10-17 year-olds: 22 youth with an anxiety disorder, 22 healthy youth born to parents with past or current anxiety disorders (at risk), and 32 healthy comparisons. Skin conductance responses and subjective fear ratings were also assessed. During conditioning, healthy comparisons showed differential activation (CS + >CS-) in regions of the fronto-amygdala circuitry. In comparison, the at-risk group showed greater activation to the safety cue (CS - >CS+) in the amygdala and dorsolateral prefrontal cortex. Failure to show differential fear conditioning in the fronto-amygdala circuitry and impairment in extinction learning was specific to anxious youth. These findings expand our ability to track anxiety-related alterations and potential resilience markers to anxiety.

Punishment has a persistent effect on error-related brain activity in highly anxious individuals twenty-four hours after conditioning

The ability to detect and respond to errors, and to subsequently recruit cognitive control to remediate those errors, is critical to successful adaptation in a changing environment. However, there is also evidence that, for anxious individuals, this error signal is enhanced, highlighting affective and motivational influences on error monitoring. These individual differences arise as a function of both genetic influences and learning experiences. In this study, we examined punishment-based modulation of the error-related negativity (ERN) in high and low anxious individuals across two days. Twenty-two low- and 25 high-anxious participants performed a Flanker task in a standard and punishment condition in three phases (Day one: acquisition and extinction 1, Day two: extinction 2). During the acquisition phase, errors in one condition were punished by a loud noise. This was followed by an immediate extinction phase (extinction 1), during which errors were no longer punished, and an identical extinction phase 24 h later (extinction 2). Only high anxious individuals showed increased ERN amplitudes in the punishment compared to the standard condition. This effect was not modulated by phase and was observed across acquisition and both extinction phases, such that anxious individuals appeared not to learn that the threat value of formerly-punished errors had changed in the course of the experiment. These data suggest that environmental factors (i.e., punishment) can have a persistent effect on the magnitude of the ERN, particularly for anxious individuals. This may point to a pathogenic mechanism linking learning experiences with the development of overactive error-monitoring in anxiety.

The Future of Contextual Fear Learning for PTSD Research: A Methodological Review of Neuroimaging Studies

There has been a great deal of recent interest in human models of contextual fear learning, particularly due to the use of such paradigms for investigating neural mechanisms related to the etiology of posttraumatic stress disorder. However, the construct of "context" in fear conditioning research is broad, and the operational definitions and methods used to investigate contextual fear learning in humans are wide ranging and lack specificity, making it difficult to interpret findings about neural activity. Here we will review neuroimaging studies of contextual fear acquisition in humans. We will discuss the methodology associated with four broad categories of how contextual fear learning is manipulated in imaging studies (colored backgrounds, static picture backgrounds, virtual reality, and configural stimuli) and highlight findings for the primary neural circuitry involved in each paradigm. Additionally, we will offer methodological recommendations for human studies of contextual fear acquisition, including using stimuli that distinguish configural learning from discrete cue associations and clarifying how context is experimentally operationalized.

Cortico-limbic connectivity changes following fear extinction and relationships with trait anxiety

Fear extinction is a powerful model of adaptive and anxiety-related maladaptive fear inhibition. This learning process is dependent upon plastic interactions between the amygdala, the anterior midcingulate cortex (aMCC), the hippocampus, and the ventromedial prefrontal cortex (vmPFC). With regard to the amygdala, the basolateral (BLA) and centromedial amygdala (CMA) serve unique roles in fear extinction. In a large sample (N = 91), the current study examined pre- to post-extinction changes in resting state functional connectivity (RSFC) of fear inhibition and expression pathways. We also examined how trait anxiety and extinction performance were associated with extinction-related changes within these neural pathways. We found stronger pre- to post-extinction RSFC in pathways known to play a role in the down-regulation of fear responses (BLA-hippocampus, aMCC-hippocampus, CMA-hippocampus, CMA-aMCC). We also found that trait anxiety was associated with strengthening of a BLA–aMCC circuit supporting fear expression following extinction learning. Furthermore, we found that physiological indices of poorer extinction learning were linked to weaker pre- to post-extinction RSFC of a BLA–hippocampus pathway important for fear extinction consolidation. Our results highlight the network changes that occur during extinction, the separable role of CMA and BLA-based circuitry and a key pathway linked to risk for anxiety pathology.

