Inter-individual differences in trait anxiety shape the functional connectivity between the bed nucleus of the stria terminalis and the amygdala during brief threat processing

Examining Brain Activity Responses during Rat Ultrasonic Vocalization Playback: Insights from a Novel fMRI Translational Paradigm

Despite decades of preclinical investigation, there remains limited understanding of the etiology and biological underpinnings of anxiety disorders. Sensitivity to potential threat is characteristic of anxiety-like behavior in humans and rodents, but traditional rodent behavioral tasks aimed to assess threat responsiveness lack translational value, especially with regard to emotionally valenced stimuli. Therefore, development of novel preclinical approaches to serve as analogues to patient assessments is needed. In humans, the fearful face task is widely used to test responsiveness to socially communicated threat signals. In rats, ultrasonic vocalizations (USVs) are analogous social cues associated with positive or negative affective states that can elicit behavioral changes in the receiver. It is therefore likely that when rats hear aversive alarm call USVs (22 kHz), they evoke translatable changes in brain activity comparable with the fearful face task. We used functional magnetic resonance imaging in male and female rats to assess changes in BOLD activity induced by exposure to aversive 22 kHz alarm calls emitted in response to threatening stimuli, prosocial (55 kHz) USVs emitted in response to appetitive stimuli, or a computer-generated 22 kHz tone. Results show patterns of regional activation that are specific to each USV stimulus. Notably, limbic regions clinically relevant to psychiatric disorders (e.g., amygdala, bed nucleus of the stria terminalis) are preferentially activated by either aversive 22 kHz or appetitive 55 kHz USVs. These results support the use of USV playback as a promising translational tool to investigate affective processing under conditions of distal threat in preclinical rat models.

Neuroticism/Negative Emotionality Is Associated with Increased Reactivity to Uncertain Threat in the Bed Nucleus of the Stria Terminalis, Not the Amygdala

Neuroticism/negative emotionality (N/NE)-the tendency to experience anxiety, fear, and other negative emotions-is a fundamental dimension of temperament with profound consequences for health, wealth, and well-being. Elevated N/NE is associated with a panoply of adverse outcomes, from reduced socioeconomic attainment to psychiatric illness. Animal research suggests that N/NE reflects heightened reactivity to uncertain threat in the bed nucleus of the stria terminalis (BST) and central nucleus of the amygdala (Ce), but the relevance of these discoveries to humans has remained unclear. Here we used a novel combination of psychometric, psychophysiological, and neuroimaging approaches to test this hypothesis in an ethnoracially diverse, sex-balanced sample of 220 emerging adults selectively recruited to encompass a broad spectrum of N/NE. Cross-validated robust-regression analyses demonstrated that N/NE is preferentially associated with heightened BST activation during the uncertain anticipation of a genuinely distressing threat (aversive multimodal stimulation), whereas N/NE was unrelated to BST activation during certain-threat anticipation, Ce activation during either type of threat anticipation, or BST/Ce reactivity to threat-related faces. It is often assumed that different threat paradigms are interchangeable assays of individual differences in brain function, yet this has rarely been tested. Our results revealed negligible associations between BST/Ce reactivity to the anticipation of threat and the presentation of threat-related faces, indicating that the two tasks are nonfungible. These observations provide a framework for conceptualizing emotional traits and disorders; for guiding the design and interpretation of biobank and other neuroimaging studies of psychiatric risk, disease, and treatment; and for refining mechanistic research.

Neuroticism/negative emotionality is associated with increased reactivity to uncertain threat in the bed nucleus of the stria terminalis, not the amygdala

Neuroticism/Negative Emotionality (N/NE)-the tendency to experience anxiety, fear, and other negative emotions-is a fundamental dimension of temperament with profound consequences for health, wealth, and wellbeing. Elevated N/NE is associated with a panoply of adverse outcomes, from reduced socioeconomic attainment to psychiatric illness. Animal research suggests that N/NE reflects heightened reactivity to uncertain threat in the bed nucleus of the stria terminalis (BST) and central nucleus of the amygdala (Ce), but the relevance of these discoveries to humans has remained unclear. Here we used a novel combination of psychometric, psychophysiological, and neuroimaging approaches to rigorously test this hypothesis in an ethnoracially diverse, sex-balanced sample of 220 emerging adults selectively recruited to encompass a broad spectrum of N/NE. Cross-validated robust-regression analyses demonstrated that N/NE is preferentially associated with heightened BST activation during the uncertain anticipation of a genuinely distressing threat (aversive multimodal stimulation), whereas N/NE was unrelated to BST activation during certain-threat anticipation, Ce activation during either type of threat anticipation, or BST/Ce reactivity to threat-related faces. It is often assumed that different threat paradigms are interchangeable assays of individual differences in brain function, yet this has rarely been tested. Our results revealed negligible associations between BST/Ce reactivity to the anticipation of threat and the presentation of threat-related faces, indicating that the two tasks are non-fungible. These observations provide a framework for conceptualizing emotional traits and disorders; for guiding the design and interpretation of biobank and other neuroimaging studies of psychiatric risk, disease, and treatment; and for informing mechanistic research.

The role and mechanism of 5-HTDRN-BNST neural circuit in anxiety and fear lesions

Central 5-hydroxytryptaminergic dorsal raphe nucleus (5-HTDRN)-bed nucleus of stria terminalis (BNST) neural circuit dysfunction is one of the important neurobiological basis of anxiety and fear disorders. Under stress, 5-hydroxytryptamine (5-HT) neurons act on BNST receptors to attenuate anxiety and fear responses or enhance anxiety and fear. In BNST, corticotropin releasing factor neurons play a role in regulating emotions by reversely regulating excitatory or inhibitory 5-HT neurons. The composition of 5-HTDRN-BNST neural circuit, the pathological changes of 5-HTDRN-BNST neural circuit function damage under stress, and the effects of 5-HTDRN-BNST neural circuit on anxiety disorder, panic disorder and post-traumatic stress disorder were analyzed and are summarized in this paper. The characteristics of functional changes of the neural circuit and its effects on brain functional activities provide a basis and ideas for the treatment of anxiety and fear disorders through the regulation of 5-HTDRN-BNST neural circuit, and they also provide a new perspective for understanding the pathological mechanism of such diseases.

Acute and chronic alcohol modulation of extended amygdala calcium dynamics

The central amygdala (CeA) and bed nucleus of the stria terminalis (BNST) are reciprocally connected nodes of the extended amygdala thought to play an important role in alcohol consumption. Studies of immediate-early genes indicate that BNST and CeA are acutely activated following alcohol drinking and may signal alcohol reward in nondependent drinkers, while stress signaling in the extended amygdala following chronic alcohol exposure drives increased drinking via negative reinforcement. However, the temporal dynamics of neuronal activation in these regions during drinking behavior are poorly understood. In this study, we used fiber photometry and the genetically encoded calcium sensor GCaMP6s to assess acute changes in neuronal activity during alcohol consumption in BNST and CeA before and after a chronic drinking paradigm. Activity was examined in the pan-neuronal population and separately in dynorphinergic neurons. BNST and CeA showed increased pan-neuronal activity during acute consumption of alcohol and other fluid tastants of positive and negative valence, as well as highly palatable chow. Responses were greatest during initial consummatory bouts and decreased in amplitude with repeated consumption of the same tastant, suggesting modulation by stimulus novelty. Dynorphin neurons showed similar consumption-associated calcium increases in both regions. Following three weeks of continuous alcohol access (CA), calcium increases in dynorphin neurons during drinking were maintained, but pan-neuronal activity and BNST-CeA coherence were altered in a sex-specific manner. These results indicate that BNST and CeA, and dynorphin neurons specifically, are engaged during drinking behavior, and activity dynamics are influenced by stimulus novelty and chronic alcohol.

