Ventromedial prefrontal cortex reactivity is altered in generalized anxiety disorder during fear generalization

Noninvasive ventromedial prefrontal cortex stimulation can enhance and impair affective learning from rewarding and threatening stimuli

The ventromedial prefrontal cortex (vmPFC) is known as a central hub involved in affective learning from appetitive/aversive stimuli, as demonstrated in numerous studies examining affective stimuli. We used vmPFC-stimulation to test whether the concept of enhanced affective learning applies to enhanced inhibition of risky decisions and overgeneralized fear. Therefore, we modulated vmPFC-excitability noninvasively via transcranial direct current stimulation (tDCS) using excitatory, inhibitory, and sham stimulation. We re-analysed previously published behavioural and magnetoencephalography data trial-wise to test whether improved learning is the mechanism underlying modulated gambling/fear generalization. Following excitatory vs. sham stimulation, participants gambled more rationally and got better at discriminating safe from threatening stimuli, as indicated by interactions between tDCS and gambling/fear stimuli. Three-way interactions with trial-number suggest that these improvements developed during the experiment. In contrast, in the inhibitory group, these abilities deteriorated over the paradigm. The neural data dovetailed with behavioural effects, in that neural correlates of modulated learning after stimulation also developed over time. Our results indicate an association between vmPFC activity and the ability to learn from appetitive/aversive stimuli. As impaired affective learning is a driving mechanism in mental disorders, these findings identify excitatory vmPFC-tDCS as a potential treatment, especially in combination with psychotherapy.

Nucleus reuniens: Modulating emotional overgeneralization in peri-adolescents with anxiety

BACKGROUND

Anxiety affects 4.4-million children in the USA with an onset between childhood and adolescence, a period marked by neural changes that impact emotions and memory. Negative overgeneralization - or responding similarly to innocuous events that share features with past aversive experiences - is common in anxiety but remains mechanistically underspecified. The nucleus reuniens (RE) has been considered a crucial candidate in the modulation of memory specificity. Our study investigated its activation and functional connectivity with the medial prefrontal cortex (mPFC) and hippocampus (HPC) as neurobiological mechanisms of negative overgeneralization in anxious youth.

METHODS

As part of a secondary data analysis, we examined data from 34 participants between 9 and 14 years of age (mean age ± SD, 11.4 ± 2.0 years; 16 females) with varying degrees of anxiety severity. During the Study session participants rated images as negative, neutral, and positive. After 12 h, participants returned for a Test session, where they performed a memory recognition test with repeated (targets) and similar (lures) images. Labeling negative relative to neutral lures as "old" (false alarms) was our operational definition of negative overgeneralization.

RESULTS

Negative relative to neutral false alarmed stimuli displayed elevated RE activation (at Study and Test) and increased functional connectivity with the Cornu Ammonis (CA) 1 (at Test). Elevated anxiety severity was associated with reductions in the RE-mPFC functional coupling for neutral relative to negative stimuli. Exploratory analyses revealed similar patterns in activation and functional connectivity with positive stimuli.

CONCLUSIONS

Our findings demonstrate the importance of the RE in negative overgeneralization and anxiety.

Fear and safety learning in anxiety- and stress-related disorders: An updated meta-analysis

Fear learning processes are believed to play a crucial role in the development and maintenance of anxiety and stress-related disorders. To integrate results across different studies, we conducted a systematic meta-analysis following PRISMA guidelines to examine differences in fear conditioning during fear acquisition, extinction, and extinction recall between individuals with anxiety-related or stress-related disorders and healthy participants. This analysis updates the work of Duits et al. (2015) while also refining distinctions between physiological and behavioral outcomes and examining extinction recall. Our meta-analysis encompasses 77 studies published from 1986 to 2022, involving 2052 patients with anxiety disorders, obsessive-compulsive disorder, or post-traumatic stress disorder, and 3258 healthy controls. The results indicate significant differences in fear acquisition, extinction, and recall between the two groups. Specifically, during acquisition patients exhibited heightened physiological and behavioral responses to the CS- and reported increased affect ratings for the CS+ . During extinction and extinction recall, patients continue to show heightened threat expectancy and negative affect ratings towards the CS- and increased affect ratings towards the CS+ . No differences were found in CS+ /CS- differentiation between groups. These findings imply that individuals with anxiety and stress-related disorders may exhibit amplified responses to safety cues and stronger reactions to threat cues during fear conditioning, lasting through extinction and extinction recall. These changes may lead to increased sensitivity in detecting fear and slower extinction process, resulting in more enduring anxiety responses. We discuss these results in the context of existing literature on fear and safety learning and consider potential underlying mechanisms.

Individual differences in functional connectivity during suppression of imagined threat

Functional magnetic resonance imaging studies typically rely on between-person analyses. To examine individual differences in functional connectivity, we used Group Iterative Multiple Model Estimation and its subgrouping function to analyze functional magnetic resonance imaging data of 54 participants who were suppressing imagined future threat. A two-stage random-effects meta-analytic approach was employed to examine individual differences. In addition to generalizable connections between brain regions, we identified individual differences in personalized models suggesting different pathways through which individuals suppress future threat. Two subgroups with distinct connectivity patterns emerged: One subgroup (n = 29; 53.70%), characterized by an additional lagged connection from the right to the left posterior cingulate cortex, exhibited comparatively higher anxiety and less brain connectivity, whereas the other subgroup (n = 25; 46.30%), showing an additional connection from the left posterior cingulate cortex to the ventromedial prefrontal cortex, was associated with lower anxiety levels and greater connectivity. This study points to individual differences in functional connectivity during emotion regulation.

Generalized expectancy of threat in threatening compared to safe contexts

Fear of threatening contexts often generalizes to similar safe contexts, but few studies have investigated how contextual information influences cue generalization. In this study, we explored whether fear responses to cues would generalize more broadly in a threatening compared to a safe context. Forty-seven participants underwent a differential cue-in-context conditioning protocol followed by a generalization test, while we recorded psychophysiological and subjective responses. Two faces appeared on a computer screen in two contexts. One face (CS+) in the threat context (CTX+) was followed by a female scream 80% of the time, while another face (CS-) was not reinforced. No faces were reinforced in the safe context (CTX-). In the generalization test, the CSs and four morphs varying in similarity with the CS+ were presented in both contexts. During acquisition, conditioned responses to the cues were registered for all measures and the differential responding between CS+ and CS- was higher in CTX+ for US-expectancy ratings and skin conductance responses, but the affective ratings and steady-state visual evoked potentials were not context-sensitive. During test, adaptive generalized responses were evident for all measures. Despite increased US-expectancy ratings in CTX+, participants exhibited similar cue generalization in both contexts, suggesting that threatening contexts do not influence cue generalization.

Interpersonal violence moderates sustained-transient threat co-activation in the vmPFC and amygdala in a community sample of youth

The increased risk for psychopathology associated with interpersonal violence exposure (IPV, e.g., physical abuse, sexual assault) is partially mediated by neurobiological alterations in threat-related processes. Evidence supports parsing neural circuitry related to transient and sustained threat, as they appear to be separable processes with distinct neurobiological underpinnings. Although childhood is a sensitive period for neurodevelopment, most prior work has been conducted in adult samples. Further, it is unknown how IPV exposure may impact transient-sustained threat neural interactions. The current study tested the moderating role of IPV exposure on sustained vmPFC-transient amygdala co-activation during an fMRI task during which threat and neutral cues were predictably or unpredictably presented. Analyses were conducted in a sample of 212 community-recruited youth (M/SDage = 11.77/2.44 years old; 51.9% male; 56.1% White/Caucasian). IPV-exposed youth evidenced a positive sustained vmPFC-transient amygdala co-activation, while youth with no IPV exposure did not show this association. Consistent with theoretical models, effects were specific to unpredictable, negative trials and to exposure to IPV (i.e., unrelated to non-IPV traumatic experiences). Although preliminary, these findings provide novel insight into how childhood IPV exposure may alter neural circuity involved in specific facets of threat processing.

