Intrinsic functional connectivity of the central nucleus of the amygdala and bed nucleus of the stria terminalis

Altered Functional Coupling of the Bed Nucleus of the Stria Terminalis and Amygdala in Spider Phobic Fear

Background: Individuals with spider phobic (SP) fear show hypervigilance and amygdala hyperactivity toward fear-associated stimuli, which may promote the development of other anxiety disorders. The amygdala is a key region within the fear network, which is connected to the anxiety system, where the bed nucleus of the stria terminalis (BNST) plays a crucial role. However, the BNST's involvement in phobic fear is unknown. Therefore, this study investigated the association of phobic fear and anxiety on these regions' functional connectivity (FC) in SP compared to healthy controls (HC). Methods: 7T-functional MRI resting-state FC of 30 individuals with SP and 45 HC was assessed to detect network differences between these groups. The association of phobic fear severity, trait anxiety, and social anxiety on FC was explored using linear regressions combined with seed-to-voxel analyses with amygdala and BNST as primary seeds, corrected for age and sex. Results: In SP, phobic fear was associated with reduced FC between the left amygdala and the right supramarginal gyrus. In contrast, anxiety severity was related to increased FC between the right BNST and the left inferior frontal gyrus. Moreover, social anxiety was related to decreased FC between bilateral BNST and left precuneus. Conclusions: These findings show changes in FC in SP, connecting fear with altered activity in the BNST and amygdala. The results suggest that persistent anxiety in phobic fear is associated with abnormal brain function in these regions, potentially explaining susceptibility to anxiety disorders and processes involved in phobic fear, such as threat perception, avoidance, and salience.

Sex and sobriety: Human brain structure and function in AUD abstinence

Women are drinking alcohol as much as men for the first time in history. Women experience more health-related consequences from alcohol use disorder (AUD), like increased prevalence of alcohol-related cancers, faster progression of alcohol-related liver disease, and greater risk for relapse compared to men. Thus, sex differences in chronic alcohol use pose a substantial public health problem. Despite these evident sex differences, our understanding of how these differences present during alcohol abstinence is limited. Investigations of brain structure and function are therefore critical for disentangling factors that lead to sex differences in AUD abstinence. This review will discuss current human neuroimaging data on sex differences in alcohol abstinence, focusing on structural and functional brain measures. Current structural imaging literature reveals that abstinent men have smaller gray and white matter volume and weaker structural connectivity compared to control men. Interestingly, abstinent women do not show differences in brain structure when compared to controls; instead, abstinent women show a relation between alcohol use and decreased measures of brain structure. Current functional brain studies reveal that abstinent men exhibit greater brain activation and stronger task-based functional connectivity to aversive stimuli than control men, while abstinent women exhibit lesser brain activation and weaker task-based functional connectivity than control women. Together, the current literature suggests that sex differences persist well into alcohol abstinence and impact brain structure and function differently. Understanding how men and women differ during alcohol abstinence can improve our understanding of sex-specific effects of alcohol, which will be critical to augment treatment methods to better serve women.

The human social cognitive network contains multiple regions within the amygdala

Reasoning about someone's thoughts and intentions-i.e., forming a "theory of mind"-is a core aspect of social cognition and relies on association areas of the brain that have expanded disproportionately in the human lineage. We recently showed that these association zones comprise parallel distributed networks that, despite occupying adjacent and interdigitated regions, serve dissociable functions. One network is selectively recruited by social cognitive processes. What circuit properties differentiate these parallel networks? Here, we show that social cognitive association areas are intrinsically and selectively connected to anterior regions of the medial temporal lobe that are implicated in emotional learning and social behaviors, including the amygdala at or near the basolateral complex and medial nucleus. The results suggest that social cognitive functions emerge through coordinated activity between internal circuits of the amygdala and a broader distributed association network, and indicate the medial nucleus may play an important role in social cognition in humans.

Ligands of the trace amine-associated receptors (TAARs): A new class of anxiolytics

Most cases of anxiety are currently treated with either benzodiazepines or serotonin reuptake inhibitors. These drugs carry with them risks for a multitude of side effects, and patient compliance suffers for this reason. There is thus a need for novel anxiolytics, and among the most compelling prospects in this vein is the study of the TAARs. The anxiolytic potential of ulotaront, a full agonist at the human TAAR1, is currently being investigated in patients with generalized anxiety disorder. Irrespective of whether this compound succeeds in clinical trials, a growing body of preclinical literature underscores the relevance of modulating the TAARs in anxiety. Multiple behavioral paradigms show anxiolytic-like effects in rodents, possibly due to increased neurogenesis and plasticity, in addition to a panoply of interactions between the TAARs and other systems. Crucially, multiple lines of evidence suggest that the TAARs, particularly TAAR1, TAAR2, and TAAR5, are expressed in the extended amygdala and hippocampus. These regions are central in the actuation of anxiety, and are particularly susceptible to neurogenic and neuroplastic effects which the TAARs are now known to regulate. The TAARs also regulate the dopamine and serotonin systems, both of which are implicated in anxiety. Ligands of the TAARs may thus constitute a new class of anxiolytics.

Data-driven, connectome-wide analysis identifies psychosis-specific brain correlates of fear and anxiety

Decades of psychosis research highlight the prevalence and the clinical significance of negative emotions, such as fear and anxiety. Translational evidence demonstrates the pivotal role of the amygdala in fear and anxiety. However, most of these approaches have used hypothesis-driven analyses with predefined regions of interest. A data-driven analysis may provide a complimentary, unbiased approach to identifying brain correlates of fear and anxiety. The aim of the current study was to identify the brain basis of fear and anxiety in early psychosis and controls using a data-driven approach. We analyzed data from the Human Connectome Project for Early Psychosis, a multi-site study of 125 people with psychosis and 58 controls with resting-state fMRI and clinical characterization. Multivariate pattern analysis of whole-connectome data was used to identify shared and psychosis-specific brain correlates of fear and anxiety using the NIH Toolbox Fear-Affect and Fear-Somatic Arousal scales. We then examined clinical correlations of Fear-Affect scores and connectivity patterns. Individuals with psychosis had higher levels of Fear-Affect scores than controls (p < 0.05). The data-driven analysis identified a cluster encompassing the amygdala and hippocampus where connectivity was correlated with Fear-Affect score (p < 0.005) in the entire sample. The strongest correlate of Fear-Affect was between this cluster and the anterior insula and stronger connectivity was associated with higher Fear-Affect scores (r = 0.31, p = 0.0003). The multivariate pattern analysis also identified a psychosis-specific correlate of Fear-Affect score between the amygdala/hippocampus cluster and a cluster in the ventromedial prefrontal cortex (VMPFC). Higher Fear-Affect scores were correlated with stronger amygdala/hippocampal-VMPFC connectivity in the early psychosis group (r = 0.33, p = 0.002), but not in controls (r = -0.15, p = 0.28). The current study provides evidence for the transdiagnostic role of the amygdala, hippocampus, and anterior insula in the neural basis of fear and anxiety and suggests a psychosis-specific relationship between fear and anxiety symptoms and amygdala/hippocampal-VMPFC connectivity. Our novel data-driven approach identifies novel, psychosis-specific treatment targets for fear and anxiety symptoms and provides complimentary evidence to decades of hypothesis-driven approaches examining the brain basis of threat processing.