Acute and chronic alcohol modulation of extended amygdala calcium dynamics

The central amygdala (CeA) and bed nucleus of the stria terminalis (BNST) are reciprocally connected nodes of the extended amygdala thought to play an important role in alcohol consumption. Studies of immediate-early genes indicate that BNST and CeA are acutely activated following alcohol drinking and may signal alcohol reward in nondependent drinkers, while increased stress signaling in the extended amygdala following chronic alcohol exposure drives increased drinking via negative reinforcement. However, the temporal dynamics of neuronal activation in these regions during drinking behavior are poorly understood. In this study, we used fiber photometry and the genetically encoded calcium sensor GCaMP6s to assess acute changes in neuronal activity during alcohol consumption in BNST and CeA before and after a chronic drinking paradigm. Activity was examined in the pan-neuronal population and separately in dynorphinergic neurons. BNST and CeA showed increased pan-neuronal activity during acute consumption of alcohol and other fluid tastants of positive and negative valence, as well as highly palatable chow. Responses were greatest during initial consummatory bouts and decreased in amplitude with repeated consumption of the same tastant, suggesting modulation by stimulus novelty. Dynorphin neurons showed similar consumption-associated calcium increases in both regions. Following three weeks of continuous alcohol access (CA), calcium increases in dynorphin neurons during drinking were maintained, but pan-neuronal activity and BNST-CeA coherence were altered in a sex-specific manner. These results indicate that BNST and CeA, and dynorphin neurons specifically, are engaged during drinking behavior, and activity dynamics are influenced by stimulus novelty and chronic alcohol.

The neurophysiological basis of stress and anxiety - comparing neuronal diversity in the bed nucleus of the stria terminalis (BNST) across species

The bed nucleus of the stria terminalis (BNST), as part of the extended amygdala, has become a region of increasing interest regarding its role in numerous human stress-related psychiatric diseases, including post-traumatic stress disorder and generalized anxiety disorder amongst others. The BNST is a sexually dimorphic and highly complex structure as already evident by its anatomy consisting of 11 to 18 distinct sub-nuclei in rodents. Located in the ventral forebrain, the BNST is anatomically and functionally connected to many other limbic structures, including the amygdala, hypothalamic nuclei, basal ganglia, and hippocampus. Given this extensive connectivity, the BNST is thought to play a central and critical role in the integration of information on hedonic-valence, mood, arousal states, processing emotional information, and in general shape motivated and stress/anxiety-related behavior. Regarding its role in regulating stress and anxiety behavior the anterolateral group of the BNST (BNSTALG) has been extensively studied and contains a wide variety of neurons that differ in their electrophysiological properties, morphology, spatial organization, neuropeptidergic content and input and output synaptic organization which shape their activity and function. In addition to this great diversity, further species-specific differences are evident on multiple levels. For example, classic studies performed in adult rat brain identified three distinct neuron types (Type I-III) based on their electrophysiological properties and ion channel expression. Whilst similar neurons have been identified in other animal species, such as mice and non-human primates such as macaques, cross-species comparisons have revealed intriguing differences such as their comparative prevalence in the BNSTALG as well as their electrophysiological and morphological properties, amongst other differences. Given this tremendous complexity on multiple levels, the comprehensive elucidation of the BNSTALG circuitry and its role in regulating stress/anxiety-related behavior is a major challenge. In the present Review we bring together and highlight the key differences in BNSTALG structure, functional connectivity, the electrophysiological and morphological properties, and neuropeptidergic profiles of BNSTALG neurons between species with the aim to facilitate future studies of this important nucleus in relation to human disease.

The effect of inherently threatening contexts on visuocortical engagement to conditioned threat

Fear and anxiety are crucial for adaptive responding in life-threatening situations. Whereas fear is a phasic response to an acute threat accompanied by selective attention, anxiety is characterized by a sustained feeling of apprehension and hypervigilance during situations of potential threat. In the current literature, fear and anxiety are usually considered mutually exclusive, with partially separated neural underpinnings. However, there is accumulating evidence that challenges this distinction between fear and anxiety, and simultaneous activation of fear and anxiety networks has been reported. Therefore, the current study experimentally tested potential interactions between fear and anxiety. Fifty-two healthy participants completed a differential fear conditioning paradigm followed by a test phase in which the conditioned stimuli were presented in front of threatening or neutral contextual images. To capture defense system activation, we recorded subjective (threat, US-expectancy), physiological (skin conductance, heart rate) and visuocortical (steady-state visual evoked potentials) responses to the conditioned stimuli as a function of contextual threat. Results demonstrated successful fear conditioning in all measures. In addition, threat and US-expectancy ratings, cardiac deceleration, and visuocortical activity were enhanced for fear cues presented in threatening compared with neutral contexts. These results are in line with an additive or interactive rather than an exclusive model of fear and anxiety, indicating facilitated defensive behavior to imminent danger in situations of potential threat.

Non-conscious processing of fear faces: a function of the implicit self-concept of anxiety

BACKGROUND

Trait anxiety refers to a stable tendency to experience fears and worries across many situations. High trait anxiety is a vulnerability factor for the development of psychopathologies. Self-reported trait anxiety appears to be associated with an automatic processing advantage for threat-related information. Self-report measures assess aspects of the explicit self-concept of anxiety. Indirect measures can tap into the implicit self-concept of anxiety.

METHODS

We examined automatic brain responsiveness to non-conscious threat as a function of trait anxiety using functional magnetic resonance imaging. Besides a self-report instrument, we administered the Implicit Association Test (IAT) to assess anxiety. We used a gender-decision paradigm presenting brief (17 ms) and backward-masked facial expressions depicting disgust and fear.

RESULTS

Explicit trait anxiety was not associated with brain responsiveness to non-conscious threat. However, a relation of the implicit self-concept of anxiety with masked fear processing in the thalamus, precentral gyrus, and lateral prefrontal cortex was observed.

CONCLUSIONS

We provide evidence that a measure of the implicit self-concept of anxiety is a valuable predictor of automatic neural responses to threat in cortical and subcortical areas. Hence, implicit anxiety measures could be a useful addition to explicit instruments. Our data support the notion that the thalamus may constitute an important neural substrate in biased non-conscious processing in anxiety.