Neural measures associated with configural threat acquisition

Contextual threat learning reflects two often competing processes: configural and elemental learning. Configural threat learning is a hippocampal-dependent process of forming a conjunctive representation of a context through binding of several multi-modal elements. In contrast, elemental threat-learning is governed by the amygdala and involves forming associative relationships between individual features within the context. Contextual learning tasks in humans however, rarely probe if a learned fear response is truly due to configural learning vs. simple elemental associations. The aim of the current study was to probe both constructs separately to enable a more refined interpretation of configural vs. elemental threat learning performance and mediating circuits. Subjects (n = 25) performed both a novel feature-identical contextual threat conditioning task and a discrete cue threat acquisition task while undergoing functional magnetic resonance imaging. Results demonstrated increased hippocampus activity for the threat configuration compared to the safe configuration. This pattern was not observed in the amygdala. In contrast, elemental threat learning was associated with increased amygdala, but not hippocampus activity. Whole-brain analyses revealed that both configural and elemental threat acquisition share neural circuitry related to fear expression. These results provide support for the importance of the hippocampus specifically in configural threat acquisition and fear expression.

I don't know where to look: the impact of intolerance of uncertainty on saccades towards non-predictive emotional face distractors

Attentional bias to uncertain threat is associated with anxiety disorders. Here we examine the extent to which emotional face distractors (happy, angry and neutral) and individual differences in intolerance of uncertainty (IU), impact saccades in two versions of the "follow a cross" task. In both versions of the follow the cross task, the probability of receiving an emotional face distractor was 66.7%. To increase perceived uncertainty regarding the location of the face distractors, in one of the tasks additional non-predictive cues were presented before the onset of the face distractors and target. We did not find IU to impact saccades towards non-cued face distractors. However, we found IU, over Trait Anxiety, to impact saccades towards non-predictive cueing of face distractors. Under these conditions, IU individuals' eyes were pulled towards angry face distractors and away from happy face distractors overall, and the speed of this deviation of the eyes was determined by the combination of the cue and emotion of the face. Overall, these results suggest a specific role of IU on attentional bias to threat during uncertainty. These findings highlight the potential of intolerance of uncertainty-based mechanisms to help understand anxiety disorder pathology and inform potential treatment targets.

Default Mode Network Subsystems are Differentially Disrupted in Posttraumatic Stress Disorder

BACKGROUND

Posttraumatic stress disorder (PTSD) is a psychiatric disorder characterized by debilitating re-experiencing, avoidance, and hyperarousal symptoms following trauma exposure. Recent evidence suggests that individuals with PTSD show disrupted functional connectivity in the default mode network, an intrinsic network that consists of a midline core, a medial temporal lobe (MTL) subsystem, and a dorsomedial prefrontal cortex (dMPFC) subsystem. The present study examined whether functional connectivity in these subsystems is differentially disrupted in PTSD.

METHODS

Sixty-nine returning war Veterans with PTSD and 44 trauma-exposed Veterans without PTSD underwent resting state functional MRI (rs-fMRI). To examine functional connectivity, seeds were placed in the core hubs of the default mode network, namely the posterior cingulate cortex (PCC) and anterior medial PFC (aMPFC), and in each subsystem.

RESULTS

Compared to controls, individuals with PTSD had reduced functional connectivity between the PCC and the hippocampus, a region of the MTL subsystem. Groups did not differ in connectivity between the PCC and dMPFC subsystem or between the aMPFC and any region within either subsystem. In the PTSD group, connectivity between the PCC and hippocampus was negatively associated with avoidance/numbing symptoms. Examination of the MTL and dMPFC subsystems revealed reduced anticorrelation between the ventromedial PFC (vMPFC) seed of the MTL subsystem and the dorsal anterior cingulate cortex in the PTSD group.

CONCLUSIONS

Our results suggest that selective alterations in functional connectivity in the MTL subsystem of the default mode network in PTSD may be an important factor in PTSD pathology and symptomatology.

Don't fear 'fear conditioning': Methodological considerations for the design and analysis of studies on human fear acquisition, extinction, and return of fear

The so-called 'replicability crisis' has sparked methodological discussions in many areas of science in general, and in psychology in particular. This has led to recent endeavours to promote the transparency, rigour, and ultimately, replicability of research. Originating from this zeitgeist, the challenge to discuss critical issues on terminology, design, methods, and analysis considerations in fear conditioning research is taken up by this work, which involved representatives from fourteen of the major human fear conditioning laboratories in Europe. This compendium is intended to provide a basis for the development of a common procedural and terminology framework for the field of human fear conditioning. Whenever possible, we give general recommendations. When this is not feasible, we provide evidence-based guidance for methodological decisions on study design, outcome measures, and analyses. Importantly, this work is also intended to raise awareness and initiate discussions on crucial questions with respect to data collection, processing, statistical analyses, the impact of subtle procedural changes, and data reporting specifically tailored to the research on fear conditioning.

Brain activation during fear extinction predicts exposure success

BACKGROUND

Exposure therapy, a gold-standard treatment for anxiety disorders, is assumed to work via extinction learning, but this has never been tested. Anxious individuals demonstrate extinction learning deficits, likely related to less ventromedial prefrontal cortex (vmPFC) and more amygdala activation, but the relationship between these deficits and exposure outcome is unknown. We tested whether anxious individuals who demonstrate better extinction learning report greater anxiety reduction following brief exposure.