Social cognitive regions of human association cortex are selectively connected to the amygdala

Reasoning about someone's thoughts and intentions - i.e., forming a theory of mind - is an important aspect of social cognition that relies on association areas of the brain that have expanded disproportionately in the human lineage. We recently showed that these association zones comprise parallel distributed networks that, despite occupying adjacent and interdigitated regions, serve dissociable functions. One network is selectively recruited by theory of mind processes. What circuit properties differentiate these parallel networks? Here, we show that social cognitive association areas are intrinsically and selectively connected to regions of the anterior medial temporal lobe that are implicated in emotional learning and social behaviors, including the amygdala at or near the basolateral complex and medial nucleus. The results suggest that social cognitive functions emerge through coordinated activity between amygdala circuits and a distributed association network, and indicate the medial nucleus may play an important role in social cognition in humans.

Psychometric Properties, Factor Structure, and Validity of the Sensitivity to Threat and Affiliative Reward Scale in Children and Adults

Callous-Unemotional (CU) traits identify children at high risk of antisocial behavior. A recent theoretical model proposed that CU traits arise from low sensitivity to threat and affiliation. To assess these dimensions, we developed the parent- and self-reported Sensitivity to Threat and Affiliative Reward Scale (STARS) and tested its psychometric properties, factor structure, and construct validity. Samples 1 (N =3 03; age 3-10; United States) and 2 (N = 854 age 5-9; Spain) were children and Sample 3 was 514 young adults (Mage = 19.89; United States). In Sample 1, differential item functioning and item response theory techniques were used to identify the best-performing items from a 64-item pool, resulting in 28 items that functioned equivalently across age and gender. Factor analysis indicated acceptable fit for the theorized two-factor structure with separate threat and affiliation factors in all three samples, which showed predictive validity in relation to CU traits in children and psychopathic traits in young adults.

Ultra-high field imaging of the amygdala - A narrative review

The amygdala is an evolutionarily conserved core structure in emotion processing and one of the key regions of interest in affective neuroscience. Results of neuroimaging studies focusing on the amygdala are, however, often heterogeneous since it is composed of functionally and neuroanatomically distinct subnuclei. Fortunately, ultra-high-field imaging offers several advances for amygdala research, most importantly more accurate representation of functional and structural properties of subnuclei and their connectivity. Most clinical studies using ultra-high-field imaging focused on major depression, suggesting either overall rightward amygdala atrophy or distinct bilateral patterns of subnuclear atrophy and hypertrophy. Other pathologies are only sparsely covered. Connectivity analyses identified widespread networks for learning and memory, stimulus processing, cognition, and social processes. They provide evidence for distinct roles of the central, basal, and basolateral nucleus, and the extended amygdala in fear and emotion processing. Amid largely sparse and ambiguous evidence, we propose theoretical and methodological considerations that will guide ultra-high-field imaging in comprehensive investigations to help disentangle the ambiguity of the amygdala's function, structure, connectivity, and clinical relevance.

Alterations in BNST Intrinsic Functional Connectivity in Early Abstinence from Alcohol Use Disorder

AIMS

Maintaining abstinence from alcohol use disorder (AUD) is extremely challenging, partially due to increased symptoms of anxiety and stress that trigger relapse. Rodent models of AUD have identified that the bed nucleus of the stria terminalis (BNST) contributes to symptoms of anxiety-like behavior and drug-seeking during abstinence. In humans, however, the BNST's role in abstinence remains poorly understood. The aims of this study were to assess BNST network intrinsic functional connectivity in individuals during abstinence from AUD compared to healthy controls and examine associations between BNST intrinsic functional connectivity, anxiety and alcohol use severity during abstinence.

METHODS

The study included resting state fMRI scans from participants aged 21-40 years: 20 participants with AUD in abstinence and 20 healthy controls. Analyses were restricted to five pre-selected brain regions with known BNST structural connections. Linear mixed models were used to test for group differences, with sex as a fixed factor given previously shown sex differences.

RESULTS

BNST-hypothalamus intrinsic connectivity was lower in the abstinent group relative to the control group. There were also pronounced sex differences in both the group and individual analyses; many of the findings were specific to men. Within the abstinent group, anxiety was positively associated with BNST-amygdala and BNST-hypothalamus connectivity, and men, not women, showed a negative relationship between alcohol use severity and BNST-hypothalamus connectivity.

CONCLUSIONS

Understanding differences in connectivity during abstinence may help explain the clinically observed anxiety and depression symptoms during abstinence and may inform the development of individualized treatments.

Nx4 Modulated Resting-State Functional Connectivity Between Amygdala and Prefrontal Cortex in a Placebo-Controlled, Crossover Trial

Background: The basic functional organization of the resting brain, assessed as resting-state functional connectivity (rsFC), can be affected by previous stress experience and it represents the basis on which subsequent stress experience develops. Notably, the rsFC between the amygdala and the cortical regions associated with emotion regulation and anxiety are affected during stress. The multicomponent drug Neurexan^® (Nx4) has previously demonstrated a reduction in amygdala activation in an emotional face matching task and it ameliorated stress-related symptoms. We, thus, investigated the effect of Nx4 on rsFC of the amygdala before stress induction compared with baseline in mildly to moderately stressed participants. Methods: In a randomized, placebo-controlled, double-blind, crossover trial 39 participants received a single dose of placebo or Nx4. Resting-state functional magnetic resonance imaging scans were performed pre-dose and 40 to 60 min post-dose, before any stress induction. First, highly connected functional hubs were identified by global functional connectivity density (gFCD) analysis. Second, by using a seed-based approach, rsFC maps of the left centromedial amygdala (CeMA) were created. The effect of Nx4 on both was evaluated. Results: The medial prefrontal cortex was identified as a relevant functional hub affected by Nx4 in an explorative whole brain gFCD analysis. Using the seed-based approach, we then demonstrated that Nx4 significantly enhanced the negative connectivity between the left CeMA and two cortical regions: the dorsolateral and medial prefrontal cortices. Conclusions: In a resting-state condition, Nx4 reduced the prefrontal cortex gFCD and strengthened the functional coupling between the amygdala and the prefrontal cortex that is relevant for emotion regulation and the stress response. Further studies should elaborate whether this mechanism represents enhanced regulatory control of the amygdala at rest and, consequently, to a diminished susceptibility to stress. ClinicalTrials.gov ID: NCT02602275.