Constitutive 5-HT2C receptor knock-out facilitates fear extinction through altered activity of a dorsal raphe-bed nucleus of the stria terminalis pathway

Serotonin 2C receptors (5-HT2CRs) are widely distributed throughout the brain and are strongly implicated in the pathophysiology of anxiety disorders such as post-traumatic stress disorder (PTSD). Although in recent years, a considerable amount of evidence supports 5-HT2CRs facilitating effect on anxiety behavior, the involvement in learned fear responses and fear extinction is rather unexplored. Here, we used a 5-HT2CR knock-out mouse line (2CKO) to gain new insights into the involvement of 5-HT2CRs in the neuronal fear circuitry. Using a cued fear conditioning paradigm, our results revealed that global loss of 5-HT2CRs exclusively accelerates fear extinction, without affecting fear acquisition and fear expression. To investigate the neuronal substrates underlying the extinction enhancing effect, we mapped the immediate-early gene product cFos, a marker for neuronal activity, in the dorsal raphe nucleus (DRN), amygdala and bed nucleus of the stria terminalis (BNST). Surprisingly, besides extinction-associated changes, our results revealed alterations in neuronal activity even under basal home cage conditions in specific subregions of the DRN and the BNST in 2CKO mice. Neuronal activity in the dorsal BNST was shifted in an extinction-supporting direction due to 5-HT2CR knock-out. Finally, the assessment of DRN-BNST connectivity using antero- and retrograde tracing techniques uncovered a discrete serotonergic pathway projecting from the most caudal subregion of the DRN (DRC) to the anterodorsal portion of the BNST (BNSTad). This serotonergic DRC-BNSTad pathway showed increased neuronal activity in 2CKO mice. Thus, our results provide new insights for the fear extinction network by revealing a specific serotonergic DRC-BNSTad pathway underlying a 5-HT2CR-sensitive mechanism with high significance in the treatment of PTSD.

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.

Chronic stress-induced synaptic changes to corticotropin-releasing factor-signaling in the bed nucleus of the stria terminalis

The sexually dimorphic bed nucleus of the stria terminalis (BNST) is comprised of several distinct regions, some of which act as a hub for stress-induced changes in neural circuitry and behavior. In rodents, the anterodorsal BNST is especially affected by chronic exposure to stress, which results in alterations to the corticotropin-releasing factor (CRF)-signaling pathway, including CRF receptors and upstream regulators. Stress increases cellular excitability in BNST CRF+ neurons by potentiating miniature excitatory postsynaptic current (mEPSC) amplitude, altering the resting membrane potential, and diminishing M-currents (a voltage-gated K+ current that stabilizes membrane potential). Rodent anterodorsal and anterolateral BNST neurons are also critical regulators of behavior, including avoidance of aversive contexts and fear learning (especially that of sustained threats). These rodent behaviors are historically associated with anxiety. Furthermore, BNST is implicated in stress-related mood disorders, including anxiety and Post-Traumatic Stress Disorders in humans, and may be linked to sex differences found in mood disorders.

Subiculum-BNST structural connectivity in humans and macaques

Invasive tract-tracing studies in rodents implicate a direct connection between the subiculum and bed nucleus of the stria terminalis (BNST) as a key component of neural pathways mediating hippocampal regulation of the Hypothalamic-Pituitary-Adrenal (HPA) axis. A clear characterisation of the connections linking the subiculum and BNST in humans and non-human primates is lacking. To address this, we first delineated the projections from the subiculum to the BNST using anterograde tracers injected into macaque monkeys, revealing evidence for a monosynaptic subiculum-BNST projection involving the fornix. Second, we used in vivo diffusion MRI tractography in macaques and humans to demonstrate substantial subiculum complex connectivity to the BNST in both species. This connection was primarily carried by the fornix, with additional connectivity via the amygdala, consistent with rodent anatomy. Third, utilising the twin-based nature of our human sample, we found that microstructural properties of these tracts were moderately heritable (h2 ∼ 0.5). In a final analysis, we found no evidence of any significant association between subiculum complex-BNST tract microstructure and indices of perceived stress/dispositional negativity and alcohol use, derived from principal component analysis decomposition of self-report data. Our findings address a key translational gap in our knowledge of the neurocircuitry regulating stress.

Coordination of social behaviors by the bed nucleus of the stria terminalis

The bed nucleus of the stria terminalis (BNST) is a sexually dimorphic, neuropeptide-rich node of the extended amygdala that has been implicated in responses to stress, drugs of abuse, and natural rewards. Its function is dysregulated in neuropsychiatric disorders that are characterized by stress- or drug-induced alterations in mood, arousal, motivation, and social behavior. However, compared to the BNST's role in mood, arousal, and motivation, its role in social behavior has remained relatively understudied. Moreover, the precise cell types and circuits underlying the BNST's role in social behavior have only recently begun to be explored using modern neuroscience techniques. Here, we systematically review the existing literature investigating the neurobiological substrates within the BNST that contribute to the coordination of various sex-dependent and sex-independent social behavioral repertoires, focusing largely on pharmacological and circuit-based behavioral studies in rodents. We suggest that the BNST coordinates social behavior by promoting appropriate assessment of social contexts to select relevant behavioral outputs and that disruption of socially relevant BNST systems by stress and drugs of abuse may be an important factor in the development of social dysfunction in neuropsychiatric disorders.

Bed nucleus of the stria terminalis and amygdala responses to unpredictable threat in children

Substantial evidence from studies in humans suggests the amygdala is pivotal for anxiety. Findings from animal models and translational studies suggests the bed nucleus of the stria terminalis (BNST) is also critical for anxiety and the anticipation of unpredictable threat in adults. However, it remains unknown whether the BNST is involved in unpredictable threat anticipation in children. Forty-two 8-10-year-olds completed resting-state functional magnetic resonance imaging (fMRI) scans and an unpredictable threat fMRI task in which they were trained to associate cues with images. Intrinsic connectivity analyses were performed to establish functional BNST and amygdala networks. BNST and amygdala activation to cues and images was tested. Significant findings were followed by task-based functional connectivity analyses. Children showed evidence for BNST and amygdala intrinsic connectivity that was similar to previous patterns observed in adults. In response to unpredictable cues relative to neutral face cues, children had a significant amygdala response but no response in the BNST. The amygdala, but not the BNST, also showed a significantly greater response to fear face images relative to neutral images. Thus, unpredictable threat activated the amygdala, but not BNST, in children. This finding is contrary to studies showing robust BNST activation to unpredictable threat in adults and may suggest that the BNST's role in threat processing emerges later in development.