The effectiveness of the DNA-V program on reducing anxiety among Chinese adolescents: Outcomes of the face-to-face and web-based versions

Many studies have indicated an alarming prevalence of anxiety among Chinese adolescents, highlighting the critical need for prevention protocols. DNA-V (Discoverer, Noticer, Advisor-Values model) is an adapted version of Acceptance and Commitment Therapy designed to prevent mental health problems in adolescents. This study investigated the effects and underlying mechanisms of DNA-V. The DNA-V prevention program was culturally adapted and optimized in both content and form specifically for Chinese adolescents, with the aim of reducing anxiety levels. A total of 139 participants (59 females) from six eighth-grade classes at an average middle school in Beijing were randomly assigned to one of three groups consisting of the DNA-V face-to-face group (two classes), the DNA-V web-based group (two classes), or the active control group (two classes). Adolescents' anxiety and cognitive fusion were measured before (Time 1), immediately after (Time 2), and 2 months after (Time 3) the program using the Chinese Secondary School Students Anxiety Scale (CSSSAS) and Cognitive Fusion Questionnaire (CFQ). Results showed that in the DNA-V face-to-face group, the anxiety score at Time 3 was significantly lower than the scores at Time 1 (p < .001, Cohen's drm = 0.56) and Time 2 (p = .043, Cohen's drm = 0.24). The cognitive fusion score at Time 3 was significantly lower than the scores at Time 1 (p = .001, Cohen's drm = 0.51) and Time 2 (p = .003, Cohen's drm = 0.37). The results of the study suggest that the DNA-V prevention program could serve as an effective tool for reducing anxiety in adolescents.

Comparison of Resting-State Functional Connectivity Between Generalized Anxiety Disorder and Social Anxiety Disorder: Differences in the Nucleus Accumbens and Thalamus Network

Background: Generalized anxiety disorder (GAD) and social anxiety disorder (SAD) are distinguished by whether anxiety is limited to social situations. However, reports on the differences in brain functional networks between GAD and SAD are few. Our objective is to understand the pathogenesis of GAD and SAD by examining the differences in resting brain function between patients with GAD and SAD and healthy controls (HCs). Methods: This study included 21 patients with SAD, 17 patients with GAD, and 30 HCs. Participants underwent psychological assessments and resting-state functional magnetic resonance imaging. Whole-brain analyses were performed to compare resting-state functional connectivity (rsFC) among the groups. In addition, logistic regression analysis was conducted on the rsFC to identify significant differences between GAD and SAD. Results: Patients with SAD and GAD had significantly higher rsFC between the bilateral postcentral gyri and bilateral amygdalae/thalami than HCs. Compared with patients with SAD, those with GAD had significantly higher rsFC between the right nucleus accumbens and bilateral thalami and between the left nucleus accumbens and right thalamus. rsFC between the left nucleus accumbens and right thalamus positively correlated with state anxiety in patients with SAD and GAD, respectively. In addition, logistic regression analysis revealed that the right nucleus accumbens and the right thalamus connectivity could distinguish SAD from GAD. Conclusions: GAD and SAD were distinguished by the right nucleus accumbens and the right thalamus connectivity. Our findings offer insights into the disease-specific neural basis of SAD and GAD. Clinical Trial Registration Number: UMIN000024087. Impact Statement This study is the first to identify a resting state functional connectivity that distinguishes social anxiety disorder (SAD) from generalized anxiety disorder (GAD) and to clarify a common connectivity in both disorders. We found that the connectivity between the right nucleus accumbens and the right thalamus differentiated SAD from GAD. Furthermore, these rsFC differences suggest an underlying basis for fear overgeneralization. Our findings shed light on the pathophysiology of these conditions and could be used as a basis for further studies to improve outcomes for such patients.

The Impact of Continuous and Partial Reinforcement on the Acquisition and Generalization of Human-Conditioned Fear

Fear over-generalization as a core symptom of anxiety disorders is manifested by fear responses even to safe stimuli that are very dissimilar to the original dangerous stimulus. The present study investigated the effects of two separate conditioned stimuli-unconditioned stimuli (CS-US) pairing procedures on fear acquisition and generalization using a perceptual discrimination fear-conditioning paradigm, with US expectancy ratings and skin conductance response (SCR) as indicators. One group accepted continuous followed by partial CS-US pairings (C-P group); the other group accepted partial followed by continuous CS-US pairings (P-C group). It was found that compared to the P-C group, the C-P group showed stronger perceptual discrimination of CS+ and CS- in the fear acquisition and showed weaker SCRs and stronger extinction of US expectancy in the generalization. These findings emphasize that CS-US pairings significantly influence fear acquisition and generalization and suggest that continuous-following partial CS-US pairings promote individual discrimination of threat and safety signals and inhibit the generalization of conditioned fear. The results of this study have implications for clinical interventions for patients experiencing negative events.

Anhedonia is associated with overgeneralization of conditioned fear during late adolescence and early adulthood

BACKGROUND

Pavlovian fear paradigms involve learning to associate cues with threat or safety. Aberrances in Pavlovian fear learning correlate with psychopathology, especially anxiety disorders. This study evaluated symptom dimensions of anxiety and depression in relation to Pavlovian fear acquisition and generalization.

METHODS

256 participants (70.31 % female) completed a Pavlovian fear acquisition and generalization paradigm at ages 18-19 and 21-22 years. Analyses focused on indices of learning (self-reported US expectancy, skin conductance). Multilevel models tested associations with orthogonal symptom dimensions (Anhedonia-Apprehension, Fears, General Distress) at each timepoint.

RESULTS

All dimensions were associated with weaker acquisition of US expectancies at each timepoint. Fears was associated with overgeneralization only at age 21-22. General Distress was associated with overgeneralization only at age 18-19. Anhedonia-Apprehension was associated with overgeneralization at ages 18-19 and 21-22.

CONCLUSIONS

Anhedonia-Apprehension disrupts Pavlovian fear acquisition and increases overgeneralization of fear. These effects may emerge during adolescence and remain into young adulthood. General Distress and Fears also contribute to overgeneralization of fear, but these effects may vary as prefrontal mechanisms of fear inhibition continue to develop during late adolescence. Targeting specific symptom dimensions, particularly Anhedonia-Apprehension, may decrease fear generalization and augment interventions built on Pavlovian principles, such as exposure therapy.

Fear conditioning and fear generalization in children and adolescents with anxiety disorders

Overgeneralization of conditioned fear is associated with anxiety disorders (AD). Most results stem from studies done in adult patients, but studies with children are rare, although the median onset of anxiety disorders lies already in childhood. Thus, the goal of the present study was to examine fear learning and generalization in youth participants, aged 10-17 years, with AD (n = 39) compared to healthy controls (HC) (n = 40). A discriminative fear conditioning and generalization paradigm was used. Ratings of arousal, valence, and US expectancy (the probability of an aversive noise following each stimulus) were measured, hypothesizing that children with AD compared to HC would show heightened ratings of arousal and US expectancy, and decreased positive valence ratings, respectively, as well as overgeneralization of fear. The results indicated that children with AD rated all stimuli as more arousing and less pleasant, and demonstrated higher US expectancy ratings to all stimuli when compared to HC. Thus, rather than displaying qualitatively different generalization patterns (e.g., a linear vs. quadratic slope of the gradient), differences between groups were more quantitative (similar, but parallel shifted gradient). Therefore, overgeneralization of conditioned fear does not seem to be a general marker of anxiety disorders in children and adolescents.

Intolerance of uncertainty affects the behavioral and neural mechanisms of higher generalization

Intolerance of uncertainty (IU) is associated with several anxiety disorders. In this study, we employed rewards and losses as unconditioned positive and negative stimuli, respectively, to explore the effects of an individual's IU level on positive and negative generalizations using magnetic resonance imaging technology. Following instrumental learning, 48 participants (24 high IU; 24 low IU) were invited to complete positive and negative generalization tasks; their behavioral responses and neural activities were recorded by functional magnetic resonance imaging. The behavior results demonstrated that participants with high IUs exhibited higher generalizations to both positive and negative cues as compared with participants having low IUs. Neuroimaging results demonstrated that they exhibited higher activation levels in the right anterior insula and the default mode network (i.e. precuneus and posterior cingulate gyrus), as well as related reward circuits (i.e. caudate and right putamen). Therefore, higher generalization scores and the related abnormal brain activation may be key markers of IU as a vulnerability factor for anxiety disorders.

The ventromedial prefrontal cortex in response to threat omission is associated with subsequent explicit safety memory

In order to memorize and discriminate threatening and safe stimuli, the processing of the actual absence of threat seems crucial. Here, we measured brain activity with fMRI in response to both threat conditioned stimuli and their outcomes by combining threat learning with a subsequent memory paradigm. Participants (N = 38) repeatedly saw a variety of faces, half of which (CS+) were associated with an aversive unconditioned stimulus (US) and half of which were not (CS-). When an association was later remembered, the hippocampus had been more active (than when forgotten). However, the ventromedial prefrontal cortex predicted subsequent memory specifically during safe associations (CS- and US omission responses) and the left dorsolateral prefrontal cortex during outcomes in general (US and US omissions). In exploratory analyses of the theoretically important US omission, we found extended involvement of the medial prefrontal cortex and an enhanced functional connectivity to visual and somatosensory cortices, suggesting a possible function in sustaining sensory information for an integration with semantic memory. Activity in visual and somatosensory cortices together with the inferior frontal gyrus also predicted memory performance one week after learning. The findings imply the importance of a close interplay between prefrontal and sensory areas during the processing of safe outcomes-or 'nothing'-to establish declarative safety memory.