METHODS

Twenty-four adults with public speaking anxiety completed (1) functional magnetic resonance imaging during a conditioning paradigm, (2) a speech exposure session, and (3) anxiety questionnaires before and two weeks postexposure. Extinction learning was assessed by comparing ratings to a conditioned stimulus (neutral image) that was previously paired with an aversive noise against a stimulus that had never been paired. Robust regression analyses examined whether brain activation during extinction learning predicted anxiety reduction two weeks postexposure.

RESULTS

On average, the conditioning paradigm resulted in acquisition and extinction effects on stimulus ratings, and the exposure session resulted in reduced anxiety two weeks post-exposure. Consistent with our hypothesis, individuals with better extinction learning (less negative stimulus ratings), greater activation in vmPFC, and less activation in amygdala, insula, and periaqueductal gray reported greater anxiety reduction two weeks postexposure.

CONCLUSION

To our knowledge, this is the first time that the theoretical link between extinction learning and exposure outcome has been demonstrated. Future work should examine whether extinction learning can be used as a prognostic test to determine who is most likely to benefit from exposure therapy.

Classical conditioning in borderline personality disorder: an fMRI study

Previous research suggests disturbed emotional learning and memory in borderline personality disorder (BPD). Studies investigating the neural correlates of aversive differential delay conditioning in BPD are currently lacking. We aimed to investigate acquisition, within-session extinction, between-session extinction recall, and reacquisition. We expected increased activation in the insula, amygdala, and anterior cingulate, and decreased prefrontal activation in BPD patients. During functional magnetic resonance imaging, 27 medication-free female BPD patients and 26 female healthy controls (HC) performed a differential delay aversive conditioning paradigm. An electric shock served as unconditioned stimulus, two neutral pictures as conditioned stimuli (CS+/CS-). Dependent variables were blood-oxygen-level-dependent response, skin conductance response (SCR), and subjective ratings (valence, arousal). No significant between-group differences in brain activation were found [all p(FDR) > 0.05]. Within-group comparisons for CS+unpaired > CS- revealed increased insula activity in BPD patients but not in HC during early acquisition; during late acquisition, both groups recruited fronto-parietal areas [p(FDR) < 0.05]. During extinction, BPD patients rated both CS+ and CS- as significantly more arousing and aversive than HC and activated the amygdala in response to CS+. In contrast, HC showed increased prefrontal activity in response to CS+ > CS during extinction. During extinction recall, there was a trend for stronger SCR to CS+ > CS in BPD patients. Amygdala habituation to CS+paired (CS+ in temporal contingency with the aversive event) during acquisition was found in HC but not in patients. Our findings suggest altered temporal response patterns in terms of increased vigilance already during early acquisition and delayed extinction processes in individuals with BPD.

What Is Going On Around Here? Intolerance of Uncertainty Predicts Threat Generalization

Attending to stimuli that share perceptual similarity to learned threats is an adaptive strategy. However, prolonged threat generalization to cues signalling safety is considered a core feature of pathological anxiety. One potential factor that may sustain over-generalization is sensitivity to future threat uncertainty. To assess the extent to which Intolerance of Uncertainty (IU) predicts threat generalization, we recorded skin conductance in 54 healthy participants during an associative learning paradigm, where threat and safety cues varied in perceptual similarity. Lower IU was associated with stronger discrimination between threat and safety cues during acquisition and extinction. Higher IU, however, was associated with generalized responding to threat and safety cues during acquisition, and delayed discrimination between threat and safety cues during extinction. These results were specific to IU, over and above other measures of anxious disposition. These findings highlight: (1) a critical role of uncertainty-based mechanisms in threat generalization, and (2) IU as a potential risk factor for anxiety disorder development.

Nothing is safe: Intolerance of uncertainty is associated with compromised fear extinction learning

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We tested how fear extinction learning varied with Intolerance of Uncertainty (IU).

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High IU predicted threat generalization during early extinction.

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High IU predicted continued responding to learned threat during late extinction.

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Future threat uncertainty may maintain learned fear in the anxiety disorders.

Extinction-resistant fear is considered to be a central feature of pathological anxiety. Here we sought to determine if individual differences in Intolerance of Uncertainty (IU), a potential risk factor for anxiety disorders, underlies compromised fear extinction. We tested this hypothesis by recording electrodermal activity in 38 healthy participants during fear acquisition and extinction. We assessed the temporality of fear extinction, by examining early and late extinction learning. During early extinction, low IU was associated with larger skin conductance responses to learned threat vs. safety cues, whereas high IU was associated with skin conductance responding to both threat and safety cues, but no cue discrimination. During late extinction, low IU showed no difference in skin conductance between learned threat and safety cues, whilst high IU predicted continued fear expression to learned threat, indexed by larger skin conductance to threat vs. safety cues. These findings suggest a critical role of uncertainty-based mechanisms in the maintenance of learned fear.