The central extended amygdala guides survival-relevant tradeoffs: Implications for understanding common psychiatric disorders

To thrive in challenging environments, individuals must pursue rewards while avoiding threats. Extensive studies in animals and humans have identified the central extended amygdala (EAc)-which includes the central nucleus of the amygdala (Ce) and bed nucleus of the stria terminalis (BST)-as a conserved substrate for defensive behavior. These studies suggest the EAc influences defensive responding and assembles fearful and anxious states. This has led to the proliferation of a view that the EAc is fundamentally a defensive substrate. Yet mechanistic work in animals has implicated the EAc in numerous appetitive and consummatory processes, yielding fresh insights into the microcircuitry of survival- and emotion-relevant response selection. Coupled with the EAc's centrality in a conserved network of brain regions that encode multisensory environmental and interoceptive information, these findings suggest a broader role for the EAc as an arbiter of survival- and emotion-relevant tradeoffs for action selection. Determining how the EAc optimizes these tradeoffs promises to improve our understanding of common psychiatric illnesses such as anxiety, depression, alcohol- and substance-use disorders, and anhedonia.

Threat vigilance and intrinsic amygdala connectivity

A well-documented amygdala-dorsomedial prefrontal circuit is theorized to promote attention to threat ("threat vigilance"). Prior research has implicated a relationship between individual differences in trait anxiety/vigilance, engagement of this circuitry, and anxiogenic features of the environment (e.g., through threat-of-shock and movie-watching). In the present study, we predicted that-for those scoring high in self-reported anxiety and a behavioral measure of threat vigilance-this circuitry is chronically engaged, even in the absence of anxiogenic stimuli. Our analyses of resting-state fMRI data (N = 639) did not, however, provide evidence for such a relationship. Nevertheless, in our planned exploratory analyses, we saw a relationship between threat vigilance behavior (but not self-reported anxiety) and intrinsic amygdala-periaqueductal gray connectivity. Here, we suggest this subcortical circuitry may be chronically engaged in hypervigilant individuals, but that amygdala-prefrontal circuitry may only be engaged in response to anxiogenic stimuli.

Tonic pain alters functional connectivity of the descending pain modulatory network involving amygdala, periaqueductal gray, parabrachial nucleus and anterior cingulate cortex

INTRODUCTION

Resting state functional connectivity (FC) is widely used to assess functional brain alterations in patients with chronic pain. However, reports of FC accompanying tonic pain in pain-free persons are rare. A network we term the Descending Pain Modulatory Network (DPMN) is implicated in healthy and pathologic pain modulation. Here, we evaluate the effect of tonic pain on FC of specific nodes of this network: anterior cingulate cortex (ACC), amygdala (AMYG), periaqueductal gray (PAG), and parabrachial nuclei (PBN).

METHODS

In 50 pain-free participants (30F), we induced tonic pain using a capsaicin-heat pain model. functional MRI measured resting BOLD signal during pain-free rest with a 32°C thermode and then tonic pain where participants experienced a previously warm temperature combined with capsaicin. We evaluated FC from ACC, AMYG, PAG, and PBN with correlation of self-report pain intensity during both states. We hypothesized tonic pain would diminish FC dyads within the DPMN.

RESULTS

Of all hypothesized FC dyads, only PAG and subgenual ACC was weakly altered during pain (F=3.34; p=0.074; pain-free>pain d=0.25). After pain induction sACC-PAG FC became positively correlated with pain intensity (R=0.38; t=2.81; p=0.007). Right PBN-PAG FC during pain-free rest positively correlated with subsequently experienced pain (R=0.44; t=3.43; p=0.001). During pain, this connection's FC was diminished (paired t=-3.17; p=0.0026). In whole-brain analyses, during pain-free rest, FC between left AMYG and right superior parietal lobule and caudate nucleus were positively correlated with subsequent pain. During pain, FC between left AMYG and right inferior temporal gyrus negatively correlated with pain. Subsequent pain positively correlated with right AMYG FC with right claustrum; right primary visual cortex and right temporo-occipitoparietal junction Conclusion: We demonstrate sACC-PAG tonic pain FC positively correlates with experienced pain and resting right PBN-PAG FC correlates with subsequent pain and is diminished during tonic pain. Finally, we reveal PAG- and right AMYG-anchored networks which correlate with subsequently experienced pain intensity. Our findings suggest specific connectivity patterns within the DPMN at rest are associated with subsequently experienced pain and modulated by tonic pain. These nodes and their functional modulation may reveal new therapeutic targets for neuromodulation or biomarkers to guide interventions.

Reciprocal midbrain-extended amygdala circuit activity in preclinical models of alcohol use and misuse

Alcohol dependence is characterized by a shift in motivation to consume alcohol from positive reinforcement (i.e., increased likelihood of future alcohol drinking based on its rewarding effects) to negative reinforcement (i.e., increased likelihood of future alcohol drinking based on alcohol-induced reductions in negative affective symptoms, including but not limited to those experienced during alcohol withdrawal). The neural adaptations that occur during this transition are not entirely understood. Mesolimbic reinforcement circuitry (i.e., ventral tegmental area [VTA] neurons) is activated during early stages of alcohol use, and may be involved in the recruitment of brain stress circuitry (i.e., extended amygdala) during the transition to alcohol dependence, after chronic periods of high-dose alcohol exposure. Here, we review the literature regarding the role of canonical brain reinforcement (VTA) and brain stress (extended amygdala) systems, and the connections between them, in acute, sub-chronic, and chronic alcohol response. Particular emphasis is placed on preclinical models of alcohol use.

Estimating Functional Connectivity by Integration of Inherent Brain Function Activity Pattern Priors

Brain functional connectivity (FC) has shown great potential in becoming biomarkers of brain status. However, the problem of accurately estimating FC from complex-noisy fMRI time series remains unsolved. Usually, a regularization function is more appropriate in fitting the real inherent properties of the brain function activity pattern, which can further limit noise interference to improve the accuracy of the estimated result. Recently, the neuroscientists widely suggested that the inherent brain function activity pattern indicates sparse, modular and overlapping topology. However, previous studies have never considered this factual characteristic. Thus, we propose a novel method by integration of these inherent brain function activity pattern priors to estimate FC. Extensive experiments on synthetic data demonstrate that our method can more accurately estimate the FC than previous. Then, we applied the estimated FC to predict the symptom severity of depressed patients, the symptom severity is related to subtle abnormal changes in the brain function activity, a more accurate FC can more effectively capture the subtle abnormal brain function activity changes. As results, our method better than others with a higher correlation coefficient of 0.4201. Moreover, the overlapping probability of each brain region can be further explored by the proposed method.