No influence of threat uncertainty on fear generalization

Fear overgeneralization and perceived uncertainty about future outcomes have been suggested as risk factors for clinical anxiety. However, little is known regarding how they influence each other. In this study, we investigated whether different levels of threat uncertainty influence fear generalization. Three groups of healthy participants underwent a differential fear conditioning protocol followed by a generalization test. All groups learned to associate one female face (conditioned stimulus, CS+) with a female scream (unconditioned stimulus, US), whereas the other face (CS-) was not associated with the scream. In order to manipulate threat uncertainty, one group (low uncertainty, n = 26) received 80%, the second group (moderate uncertainty, n = 32) received 60%, and the third group (high uncertainty, n = 30) 40% CS-US contingency. In the generalization test, all groups saw CS+ and CS- again along with four morphs resembling the CSs in steps of 20%. Subjective (expectancy, valence, and arousal ratings), psychophysiological (skin conductance response, SCR), and visuocortical (steady-state visual evoked potentials, ssVEPs) indices of fear were registered. Participants expected the US according to their reinforcement schedules and the discriminative responses to CS+/CS- increased with more uncertainty in skin conductance. However, acquisition of conditioned fear was not evident in ssVEPs. During the generalization test, we found no effect of threat uncertainty in any of the measured variables, but the strength of generalization for threat expectancy ratings was positively correlated with dispositional intolerance of uncertainty. This study suggests that mere threat uncertainty does not modulate fear generalization.

Neuroproteomics: Unveiling the Molecular Insights of Psychiatric Disorders with a Focus on Anxiety Disorder and Depression

Anxiety and depression are two of the most common mental disorders worldwide, with a lifetime prevalence of up to 30%. These disorders are complex and have a variety of overlapping factors, including genetic, environmental, and behavioral factors. Current pharmacological treatments for anxiety and depression are not perfect. Many patients do not respond to treatment, and those who do often experience side effects. Animal models are crucial for understanding the complex pathophysiology of both disorders. These models have been used to identify potential targets for new treatments, and they have also been used to study the effects of environmental factors on these disorders. Recent proteomic methods and technologies are providing new insights into the molecular mechanisms of anxiety disorder and depression. These methods have been used to identify proteins that are altered in these disorders, and they have also been used to study the effects of pharmacological treatments on protein expression. Together, behavioral and proteomic research will help elucidate the factors involved in anxiety disorder and depression. This knowledge will improve preventive strategies and lead to the development of novel treatments.

Nucleus Reuniens: Modulating Negative Overgeneralization in Periadolescents with Anxiety

Background

Anxiety affects 4.4-million children in the United States with an onset between childhood and adolescence, a period marked by neural changes that impact emotions and memory. Negative overgeneralization - or responding similarly to innocuous events that share features with past aversive experiences - is common in anxiety but remains mechanistically underspecified. The nucleus reuniens (RE) has been considered a crucial candidate in the modulation of memory specificity. Our study investigated its activation and functional connectivity with the medial prefrontal cortex (mPFC) and hippocampus (HPC) as neurobiological mechanisms of negative overgeneralization in anxious youth.

Methods

As part of a secondary data analysis, we examined data from 34 participants between 9-14 years (mean age ± SD, 11.4 ± 2.0 years, 16 females) with varying degrees of anxiety severity. During the Study session participants rated images as negative, neutral, and positive. After 12-hours, participants returned for a Test session, where they performed a memory recognition test with repeated (targets) and similar (lures) images. Labeling negative relative to neutral lures as "old" (false alarms) was our operational definition of negative overgeneralization.

Results

Negative relative to neutral false alarmed stimuli displayed elevated RE activation (at Study and Test) and increased functional connectivity with the CA1 (at Test only). Elevated anxiety severity was associated with reductions in the RE-mPFC functional coupling for neutral relative to negative stimuli. Exploratory analyses revealed similar patterns in activation and functional connectivity with positive stimuli.

Conclusions

Our findings demonstrate the importance of the RE in the overgeneralization of memories in anxious youth.

Reduced vmPFC-insula functional connectivity in generalized anxiety disorder: a Bayesian confirmation study

Differences in the correlated activity of networked brain regions have been reported in individuals with generalized anxiety disorder (GAD) but an overreliance on null-hypothesis significance testing (NHST) limits the identification of disorder-relevant relationships. In this preregistered study, we applied both a Bayesian statistical framework and NHST to the analysis of resting-state fMRI scans from females with GAD and matched healthy comparison females. Eleven a-priori hypotheses about functional connectivity (FC) were evaluated using Bayesian (multilevel model) and frequentist (t-test) inference. Reduced FC between the ventromedial prefrontal cortex (vmPFC) and the posterior-mid insula (PMI) was confirmed by both statistical approaches and was associated with anxiety sensitivity. FC between the vmPFC-anterior insula, the amygdala-PMI, and the amygdala-dorsolateral prefrontal cortex (dlPFC) region pairs did not survive multiple comparison correction using the frequentist approach. However, the Bayesian model provided evidence for these region pairs having decreased FC in the GAD group. Leveraging Bayesian modeling, we demonstrate decreased FC of the vmPFC, insula, amygdala, and dlPFC in females with GAD. Exploiting the Bayesian framework revealed FC abnormalities between region pairs excluded by the frequentist analysis and other previously undescribed regions in GAD, demonstrating the value of applying this approach to resting-state FC data in clinical investigations.

Common and exclusive spontaneous neural activity patterns underlying pure generalized anxiety disorder and comorbid generalized anxiety disorder and depression

BACKGROUND

This study aimed to identify common and exclusive neural substrates underlying pure generalized anxiety disorder (GAD, G0) and comorbid GAD and depression (G1), assess whether they could assist in diagnosis and prediction of treatment response, and determine whether comorbid depression in GAD patients would change their neural plasticity.

METHODS

A longitudinal study was conducted, involving 98 patients (40 in the G0 group and 58 in the G1 group) and 54 healthy controls (HCs). The fractional amplitude of low-frequency fluctuations (fALFF), support vector machine, and support vector regression were employed.

RESULTS

The shared neural underpinnings across the two subtypes of GAD were hyperactivity in the right cerebellar Crus II and inferior temporal gyrus and hypoactivity in the right postcentral gyrus. The G1 group showed hypoactivity in the frontal gyrus, compared with HCs, and hyperactivity in the middle temporal gyrus, compared with the G0 group or HCs. These alterations could aid in diagnosis and the prediction of treatment response with high accuracy. After treatment, both the G1 and G0 groups showed higher fALFF than those before treatment but were located in different brain regions.

LIMITATIONS

The study was performed in a single center and subjects showed a fairly homogeneous ethnicity.

CONCLUSIONS

Common and exclusive neural substrates underlying the two subtypes of GAD were identified, which could assist in diagnosis and the prediction of treatment response. Pharmacotherapy for the two subtypes of GAD recruited different pathways, suggesting that comorbid depression in GAD patients would change their neural plasticity.

Expanding the canon: An inclusive neurobiology of thalamic and subthalamic fear circuits

Appropriate expression of fear in the face of threats in the environment is essential for survival. The sustained expression of fear in the absence of threat signals is a central pathological feature of trauma- and anxiety-related disorders. Our understanding of the neural circuitry that controls fear inhibition coalesces around the amygdala, hippocampus, and prefrontal cortex. By discussing thalamic and sub-thalamic influences on fear-related learning and expression in this review, we suggest a more inclusive neurobiological framework that expands our canonical view of fear. First, we visit how fear-related learning and expression is influenced by the aforementioned canonical brain regions. Next, we review emerging data that shed light on new roles for thalamic and subthalamic nuclei in fear-related learning and expression. Then, we highlight how these neuroanatomical hubs can modulate fear via integration of sensory and salient stimuli, gating information flow and calibrating behavioral responses, as well as maintaining and updating memory representations. Finally, we propose that the presence of this thalamic and sub-thalamic neuroanatomy in parallel with the tripartite prefrontal cortex-amygdala-hippocampus circuit allows for dynamic modulation of information based on interoceptive and exteroceptive signals. This article is part of the Special Issue on "Fear, Anxiety and PTSD".