Uncontrollable and unpredictable stress interacts with subclinical depression and anxiety scores in determining anxiety response

According to learned helplessness theory, uncontrollable stress is assumed to be a critical etiological factor in the pathogenesis of depression. In contrast, unpredictability of stressors is assumed to facilitate the development of sustained anxiety. Despite the frequent co-morbidity of depression and anxiety disorders, these two factors have rarely been studied simultaneously in humans. Therefore, we investigated whether there are interaction effects of uncontrollability and unpredictability on anxiety response in healthy participants. Seventy-nine healthy participants performed a visual dot probe task with emotional faces, while receiving mild electrical shocks in four different conditions (2 × 2 factorial design). In (un)controllable conditions, participants were (not) able to attenuate shock intensity. In (un)predictable conditions, participants were (not) able to anticipate shock occurrence. Before the experiment, participants' subclinical depression and anxiety scores were measured using the Beck Depression and Anxiety Inventories (BDI/BAI). During the experiment, continuous skin conductance and self-reported state anxiety were assessed and attentional biases towards angry faces were calculated. As expected, participants showed greater anxiety in uncontrollable compared to controllable and in unpredictable compared to predictable conditions. Additionally, anxiety decreased within the test sessions in participants with low BDI/BAI scores but not in participants with higher BDI/BAI scores. Most importantly, controllability and predictability interacted with each other and with BDI/BAI scores with regard to anxiety. Our results provide evidence that uncontrollability and unpredictability of stressors not only have separate but also interaction effects on several anxiety measures in susceptible individuals and may provide insights into the psychological mechanisms underlying a depressive/anxiety co-morbidity.

Intolerance of uncertainty predicts fear extinction in amygdala-ventromedial prefrontal cortical circuitry

BACKGROUND

Coordination of activity between the amygdala and ventromedial prefrontal cortex (vmPFC) is important for fear-extinction learning. Aberrant recruitment of this circuitry is associated with anxiety disorders. Here, we sought to determine if individual differences in future threat uncertainty sensitivity, a potential risk factor for anxiety disorders, underly compromised recruitment of fear extinction circuitry. Twenty-two healthy subjects completed a cued fear conditioning task with acquisition and extinction phases. During the task, pupil dilation, skin conductance response, and functional magnetic resonance imaging were acquired. We assessed the temporality of fear extinction learning by splitting the extinction phase into early and late extinction. Threat uncertainty sensitivity was measured using self-reported intolerance of uncertainty (IU).

RESULTS

During early extinction learning, we found low IU scores to be associated with larger skin conductance responses and right amygdala activity to learned threat vs. safety cues, whereas high IU scores were associated with no skin conductance discrimination and greater activity within the right amygdala to previously learned safety cues. In late extinction learning, low IU scores were associated with successful inhibition of previously learned threat, reflected in comparable skin conductance response and right amgydala activity to learned threat vs. safety cues, whilst high IU scores were associated with continued fear expression to learned threat, indexed by larger skin conductance and amygdala activity to threat vs. safety cues. In addition, high IU scores were associated with greater vmPFC activity to threat vs. safety cues in late extinction. Similar patterns of IU and extinction learning were found for pupil dilation. The results were specific for IU and did not generalize to self-reported trait anxiety.

CONCLUSIONS

Overall, the neural and psychophysiological patterns observed here suggest high IU individuals to disproportionately generalize threat during times of uncertainty, which subsequently compromises fear extinction learning. More broadly, these findings highlight the potential of intolerance of uncertainty-based mechanisms to help understand pathological fear in anxiety disorders and inform potential treatment targets.

Neuroimaging and Anxiety: the Neural Substrates of Pathological and Non-pathological Anxiety

Advances in the use of noninvasive neuroimaging to study the neural correlates of pathological and non-pathological anxiety have shone new light on the underlying neural bases for both the development and manifestation of anxiety. This review summarizes the most commonly observed neural substrates of the phenotype of anxiety. We focus on the neuroimaging paradigms that have shown promise in exposing this relevant brain circuitry. In this way, we offer a broad overview of how anxiety is studied in the neuroimaging laboratory and the key findings that offer promise for future research and a clearer understanding of anxiety.