Better living through understanding the insula: Why subregions can make all the difference

Insula function is considered critical for many motivated behaviors, with proposed functions ranging from attention, behavioral control, emotional regulation, goal-directed and aversion-resistant responding. Further, the insula is implicated in many neuropsychiatric conditions including substance abuse. More recently, multiple insula subregions have been distinguished based on anatomy, connectivity, and functional contributions. Generally, posterior insula is thought to encode more somatosensory inputs, which integrate with limbic/emotional information in middle insula, that in turn integrate with cognitive processes in anterior insula. Together, these regions provide rapid interoceptive information about the current or predicted situation, facilitating autonomic recruitment and quick, flexible action. Here, we seek to create a robust foundation from which to understand potential subregion differences, and provide direction for future studies. We address subregion differences across humans and rodents, so that the latter's mechanistic interventions can best mesh with clinical relevance of human conditions. We first consider the insula's suggested roles in humans, then compare subregional studies, and finally describe rodent work. One primary goal is to encourage precision in describing insula subregions, since imprecision (e.g. including both posterior and anterior studies when describing insula work) does a disservice to a larger understanding of insula contributions. Additionally, we note that specific task details can greatly impact recruitment of various subregions, requiring care and nuance in design and interpretation of studies. Nonetheless, the central ethological importance of the insula makes continued research to uncover mechanistic, mood, and behavioral contributions of paramount importance and interest. This article is part of the special Issue on 'Neurocircuitry Modulating Drug and Alcohol Abuse'.

Distinctive Regulation of Emotional Behaviors and Fear-Related Gene Expression Responses in Two Extended Amygdala Subnuclei With Similar Molecular Profiles

The central nucleus of the amygdala (CeA) and the lateral division of the bed nucleus of the stria terminalis (BNST) are the two major nuclei of the central extended amygdala that plays essential roles in threat processing, responsible for emotional states such as fear and anxiety. While some studies suggested functional differences between these nuclei, others showed anatomical and neurochemical similarities. Despite their complex subnuclear organization, subnuclei-specific functional impact on behavior and their underlying molecular profiles remain obscure. We here constitutively inhibited neurotransmission of protein kinase C-δ-positive (PKCδ+) neurons-a major cell type of the lateral subdivision of the CeA (CeL) and the oval nucleus of the BNST (BNSTov)-and found striking subnuclei-specific effects on fear- and anxiety-related behaviors, respectively. To obtain molecular clues for this dissociation, we conducted RNA sequencing in subnuclei-targeted micropunch samples. The CeL and the BNSTov displayed similar gene expression profiles at the basal level; however, both displayed differential gene expression when animals were exposed to fear-related stimuli, with a more robust expression change in the CeL. These findings provide novel insights into the molecular makeup and differential engagement of distinct subnuclei of the extended amygdala, critical for regulation of threat processing.

BNST and amygdala connectivity are altered during threat anticipation in schizophrenia

In schizophrenia, impairments in affect are prominent and anxiety disorders are prevalent. Neuroimaging studies of fear and anxiety in schizophrenia have focused on the amygdala and show alterations in connectivity. Emerging evidence suggests that the bed nucleus of the stria terminalis (BNST) also plays a critical role in anxiety, especially during anticipation of an unpredictable threat; however, previous studies have not examined the BNST in schizophrenia. In the present study, we examined BNST function and connectivity in people with schizophrenia (n = 31; n = 15 with comorbid anxiety) and controls (n = 15) during anticipation of unpredictable and predictable threat. A secondary analysis tested for differences in activation and connectivity of the central nucleus of the amygdala (CeA), which has also been implicated in threat anticipation. Analyses tested for group differences in both activation and connectivity during anticipation of unpredictable threat and predictable threat (p < .05). Relative to controls, individuals with schizophrenia showed stronger BNST-middle temporal gyrus (MTG) connectivity during unpredictable threat anticipation and stronger BNST-MTG and BNST-dorsolateral prefrontal connectivity during predictable threat anticipation. Comparing subgroups of individuals with schizophrenia and a comorbid anxiety disorder (SZ+ANX) to those without an anxiety disorder (SZ-ANX) revealed broader patterns of altered connectivity. During unpredictable threat anticipation, the SZ+ANX group had stronger BNST connectivity with regions of the salience network (insula, dorsal anterior cingulate cortex). During predictable threat anticipation, the SZ+ANX group had stronger BNST connectivity with regions associated with fear processing (insula, extended amygdala, prefrontal cortex). A secondary CeA analysis revealed a different pattern; the SZ+ANX group had weaker CeA connectivity across multiple brain regions during threat anticipation compared to the SZ-ANX group. These findings provide novel evidence for altered functional connectivity during threat anticipation in schizophrenia, especially in individuals with comorbid anxiety.

PACAP orchestration of stress-related responses in neural circuits

Pituitary adenylate cyclase activating polypeptide (PACAP) is a pleiotropic polypeptide that can activate G protein-coupled PAC1, VPAC1, and VPAC2 receptors, and has been implicated in stress signaling. PACAP and its receptors are widely distributed throughout the nervous system and other tissues and can have a multitude of effects. Human and animal studies suggest that PACAP plays a role responding to a variety of threats and stressors. Here we review the roles of PACAP in several regions of the central nervous system (CNS) as they relate to several behavioral functions. For example, in the bed nucleus of the stria terminalis (BNST), PACAP is upregulated following chronic stress and may drive anxiety-like behavior. PACAP can also influence both the consolidation and expression of fear memories, as demonstrated by studies in several fear-related areas, such as the amygdala, hippocampus, and prefrontal cortex. PACAP can also mediate the emotional component of pain, as PACAP in the central nucleus of the amygdala (CeA) is able to decrease pain sensitivity thresholds. Outside of the central nervous system, PACAP may drive glucocorticoid release via enhanced hypothalamic-pituitary-adrenal axis activity and may participate in infection-induced stress responses. Together, this suggests that PACAP exerts effects on many stress-related systems and may be an important driver of emotional behavior.

Structural and resting state functional connectivity beyond the cortex

Mapping the structural and functional connectivity of the central nervous system has become a key area within neuroimaging research. While detailed network structures across the entire brain have been probed using animal models, non-invasive neuroimaging in humans has thus far been dominated by cortical investigations. Beyond the cortex, subcortical nuclei have traditionally been less accessible due to their smaller size and greater distance from radio frequency coils. However, major neuroimaging developments now provide improved signal and the resolution required to study these structures. Here, we present an overview of the connectivity between the amygdala, brainstem, cerebellum, spinal cord and the rest of the brain. While limitations to their imaging and analyses remain, we also provide some recommendations and considerations for mapping brain connectivity beyond the cortex.