Impact of observational and direct learning on fear conditioning generalization in humans

Humans gain knowledge about threats not only from their own experiences but also from observing others' behavior. A neutral stimulus is associated with a threat stimulus for several times and the neutral stimulus will evoke fear responses, which is known as fear conditioning. When encountering a new event that is similar to one previously associated with a threat, one may feel afraid and produce fear responses. This is called fear generalization. Previous studies have mostly focused on fear conditioning and generalization based on direct learning, but few have explored how observational fear learning affects fear conditioning and generalization. To the best of our knowledge, no previous study has focused on the neural correlations of fear conditioning and generalization based on observational learning. In the present study, 58 participants performed a differential conditioning paradigm in which they learned the associations between neutral cues (i.e., geometric figures) and threat stimuli (i.e., electric shock). The learning occurred on their own (i.e., direct learning) and by observing other participant's responses (i.e., observational learning); the study used a within-subjects design. After each learning condition, a fear generalization paradigm was conducted by each participant independently while their behavioral responses (i.e., expectation of a shock) and electroencephalography (EEG) recordings or responses were recorded. The shock expectancy ratings showed that observational learning, compared to direct learning, reduced the differentiation between the conditioned threatening stimuli and safety stimuli and the increased shock expectancy to the generalization stimuli. The EEG indicated that in fear learning, threatening conditioned stimuli in observational and direct learning increased early discrimination (P1) and late motivated attention (late positive potential [LPP]), compared with safety conditioned stimuli. In fear generalization, early discrimination, late motivated attention, and orienting attention (alpha-event-related desynchronization [alpha-ERD]) to generalization stimuli were reduced in the observational learning condition. These findings suggest that compared to direct learning, observational learning reduces differential fear learning and increases the generalization of fear, and this might be associated with reduced discrimination and attentional function related to generalization stimuli.

Anterior cingulate cortex, but not amygdala, modulates the anxiogenesis induced by living with conspecifics subjected to chronic restraint stress in male mice

Cohabitation with a partner undergoing chronic restraint stress (CRE) induces anxiogenic-like behaviors through emotional contagion. We hypothesized that the anterior cingulate cortex (ACC) and the amygdala would be involved in the modulation of this emotional process. This study investigated the role of the ACC and amygdala in empathy-like behavior (e.g., anxiety-like responses) induced by living with a mouse subjected to CRE. Male Swiss mice were housed in pairs for 14 days and then allocated into two groups: cagemate stress (one animal of the pair was subjected to 14 days of restraint stress) and cagemate control (no animal experienced stress). Twenty-four hours after the last stress session, cagemates had their brains removed for recording FosB labeling in the ACC and amygdala (Exp.1). In experiments 2 and 3, 24 h after the last stress session, the cagemates received 0.1 μL of saline or cobalt chloride (CoCl₂ 1 mM) into the ACC or amygdala, and then exposed to the elevated plus-maze (EPM) for recording anxiety. Results showed a decrease of FosB labeling in the ACC without changing immunofluorescence in the amygdala of stress cagemate mice. Cohabitation with mice subjected to CRE provoked anxiogenic-like behaviors. Local inactivation of ACC (but not the amygdala) reversed the anxiogenic-like effects induced by cohabitation with a partner undergoing CRE. These results suggest the involvement of ACC, but not the amygdala, in anxiety induced by emotional contagion.

Developmental aspects of fear generalization - A MEG study on neurocognitive correlates in adolescents versus adults

BACKGROUND

Fear generalization is pivotal for the survival-promoting avoidance of potential danger, but, if too pronounced, it promotes pathological anxiety. Similar to adult patients with anxiety disorders, healthy children tend to show overgeneralized fear responses.

OBJECTIVE

This study aims to investigate neuro-developmental aspects of fear generalization in adolescence - a critical age for the development of anxiety disorders.

METHODS

We compared healthy adolescents (14-17 years) with healthy adults (19-34 years) regarding their fear responses towards tilted Gabor gratings (conditioned stimuli, CS; and slightly differently titled generalization stimuli, GS). In the conditioning phase, CS were paired (CS+) or remained unpaired (CS-) with an aversive stimulus (unconditioned stimuli, US). In the test phase, behavioral, peripheral and neural responses to CS and GS were captured by fear- and UCS expectancy ratings, a perceptual discrimination task, pupil dilation and source estimations of event-related magnetic fields.

RESULTS

Closely resembling adults, adolescents showed robust generalization gradients of fear ratings, pupil dilation, and estimated neural source activity. However, in the UCS expectancy ratings, adolescents revealed shallower generalization gradients indicating overgeneralization. Moreover, adolescents showed stronger visual cortical activity after as compared to before conditioning to all stimuli.

CONCLUSION

Various aspects of fear learning and generalization appear to be mature in healthy adolescents. Yet, cognitive aspects might show a slower course of development.

An fMRI study of cognitive regulation of reward processing in generalized anxiety disorder (GAD)

BACKGROUND

Cognitive regulation can affect the process of decision making. Generalized anxiety disorder (GAD) patients seem to have an impairment in cognitive regulation of reward processing concerning food stimuli. This study aims to explore the impact of GAD in cognitive regulation of food-related rewards.

METHODS

GAD patients (n=11) and healthy controls (n=15) performed a cognitive regulation craving task with food images while undergoing a functional magnetic resonance imaging (fMRI) acquisition. Between-group differences in functional connectivity were measured using dorsolateral prefrontal cortex (dlPFC) and ventromedial prefrontal cortex (vmPFC) seeds during cognitive regulation.

RESULTS

During cognitive regulation, there was a significant interaction for functional connectivity between the right dlPFC and bilateral vmPFC with the thalamus. GAD patients had lower functional connectivity for cognitive regulation conditions (distance and indulge) than for the non-regulated condition in these clusters, while control participants presented the opposite pattern. GAD group presented fixed food valuation scores after cognitive regulation.

CONCLUSIONS

GAD participants showed inflexibility while valuating food images, that could be produced by cognitive regulation deficits underpinned by functional connectivity alterations between prefrontal regions and the thalamus. These results show cognitive inflexibility and difficulty in the modulation of cognitive responses during decision making in GAD patients.

A meta-analysis of conditioned fear generalization in anxiety-related disorders

Generalization of conditioned fear is adaptive in some situations but maladaptive when fear excessively generalizes to innocuous stimuli with incidental resemblance to a genuine threat cue. Recently, empirical interest in fear generalization as a transdiagnostic explanatory mechanism underlying anxiety-related disorders has accelerated. As there are now several studies of fear generalization across multiple types of anxiety-related disorders, the authors conducted a meta-analysis of studies reporting behavioral measures (subjective ratings and psychophysiological indices) of fear generalization in anxiety-related disorder vs. comparison groups. We conducted systematic searches of electronic databases (conducted from January-October 2020) for fear generalization studies involving anxiety-related disorder groups or subclinical analog groups. A total of 300 records were full-text screened and two unpublished datasets were obtained, yielding 16 studies reporting behavioral fear generalization measures. Random-effects meta-analytic models and meta-regressions were applied to the identified data. Fear generalization was significantly heightened in anxiety-related disorder participants (N = 439) relative to comparison participants (N = 428). We did not identify any significant clinical, sample, or methodological moderators. Heightened fear generalization is quantitatively supported as distinguishing anxiety-related disorder groups from comparison groups. Evidence suggests this effect is transdiagnostic, relatively robust to experimental or sample parameters, and that generalization paradigms are a well-supported framework for neurobehavioral investigations of learning and emotion in anxiety-related disorders. We discuss these findings in the context of prior fear conditioning meta-analyses, past neuroimaging investigations of fear generalization in anxiety-related disorders, and future directions and challenges for the field.

The Relationship Between Self-Reported Misophonia Symptoms and Auditory Aversive Generalization Leaning: A Preliminary Report

Misophonia is characterized by excessive aversive reactions to specific "trigger" sounds. Although this disorder is increasingly recognized in the literature, its etiological mechanisms and maintaining factors are currently unclear. Several etiological models propose a role of Pavlovian conditioning, an associative learning process heavily researched in similar fear and anxiety-related disorders. In addition, generalization of learned associations has been noted as a potential causal or contributory factor. Building upon this framework, we hypothesized that Misophonia symptoms arise as a consequence of overgeneralized associative learning, in which aversive responses to a noxious event also occur in response to similar events. Alternatively, heightened discrimination between conditioned threat and safety cues may be present in participants high in Misophonia symptoms, as predicted by associative learning models of Misophonia. This preliminary report (n = 34) examines auditory generalization learning using self-reported behavioral (i.e., valence and arousal ratings) and EEG alpha power reduction. Participants listened to three sine tones differing in pitch, with one pitch (i.e., CS+) paired with an aversive loud white noise blast, prompting aversive Pavlovian generalization learning. We assessed the extent to which overgeneralization versus heightened discrimination learning is associated with self-reported Misophonia symptoms, by comparing aversive responses to the CS+ and other tones similar in pitch. Behaviorally, all participants learned the contingencies between CS+ and noxious noise, with individuals endorsing elevated Misophonia showing heightened aversive sensitivity to all stimuli, regardless of conditioning and independent of hyperacusis status. Across participants, parieto-occipital EEG alpha-band power reduction was most pronounced in response to the CS+ tone, and this difference was greater in those with self-reported Misophonia symptoms. The current preliminary findings do not support the notion that overgeneralization is a feature of self-reported emotional experience in Misophonia, but that heightened sensitivity and discrimination learning may be present at the neural level.