Centromedial amygdala is more relevant for phobic confrontation relative to the bed nucleus of stria terminalis in patients with spider phobia

Recent studies indicate differential involvement of the centromedial amygdala (CM) and the bed nucleus of the stria terminalis (BNST) during processing (anticipation and confrontation) of threat stimuli. Here, temporal predictability was shown to be a relevant factor. In this study, we want to investigate the relevance of these effects, which were found in healthy subjects, for anxiety disorders. Therefore, we investigated the differential involvement of CM and BNST in the anticipation and confrontation of phobic stimuli under variation of temporal predictability in spider phobia. 21 patients with spider phobia and 21 healthy controls underwent a temporally predictable/unpredictable phobic and neutral anticipation and confrontation paradigm using functional magnetic resonance imaging (fMRI) and ROI analyses. During the anticipation phase, healthy controls showed higher CM and BNST activity during the predictable compared with the unpredictable condition compared with the anxiety patients. During a confrontation phase that followed the anticipation phase, CM was more activated than BNST during the phobic compared with the neutral confrontation. While this effect was independent of threat predictability in patients, healthy controls showed higher activation in the CM compared with the BNST only during the predictable spider confrontation compared with the predictable bird confrontation. The results contribute to a better understanding of the separate roles of the CM and BNST during phobic processes. The CM was found to be more relevant to phobic confrontation in patients with spider phobia compared with the BNST.

Brain Injury and Mental Health Among the Victims of Intimate Partner Violence: A Case-Series Exploratory Study

Intimate partner violence (IPV) survivors frequently report face, head, and neck as their injury site. Many mild traumatic brain injuries (TBIs) are undiagnosed or underreported among IPV survivors while these injuries may be linked to changes in brain function or pathology. TBI sustained due to IPV often occurs over time and ranges in severity. The aim of this case-series study was to explore risk factors, symptoms, and brain changes unique to survivors of intimate partner violence with suspicion of TBI. This case-series exploratory study examines the potential relationships among IPV, mental health issues, and TBI. Participants of this study included six women: 3 women with a history of IPV without any experience of concussive blunt force to the head, and 3 women with a history of IPV with concussive head trauma. Participants completed 7T MRI of the brain, self-report psychological questionnaires regarding their mental health, relationships, and IPV, and the Structured Clinical Interview. MRI scans were analyzed for cerebral hemorrhage, white matter disturbance, and cortical thinning. Results indicated significant differences in resting-state connectivity among survivors of partner violence as well as differences in relationship dynamics and mental health symptoms. White matter hyperintensities are also observed among the survivors. Developing guidelines and recommendations for TBI-risk screening, referrals, and appropriate service provision is crucial for the effective treatment of TBI-associated IPV. Early and accurate characterization of TBI in survivors of IPV may relieve certain neuropsychological consequences.

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.

Mental Resilience and Coping With Stress: A Comprehensive, Multi-level Model of Cognitive Processing, Decision Making, and Behavior

Aversive events can evoke strong emotions that trigger cerebral neuroactivity to facilitate behavioral and cognitive shifts to secure physiological stability. However, upon intense and/or chronic exposure to such events, the neural coping processes can be maladaptive and disrupt mental well-being. This maladaptation denotes a pivotal point when psychological stress occurs, which can trigger subconscious, "automatic" neuroreactivity as a defence mechanism to protect the individual from potential danger including overwhelming unpleasant feelings and disturbing or threatening thoughts.The outcomes of maladaptive neural activity are cognitive dysfunctions such as altered memory, decision making, and behavior that impose a risk for mental disorders. Although the neurocognitive phenomena associated with psychological stress are well documented, the complex neural activity and pathways related to stressor detection and stress coping have not been outlined in detail. Accordingly, we define acute and chronic stress-induced pathways, phases, and stages in relation to novel/unpredicted, uncontrollable, and ambiguous stressors. We offer a comprehensive model of the stress-induced alterations associated with multifaceted pathophysiology related to cognitive appraisal and executive functioning in stress.

Extended-amygdala intrinsic functional connectivity networks: A population study

Pre-clinical and human neuroimaging research implicates the extended-amygdala (ExtA) (including the bed nucleus of the stria terminalis [BST] and central nucleus of the amygdala [CeA]) in networks mediating negative emotional states associated with stress and substance-use behaviours. The extent to which individual ExtA structures form a functionally integrated unit is controversial. We utilised a large sample (n > 1,000 healthy young adult humans) to compare the intrinsic functional connectivity networks (ICNs) of the BST and CeA using task-free functional magnetic resonance imaging (fMRI) data from the Human Connectome Project. We assessed whether inter-individual differences within these ICNs were related to two principal components representing negative disposition and alcohol use. Building on recent primate evidence, we tested whether within BST-CeA intrinsic functional connectivity (iFC) was heritable and further examined co-heritability with our principal components. We demonstrate the BST and CeA to have discrete, but largely overlapping ICNs similar to previous findings. We found no evidence that within BST-CeA iFC was heritable; however, post hoc analyses found significant BST iFC heritability with the broader superficial and centromedial amygdala regions. There were no significant correlations or co-heritability associations with our principal components either across the ICNs or for specific BST-Amygdala iFC. Possible differences in phenotype associations across task-free, task-based, and clinical fMRI are discussed, along with suggestions for more causal investigative paradigms that make use of the now well-established ExtA ICNs.

Somatostatin Neurons of the Bed Nucleus of Stria Terminalis Enhance Associative Fear Memory Consolidation in Mice

Excessive fear learning and generalized, extinction-resistant fear memories are core symptoms of anxiety and trauma-related disorders. Despite significant evidence from clinical studies reporting hyperactivity of the bed nucleus of stria terminalis (BNST) under these conditions, the role of BNST in fear learning and expression is still not clarified. Here, we tested how BNST modulates fear learning in male mice using a chemogenetic approach. Activation of GABAergic neurons of BNST during fear conditioning or memory consolidation resulted in enhanced cue-related fear recall. Importantly, BNST activation had no acute impact on fear expression during conditioning or recalls, but it enhanced cue-related fear recall subsequently, potentially via altered activity of downstream regions. Enhanced fear memory consolidation could be replicated by selectively activating somatostatin (SOM), but not corticotropin-releasing factor (CRF), neurons of the BNST, which was accompanied by increased fear generalization. Our findings suggest the significant modulation of fear memory strength by specific circuits of the BNST.SIGNIFICANCE STATEMENT The bed nucleus of stria terminalis (BNST) mediates different defensive behaviors, and its connections implicate its integrative modulatory role in fear memory formation; however, the involvement of BNST in fear learning has yet to be elucidated in detail. Our data highlight that BNST stimulation enhances fear memory formation without direct effects on fear expression. Our study identified somatostatin (SOM) cells within the extended amygdala as specific neurons promoting fear memory formation. These data underline the importance of anxiety circuits in maladaptive fear memory formation, indicating elevated BNST activity as a potential vulnerability factor to anxiety and trauma-related disorders.