Brain morphology correlates of interindividual differences in conditioned fear acquisition and extinction learning

The neural circuits underlying fear learning have been intensively investigated in pavlovian fear conditioning paradigms across species. These studies established a predominant role for the amygdala in fear acquisition, while the ventromedial prefrontal cortex (vmPFC) has been shown to be important in the extinction of conditioned fear. However, studies on morphological correlates of fear learning could not consistently confirm an association with these structures. The objective of the present study was to investigate if interindividual differences in morphology of the amygdala and the vmPFC are related to differences in fear acquisition and extinction learning in humans. We performed structural magnetic resonance imaging in 68 healthy participants who underwent a differential cued fear conditioning paradigm. Volumes of subcortical structures as well as cortical thickness were computed by the semi-automated segmentation software Freesurfer. Stronger acquisition of fear as indexed by skin conductance responses was associated with larger right amygdala volume, while the degree of extinction learning was positively correlated with cortical thickness of the right vmPFC. Both findings could be conceptually replicated in an independent sample of 53 subjects. The data complement our understanding of the role of human brain morphology in the mechanisms of the acquisition and extinction of conditioned fear.

From Pavlov to PTSD: the extinction of conditioned fear in rodents, humans, and anxiety disorders

Nearly 100 years ago, Ivan Pavlov demonstrated that dogs could learn to use a neutral cue to predict a biologically relevant event: after repeated predictive pairings, Pavlov's dogs were conditioned to anticipate food at the sound of a bell, which caused them to salivate. Like sustenance, danger is biologically relevant, and neutral cues can take on great salience when they predict a threat to survival. In anxiety disorders such as posttraumatic stress disorder (PTSD), this type of conditioned fear fails to extinguish, and reminders of traumatic events can cause pathological conditioned fear responses for decades after danger has passed. In this review, we use fear conditioning and extinction studies to draw a direct line from Pavlov to PTSD and other anxiety disorders. We explain how rodent studies have informed neuroimaging studies of healthy humans and humans with PTSD. We describe several genes that have been linked to both PTSD and fear conditioning and extinction and explain how abnormalities in fear conditioning or extinction may reflect a general biomarker of anxiety disorders. Finally, we explore drug and neuromodulation treatments that may enhance therapeutic extinction in anxiety disorders.

The conditioning and extinction of fear in youths: what's sex got to do with it?

Adult work shows differences in emotional processing influenced by sexes of both the viewer and expresser of facial expressions. We investigated this in 120 healthy youths (57 boys; 10-17 years old) randomly assigned to fear conditioning and extinction tasks using either neutral male or female faces as the conditioned threat and safety cues, and a fearful face paired with a shrieking scream as the unconditioned stimulus. Fear ratings and skin conductance responses (SCRs) were assessed. Male faces triggered increased fear ratings in all participants during conditioning and extinction. Greater differential SCRs were observed in boys viewing male faces and in girls viewing female faces during conditioning. During extinction, differential SCR findings remained significant in boys viewing male faces. Our findings demonstrate how sex of participant and sex of target interact to shape fear responses in youths, and how the type of measure may lead to distinct profiles of fear responses.

Oxytocin's role in anxiety: a critical appraisal

A growing literature suggests that the oxytocin (OT) system may play a role in human anxiety states, anxiety-related traits, and moreover, that this system may be a target for the development of novel anxiolytic treatments. However, studies of OT's acute and chronic effects on various aspects of anxiety have produced mixed results. In this forward-looking review, we discuss the myriad phenomena to which the term "anxiety" is applied in the OT literature and the problem this presents developing a coherent picture of OT's role in anxiety. We then survey several different fields of research that support the role of the OT system in human anxiety, including evolutionary perspectives, translational and neuroimaging research, genetic studies, and clinical trials of intranasal OT. As an outgrowth of this data, we propose a "bowtie" model of OT's role at the interface of social attachment and anxiety. We next direct attention to understudied brain regions and neural circuits which may be important to study in OT experiments in humans anxiety disorders. Finally, we conclude by proposing questions and priorities for studying both the clinical potential of OT in anxiety, as well as mechanisms that may underlie this potential. Crucially, these priorities include targeted proof-of-concept clinical trials of IN OT in certain anxiety disorders, including investigations of individual moderators of OT's anxiolytic effects (i.e. sex, genetic factors, and early experience). This article is part of a Special Issue entitled Oxytocin and Social Behav.

Avoidant symptoms in PTSD predict fear circuit activation during multimodal fear extinction

Convergent evidence suggests that individuals with posttraumatic stress disorder (PTSD) exhibit exaggerated avoidance behaviors as well as abnormalities in Pavlonian fear conditioning. However, the link between the two features of this disorder is not well understood. In order to probe the brain basis of aberrant extinction learning in PTSD, we administered a multimodal classical fear conditioning/extinction paradigm that incorporated affectively relevant information from two sensory channels (visual and tactile) while participants underwent fMRI scanning. The sample consisted of fifteen OEF/OIF veterans with PTSD. In response to conditioned cues and contextual information, greater avoidance symptomatology was associated with greater activation in amygdala, hippocampus, vmPFC, dmPFC, and insula, during both fear acquisition and fear extinction. Heightened responses to previously conditioned stimuli in individuals with more severe PTSD could indicate a deficiency in safety learning, consistent with PTSD symptomatology. The close link between avoidance symptoms and fear circuit activation suggests that this symptom cluster may be a key component of fear extinction deficits in PTSD and/or may be particularly amenable to change through extinction-based therapies.