Fear one, fear them all: A systematic review and meta-analysis of fear generalization in pathological anxiety

It is a defining feature of anxiety disorders that fear is elicited by a circumscribed class of stimuli rather than by only one specific exemplar of that class. Therefore, fear generalization, a mechanism by which associative fear extends from one conditioned stimulus to similar cues, has been central to theories on anxiety. Yet, experimental evidence for the link between generalization and pathological anxiety, as well as its moderators, has not been formally integrated. This systematic review and meta-analysis of empirical findings clarifies the relationship between fear generalization and pathological anxiety. In conclusion, enhanced fear generalization is associated with several anxiety disorders and stress-related disorders, which is supported statistically by a small, but robust effect size of g = 0.44 for risk ratings as an index of fear generalization. However, empirical results are inconsistent across disorders and they rarely allow for conclusions on their causality in the disorders' etiology. Therefore, based on theoretical considerations, we recommend directions for intensified research, especially on the causal relationship between overgeneralization and pathological fear.

Plexin-A1 expression in the inhibitory neurons of infralimbic cortex regulates the specificity of fear memory in male mice

Maintaining appropriate levels of fear memory specificity is crucial for individual's survival and mental health, whereas overgeneralized fear commonly occurs in neuropsychiatric disorders, including posttraumatic stress disorder and generalized anxiety disorder. However, the molecular mechanisms regulating fear memory specificity remain poorly understood. The medial prefrontal cortex (mPFC) is considered as a key brain region in fear memory regulation. Previous transcriptomic studies have identified that plexin-A1, a transmembrane receptor critical for axon development, was downregulated in the mPFC after fear memory training. In this study, we identified that learning-induced downregulation of the mRNA and protein levels of plexin-A1 specifically occurred in the inhibitory but not excitatory neurons in the infralimbic cortex (IL) of mPFC. Further studies of plexin-A1 by virus-mediated over-expression of functional mutants selectively in the IL inhibitory neurons revealed the critical roles of plexin-A1 for regulating memory specificity and anxiety. Moreover, our findings revealed that plexin-A1 regulated the distribution of glutamic acid decarboxylase 67, a GABA synthetase, which in turn modulated the activity of IL and its downstream brain regions. Collectively, our findings elucidate the molecular modifier of IL inhibitory neurons in regulating memory specificity and anxiety, and provide candidates for developing therapeutic strategies for the prevention or treatment of a series of fear generalization-related neuropsychiatric disorders.

Association of Generalized Anxiety Disorder With Autonomic Hypersensitivity and Blunted Ventromedial Prefrontal Cortex Activity During Peripheral Adrenergic Stimulation: A Randomized Clinical Trial

IMPORTANCE

β-Adrenergic stimulation elicits heart palpitations and dyspnea, key features of acute anxiety and sympathetic arousal, yet no neuroimaging studies have examined how the pharmacologic modulation of interoceptive signals is associated with fear-related neurocircuitry in individuals with generalized anxiety disorder (GAD).

OBJECTIVE

To examine the neural circuitry underlying autonomic arousal induced via isoproterenol, a rapidly acting, peripheral β-adrenergic agonist akin to adrenaline.

DESIGN, SETTING, AND PARTICIPANTS

This crossover randomized clinical trial of 58 women with artifact-free data was conducted from January 1, 2017, to November 31, 2019, at the Laureate Institute for Brain Research in Tulsa, Oklahoma.

EXPOSURES

Functional magnetic resonance imaging was used to assess neural responses during randomized intravenous bolus infusions of isoproterenol (0.5 and 2.0 μg) and saline, each administered twice in a double-blind fashion.

MAIN OUTCOMES AND MEASURES

Blood oxygen level-dependent responses across the whole brain during isoproterenol administration in patients with GAD vs healthy comparators. Cardiac and respiratory responses, as well as interoceptive awareness and anxiety, were also measured during the infusion protocol.

RESULTS

Of the 58 female study participants, 29 had GAD (mean [SD] age, 26.9 [6.8] years) and 29 were matched healthy comparators (mean [SD] age, 24.4 [5.0] years). During the 0.5-μg dose of isoproterenol, the GAD group exhibited higher heart rate responses (b = 5.34; 95% CI, 2.06-8.61; P = .002), higher intensity ratings of cardiorespiratory sensations (b = 8.38; 95% CI, 2.05-14.71; P = .01), higher levels of self-reported anxiety (b = 1.04; 95% CI, 0.33-1.76; P = .005), and significant hypoactivation in the ventromedial prefrontal cortex (vmPFC) that was evident throughout peak response (Cohen d = 1.55; P < .001) and early recovery (Cohen d = 1.52; P < .001) periods. Correlational analysis of physiological and subjective indexes and percentage of signal change extracted during the 0.5-μg dose revealed that vmPFC hypoactivation was inversely correlated with heart rate (r56 = -0.51, adjusted P = .001) and retrospective intensity of both heartbeat (r56 = -0.50, adjusted P = .002) and breathing (r56 = -0.44, adjusted P = .01) sensations. Ventromedial prefrontal cortex hypoactivation correlated inversely with continuous dial ratings at a trend level (r56 = -0.38, adjusted P = .051), whereas anxiety (r56 = -0.28, adjusted P = .27) and chronotropic dose 25 (r56 = -0.14, adjusted P = .72) showed no such association.

CONCLUSIONS AND RELEVANCE

In this crossover randomized clinical trial, women with GAD exhibited autonomic hypersensitivity during low levels of adrenergic stimulation characterized by elevated heart rate, heightened interoceptive awareness, increased anxiety, and a blunted neural response localized to the vmPFC. These findings support the notion that autonomic hyperarousal may be associated with regulatory dysfunctions in the vmPFC, which could serve as a treatment target to help patients with GAD more appropriately appraise and regulate signals of sympathetic arousal.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT02615119.

Heightened false alarms of conditioned threat predict longitudinal increases in GAD and SAD symptoms over the first year of college

Lab-based fear-conditioning studies have repeatedly implicated exaggerated threat reactivity to benign (unreinforced) stimuli as concurrent markers of clinical anxiety, but little work has examined the strength of false alarms as a longitudinal predictor of anxiety problems. As such, we tested whether heightened false alarms of conditioned threat assessed in participants' first semester of college predicted second-semester symptoms of generalized anxiety disorder (GAD) and social anxiety disorder (SAD) - two anxiety conditions that are common in college students, have been associated with excessive false alarms, and have yet to be assessed with longitudinal conditioning designs. Here, we focused on the predictive effects of behavioral threat responses (threat expectancy, subjective anxiety, avoidance) given their greater potential for translation to the clinic. Results implicate conditioning-related increases in anxiety to safe stimuli resembling the danger-cue as prospective predictors of GAD. In contrast, SAD was predicted by non-specific elevations in anxiety to a broad set of safe stimuli, as well as by increased threat expectancy toward cues least resembling the conditioned danger cue. These findings suggest that risk for GAD and SAD are captured by distinct, behavioral indicators of false-alarms that may be more feasibly collected in clinical settings compared to alternative experimental anxiety measures like psychophysiological responses.

Effect of trait anxiety on cognitive flexibility: Evidence from event-related potentials and resting-state EEG

Individuals with anxiety often exhibit cognitive flexibility impairment; however, the neural underpinnings of this cognitive impairment remain unclear. In this study, 45 participants were instructed to complete a task-switching assessment of shifting function by EEG technology, and 200 participants were included in microstate analysis to study why cognitive flexibility is impaired and the neuromechanism. Behaviorally, a positive correlation between trait anxiety scores and set shifting cost was found. At the EEG level, there was a positive correlation between trait anxiety scores and frontal P2 peaks under the shifting condition, which was related to the activation of the stimulus-response associations by attention. Furthermore, microstate analysis was used to analyze EEG functional networks, and TA scores had significant positive correlations with the Occurrence of class D and the Contribution of class D, which was related to the dorsal attention network. These results provided direct neuroelectrophysiological evidence that trait anxiety impairs cognitive flexibility when shifting is required.

Parsing neural circuits of fear learning and extinction across basic and clinical neuroscience: Towards better translation

Over the past decades, studies of fear learning and extinction have advanced our understanding of the neurobiology of threat and safety learning. Animal studies can provide mechanistic/causal insights into human brain regions and their functional connectivity involved in fear learning and extinction. Findings in humans, conversely, may further enrich our understanding of neural circuits in animals by providing macroscopic insights at the level of brain-wide networks. Nevertheless, there is still much room for improvement in translation between basic and clinical research on fear learning and extinction. Through the lens of neural circuits, in this article, we aim to review the current knowledge of fear learning and extinction in both animals and humans, and to propose strategies to fill in the current knowledge gap for the purpose of enhancing clinical benefits.