Functional anatomy of the bed nucleus of the stria terminalis-hypothalamus neural circuitry: Implications for valence surveillance, addiction, feeding, and social behaviors

The bed nucleus of the stria terminalis (BNST) is a medial basal forebrain structure that modulates the hypothalamo-pituitary-adrenal (HPA) axis. The heterogeneous subnuclei of the BNST integrate inputs from mood and reward-related areas and send direct inhibitory projections to the hypothalamus. The connections between the BNST and hypothalamus are conserved across species, promote activation of the HPA axis, and can increase avoidance of aversive environments, which is historically associated with anxiety behaviors. However, BNST-hypothalamus circuitry is also implicated in motivated behaviors, drug seeking, feeding, and sexual behavior. These complex and diverse roles, as well its sexual dimorphism, indicate that the BNST-hypothalamus circuitry is an essential component of the neural circuitry that may underlie various psychiatric diseases, ranging from anorexia to anxiety to addiction. The following review is a cross-species exploration of BNST-hypothalamus circuitry. First, we describe the BNST subnuclei, microcircuitry and complex reciprocal connections with the hypothalamus. We will then discuss the behavioral functions of BNST-hypothalamus circuitry, including valence surveillance, addiction, feeding, and social behavior. Finally, we will address sex differences in morphology and function of the BNST and hypothalamus.

Roles of the bed nucleus of the stria terminalis and amygdala in fear reactions

The bed nucleus of the stria terminalis (BNST) plays a critical modulatory role in driving fear responses. Part of the so-called extended amygdala, this region shares many functions and connections with the substantially more investigated amygdala proper. In this chapter, we review contributions of the BNST and amygdala to subjective, behavioral, and physiological aspects of fear. Despite the fact that both regions are together involved in each of these aspects of fear, they appear complimentary in their contributions. Specifically, the basolateral amygdala (BLA), through its connections to sensory and orbitofrontal regions, is ideally poised for fast learning and controlling fear reactions in a variety of situations. The central amygdala (CeA) relies on BLA input and is particularly important for adjusting physiological and behavioral responses under acute threat. In contrast, the BNST may profit from more extensive striatal and dorsomedial prefrontal connections to drive anticipatory responses under more ambiguous conditions that allow more time for planning. Thus current evidence suggests that the BNST is ideally suited to play a critical role responding to distant or ambiguous threats and could thereby facilitate goal-directed defensive action.

BNST and amygdala activation to threat: Effects of temporal predictability and threat mode

Recent animal and human studies highlight the uncertainty about the onset of an aversive event as a crucial factor for the involvement of the centromedial amygdala (CM) and bed nucleus of the stria terminalis (BNST) activity. However, studies investigating temporally predictable or unpredictable threat anticipation and confrontation processes are rare. Furthermore, the few existing fMRI studies analyzing temporally predictable and unpredictable threat processes used small sample sizes or limited fMRI paradigms. Therefore, we measured functional brain activity in 109 predominantly female healthy participants during a temporally predictable-unpredictable threat paradigm, which aimed to solve limited aspects of recent studies. Results showed higher BNST activity compared to the CM during the cue indicating that the upcoming confrontation is aversive relative to the cue indicating an upcoming neutral confrontation. Both the CM and BNST showed higher activity during the confrontation with unpredictable and aversive stimuli, but the reaction to aversive confrontation relative to neutral confrontation was stronger in the CM compared to the BNST. Additional modulation analyses by NPSR1 rs324981 genotype revealed higher BNST activity relative to the CM in unpredictable anticipation relative to predictable anticipation in T-carriers compared to AA carriers. Our results indicate that during the confrontation with aversive or neutral stimuli, temporal unpredictability modulates CM and BNST activity. Further, there is a differential activity concerning threat processing, as BNST is more involved when focussing on fear-related anticipation processes and CM is more involved when focussing on threat confrontation.

It takes two: Bilateral bed nuclei of the stria terminalis mediate the expression of contextual fear, but not of moderate cued fear

A growing body of research supports a prominent role for the bed nucleus of the stria terminalis (BST) in the expression of adaptive and perhaps even pathological anxiety. The traditional premise that the BST is required for long-duration responses to threats, but not for fear responses to distinct, short-lived cues may, however, be oversimplified. A thorough evaluation of the involvement of the BST in cued and contextual fear is therefore warranted. In a series of preregistered experiments using male Wistar rats, we first addressed the involvement of the BST in cued fear. Following up on earlier work where we found that BST lesions disrupted auditory fear while the animals were in a rather high stress state, we here show that the BST is not required for the expression of more specific fear for the tone under less stressful conditions. In the second part, we corroborate that the same lesion method does attenuate contextual fear. Furthermore, despite prior indications for an asymmetric recruitment of the BST during the expression of anxiety, we found that bilateral lesioning of the BST is required for a significant attenuation of the expression of contextual fear. A functional BST in only one hemisphere resulted in increased variability in the behavioral outcome. We conclude that, in animals that acquired a fear memory with an intact brain, the bilateral BST mediates the expression of contextual fear, but not of unambiguous cued fear.

A high-resolution fMRI investigation of BNST and centromedial amygdala activity as a function of affective stimulus predictability, anticipation, and duration

Relative to the centromedial amygdala (CM), the bed nucleus of the stria terminalis (BNST) may exhibit more sustained activation toward threat, sensitivity to unpredictability and activation during anxious anticipation. These factors are often intertwined. For example, greater BNST (vs CM) activation during a block of aversive stimuli may reflect either more sustained activation to the stimuli or greater activation due to the anticipation of upcoming stimuli. To further investigate these questions, we had participants (19 females, 9 males) complete a task adapted from a study conducted by Somerville, Whalen and Kelly in 2013, during high-resolution 7-Tesla fMRI BOLD acquisition. We found a larger response to negative vs neutral blocks (sustained threat) than to images (transient) in the BNST, but not the CM. However, in an additional analysis, we also found BNST, but not CM, activation to the onset of the anticipation period on negative vs neutral trials, possibly contributing to BNST activation across negative blocks. Predictability did not affect CM or BNST activation. These results suggest a BNST role in anxious anticipation and highlight the need for further research clarifying the temporal response characteristics of these regions.

Imaging the socially-anxious brain: recent advances and future prospects

Social anxiety disorder (SAD) is serious psychiatric condition with a genetic background. Insight into the neurobiological alterations underlying the disorder is essential to develop effective interventions that could relieve SAD-related suffering. In this expert review, we consider recent neuroimaging work on SAD. First, we focus on new results from magnetic resonance imaging studies dedicated to outlining biomarkers of SAD, including encouraging findings with respect to structural and functional brain alterations associated with the disorder. Furthermore, we highlight innovative studies in the field of neuroprediction and studies that established the effects of treatment on brain characteristics. Next, we describe novel work aimed to delineate endophenotypes of SAD, providing insight into the genetic susceptibility to develop the disorder. Finally, we outline outstanding questions and point out directions for future research.

Threat bias and resting state functional connectivity of the amygdala and bed nucleus stria terminalis

BACKGROUND

Previous research has distinguished the activations of the amygdala and bed nucleus of stria terminalis (BNST) during threat-related contingencies. However, how intrinsic connectivities of the amygdala and BNST relate to threat bias remains unclear. Here, we investigated how resting state functional connectivity (rsFC) of the amygdala and BNST in healthy controls (HC) and patients with anxiety-related disorders (PAD) associate with threat bias in a dot-probe task.