Sex differences in the persistence of the amygdala response to negative material

Previous studies have indicated that men and women have different amygdala responses to novel (vs familiar) and valenced (positive vs negative) material. It is not known, however, whether these affective sex differences are related. In this study, we tested whether women have more persistent amygdala responses to familiar, negative material than men do. During fMRI, male and female participants viewed evocative images that varied in novelty and valence. Women and men showed equivalent responses to novel negative material, but women showed a sustained amygdala response to familiar negative material relative to men, indicating that women's amygdala responses were more persistent over multiple repetitions of negative material. Individuals with more persistent amygdala responses also reported greater levels of negative effect. These findings have implications for sex differences in the incidence of affective disorders.

A risk variant for alcoholism in the NMDA receptor affects amygdala activity during fear conditioning in humans

People at high risk for alcoholism show deficits in aversive learning, as indicated by impaired electrodermal responses during fear conditioning, a basic form of associative learning that depends on the amygdala. A positive family history of alcohol dependence has also been related to decreased amygdala responses during emotional processing. In the present study we report reduced amygdala activity during the acquisition of conditioned fear in healthy carriers of a risk variant for alcoholism (rs2072450) in the NR2A subunit-containing N-methyl-d-aspartate (NMDA)-receptor. These results indicate that rs2072450 might confer risk for alcohol dependence through deficient fear acquisition indexed by a diminished amygdala response during aversive learning, and provide a neural basis for a weak behavioral inhibition previously documented in individuals at high risk for alcohol dependence. Carriers of the risk variant additionally exhibit dampened insula activation, a finding that further strengthens our data, given the importance of this brain region in fear conditioning.

Enhanced discrimination between threatening and safe contexts in high-anxious individuals

Trait anxiety, a stable personality trait associated with increased fear responses to threat, is regarded as a risk factor for the development and maintenance of anxiety disorders. Although the effect of trait anxiety has been examined with regard to explicit threat cues, little is known about the effect of trait anxiety on contextual threat learning. To assess this issue, extreme groups of low and high trait anxiety underwent a contextual fear conditioning protocol using virtual reality. Two virtual office rooms served as the conditioned contexts. One virtual office room (CXT+) was paired with unpredictable electrical stimuli. In the other virtual office room, no electrical stimuli were delivered (CXT-). High-anxious participants tended to show faster acquisition of startle potentiation in the CXT+ versus the CXT- than low-anxious participants. This enhanced contextual fear learning might function as a risk factor for anxiety disorders that are characterized by sustained anxiety.

A phenotype of early infancy predicts reactivity of the amygdala in male adults

One of the central questions that has occupied those disciplines concerned with human development is the nature of continuities and discontinuities from birth to maturity. The amygdala has a central role in the processing of novelty and emotion in the brain. Although there is considerable variability among individuals in the reactivity of the amygdala to novel and emotional stimuli, the origin of these individual differences is not well understood. Four-month old infants called high reactive (HR) demonstrate a distinctive pattern of vigorous motor activity and crying to specific unfamiliar visual, auditory and olfactory stimuli in the laboratory. Low-reactive infants show the complementary pattern. Here, we demonstrate that the HR infant phenotype predicts greater amygdalar reactivity to novel faces almost two decades later in adults. A prediction of individual differences in brain function at maturity can be made on the basis of a single behavioral assessment made in the laboratory at 4 months of age. This is the earliest known human behavioral phenotype that predicts individual differences in patterns of neural activity at maturity. These temperamental differences rooted in infancy may be relevant to understanding individual differences in vulnerability and resilience to clinical psychiatric disorder. Males who were HR infants showed particularly high levels of reactivity to novel faces in the amygdala that distinguished them as adults from all other sex/temperament subgroups, suggesting that their amygdala is particularly prone to engagement by unfamiliar faces. These findings underline the importance of taking gender into account when studying the developmental neurobiology of human temperament and anxiety disorders. The genetic study of behavioral and biologic intermediate phenotypes (or 'endophenotypes') indexing anxiety-proneness offers an important alternative to examining phenotypes based on clinically defined disorder. As the HR phenotype is characterized by specific patterns of reactivity to elemental visual, olfactory and auditory stimuli, well before complex social behaviors such as shyness or fearful interaction with strangers can be observed, it may be closer to underlying neurobiological mechanisms than behavioral profiles observed later in life. This possibility, together with the fact that environmental factors have less time to impact the 4-month phenotype, suggests that this temperamental profile may be a fruitful target for high-risk genetic studies.