Neural substrates of human fear generalization: A 7T-fMRI investigation

Fear generalization - the tendency to interpret ambiguous stimuli as threatening due to perceptual similarity to a learned threat - is an adaptive process. Overgeneralization, however, is maladaptive and has been implicated in a number of anxiety disorders. Neuroimaging research has indicated several regions sensitive to effects of generalization, including regions involved in fear excitation (e.g., amygdala, insula) and inhibition (e.g., ventromedial prefrontal cortex). Research has suggested several other small brain regions may play an important role in this process (e.g., hippocampal subfields, bed nucleus of the stria terminalis [BNST], habenula), but, to date, these regions have not been examined during fear generalization due to limited spatial resolution of standard human neuroimaging. To this end, we utilized the high spatial resolution of 7T fMRI to characterize the neural circuits involved in threat discrimination and generalization. Additionally, we examined potential modulating effects of trait anxiety and intolerance of uncertainty on neural activation during threat generalization. In a sample of 31 healthy undergraduate students, significant positive generalization effects (i.e., greater activation for stimuli with increasing perceptual similarity to a learned threat cue) were observed in the visual cortex, thalamus, habenula and BNST, while negative generalization effects were observed in the dentate gyrus, CA1, and CA3. Associations with individual differences were underpowered, though preliminary findings suggested greater generalization in the insula and primary somatosensory cortex may be correlated with self-reported anxiety. Overall, findings largely support previous neuroimaging work on fear generalization and provide additional insight into the contributions of several previously unexplored brain regions.

The regulatory roles of progesterone and estradiol on emotion processing in women

Emotion processing is known to interact with memory. Ovarian steroid hormones, such as progesterone and estradiol, modulate emotion processing and memory. However, it is unclear how these hormones influence brain activity when emotion processing is integrated with working memory (WM). Therefore, the objective of this study was to examine the relationship between endogenous hormonal concentration and brain activity during emotion processing in the context of a WM n-back task in 74 young women using functional magnetic resonance imaging (fMRI). Results show that positive emotion processing activates reward-related areas, such as the caudate and putamen, whereas negative emotion processing activates a corticolimbic network, including the amygdala and hippocampus. Furthermore, our findings provide evidence that progesterone modulates more bottom-up brain activation during both positive and negative emotion processing, whereas estradiol activates lateralized, top-down regulation. These findings provide insight on the neural correlates of emotion processing during an n-back task in young women and highlight how important it is to consider women's endogenous hormonal concentration in neurobiological and cognition research.

Alterations in connectivity of the bed nucleus of the stria terminalis during early abstinence in individuals with alcohol use disorder

BACKGROUND

For individuals with Alcohol Use Disorder (AUD), long-term recovery is difficult in part due to symptoms of anxiety that occur during early abstinence and can trigger relapse. Research in rodent models of AUD has identified the bed nucleus of the stria terminalis (BNST), a small, sexually dimorphic, subcortical region, as critical for regulating anxiety-like behaviors during abstinence, particularly in female mice. Furthermore, prolonged alcohol use and subsequent abstinence alter BNST afferent and efferent connections to other brain regions. To our knowledge, however, no studies of early abstinence have investigated BNST structural connectivity in humans during abstinence; this study addresses that gap.

METHODS

Nineteen participants with AUD currently in early abstinence and 20 healthy controls completed a diffusion tensor imaging (DTI) scan. BNST structural connectivity was evaluated using probabilistic tractography. A linear mixed model was used to test between-groups differences in BNST network connectivity. Exploratory analyses were conducted to test for correlations between BNST connectivity and alcohol use severity and anxiety within the abstinence group. Sex was included as a factor for all analyses.

RESULTS

The BNST showed stronger structural connectivity with the BNST network in early abstinence women than in control women, which was not seen in men. Women also showed region-specific differences, with stronger BNST-hypothalamus structural connectivity but weaker vmPFC-BNST structural connectivity than men. Exploratory analyses also demonstrated a relationship between alcohol use severity and vmPFC-BNST structural connectivity that was moderated by sex.

CONCLUSIONS

This study is the first to demonstrate BNST structural connectivity differences in early abstinence and revealed key sex differences. The sex-specific differences in BNST structural connectivity during early abstinence could underlie known sex differences in abstinence symptoms and relapse risk and help to inform potential sex-specific treatments.

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.

Altered functional connectivity of the amygdala in Crohn's disease

Crohn's disease (CD), a chronic inflammatory bowel disease, involved in brain structural and functional changes, including the amygdala. Amygdala is a key structure in the limbic system and its related circuits are implicated in processing of emotion, pain and sensory. However, limited study of the amygdala is elucidated in CD. This study mainly investigated altered functional connectivity (FC) of the amygdala in CD patients during resting-state. Magnetic resonance imaging scans were acquired from 42 CD patients and 35 healthy controls (HCs). Whole amygdala bilaterally were selected as regions of interest (ROIs). Voxel-based morphometry and FC methods were applied to investigate the differences of structure or intrinsic connectivity of the amygdala between the two groups, separately. Pearson correlations were performed to explore relationships between the clinical characteristics and neuroimaging findings in CD patients. Based on the whole amygdala bilaterally as ROIs, compared with HCs, CD patients showed no statistical differences of grey matter destiny but exhibited decreased FC between the amygdala and insula, parahippocampus, as well as anterior middle cingulate cortex/dorsal anterior cingulate cortex. CD patients had negative correlation between the disease duration and amygdala-insula connectivity. In the patient group, patients with higher anxiety or depression scores revealed increased FC of the amygdala with thalamus and orbitofrontal cortex. Our results reveal that aberrant FC of the amygdala may be involved in processing of visceral pain and sensation, and emotion in CD. These findings may further enhance the understanding of neural mechanisms of CD.

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.

The amygdala instructs insular feedback for affective learning

Affective responses depend on assigning value to environmental predictors of threat or reward. Neuroanatomically, this affective value is encoded at both cortical and subcortical levels. However, the purpose of this distributed representation across functional hierarchies remains unclear. Using fMRI in mice, we mapped a discrete cortico-limbic loop between insular cortex (IC), central amygdala (CE), and nucleus basalis of Meynert (NBM), which decomposes the affective value of a conditioned stimulus (CS) into its salience and valence components. In IC, learning integrated unconditioned stimulus (US)-evoked bodily states into CS valence. In turn, CS salience in the CE recruited these CS representations bottom-up via the cholinergic NBM. This way, the CE incorporated interoceptive feedback from IC to improve discrimination of CS valence. Consequently, opto-/chemogenetic uncoupling of hierarchical information flow disrupted affective learning and conditioned responding. Dysfunctional interactions in the IC↔CE/NBM network may underlie intolerance to uncertainty, observed in autism and related psychiatric conditions.

