Pilot multimodal twin imaging study of generalized anxiety disorder

Sex-Specific Distributed White Matter Microarchitectural Alterations in Preadolescent Youths With Anxiety Disorders: A Mega-Analytic Study

OBJECTIVE

Anxiety disorders are among the most common psychiatric disorders in youths and emerge during childhood. This is also a period of rapid white matter (WM) development, which is critical for efficient neuronal communication. Previous work in preadolescent children with anxiety disorders demonstrated anxiety disorder-related reductions in WM microstructural integrity (fractional anisotropy [FA]) in the uncinate fasciculus (UF), the major WM tract facilitating prefrontal cortical-limbic structural connectivity. Importantly, this association was found only in boys with anxiety disorders. To confirm this finding and more comprehensively understand WM changes in childhood anxiety, this mega-analytic study characterizes WM alterations related to anxiety disorders and sex in the largest sample of preadolescent children to date.

METHODS

Diffusion tensor imaging data from published studies of preadolescent children with anxiety disorders and healthy volunteers (ages 8-12) (N=198) were combined with a new data set (N=97) for a total sample of 165 children with anxiety disorders and 132 healthy volunteers. Children with anxiety disorders met DSM-5 criteria for current generalized, separation, and/or social anxiety disorder. Analyses of tractography and voxel-wise data assessed between-group differences (anxiety disorder vs. healthy volunteer), effects of sex, and their interaction.

RESULTS

Tract-based and voxel-wise analyses confirmed a significant reduction in UF FA in boys but not girls with anxiety disorders. Results also demonstrated other significant widespread anxiety disorder-related WM alterations specifically in boys, including in multiple commissural, association, projection, and brainstem regions.

CONCLUSIONS

In addition to confirming male-specific anxiety disorder-related reductions in UF FA, the results demonstrate that anxiety disorders in boys and not girls are associated with broadly distributed WM alterations across the brain. These findings support further studies focused on understanding the extent to which WM alterations in boys with anxiety disorders are involved in pathophysiological processes that mediate anxiety disorders. The findings also suggest the possibility that WM microarchitecture could serve as a novel treatment target for childhood anxiety disorders.

Microstructural white matter alterations associated with social anxiety disorders: A systematic review

BACKGROUND

Social anxiety disorder (SAD) is a psychiatric condition characterized by impaired social functioning that negatively impacts individuals' quality of life. Previous neuroimaging studies have revealed morphological and functional changes in various brain regions associated with SAD. Recent advances in diffusion tensor imaging (DTI) and diffusion-weighted imaging (DWI) have enabled the investigation of microstructural white matter (WM) alterations in SAD. This study aims to provide an overview of DTI/DWI studies exploring WM microstructure changes in SAD.

METHODS

A systematic search on PubMed, Scopus, Web of Science, and PsycINFO was conducted for relevant records on July 8, 2023. An exploratory meta-analysis was also performed.

RESULTS

Eight studies were reviewed. Consistent findings indicated reduced fractional anisotropy and increased diffusivity measures in different WM tracts in SAD patients compared to healthy controls. These alterations were mostly observed within regions of the fronto-limbic network, like uncinate fasciculus (UF) and superior and inferior longitudinal fasciculi (SLF and ILF). Finally, our exploratory meta-analysis on four studies utilizing a voxel-wise analytic approach yielded no significant differences between SAD patients and controls.

LIMITATIONS

Limited number of studies, small sample sizes, and heterogeneity in analysis methods.

CONCLUSIONS

Patients with SAD exhibited altered WM integrity, particularly in the UF, SLF, and ILF, compared to healthy controls. However, due to the limited number of included studies, our meta-analysis yielded no significant differences between SAD patients and controls. Therefore, future research is crucial to unravel the link between altered WM structure and the involvement of other limbic and cortical structures in SAD pathogenesis.

Examining the relationship between anxiety and regional brain volumes in the National Alzheimer's Coordinating Center uniform, imaging, and biomarker datasets

Anxiety has been associated with a greater risk of Alzheimer's disease (AD). Existing research has identified structural differences in regional brain tissue in participants with anxiety, but results have been inconsistent. We sought to determine the association between anxiety and regional brain volumes, and the moderation effect of APOE ε4. Using data from participants in the National Alzheimer's Coordinating Center (NACC) Uniform Data Set, with complete imaging (MRI) and biomarker data (n = 1533), multiple linear regression estimated the adjusted effect of anxiety on 30 structural MRI regions. The moderation effect of APOE ε4 on the relation between structural MRI regions and anxiety was assessed as was the moderation effect of cognitive status. False discovery rate was used to adjust for multiple comparisons. After controlling for intracranial volume, age, sex, years of education, race, Hispanic ethnicity, and cognitive status, seven MRI regions demonstrated lower volumes among participants with anxiety: total cerebrum gray matter volume, right hippocampus volume, hippocampal volume (total), right and left frontal lobe cortical gray matter volume, and right and total temporal lobe cortical gray matter volume. Findings suggest that anxiety is associated with significant atrophy in multiple brain regions, with corresponding ventricular enlargement. Future research should investigate if anxiety-related changes to brain morphology contribute to greater AD risk.