Revise the revised? New dimensions of the neuroanatomical hypothesis of panic disorder

In 2000, Gorman et al. published a widely acknowledged revised version of their 1989 neuroanatomical hypothesis of panic disorder (PD). Herein, a 'fear network' was suggested to mediate fear- and anxiety-related responses: panic attacks result from a dysfunctional coordination of 'upstream' (cortical) and 'downstream' (brainstem) sensory information leading to heightened amygdala activity with subsequent behavioral, autonomic and neuroendocrine activation. Given the emergence of novel imaging methods such as fMRI and the publication of numerous neuroimaging studies regarding PD since 2000, a comprehensive literature search was performed regarding structural (CT, MRI), metabolic (PET, SPECT, MRS) and functional (fMRI, NIRS, EEG) studies on PD, which will be reviewed and critically discussed in relation to the neuroanatomical hypothesis of PD. Recent findings support structural and functional alterations in limbic and cortical structures in PD. Novel insights regarding structural volume increase or reduction, hyper- or hypoactivity, laterality and task-specificity of neural activation patterns emerged. The assumption of a generally hyperactive amygdala in PD seems to apply more to state than trait characteristics of PD, and involvement of further areas in the fear circuit, such as anterior cingulate and insula, is suggested. Furthermore, genetic risk variants have been proposed to partly drive fear network activity. Thus, the present state of knowledge generally supports limbic and cortical prefrontal involvement as originally proposed in the neuroanatomical hypothesis. Some modifications might be suggested regarding a potential extension of the fear circuit, genetic factors shaping neural network activity and neuroanatomically informed clinical subtypes of PD potentially guiding future treatment decisions.

Worry as a predictor of fear acquisition in a nonclinical sample

People seem to differ in their conditionability, that is, the ease by which fear associations (neutral stimulus-unconditioned stimulus [CS-US] contingencies) are learned. Recently, the level of trait worry has been proposed as a predictor of heightened conditionability. The current research aimed to (a) further investigate this influence of individual differences in trait worry on the strength of fear acquisition, (b) explore whether this association could be explained by trait anxiety, and (c) assess possible underlying mechanisms of this relationship. In a nonclinical sample, the amount of trait worry predicted heightened conditionability in a differential fear conditioning paradigm, both in fear ratings and in performance on a secondary probe reaction time task. A significant correlation was observed for general conditioning to the CS+ and also for differential conditioning (taking into account excitatory and inhibitory responding) in Experiment 1. These associations could not be fully explained by trait anxiety. US inflation and strengthening of the CS-US contingency through rehearsal are discussed as possible underlying mechanisms.

Medial prefrontal cortex activity during the extinction of conditioned fear: an investigation using functional near-infrared spectroscopy

The majority of fear conditioning studies in humans have focused on fear acquisition rather than fear extinction. For this reason only a few functional imaging studies on fear extinction are available. A large number of animal studies indicate the medial prefrontal cortex (mPFC) as neuronal substrate of extinction. We therefore determined mPFC contribution during extinction learning after a discriminative fear conditioning in 34 healthy human subjects by using functional near-infrared spectroscopy. During the extinction training, a previously conditioned neutral face (conditioned stimulus, CS+) no longer predicted an aversive scream (unconditioned stimulus, UCS). Considering differential valence and arousal ratings as well as skin conductance responses during the acquisition phase, we found a CS+ related increase in oxygenated haemoglobin concentration changes within the mPFC over the time course of extinction. Late CS+ trials further revealed higher activation than CS- trials in a cluster of probe set channels covering the mPFC. These results are in line with previous findings on extinction and further emphasize the mPFC as significant for associative learning processes. During extinction, the diminished fear association between a former CS+ and a UCS is inversely correlated with mPFC activity--a process presumably dysfunctional in anxiety disorders.

Individual differences in emotionality and peri-traumatic processing

BACKGROUND AND OBJECTIVES

Recent cognitive models propose that intrusive trauma memories arise and persist because high levels of emotional arousal triggered by the trauma disrupt conceptual processing of elements of the event, while enhancing sensory/perceptual processing. A trauma film analogue design was used to investigate if the predicted facilitating effects on intrusions from inhibiting conceptual processing and predicted attenuating effects on intrusions from inhibiting sensory processing are moderated by individual differences in emotionality.

METHODS

One hundred and five non-clinical participants viewed a traumatic film while undertaking a conceptual interference task, a sensory interference task, or no interference task. Participants recorded the frequency and intensity of intrusions over the following week.

RESULTS

There was no facilitating effect for the conceptual interference task compared to no interference task. A significant attenuation of the frequency of intrusions was evident for those undertaking sensory interference (ŋ(2) = .04). This effect, however, was only present for those with high trait anxiety (d = .82) and not for those with low trait anxiety (d = .08). Relative to high trait anxious controls, high anxious participants who undertook sensory interference also reported lower intensity of intrusions (d = .66).