METHODS

Imaging and behavioral data of 30 PAD and 83 HC were obtained from the Nathan Kline Institute - Rockland sample and processed according to published routines. All imaging results were evaluated at voxel p < 0.001 and cluster p < 0.05, FWE corrected in SPM.

RESULTS

PAD and HC did not show differences in whole brain rsFC with either the amygdala or BNST. In linear regressions threat bias was positively correlated with amygdala-thalamus/anterior cingulate cortex (ACC) rsFC in HC but not PAD, and with BNST-caudate rsFC in PAD but not HC. Slope tests confirmed group differences in the correlations between threat bias and amygdala-thalamus/ACC as well as BNST-caudate rsFC.

LIMITATIONS

As only half of the patients included were diagnosed with comorbid anxiety, the current findings need to be considered with the clinical heterogeneity and require replication in populations specifically with anxiety disorders.

CONCLUSIONS

Together, these results suggest amygdala and BNST connectivities as new neural markers of anxiety disorders. Whereas amygdala-thalamus/ACC rsFC support adaptive regulation of threat response in the HC, BNST-caudate rsFC may reflect maladaptive neural processes that are dominated by anticipatory anxiety.

Increased BNST reactivity to affective images is associated with greater α-amylase response to social stress

While rodent research suggests that the bed nucleus of the stria terminalis (BNST) and centromedial amygdala (CM) coordinate the hormonal stress response, little is known about the BNST’s role in the human stress response. The human BNST responds to negatively valenced stimuli, which likely subserves its role in responding to threat. Thus, variation in BNST reactivity to negatively valenced stimuli may relate to differences in the stress response. We measured participants’ blood oxygenated level-dependent response to affective images and salivary cortisol and α-amylase (AA) levels in response to a subsequent Trier social stress test (TSST). Greater BNST activation to emotionally evocative images was associated with a larger TSST-evoked AA, but not cortisol response. This association remained after controlling for CM activation, which was not related to the cortisol or AA response. These results suggest that the BNST response to negatively valenced images subserves its role in coordinating the stress response, a BNST role in the stress response independent from the CM, and highlight the need for investigation of the conditions under which BNST activation predicts the cortisol response. Our findings are critical for the future study of mood and anxiety disorders, as dysregulation of the stress system plays a key role in their pathogenesis.

Higher resting-state BNST-CeA connectivity is associated with greater corrugator supercilii reactivity to negatively valenced images

The bed nucleus of the stria terminalis (BNST) and central nucleus of the amygdala (CeA) are hypothesized to be the output nodes of the extended amygdala threat response, integrating multiple signals to coordinate the threat response via outputs to the hypothalamus and brainstem. The BNST and CeA are structurally and functionally connected, suggesting interactions between these regions may regulate how the response to provocation unfolds. However, the relationship between human BNST-CeA connectivity and the behavioral response to affective stimuli is little understood. To investigate whether individual differences in BNST-CeA connectivity are related to the affective response to negatively valenced stimuli, we tested relations between resting-state BNST-CeA connectivity and both facial electromyographic (EMG) activity of the corrugator supercilii muscle and eyeblink startle magnitude during affective image presentation within the Refresher sample of the Midlife in the United States (MIDUS) study. We found that higher right BNST-CeA connectivity was associated with greater corrugator activity to negative, but not positive, images. There was a trend-level association between right BNST-CeA connectivity and trait negative affect. Eyeblink startle magnitude was not significantly related to BNST-CeA connectivity. These results suggest that functional interactions between BNST and CeA contribute to the behavioral response to negative emotional events.

The spontaneous activity and functional network of the occipital cortex is correlated with state anxiety in healthy adults

The occipital lobe has been implicated in anxiety disorder, however, its contributions to anxiety in healthy adults remain less clear. We conducted a resting-state functional magnetic resonance imaging study to explore the relationship between the amplitude of low-frequency fluctuation (ALFF), functional connectivity (FC), and state anxiety level in the healthy population. First, the results showed that the ALFF of the left inferior occipital gyrus (IOG) was negatively correlated with state anxiety. Furthermore, state anxiety was positively correlated with the FC between the left IOG and the right medial superior frontal gyrus and right cerebellum 8 area and negatively correlated with the FC between the left IOG and the left superior parietal gyrus. These results indicate that the occipital lobe of healthy individuals is involved in processing of anxiety in part through a frontal-parietal network.

Social anxiety is associated with BNST response to unpredictability

BACKGROUND

Anxiety disorders are highly prevalent and cause substantial suffering and impairment. Whereas the amygdala has well-established contributions to anxiety, evidence from rodent and nonhuman primate models suggests that the bed nucleus of the stria terminalis (BNST) may play a critical, and possibly distinct, role in human anxiety disorders. The BNST mediates hypervigilance and anticipatory anxiety in response to an unpredictable or ambiguous threat, core symptoms of social anxiety, yet little is known about the BNST's role in social anxiety.

METHODS

Functional magnetic resonance imaging was used to measure neural responses during a cued anticipation task with an unpredictable, predictable threat, and predictable neutral cues followed by threat or neutral images. Social anxiety was examined using a dimensional approach (N = 44 adults).

RESULTS

For unpredictable cues, higher social anxiety was associated with lower BNST-amygdala connectivity. For unpredictable images, higher social anxiety was associated with greater connectivity between the BNST and both the ventromedial prefrontal cortex and the posterior cingulate cortex and lower connectivity between the BNST and postcentral gyrus. Social anxiety moderated the BNST-amygdala dissociation for unpredictable images; higher social anxiety was associated with BNST > amygdala response to unpredictable threat relative to unpredictable neutral images.

CONCLUSIONS

Social anxiety was associated with alterations in BNST responses to unpredictability, particularly in the BNST's interactions with other brain regions, including the amygdala and prefrontal cortex. To our knowledge, these findings provide the first evidence for the BNST's role in social anxiety, which may be a potential new target for prevention and intervention.

Pre-specified Anxiety Predicts Future Decision-Making Performances Under Different Temporally Constrained Conditions

In real-life circumstances, people occasionally require making forced decisions when encountering unpredictable events and situations that yield socially and privately unfavorable consequences. In order to prevent future negative consequences, it is beneficial to successfully predict future decision-making behaviors based on various types of information, including behavioral traits and/or psychological states. For this prospective purpose, the present study used the Iowa Gambling Task, which simulates multiple aspects of real-life decision-making processes, such as choice preference, selection and evaluation of output feedback, and investigated how anxiety profiles predict decision-making performances under conditions with different temporal pressures on task execution. To conduct a temporally causal analysis, we assessed the trait and state anxiety profiles of 33 young participants prior to the task and analyzed their subsequent decision-making performances. We separated two disadvantageous card decks with high rewards and losses into high- and middle-risk decks, and calculated local performance indexes for decision-making immediately after salient penalty events for the high-risk deck in addition to traditional global performance indexes concerning overall trial outcomes such as final winnings and net scores. For global decision-making, higher trait anxiety predicted more risky choices solely in the self-paced condition without temporal pressure. For local decision-making, state anxiety predicted risk-taking performances differently in the self- and forced-paced conditions. In the self-paced condition, higher state anxiety predicted higher risk-avoidance. In the forced-paced condition, higher state anxiety predicted more frequent choices of the middle-risk deck. These findings suggest not only that pre-specified anxiety profiles can effectively predict future decision-making behaviors under different temporal pressures, but also newly indicate that behavioral mechanisms for moderate risk-taking under an emergent condition should be focused on to effectively prevent future unfavorable consequences when actually encountering negative events.