General additive models address statistical issues in diffusion MRI: An example with clinically anxious adolescents

Statistical models employed to test for group differences in quantized diffusion-weighted MRI white matter tracts often fail to account for the large number of data points per tract in addition to the distribution, type, and interdependence of the data. To address these issues, we propose the use of Generalized Additive Models (GAMs) and supply code and examples to aid in their implementation. Specifically, using diffusion data from 73 periadolescent clinically anxious and no-psychiatric-diagnosis control participants, we tested for group tract differences and show that a GAM allows for the identification of differences within a tract while accounting for the nature of the data as well as covariates and group factors. Further, we then used these tract differences to investigate their association with performance on a memory test. When comparing our high versus low anxiety groups, we observed a positive association between the left uncinate fasciculus and memory overgeneralization for negatively valenced stimuli. This same association was not evident in the right uncinate or anterior forceps. These findings illustrate that GAMs are well-suited for modeling diffusion data while accounting for various aspects of the data, and suggest that the adoption of GAMs will be a powerful investigatory tool for diffusion-weighted analyses.

Brain Stimulation for Emotion Regulation in Adolescents With Psychiatric Disorders: Study Protocol for a Clinical-Transdiagnostical, Randomized, Triple-Blinded and Sham-Controlled Neurotherapeutic Trial

BACKGROUND

Anxiety, conduct and depressive disorders represent three highly prevalent psychiatric conditions in adolescents. A shared underpinning of these disorders is a shortcoming in emotion regulation, connected to the functioning of the ventromedial prefrontal cortex. Thus, an intervention able to target the suggested neural correlate seems to be highly desirable, aiming to hinder a maladaptive development of emotion regulation abilities and chronification of associated psychiatric disorders. As transcranial direct current stimulation (tDCS) was repeatedly demonstrated as a safe and non-invasive method to modulate specific brain activity, research is in demand to evaluate neurotherapeutic applications in adolescents with psychiatric disorders.

METHOD

This transdiagnostic, randomized, triple-blind and sham-controlled clinical neurostimulation trial primary aims to investigate if emotion regulation abilities are increased after tDCS in adolescents with psychiatric disorders. Secondly, disorder-specific changes in the anxiety, depression or conduct disorder will be investigated, as well as changes in quality of life, and cognitive and emotional functioning after tDCS intervention. We will include 108 adolescents with psychiatric disorders, displaying a substantial deficit in emotion regulation. Of these, one third each has to be primarily diagnosed with a depressive, anxiety or conduct disorder, respectively. Participants will be randomized to the experimental group (n = 54) receiving real anodal tDCS, or to the control group (n = 54) receiving sham tDCS. Brain stimulation will be applied for 20 min on five consecutive days twice targeting the ventromedial prefrontal cortex (vmPFC). Changes in emotion regulation, together with changes in disorder-specific clinical symptoms will be recorded by multi-informant psychological ratings. To inspect changes in behavior and gaze, computerized tasks and an eye tracker system will be used. Changes in brain responses to emotional and cognitive stimuli will be examined with three functional magnetic resonance imaging (fMRI) paradigms. In addition, a resting state MRI will be acquired to investigate possible changes in brain connectivity.

DISCUSSION

By investigating "emotion regulation" as transdiagnostic treatment target, this project is oriented toward the Research Domain Criteria framework with a dimensional view on mental illness. The study aims at investigating the potential of tDCS as non-invasive intervention for depressive, anxiety and conduct disorders in adolescents and broadening the scientific foundation for its clinical application.

CLINICAL TRIAL REGISTRATION

The study is ongoing and has been registered in the German Registry of Clinical Trials (DRKS-ID: DRKS00025601X) on the 28.06.2021.

Human Primary Olfactory Amygdala Subregions Form Distinct Functional Networks, Suggesting Distinct Olfactory Functions

Three subregions of the amygdala receive monosynaptic projections from the olfactory bulb, making them part of the primary olfactory cortex. These primary olfactory areas are located at the anterior-medial aspect of the amygdala and include the medial amygdala (MeA), cortical amygdala (CoA), and the periamygdaloid complex (PAC). The vast majority of research on the amygdala has focused on the larger basolateral and basomedial subregions, which are known to be involved in implicit learning, threat responses, and emotion. Fewer studies have focused on the MeA, CoA, and PAC, with most conducted in rodents. Therefore, our understanding of the functions of these amygdala subregions is limited, particularly in humans. Here, we first conducted a review of existing literature on the MeA, CoA, and PAC. We then used resting-state fMRI and unbiased k-means clustering techniques to show that the anatomical boundaries of human MeA, CoA, and PAC accurately parcellate based on their whole-brain resting connectivity patterns alone, suggesting that their functional networks are distinct, relative both to each other and to the amygdala subregions that do not receive input from the olfactory bulb. Finally, considering that distinct functional networks are suggestive of distinct functions, we examined the whole-brain resting network of each subregion and speculated on potential roles that each region may play in olfactory processing. Based on these analyses, we speculate that the MeA could potentially be involved in the generation of rapid motor responses to olfactory stimuli (including fight/flight), particularly in approach/avoid contexts. The CoA could potentially be involved in olfactory-related reward processing, including learning and memory of approach/avoid responses. The PAC could potentially be involved in the multisensory integration of olfactory information with other sensory systems. These speculations can be used to form the basis of future studies aimed at clarifying the olfactory functions of these under-studied primary olfactory areas.

Salience and central executive networks track overgeneralization of conditioned-fear in post-traumatic stress disorder

BACKGROUND

Generalization of conditioned-fear, a core feature of post-traumatic stress disorder (PTSD), has been the focus of several recent neuroimaging studies. A striking outcome of these studies is the frequency with which neural correlates of generalization fall within hubs of well-established functional networks including salience (SN), central executive (CEN), and default networks (DN). Neural substrates of generalization found to date may thus reflect traces of large-scale brain networks that form more expansive neural representations of generalization. The present study includes the first network-based analysis of generalization and PTSD-related abnormalities therein.

METHODS

fMRI responses in established intrinsic connectivity networks (ICNs) representing SN, CEN, and DN were assessed during a generalized conditioned-fear task in male combat veterans (N = 58) with wide-ranging PTSD symptom severity. The task included five rings of graded size. Extreme sizes served as conditioned danger-cues (CS+: paired with shock) and safety-cues (CS-), and the three intermediate sizes served as generalization stimuli (GSs) forming a continuum-of-size between CS+ and CS-. Generalization-gradients were assessed as behavioral and ICN response slopes from CS+, through GSs, to CS-. Increasing PTSD symptomatology was predicted to relate to less-steep slopes indicative of stronger generalization.

RESULTS

SN, CEN, and DN responses fell along generalization-gradients with levels of generalization within and between SN and CEN scaling with PTSD symptom severity.

CONCLUSIONS

Neural substrates of generalized conditioned-fear include large-scale networks that adhere to the functional organization of the brain. Current findings implicate levels of generalization in SN and CEN as promising neural markers of PTSD.

Elevated fear responses to threatening cues in rats with early life stress is associated with greater excitability and loss of gamma oscillations in ventral-medial prefrontal cortex

Stress experienced early in development can have profound influences on developmental trajectories and ultimately behaviors in adulthood. Potent stressors during brain maturation can profoundly disrupt prefrontal cortical areas in particular, which can set the stage for prefrontal-dependent alterations in fear regulation and risk of drug abuse in adulthood. Despite these observations, few studies have investigated in vivo signaling in prefrontal signals in animals with a history of early life stress (ELS). Here, rats with ELS experienced during the first post-natal week were then tested on a conditioned suppression paradigm during adulthood. During conditioned suppression, electrophysiological recordings were made in the ventral medial prefrontal cortex (vmPFC) during presentations of a fear-associated cue that resolved both single-unit activity and local field potentials (LFPs). Relative to unstressed controls, ELS-experienced rats showed greater fear-related suppression of lever pressing. During presentations of the fear-associated cue (CS+), neurons in the vmPFC of ELS animals showed a significant increase in the probability of excitatory encoding relative to controls, and excitatory phasic responses in the ELS animals were reliably of higher magnitude than Controls. In contrast, vmPFC neurons in ELS subjects better discriminated between the shock-associated CS+ and the neutral ("safe") CS- cue than Controls. LFPs recorded in the same locations revealed that high gamma band (65-95 Hz) oscillations were strongly potentiated in Controls during presentation of the fear-associated CS+ cue, but this potentiation was abolished in ELS subjects. Notably, no other LFP spectra differed between ELS and Controls for either the CS+ or CS-. Collectively, these data suggest that ELS experience alters the neurobehavioral functions of PFC in adulthood that are critical for processing fear regulation. As such, these alterations may also provide insight into increased susceptibility to other PFC-dependent processes such as risk-based choice, motivation, and regulation of drug use and relapse in ELS populations.