CONCLUSIONS

This is the first trauma film analogue study to show that the attenuating effect of concurrent sensory/perceptual processing on the frequency and intensity of subsequent intrusions is evident only for people with high trait anxiety. The results have implications for conceptual models of intrusion development and for their application to the prevention of post traumatic distress.

Neuroticism modifies psychophysiological responses to fearful films

BACKGROUND

Neuroticism is a personality component frequently found in anxious and depressive psychiatric disorders. The influence of neuroticism on negative emotions could be due to its action on stimuli related to fear and sadness, but this remains debated. Our goal was thus to better understand the impact of neuroticism through verbal and physiological assessment in response to stimuli inducing fear and sadness as compared to another negative emotion (disgust).

METHODS

Fifteen low neurotic and 18 high neurotic subjects were assessed on an emotional attending task by using film excerpts inducing fear, disgust, and sadness. We recorded skin conductance response (SCR) and corrugator muscle activity (frowning) as indices of emotional expression.

RESULTS

SCR was larger in high neurotic subjects than in low neurotics for fear relative to sadness and disgust. Moreover, corrugator activity and SCR were larger in high than in low neurotic subjects when fear was induced.

CONCLUSION

After decades of evidence that individuals higher in neuroticism experience more intense emotional reactions to even minor stressors, our results indicate that they show greater SCR and expressive reactivity specifically to stimuli evoking fear rather than to those inducing sadness or disgust. Fear processing seems mainly under the influence of neuroticism. This modulation of autonomic activity by neurotics in response to threat/fear may explain their increased vulnerability to anxious psychopathologies such as PTSD (post traumatic stress disorder).

Structural evidence for involvement of a left amygdala-orbitofrontal network in subclinical anxiety

Functional neuroimaging implicates hyperactivity of amygdala-orbitofrontal circuitry as a common neurobiological mechanism underlying the development of anxiety. Less is known about anxiety-related structural differences in this network. In this study, a sample of healthy adults with no history of anxiety disorders completed a 3T MRI scan and self-report mood inventories. Post-processing quantitative MRI image analysis included segmentation and volume estimation of subcortical structures, which were regressed on anxiety inventory scores, with depression scores used to establish discriminant validity. We then used a quantitative vertex-based post-processing method to correlate (1) anxiety scores and (2) left amygdala volumes with cortical thickness across the whole cortical mantle. Left amygdala volumes predicted anxiety, with decreased amygdala volume associated with higher anxiety on both state and trait anxiety measures. A negative correlation between left amygdala volume and cortical thickness overlapped with a positive correlation between anxiety and cortical thickness in left lateral orbitofrontal cortex. These results suggest a structural anxiety network that corresponds with a large body of evidence from functional neuroimaging. Such findings raise the possibility that structural abnormalities may result in a greater vulnerability to anxiety or conversely that elevated anxiety symptoms may result in focal structural changes.

Structural correlates of trait anxiety: reduced thickness in medial orbitofrontal cortex accompanied by volume increase in nucleus accumbens

Structural deficiencies within the medial prefrontal cortex have been shown in anxiety-related psychiatric disorders such as panic disorder, post traumatic stress disorder and obsessive compulsive disorder. In healthy subjects, trait anxiety as the individual's disposition to experience anxiety-relevant feelings or thoughts has been shown to be a risk factor for psychiatric disorders. We aimed at exploring the structural correlates of trait anxiety in normal participants. We acquired high-resolution MRI scans from 34 subjects and used FreeSurfer to obtain a measure of cortical thickness. We correlated cortical thickness with self-rated trait anxiety in a whole brain analysis. Automatic subcortical segmentations of the FreeSurfer pipeline were used to relate nucleus accumbens (NAcc) and amygdala volume to trait anxiety. Trait anxiety was negatively correlated with cortical thickness in the right medial orbitofrontal cortex (mOFC) and positively correlated with the bilateral volume of NAcc. Cortical thickness measures extracted from mOFC were negatively associated with the volume of left NAcc. Since, like in anxiety-related psychiatric disorders, in the healthy sample studied here, trait anxiety was associated with a reduction of cortical thickness in mOFC we suggest that this thinning is a structural precondition rather than a consequence of psychiatric illnesses.

Punishment has a lasting impact on error-related brain activity

The current study examined whether punishment has direct and lasting effects on error-related brain activity, and whether this effect is larger with increasing trait anxiety. Participants were told that errors on a flanker task would be punished in some blocks but not others. Punishment was applied following 50% of errors in punished blocks during the first half of the experiment (i.e., acquisition), but never in the second half (i.e., extinction). The ERN was enhanced in the punished blocks in both experimental phases--this enhancement remained stable throughout the extinction phase. More anxious individuals were characterized by larger punishment-related modulations in the ERN. The study reveals evidence for lasting, punishment-based modulations of the ERN that increase with anxiety. These data suggest avenues for research to examine more specific learning-related mechanisms that link anxiety to overactive error monitoring.