Effective connectivity between bed nucleus of the stria terminalis and amygdala: Reproducibility and relation to anxiety

In a previous study, we investigated the resting‐state fMRI effective connectivity (EC) between the bed nucleus of the stria terminalis (BNST) and the laterobasal (LB), centromedial (CM), and superficial (SF) amygdala. We found strong negative EC from all amygdala nuclei to the BNST, while the BNST showed positive EC to the amygdala. However, the validity of these findings remains unclear, since a reproduction in different samples has not been done. Moreover, the association of EC with measures of anxiety offers deeper insight, due to the known role of the BNST and amygdala in fear and anxiety. Here, we aimed to reproduce our previous results in three additional samples. We used spectral Dynamic Causal Modeling to estimate the EC between the BNST, the LB, CM, and SF, and its association with two measures of self‐reported anxiety. Our results revealed consistency over samples with regard to the negative EC from the amygdala nuclei to the BNST, while the positive EC from BNST to the amygdala was also found, but weaker and more heterogenic. Moreover, we found the BNST‐BNST EC showing a positive and the CM‐BNST EC, showing a negative association with anxiety. Our study suggests a reproducible pattern of negative EC from the amygdala to the BNST along with weaker positive EC from the BNST to the amygdala. Moreover, less BNST self‐inhibition and more inhibitory influence from the CM to the BNST seems to be a pattern of EC that is related to higher anxiety.

Anxiety and the Neurobiology of Temporally Uncertain Threat Anticipation

When extreme, anxiety-a state of distress and arousal prototypically evoked by uncertain danger-can be debilitating. Uncertain anticipation is a shared feature of situations that elicit signs and symptoms of anxiety across psychiatric disorders, species, and assays. Despite the profound significance of anxiety for human health and wellbeing, the neurobiology of uncertain-threat anticipation remains unsettled. Leveraging a paradigm adapted from animal research and optimized for fMRI signal decomposition, we examined the neural circuits engaged during the anticipation of temporally uncertain and certain threat in 99 men and women. Results revealed that the neural systems recruited by uncertain and certain threat anticipation are anatomically colocalized in frontocortical regions, extended amygdala, and periaqueductal gray. Comparison of the threat conditions demonstrated that this circuitry can be fractionated, with frontocortical regions showing relatively stronger engagement during the anticipation of uncertain threat, and the extended amygdala showing the reverse pattern. Although there is widespread agreement that the bed nucleus of the stria terminalis and dorsal amygdala-the two major subdivisions of the extended amygdala-play a critical role in orchestrating adaptive responses to potential danger, their precise contributions to human anxiety have remained contentious. Follow-up analyses demonstrated that these regions show statistically indistinguishable responses to temporally uncertain and certain threat anticipation. These observations provide a framework for conceptualizing anxiety and fear, for understanding the functional neuroanatomy of threat anticipation in humans, and for accelerating the development of more effective intervention strategies for pathological anxiety.SIGNIFICANCE STATEMENT Anxiety-an emotion prototypically associated with the anticipation of uncertain harm-has profound significance for public health, yet the underlying neurobiology remains unclear. Leveraging a novel neuroimaging paradigm in a relatively large sample, we identify a core circuit responsive to both uncertain and certain threat anticipation, and show that this circuitry can be fractionated into subdivisions with a bias for one kind of threat or the other. The extended amygdala occupies center stage in neuropsychiatric models of anxiety, but its functional architecture has remained contentious. Here we demonstrate that its major subdivisions show statistically indistinguishable responses to temporally uncertain and certain threat. Collectively, these observations indicate the need to revise how we think about the neurobiology of anxiety and fear.

Psychotherapy in pain management: New viewpoints and treatment targets based on a brain theory

The current paper provides an explanation of neurophysiological pain processing based the Dimensional Systems Model (DSM), a theory of higher cortical functions in which the cortical column is considered the binary digit for all cortical functions. Within the discussion, novel views on the roles of the basal ganglia, cerebellum, and cingulate cortex are presented. Additionally, an applied Clinical Biopsychological Model (CBM) based on the DSM will be discussed as related to psychological treatment with chronic pain patients. Three specific areas that have not been adequately addressed in the psychological treatment of chronic pain patients will be discussed based on the CBM. The treatment approaches have been effectively used in a clinical setting. Conclusions focus on a call for researchers and clinicians to fully evaluate the value of both the DSM and CBM.

BNST-insula structural connectivity in humans

The bed nucleus of the stria terminalis (BNST) is emerging as a critical region in multiple psychiatric disorders including anxiety, PTSD, and alcohol and substance use disorders. In conjunction with growing knowledge of the BNST, an increasing number of studies examine connections of the BNST and how those connections impact BNST function. The importance of this BNST network is highlighted by rodent studies demonstrating that projections from other brain regions regulate BNST activity and influence BNST-related behavior. While many animal and human studies replicate the components of the BNST network, to date, structural connections between the BNST and insula have only been described in rodents and have yet to be shown in humans. In this study, we used probabilistic tractography to examine BNST-insula structural connectivity in humans. We used two methods of dividing the insula: 1) anterior and posterior insula, to be consistent with much of the existing insula literature; and 2) eight subregions that represent informative cytoarchitectural divisions. We found evidence of a BNST-insula structural connection in humans, with the strongest BNST connectivity localized to the anteroventral insula, a region of agranular cortex. BNST-insula connectivity differed by hemisphere and was moderated by sex. These results translate rodent findings to humans and lay an important foundation for future studies examining the role of BNST-insula pathways in psychiatric disorders.

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.

Individual-specific functional connectivity of the amygdala: A substrate for precision psychiatry

The amygdala is central to the pathophysiology of many psychiatric illnesses. An imprecise understanding of how the amygdala fits into the larger network organization of the human brain, however, limits our ability to create models of dysfunction in individual patients to guide personalized treatment. Therefore, we investigated the position of the amygdala and its functional subdivisions within the network organization of the brain in 10 highly sampled individuals (5 h of fMRI data per person). We characterized three functional subdivisions within the amygdala of each individual. We discovered that one subdivision is preferentially correlated with the default mode network; a second is preferentially correlated with the dorsal attention and fronto-parietal networks; and third subdivision does not have any networks to which it is preferentially correlated relative to the other two subdivisions. All three subdivisions are positively correlated with ventral attention and somatomotor networks and negatively correlated with salience and cingulo-opercular networks. These observations were replicated in an independent group dataset of 120 individuals. We also found substantial across-subject variation in the distribution and magnitude of amygdala functional connectivity with the cerebral cortex that related to individual differences in the stereotactic locations both of amygdala subdivisions and of cortical functional brain networks. Finally, using lag analyses, we found consistent temporal ordering of fMRI signals in the cortex relative to amygdala subdivisions. Altogether, this work provides a detailed framework of amygdala-cortical interactions that can be used as a foundation for models relating aberrations in amygdala connectivity to psychiatric symptoms in individual patients.