Social relevance modulates multivariate neural representations of threat generalization in children and adults

Few studies have examined threat generalization across development and no developmental studies have compared the generalization of social versus nonsocial threat, making it difficult to identify contextual factors that contribute to threat learning across development. The present study assessed youth and adults' multivoxel neural representations of social versus nonsocial threat stimuli. Twenty adults (M_age  = 25.7 ± 4.9) and 16 youth (M_age  = 14.1 ± 1.7) completed two conditioning and extinction recall paradigms: one social and one nonsocial paradigm. Three weeks after conditioning, participants underwent a functional magnetic resonance imaging extinction recall task that presented the extinguished threat cue (CS+), a safety cue (CS-), and generalization stimuli (GS) consisting of CS-/CS+ blends. Across age groups, neural activity patterns and self-reported fear and memory ratings followed a linear generalization gradient for social threat stimuli and a quadratic generalization gradient for nonsocial threat stimuli, indicating enhanced threat/safety discrimination for social relative to nonsocial threat stimuli. The amygdala and ventromedial prefrontal cortex displayed the greatest neural pattern differentiation between the CS+ and GS/CS-, reinforcing their role in threat learning and extinction recall. Contrary to predictions, age did not influence threat representations. These findings highlight the importance of the social relevance of threat on generalization across development.

Fear conditioning and extinction in obsessive-compulsive disorder: A systematic review

Laboratory experiments using fear conditioning and extinction protocols help lay the groundwork for designing, testing, and optimizing innovative treatments for anxiety-related disorders. Yet, there is limited basic research on fear conditioning and extinction in obsessive-compulsive disorder (OCD). This is surprising because exposure-based treatments based on associative learning principles are among the most popular and effective treatment options for OCD. Here, we systematically review and critically assess existing aversive conditioning and extinction studies of OCD. Across 12 studies, there was moderate evidence that OCD is associated with abnormal acquisition of conditioned responses that differ from comparison groups. There was relatively stronger evidence of OCD's association with impaired extinction processes. This included multiple studies finding elevated conditioned responses during extinction learning and poorer threat/safety discrimination during recall, although a minority of studies yielded results inconsistent with this conclusion. Overall, the conditioning model holds value for OCD research, but more work is necessary to clarify emerging patterns of results and increase clinical translational utility to the level seen in other anxiety-related disorders. We detail limitations in the literature and suggest next steps, including modeling OCD with more complex conditioning methodology (e.g., semantic/conceptual generalization, avoidance) and improving individual-differences assessment with dimensional techniques.

Neural signatures of heterogeneity in risk-taking and strategic consistency

People display a high degree of heterogeneity in risk-taking behaviour, but this heterogeneity remains poorly understood. Here, we use a neural trait approach to examine if task-independent, brain-based differences can help uncover the sources of heterogeneity in risky decision-making. We extend prior research in two key ways. First, we disentangled risk-taking and strategic consistency using novel measures afforded by the Balloon Analogue Risk Task. Second, we applied a personality neuroscience framework to explore why personality traits are typically only weakly related to risk-taking behaviour. We regressed participants' (N = 104) source localized resting-state electroencephalographic activity on risk-taking and strategic consistency. Results revealed that higher levels of resting-state delta-band current density (reflecting reduced cortical activation) in the left dorsal anterior cingulate cortex and the left dorsolateral prefrontal cortex were associated with increased risk-taking and decreased strategic consistency, respectively. These results suggest that heterogeneity in risk-taking behaviour is associated with neural dispositions related to sensitivity to the risk of loss, whereas heterogeneity in strategic consistency is associated with neural dispositions related to strategic decision-making. Finally, extraversion, neuroticism, openness, and self-control were broadly associated with both of the identified neural traits, which in turn mediated indirect associations between personality traits and behavioural measures. These results provide an explanation for the weak direct relationships between personality traits and risk-taking behaviour, supporting a personality neuroscience framework of traits and decision-making.

Transcranial Direct Current Stimulation of the Ventromedial Prefrontal Cortex Modulates Perceptual and Neural Patterns of Fear Generalization

BACKGROUND

Overgeneralization of fear is a pathogenic marker of anxiety and stress-related disorders and has been linked with perceptual discrimination deficits, reduced fear inhibition, and prefrontal hyporeactivity to safety-signaling stimuli. We aimed to examine whether behavioral and neural patterns of fear generalization are influenced by the fear-inhibiting ventromedial prefrontal cortex (vmPFC).

METHODS

Three groups of healthy participants received excitatory (n = 27), inhibitory (n = 26), or sham (n = 26) transcranial direct current stimulation of the vmPFC after a fear conditioning phase and before a fear generalization phase. We obtained, as dependent variables, fear ratings and unconditioned stimulus-expectancy ratings, perceptual aspects of fear generalization (perceptual discrimination), pupil dilations, and source estimations of event-related fields elicited by conditioned and generalization stimuli.

RESULTS

After inhibitory (compared with excitatory and sham) vmPFC stimulation, we observed reduced performance in perceptual discrimination and less negative inhibitory gradients in frontal structures at midlatency and late time intervals. Fear and unconditioned stimulus-expectancy ratings as well as pupil dilation remained unaffected by stimulation.

CONCLUSIONS

These findings reveal a causal contribution of vmPFC reactivity to generalization patterns and suggest that vmPFC hyporeactivity consequent on inhibitory vmPFC stimulation may serve as a model for pathological processes of fear generalization (reduced discrimination, impaired fear inhibition via frontal brain structures). This encourages further basic and clinical research on the potential of targeted brain stimulation to modulate fear generalization and overgeneralization.

Behavioral and Magnetoencephalographic Correlates of Fear Generalization are Associated with Responses to Later Virtual Reality Exposure Therapy in Spider Phobia

BACKGROUND

As overgeneralization of fear is a pathogenic marker of anxiety disorders, we investigated whether pre-treatment levels of fear generalization in spider-phobic patients are related to their response to exposure-based treatment, in order to identify pre-treatment moderators of treatment success.

METHODS

Ninety patients with spider phobia completed pre-treatment clinical and magnetoencephalography (MEG) assessments, one session of virtual reality exposure therapy, and a post-treatment clinical assessment. Based on the primary outcome (30% symptom reduction in self-reported symptoms) they were categorized as responders or non-responders. In a pre-treatment MEG fear generalization paradigm involving fear conditioning with two unconditioned stimuli (UCS), we obtained fear ratings, UCS-expectancy ratings, and event-related fields to conditioned stimuli (CS-, CS+) and 7 different generalization stimuli (GS) on a perceptual continuum from CS- to CS+.

RESULTS

Prior to treatment, non-responders showed behavioral overgeneralization indicated by more linear generalization gradients in fear ratings. Analyses of MEG source estimations revealed that non-responders showed a decline of their (inhibitory) frontal activations to safety-signaling CS- and GS compared to CS+ over time, while responders maintained these activations at early (<300ms) and late processing stages.

CONCLUSIONS

Results provide initial evidence that pre-treatment differences of behavioral and neural markers of fear generalization may act as moderators of later responses to behavioral exposure. Stimulating further research on fear generalization as a potential predictive marker, our findings are an important first step in the attempt to identify patients who may not profit from ET, and to personalize and optimize treatment strategies for this vulnerable patient group.

Predisposing Variations in Fear-Related Brain Networks Prospectively Predict Fearful Feelings during the 2019 Coronavirus (COVID-19) Pandemic

The novel coronavirus (COVID-19) pandemic has led to a surge in mental distress and fear-related disorders, including posttraumatic stress disorder (PTSD). Fear-related disorders are characterized by dysregulations in fear and the associated neural pathways. In the present study, we examined whether individual variations in the fear neural connectome can predict fear-related symptoms during the COVID-19 pandemic. Using machine learning algorithms and back-propagation artificial neural network (BP-ANN) deep learning algorithms, we demonstrated that the intrinsic neural connectome before the COVID-19 pandemic could predict who would develop high fear-related symptoms at the peak of the COVID-19 pandemic in China (Accuracy rate = 75.00%, Sensitivity rate = 65.83%, Specificity rate = 84.17%). More importantly, prediction models could accurately predict the level of fear-related symptoms during the COVID-19 pandemic by using the prepandemic connectome state, in which the functional connectivity of lvmPFC (left ventromedial prefrontal cortex)-rdlPFC (right dorsolateral), rdACC (right dorsal anterior cingulate cortex)-left insula, lAMY (left amygdala)-lHip (left hippocampus) and lAMY-lsgACC (left subgenual cingulate cortex) was contributed to the robust prediction. The current study capitalized on prepandemic data of the neural connectome of fear to predict participants who would develop high fear-related symptoms in COVID-19 pandemic, suggesting that individual variations in the intrinsic organization of the fear circuits represent a neurofunctional marker that renders subjects vulnerable to experience high levels of fear during the COVID-19 pandemic.