Sex-Dependent Modulation of Anxiety and Fear by 5-HT1A Receptors in the Bed Nucleus of the Stria Terminalis

Serotonin (5-hydroxytryptamine; 5-HT) coordinates behavioral responses to stress through a variety of presynaptic and postsynaptic receptors distributed across functionally diverse neuronal networks in the central nervous system. Efferent 5-HT projections from the dorsal raphe nucleus (DRN) to the bed nucleus of the stria terminalis (BNST) are generally thought to enhance anxiety and aversive learning by activating 5-HT_2C receptor (5-HT_2CR) signaling in the BNST, although an opposing role for postsynaptic 5-HT_1A receptors has recently been suggested. In the present study, we sought to delineate a role for postsynaptic 5-HT_1A receptors in the BNST in aversive behaviors using a conditional knockdown of the 5-HT_1A receptor. Both males and females were tested to dissect out sex-specific effects. We found that male mice have significantly reduced fear memory recall relative to female mice and inactivation of 5-HT_1A receptor in the BNST increases contextual fear conditioning in male mice so that they resemble the females. This coincided with an increase in neuronal excitability in males, suggesting that 5-HT_1A receptor deletion may enhance contextual fear recall by disinhibiting fear memory circuits in the BNST. Interestingly, 5-HT_1A receptor knockdown did not significantly alter anxiety-like behavior in male or female mice, which is in agreement with previous findings that anxiety and fear are modulated by dissociable circuits in the BNST. Overall, these results suggest that BNST 5-HT_1A receptors do not significantly alter behavior under basal conditions, but can act as a molecular brake that buffer against excessive activation of aversive circuits in more threatening contexts.

What drives prioritized visual processing? A motivational relevance account

Emotion is fundamental to our being, and an essential aspect guiding behavior when rapid responding is required. This includes whether we approach or avoid a stimulus, and the accompanying physiological responses. A common tenet is that threat-related content drives stimulus processing and biases visual attention, so that rapid responding can be initiated. In this paper, it will be argued instead that prioritization of threatening stimuli should be encompassed within a motivational relevance framework. To more fully understand what is, or is not, prioritized for visual processing one must, however, additionally consider: (i) stimulus ambiguity and perceptual saliency; (ii) task demands, including both perceptual load and cognitive load; and (iii) endogenous/affective states of the individual. Combined with motivational relevance, this then leads to a multifactorial approach to understanding the drivers of prioritized visual processing. This accords with current recognition that the brain basis allowing for visual prioritization is also multifactorial, including transient, dynamic and overlapping networks. Taken together, the paper provides a reconceptualization of how "emotional" information prioritizes visual processing.

Bed nucleus of the stria terminalis regulates fear to unpredictable threat signals

The bed nucleus of the stria terminalis (BNST) has been implicated in conditioned fear and anxiety, but the specific factors that engage the BNST in defensive behaviors are unclear. Here we examined whether the BNST mediates freezing to conditioned stimuli (CSs) that poorly predict the onset of aversive unconditioned stimuli (USs) in rats. Reversible inactivation of the BNST selectively reduced freezing to CSs that poorly signaled US onset (e.g., a backward CS that followed the US), but did not eliminate freezing to forward CSs even when they predicted USs of variable intensity. Additionally, backward (but not forward) CSs selectively increased Fos in the ventral BNST and in BNST-projecting neurons in the infralimbic region of the medial prefrontal cortex (mPFC), but not in the hippocampus or amygdala. These data reveal that BNST circuits regulate fear to unpredictable threats, which may be critical to the etiology and expression of anxiety.

Resting-state fMRI effective connectivity between the bed nucleus of the stria terminalis and amygdala nuclei

The bed nucleus of the stria terminalis (BNST) and the laterobasal nucleus (LB), centromedial nucleus (CM), and superficial nucleus (SF) of the amygdala form an interconnected dynamical system, whose combined activity mediates a variety of behavioral and autonomic responses in reaction to homeostatic challenges. Although previous research provided deeper insight into the structural and functional connections between these nuclei, studies investigating their resting-state functional magnetic resonance imaging (fMRI) connectivity were solely based on undirected connectivity measures. Here, we used high-quality data of 391 subjects from the Human Connectome Project to estimate the effective connectivity (EC) between the BNST, the LB, CM, and SF through spectral dynamic causal modeling, the relation of the EC estimates with age and sex as well as their stability over time. Our results reveal a time-stable asymmetric EC structure with positive EC between all amygdala nuclei, which strongly inhibited the BNST while the BNST exerted positive influence onto all amygdala nuclei. Simulation of the impulse response of the estimated system showed that this EC structure shapes partially antagonistic (out of phase) activity flow between the BNST and amygdala nuclei. Moreover, the BNST-LB and BNST-CM EC parameters were less negative in males. In conclusion, our data points toward partially separated information processing between BNST and amygdala nuclei in the resting-state.

Phasic amygdala and BNST activation during the anticipation of temporally unpredictable social observation in social anxiety disorder patients

Anticipation of potentially threatening social situations is a key process in social anxiety disorder (SAD). In other anxiety disorders, recent research of neural correlates of anticipation of temporally unpredictable threat suggests a temporally dissociable involvement of amygdala and bed nucleus of the stria terminalis (BNST) with phasic amygdala responses and sustained BNST activation. However, the temporal profile of amygdala and BNST responses during temporal unpredictability of threat has not been investigated in patients suffering from SAD. We used functional magnetic resonance imaging (fMRI) to investigate neural activation in the central nucleus of the amygdala (CeA) and the BNST during anticipation of temporally unpredictable aversive (video camera observation) relative to neutral (no camera observation) events in SAD patients compared to healthy controls (HC). For the analysis of fMRI data, we applied two regressors (phasic/sustained) within the same model to detect temporally dissociable brain responses. The aversive condition induced increased anxiety in patients compared to HC. SAD patients compared to HC showed increased phasic activation in the CeA and the BNST for anticipation of aversive relative to neutral events. SAD patients as well as HC showed sustained activity alterations in the BNST for aversive relative to neutral anticipation. No differential activity during sustained threat anticipation in SAD patients compared to HC was found. Taken together, our study reveals both CeA and BNST involvement during threat anticipation in SAD patients. The present results point towards potentially SAD-specific threat processing marked by elevated phasic but not sustained CeA and BNST responses when compared to HC.

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fMRI in SAD during anticipation of temporally unpredictable aversive events.

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Anticipation of social observation induces increased anxiety in SAD patients.

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SAD patients show elevated phasic activity in fundamental anxiety network regions.