The Sensitivity to Threat and Affiliative Reward (STAR) model and the development of callous-unemotional traits

Research implicates callous-unemotional (CU) traits (i.e., lack of empathy, prosociality, and guilt, and reduced sensitivity to others' emotions) in the development of severe and persistent antisocial behavior. To improve etiological models of antisocial behavior and develop more effective treatments, we need a better understanding of the origins of CU traits. In this review, we discuss the role of two psychobiological and mechanistic precursors to CU traits: low affiliative reward (i.e., deficits in seeking out or getting pleasure from social bonding and closeness with others) and low threat sensitivity (i.e., fearlessness to social and non-social threat). We outline the Sensitivity to Threat and Affiliative Reward (STAR) model and review studies that have examined the development of affiliative reward and threat sensitivity across animal, neuroimaging, genetic, and behavioral perspectives. We next evaluate evidence for the STAR model, specifically the claim that CU traits result from deficits in both affiliative reward and threat sensitivity. We end with constructive suggestions for future research to test the hypotheses generated by the STAR model.

Resting-state connectivity of the bed nucleus of the stria terminalis and the central nucleus of the amygdala in clinical anxiety

Background

The central nucleus of the amygdala and bed nucleus of the stria terminalis are involved primarily in phasic and sustained aversive states. Although both structures have been implicated in pathological anxiety, few studies with a clinical population have specifically focused on them, partly because of their small size. Previous work in our group used high-resolution imaging to map the restingstate functional connectivity of the bed nucleus of the stria terminalis and the central nucleus of the amygdala in healthy subjects at 7 T, confirming and extending structural findings in humans and animals, while providing additional insight into cortical connectivity that is potentially unique to humans.

Methods

In the current follow-up study, we contrasted resting-state functional connectivity in the bed nucleus of the stria terminalis and central nucleus of the amygdala at 7 T between healthy volunteers (n = 30) and patients with generalized and/or social anxiety disorder (n = 30).

Results

Results revealed significant voxel-level group differences. Compared with healthy volunteers, patients showed stronger resting-state functional connectivity between the central nucleus of the amygdala and the lateral orbitofrontal cortex and superior temporal sulcus. They also showed weaker resting-state functional connectivity between the bed nucleus of the stria terminalis and the dorsolateral prefrontal cortex and occipital cortex.

Limitations

These findings depart from a previous report of resting-state functional connectivity in the central nucleus of the amygdala and bed nucleus of the stria terminalis under sustained threat of shock in healthy volunteers.

Conclusion

This study provides functional MRI proxies of the functional dissociation of the bed nucleus of the stria terminalis and central nucleus of the amygdala, and suggests that resting-state functional connectivity of key structures in the processing of defensive responses do not recapitulate changes related to induced state anxiety. Future work needs to replicate and further probe the clinical significance of these findings.

Examining the contribution of histone modification to sex differences in learning and memory

The epigenome serves as a signal integration platform that encodes information from experience and environment that adds tremendous complexity to the regulation of transcription required for memory, beyond the directions encoded in the genome. To date, our understanding of how epigenetic mechanisms integrate information to regulate gene expression required for memory is primarily obtained from male derived data despite sex-specific life experiences and sex differences in consolidation and retrieval of memory, and in the molecular mechanisms that mediate these processes. In this review, we examine the contribution of chromatin modification to learning and memory in both sexes. We provide examples of how exposure to a number of internal and external factors influence the epigenome in sex-similar and sex-specific ways that may ultimately impact transcription required for memory processes. We also pose a number of key open questions and identify areas requiring further investigation as we seek to understand how histone modifying mechanisms shape memory in females.

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.

Dispositional negativity, cognition, and anxiety disorders: An integrative translational neuroscience framework

When extreme, anxiety can become debilitating. Anxiety disorders, which often first emerge early in development, are common and challenging to treat, yet the underlying mechanisms have only recently begun to come into focus. Here, we review new insights into the nature and biological bases of dispositional negativity, a fundamental dimension of childhood temperament and adult personality and a prominent risk factor for the development of pediatric and adult anxiety disorders. Converging lines of epidemiological, neurobiological, and mechanistic evidence suggest that dispositional negativity increases the likelihood of psychopathology via specific neurocognitive mechanisms, including attentional biases to threat and deficits in executive control. Collectively, these observations provide an integrative translational framework for understanding the development and maintenance of anxiety disorders in adults and youth and set the stage for developing improved intervention strategies.

Connectivity-Based Parcellation of the Amygdala Predicts Social Skills in Adolescents with Autism Spectrum Disorder

Amygdala dysfunction plays a role in the social impairments in autism spectrum disorders (ASD), but it is unclear which of its subregions are abnormal in ASD. This study compared the volume and functional connectivity (FC) strength of three FC-defined amygdala subregions between ASD and controls, and assessed their relation to social skills in ASD. A subregion associated with the social perception network was enlarged in ASD (F₁ = 7.842, p = .008) and its volume correlated significantly with symptom severity (social skills: r = .548, p = .009). Posthoc analysis revealed that the enlargement was driven by the vmPFC amygdala network. These findings refine our understanding of abnormal amygdala connectivity in ASD and may inform future strategies for therapeutic interventions targeting the amygdalofrontal pathway.

Altered Neurobiological Processing of Unintentional Social Norm Violations: A Multiplex, Multigenerational Functional Magnetic Resonance Imaging Study on Social Anxiety Endophenotypes

BACKGROUND

Patients with social anxiety disorder (SAD) fear negative evaluation in social situations. Specifically, previous work indicated that social anxiety is associated with increased medial prefrontal cortex activation in response to unintentional social norm (SN) transgressions, accompanied by increased embarrassment ratings for such SN violations. Here, we used data from the multiplex, multigenerational LFLSAD (Leiden Family Lab study on Social Anxiety Disorder), which involved two generations of families genetically enriched for SAD, and investigated whether these neurobiological and behavioral correlates of unintentional SN processing are SAD endophenotypes. Of four endophenotype criteria, we examined two: first, the cosegregation of these characteristics with social anxiety (SA) within families of SAD probands (criterion 4), and second, the heritability of the candidate endophenotypes (criterion 3).