Negative Overgeneralization is Associated with Anxiety and Mechanisms of Pattern Completion in Peripubertal Youth

This study examines neural mechanisms of negative overgeneralization, the increased likelihood of generalizing negative information, in peri-puberty. Theories suggest that weak pattern separation (overlapping representations are made distinct, indexed by DG/CA3 hippocampal subfield activation) underlies negative overgeneralization. We alternatively propose that neuro-maturational changes that favor pattern completion (cues reinstate stored representations, indexed by CA1 activation) are modulated by circuitry involved in emotional responding (amygdala, medial prefrontal cortices [mPFC]) to drive negative overgeneralization. Youth (N=34, 9-14 years) recruited from community and clinic settings participated in an emotional mnemonic similarity task while undergoing MRI. At Study, participants indicated the valence of images; at Test, participants made recognition memory judgments. Critical lure stimuli, that were similar to images at Study, were presented at Test, and errors ("false alarms") to negative relative to neutral stimuli reflected negative overgeneralization. Negative overgeneralization was related to greater and more similar patterns of activation in CA1 and both dorsal and ventral mPFC for negative relative to neutral stimuli. At Study, amygdala exhibited greater functional coupling with CA1 and dorsal mPFC during negative items that were later generalized. Negative overgeneralization is rooted in amygdala and mPFC modulation at encoding and pattern completion at retrieval.

Influence of Perceptual and Conceptual Information on Fear Generalization: A Behavioral and Event-Related Potential Study

Learned fear can be generalized through both perceptual and conceptual information. This study investigated how perceptual and conceptual similarities influence this generalization process. Twenty-three healthy volunteers completed a fear-generalization test as brain activity was recorded in the form of event-related potentials (ERPs). Participants were exposed to a de novo fear acquisition paradigm with four categories of conditioned stimuli (CS): two conceptual cues (animals and furniture); and two perceptual cues (blue and purple shapes). Animals (C+) and purple shapes (P+) were paired with the unconditioned stimulus (US), whereas furniture (C-) and blue shapes (P-) never were. The generalized stimuli were thus blue animals (C+P+, determined danger), blue furniture (C-P+, perceptual danger), purple animals (C+P-, conceptual danger), and purple furniture (C-P-, determined safe). We found that perceptual cues elicited larger fear responses and shorter reaction times than did conceptual cues during fear acquisition. This suggests that a perceptually related pathway might evoke greater fear than a conceptually based route. During generalization, participants were more afraid of C+ exemplars than of C- exemplars. Furthermore, C+ trials elicited greater N400 amplitudes. Thus, participants appear able to use conceptually based cues to infer the value of the current stimuli. Additionally, compared with C+ exemplars, we found an enhanced late positive potential effect in response to C- exemplars, which seems to reflect a late inhibitory process and might index safety learning. These findings may offer new insights into the pathological mechanism of anxiety disorders.

A Decision Architecture for Safety Computations

Accurately estimating safety is critical to pursuing nondefensive survival behaviors. However, little attention has been paid to how the human brain computes safety. We conceptualize a model that consists of two components: (i) threat-oriented evaluations that focus on threat value, imminence, and predictability; and (ii) self-oriented evaluations that focus on the agent's experience, strategies, and ability to control the situation. Our model points to the dynamic interaction between these two components as a mechanism of safety estimation. Based on a growing body of human literature, we hypothesize that distinct regions of the ventromedial prefrontal cortex (vmPFC) respond to threat and safety to facilitate survival decisions. We suggest safety is not an inverse of danger, but reflects independent computations that mediate defensive circuits and behaviors.

Altered Task-Evoked Corticolimbic Responsivity in Generalized Anxiety Disorder

Generalized anxiety disorder (GAD) is marked by uncontrollable, persistent worry and exaggerated response to uncertainty. Here, we review and summarize the findings from the GAD literature that employs functional neuroimaging methods. In particular, the present review focuses on task-based blood oxygen level-dependent (BOLD) functional magnetic resonance imaging (fMRI) studies. We find that select brain regions often regarded as a part of a corticolimbic circuit (e.g., amygdala, anterior cingulate cortex, prefrontal cortex) are consistently targeted for a priori hypothesis-driven analyses, which, in turn, shows varying degrees of abnormal BOLD responsivity in GAD. Data-driven whole-brain analyses show the insula and the hippocampus, among other regions, to be affected by GAD, depending on the task used in each individual study. Overall, while the heterogeneity of the tasks and sample size limits the generalizability of the findings thus far, some promising convergence can be observed in the form of the altered BOLD responsivity of the corticolimbic circuitry in GAD.

A Systematic Review on the Effect of Transcranial Direct Current and Magnetic Stimulation on Fear Memory and Extinction

Anxiety disorders are among the most prevalent mental disorders. Present treatments such as cognitive behavior therapy and pharmacological treatments show only moderate success, which emphasizes the importance for the development of new treatment protocols. Non-invasive brain stimulation methods such as repetitive transcranial magnetic stimulation (rTMS) and transcranial direct current stimulation (tDCS) have been probed as therapeutic option for anxiety disorders in recent years. Mechanistic information about their mode of action, and most efficient protocols is however limited. Here the fear extinction model can serve as a model of exposure therapies for studying therapeutic mechanisms, and development of appropriate intervention protocols. We systematically reviewed 30 research articles that investigated the impact of rTMS and tDCS on fear memory and extinction in animal models and humans, in clinical and healthy populations. The results of these studies suggest that tDCS and rTMS can be efficient methods to modulate fear memory and extinction. Furthermore, excitability-enhancing stimulation applied over the vmPFC showed the strongest potential to enhance fear extinction. We further discuss factors that determine the efficacy of rTMS and tDCS in the context of the fear extinction model and provide future directions to optimize parameters and protocols of stimulation for research and treatment.

Anxiety during abstinence from alcohol: A systematic review of rodent and human evidence for the anterior insula's role in the abstinence network

Alcohol Use Disorder (AUD) is a chronic, relapsing disease that impacts almost a third of Americans. Despite effective treatments for attaining sobriety, the majority of patients relapse within a year, making relapse a substantial barrier to long-term treatment success. A major factor contributing to relapse is heightened negative affect that results from the combination of abstinence-related increases in stress-reactivity and decreases in reward sensitivity. Substantial research has contributed to the understanding of reward-related changes in AUD. However, less is known about anxiety during abstinence, a critical component of understanding addiction as anxiety during abstinence can trigger relapse. Most of what we know about abstinence-related negative affect comes from rodent studies which have identified key brain regions responsible for abstinence-related behaviors. This abstinence network is composed of brain regions that make up the extended amygdala: the nucleus accumbens (NAcc), the central nucleus of the amygdala (CeA), and the bed nucleus of the stria terminalis (BNST). More recently, emerging evidence from rodent and human studies suggests a fourth brain region, the anterior insula, might be part of the abstinence network. Here, we review current rodent and human literature on the extended amygdala's role in alcohol abstinence and anxiety, present evidence for the anterior insula's role in the abstinence network, and provide future directions for research to further elucidate the neural underpinnings of abstinence in humans. A better understanding of the abstinence network is critical toward understanding and possibly preventing relapse in AUD.

Intranasal oxytocin decreases fear generalization in males, but does not modulate discrimination threshold

BACKGROUND

A previously acquired fear response often spreads to perceptually or conceptually close stimuli or contexts. This process, known as fear generalization, facilitates the avoidance of danger, and dysregulations in this process play an important role in anxiety disorders. Oxytocin (OT) has been shown to modulate fear learning, yet effects on fear generalization remain unknown.

METHODS

We employed a randomized, placebo-controlled, double-blind, between-subject design during which healthy male participants received either intranasal OT or placebo (PLC) following fear acquisition and before fear generalization with concomitant acquisition of skin conductance responses (SCRs). Twenty-four to 72 h before the fear learning and immediately after the fear generalization task, participants additionally complete a discrimination threshold task.

RESULTS

Relative to PLC, OT significantly reduced perceived risk and SCRs towards the CS+ and GS1 (the generalization stimulus that is most similar to CS+) during fear generalization, whereas the discrimination threshold was not affected.

CONCLUSIONS

Together, the results suggest that OT can attenuate fear generalization in the absence of effects on discrimination threshold. This study provides the first evidence for effects of OT on fear generalization in humans and suggests that OT may have therapeutic potential in anxiety disorders characterized by dysregulated fear generalization.