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Evidence of SAD-specific threat processing.

The central extended amygdala in fear and anxiety: Closing the gap between mechanistic and neuroimaging research

Anxiety disorders impose a staggering burden on public health, underscoring the need to develop a deeper understanding of the distributed neural circuits underlying extreme fear and anxiety. Recent work highlights the importance of the central extended amygdala, including the central nucleus of the amygdala (Ce) and neighboring bed nucleus of the stria terminalis (BST). Anatomical data indicate that the Ce and BST form a tightly interconnected unit, where different kinds of threat-relevant information can be integrated to assemble states of fear and anxiety. Neuroimaging studies show that the Ce and BST are engaged by a broad spectrum of potentially threat-relevant cues. Mechanistic work demonstrates that the Ce and BST are critically involved in organizing defensive responses to a wide range of threats. Studies in rodents have begun to reveal the specific molecules, cells, and microcircuits within the central extended amygdala that underlie signs of fear and anxiety, but the relevance of these tantalizing discoveries to human experience and disease remains unclear. Using a combination of focal perturbations and whole-brain imaging, a new generation of nonhuman primate studies is beginning to close this gap. This work opens the door to discovering the mechanisms underlying neuroimaging measures linked to pathological fear and anxiety, to understanding how the Ce and BST interact with one another and with distal brain regions to govern defensive responses to threat, and to developing improved intervention strategies.

Functional Connectivity within the Primate Extended Amygdala Is Heritable and Associated with Early-Life Anxious Temperament

Children with an extremely inhibited, anxious temperament (AT) are at increased risk for anxiety disorders and depression. Using a rhesus monkey model of early-life AT, we previously demonstrated that metabolism in the central extended amygdala (EAc), including the central nucleus of the amygdala (Ce) and bed nucleus of the stria terminalis (BST), is associated with trait-like variation in AT. Here, we use fMRI to examine relationships between Ce-BST functional connectivity and AT in a large multigenerational family pedigree of rhesus monkeys (n = 170 females and 208 males). Results demonstrate that Ce-BST functional connectivity is heritable, accounts for a significant but modest portion of the variance in AT, and is coheritable with AT. Interestingly, Ce-BST functional connectivity and AT-related BST metabolism were not correlated and accounted for non-overlapping variance in AT. Exploratory analyses suggest that Ce-BST functional connectivity is associated with metabolism in the hypothalamus and periaqueductal gray. Together, these results suggest the importance of coordinated function within the EAc for determining individual differences in AT and metabolism in brain regions associated with its behavioral and neuroendocrine components.SIGNIFICANCE STATEMENT Anxiety disorders directly impact the lives of nearly one in five people, accounting for substantial worldwide suffering and disability. Here, we use a nonhuman primate model of anxious temperament (AT) to understand the neurobiology underlying the early-life risk to develop anxiety disorders. Leveraging the same kinds of neuroimaging measures routinely used in human studies, we demonstrate that coordinated activation between the central nucleus of the amygdala and the bed nucleus of the stria terminalis is correlated with, and coinherited with, early-life AT. Understanding how these central extended amygdala regions work together to produce extreme anxiety provides a neural target for early-life interventions with the promise of preventing lifelong disability in at-risk children.

Intrinsic functional connectivity of the central extended amygdala

The central extended amygdala (EAc)-including the bed nucleus of the stria terminalis (BST) and central nucleus of the amygdala (Ce)-plays a critical role in triggering fear and anxiety and is implicated in the development of a range of debilitating neuropsychiatric disorders. Although it is widely believed that these disorders reflect the coordinated activity of distributed neural circuits, the functional architecture of the EAc network and the degree to which the BST and the Ce show distinct patterns of functional connectivity is unclear. Here, we used a novel combination of imaging approaches to trace the connectivity of the BST and the Ce in 130 healthy, racially diverse, community-dwelling adults. Multiband imaging, high-precision registration techniques, and spatially unsmoothed data maximized anatomical specificity. Using newly developed seed regions, whole-brain regression analyses revealed robust functional connectivity between the BST and Ce via the sublenticular extended amygdala, the ribbon of subcortical gray matter encompassing the ventral amygdalofugal pathway. Both regions displayed coupling with the ventromedial prefrontal cortex (vmPFC), midcingulate cortex (MCC), insula, and anterior hippocampus. The BST showed stronger connectivity with the thalamus, striatum, periaqueductal gray, and several prefrontal territories. The only regions showing stronger functional connectivity with the Ce were neighboring regions of the dorsal amygdala, amygdalohippocampal area, and anterior hippocampus. These observations provide a baseline against which to compare a range of special populations, inform our understanding of the role of the EAc in normal and pathological fear and anxiety, and showcase image registration techniques that are likely to be useful for researchers working with "deidentified" neuroimaging data.

The Factorial Structure of Trait Anxiety and Its Mediating Effect Between Mindfulness and Depression

Background: Increasing studies have found that high trait anxiety is a key susceptibility phenotype that causes depression. Mindfulness-based interventions can target on dealing with depressogenic vulnerability effectively. Evidence indicates that trait anxiety could affect the trajectory of anti-depressive psychotherapy, and play an important role in the relationship between mindfulness and depression. Furthermore, related studies have found that trait anxiety could involve factors beyond anxiety and be a two-factor construct instead of one-dimensional concept. This viewpoint provides a new prospective for exploring the pathways of the two factors of trait anxiety in the complex relationship and further understand the potential mechanism of vulnerable personality mediated the link of mindfulness and depression. Methods: A cross-sectional survey and a preliminary intervention study were conducted. Thousand two hundred and sixty-two subjects completed a set of self-reported questionnaires that evaluated trait anxiety, mindfulness, and depressive symptoms. Twenty-Three eligible participants with depression were recruited to attend mindfulness-based cognitive training for eight weeks. The same questionnaires were completed 1 week before the training and 6 months after the training. Factor analysis was performed on the 1262-subject sample to explore and confirm the factorial structure of trait anxiety. In addition, mediating effect analysis was conducted in the two studies to test whether two factors of trait anxiety were mediators of the relationship between mindfulness and depression. Results: The exploratory factor analysis extracted two dimensions of trait anxiety, namely, trait anxiety-present factor (TA-P) and trait anxiety-absent factor (TA-A). And confirmatory factor analysis showed that the fit of the two-factor model was acceptable. Both TA-P and TA-A were significantly negatively correlated with mindfulness and positively correlated with depression, and they played a mediating role between mindfulness and depression. The two factors of trait anxiety had multiple mediating effects on the relationship between mindfulness and depression, and the mediating effect of the TA-P factor was stronger than that of the TA-A factor. Conclusion: Our results demonstrated a two-factor model of trait anxiety in the Chinese population. TA-P and TA-A played a multiple mediating role in the relationship between mindfulness and depression. The findings provide new perspectives for psychological interventions to treat depression for people with susceptible personalities. Aiming to reduce negative emotional tendencies (TA-P factor) and enhance positive cognition (TA-A factor) may achieve the early prevention and efficient treatment of depression.