METHODS

Participants (n = 110, age range 9.0-61.5 years, eight families) performed the revised Social Norm Processing Task; functional magnetic resonance imaging data and behavioral ratings related to this paradigm were used to examine whether brain activation in response to processing unintentional SN violations and ratings of embarrassment were associated with SA levels. Next, heritability of these measurements was estimated.

RESULTS

As expected, voxelwise functional magnetic resonance imaging analyses revealed positive associations between SA levels and brain activation in the medial prefrontal cortex and medial temporal gyrus, superior temporal gyrus, and superior temporal sulcus, and these brain activation levels displayed moderate to moderately high heritability. Furthermore, although SA levels correlated positively with behavioral ratings of embarrassment for SN transgressions, these behavioral characteristics were not heritable.

CONCLUSIONS

These results show, for the first time, that brain responses in the medial prefrontal cortex and medial temporal gyrus, superior temporal gyrus, and superior temporal sulcus, related to processing unintentional SN violations, provide a neurobiological candidate endophenotype of SAD.

Brain functional connectivity is altered in patients with Takotsubo Syndrome

Takotsubo syndrome (TTS) is an acute, reversible cardiomyopathy. The central autonomic nervous system (ANS) is believed to play a role in this disease. The aim of the present study was to investigate the patterns of brain functional connectivity in a sample of patients who had experienced a previous episode of TTS. Brain functional connectivity, both at rest and in response to the stressful stimulus of topical cold stimulation, was explored using functional magnetic resonance imaging (fMRI), network-based statistics (NBS) and graph theory analysis (GTA) in a population consisting of eight patients with a previous episode of TTS and eight sex- and age-matched controls. At rest, a network characterized by increased connectivity in the TTS group compared to controls and comprising elements of the central ANS was identified. GTA revealed increased local efficiency, clustering and strength in regions of the bilateral hippocampus in subjects with a previous episode of TTS. When stressed by local exposure to cold, the TTS group differed significantly from both a pre-stress baseline interval and from the control group, showing increased connectivity in a network that included the left amygdala and the right insula. Based on the results, patients with TTS display a reorganization of cortical and subcortical networks, including areas associated with the emotional response and autonomic regulation. The findings tend to support the hypothesis that a deregulation of autonomic control at the central level plays a significant role in this syndrome.

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.

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.

New Frontiers in Anxiety Research: The Translational Potential of the Bed Nucleus of the Stria Terminalis

After decades of being overshadowed by the amygdala, new perspectives suggest that a tiny basal forebrain region known as the bed nucleus of the stria terminalis (BNST) may hold key insights into understanding and treating anxiety disorders. Converging research indicates that the amygdala and BNST play complementary but distinct functional roles during threat processing, with the BNST specializing in the detection of a potential threat to maintain hypervigilance and anxiety, while the amygdala responds to the perceived presence of an aversive stimulus (i.e., fear). Therefore, given that human anxiety is largely driven by future-oriented hypothetical threats that may never occur, studies involving the BNST stand at the forefront of essential future research with the potential to bring about profound insights for understanding and treating anxiety disorders. In this article, we present a narrative review on the BNST, summarizing its roles in anxiety and the stress response and highlighting the most recent advances in the clinical realm. Furthermore, we discuss oversights in the current state of anxiety research and identify avenues for future exploration.

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.

Visualizing the Human Subcortex Using Ultra-high Field Magnetic Resonance Imaging

With the recent increased availability of ultra-high field (UHF) magnetic resonance imaging (MRI), substantial progress has been made in visualizing the human brain, which can now be done in extraordinary detail. This review provides an extensive overview of the use of UHF MRI in visualizing the human subcortex for both healthy and patient populations. The high inter-subject variability in size and location of subcortical structures limits the usability of atlases in the midbrain. Fortunately, the combined results of this review indicate that a large number of subcortical areas can be visualized in individual space using UHF MRI. Current limitations and potential solutions of UHF MRI for visualizing the subcortex are also discussed.

Altered functional connectivity of the subthalamus and the bed nucleus of the stria terminalis in obsessive-compulsive disorder

BACKGROUND

The assessment of inter-regional functional connectivity (FC) has allowed for the description of the putative mechanism of action of treatments such as deep brain stimulation (DBS) of the nucleus accumbens in patients with obsessive-compulsive disorder (OCD). Nevertheless, the possible FC alterations of other clinically-effective DBS targets have not been explored. Here we evaluated the FC patterns of the subthalamic nucleus (STN) and the bed nucleus of the stria terminalis (BNST) in patients with OCD, as well as their association with symptom severity.

METHODS

Eighty-six patients with OCD and 104 healthy participants were recruited. A resting-state image was acquired for each participant and a seed-based analysis focused on our two regions of interest was performed using statistical parametric mapping software (SPM8). Between-group differences in FC patterns were assessed with two-sample t test models, while the association between symptom severity and FC patterns was assessed with multiple regression analyses.

RESULTS

In comparison with controls, patients with OCD showed: (1) increased FC between the left STN and the right pre-motor cortex, (2) decreased FC between the right STN and the lenticular nuclei, and (3) increased FC between the left BNST and the right frontopolar cortex. Multiple regression analyses revealed a negative association between clinical severity and FC between the right STN and lenticular nucleus.

CONCLUSIONS

This study provides a neurobiological framework to understand the mechanism of action of DBS on the STN and the BNST, which seems to involve brain circuits related with motor response inhibition and anxiety control, respectively.

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.

Extended amygdala connectivity changes during sustained shock anticipation

The bed nucleus of the stria terminalis (BNST) and central amygdala (CeA) of the extended amygdala are small, anatomically interconnected brain regions. They are thought to mediate responses to sustained, unpredictable threat stimuli and phasic, predictable threat stimuli, respectively. They perform these operations largely through their interconnected networks. In two previous studies, we mapped and contrasted the resting functional connectivity networks of the BNST and CeA at 7 Tesla with high resolution. This follow-up study investigates the changes in functional connectivity of these structures during sustained anticipation of electric shock. Results show that the BNST and CeA become less strongly coupled with the ventromedial prefrontal cortex (vmPFC), cingulate, and nucleus accumbens in shock threat relative to a safety condition. In addition, the CeA becomes more strongly coupled with the thalamus under threat. An exploratory, whole-brain connectivity analysis reveals that, although the BNST/CeA exhibits generally decreased connectivity, many other cortical regions demonstrate greater coupling under threat than safety. Understanding the differential network structures of these two regions and how they contribute to processing under threat will help elucidate the building blocks of the anxious state.