Impact of Stress on Brain Morphology: Insights into Structural Biomarkers of Stress-related Disorders

Exposure to acute and chronic stress has a broad range of structural effects on the brain. The brain areas commonly targeted in the stress response models include the hippocampus, the amygdala, and the prefrontal cortex. Studies in patients suffering from the so-called stress-related disorders -embracing post-traumatic stress, major depressive and anxiety disorders- have fairly replicated animal models of stress response -particularly the neuroendocrine and the inflammatory models- by finding alterations in different brain areas, even in the early neurodevelopment. Therefore, this narrative review aims to provide an overview of structural neuroimaging findings and to discuss how these studies have contributed to our knowledge of variability in response to stress and the ulterior development of stress-related disorders. There are a gross number of studies available but neuroimaging research of stress-related disorders as a single category is still in its infancy. Although the available studies point at particular brain circuitries involved in stress and emotion regulation, the pathophysiology of these abnormalities -involving genetics, epigenetics and molecular pathways-, their relation to intraindividual stress responses -including personality characteristics, self-perception of stress conditions…-, and their potential involvement as biomarkers in diagnosis, treatment prescription and prognosis are discussed.

Corticolimbic structural connectivity encapsulates real-world emotional reactivity and happiness

Emotional reactivity to everyday events predicts happiness, but the neural circuits underlying this relationship remain incompletely understood. Here, we combined experience sampling methods and diffusion magnetic resonance imaging to examine the association among corticolimbic structural connectivity, real-world emotional reactivity and daily experiences of happiness from 79 young adults (35 females). Participants recorded momentary assessments of emotional and happiness experiences five times a day for a week, approximately 2 weeks after brain scanning. Model-based emotional reactivity scores, which index the degree to which moment-to-moment affective state varies with the occurrence of positive or negative events, were computed. Results showed that stronger microstructural integrity of the uncinate fasciculus and the external capsule was associated with both greater positive and negative emotional reactivity scores. The relationship between these fiber tracts and experienced happiness was explained by emotional reactivity. Importantly, this indirect effect was observed for emotional reactivity to positive but not negative real-world events. Our findings suggest that the corticolimbic circuits supporting socioemotional functions are associated with emotional reactivity and happiness in the real world.

Cingulum and Uncinate Fasciculus Microstructural Abnormalities in Parkinson's Disease: A Systematic Review of Diffusion Tensor Imaging Studies

Diffusion tensor imaging (DTI) is gaining traction in neuroscience research as a tool for evaluating neural fibers. The technique can be used to assess white matter (WM) microstructure in neurodegenerative disorders, including Parkinson disease (PD). There is evidence that the uncinate fasciculus and the cingulum bundle are involved in the pathogenesis of PD. These fasciculus and bundle alterations correlate with the symptoms and stages of PD. PRISMA 2022 was used to search PubMed and Scopus for relevant articles. Our search revealed 759 articles. Following screening of titles and abstracts, a full-text review, and implementing the inclusion criteria, 62 papers were selected for synthesis. According to the review of selected studies, WM integrity in the uncinate fasciculus and cingulum bundles can vary according to symptoms and stages of Parkinson disease. This article provides structural insight into the heterogeneous PD subtypes according to their cingulate bundle and uncinate fasciculus changes. It also examines if there is any correlation between these brain structures' structural changes with cognitive impairment or depression scales like Geriatric Depression Scale-Short (GDS). The results showed significantly lower fractional anisotropy values in the cingulum bundle compared to healthy controls as well as significant correlations between FA and GDS scores for both left and right uncinate fasciculus regions suggesting that structural damage from disease progression may be linked to cognitive impairments seen in advanced PD patients. This review help in developing more targeted treatments for different types of Parkinson's disease, as well as providing a better understanding of how cognitive impairments may be related to these structural changes. Additionally, using DTI scans can provide clinicians with valuable information about white matter tracts which is useful for diagnosing and monitoring disease progression over time.

Morphological similarity of amygdala-ventral prefrontal pathways represents trait anxiety in younger and older adults

Stronger amygdala-ventral prefrontal white matter connectivity has been associated with lower trait anxiety, possibly reflecting an increased capacity for efficient communication between the two regions. However, there are also reports arguing against this brain-anxiety association. To address these inconsistencies in the literature, we tested the possibility that idiosyncratic tract morphology may account for meaningful individual differences in trait anxiety, even among those with comparable microstructural integrity. Here, we adopted intersubject representational similarity analysis, an analytic framework that captures multivariate patterns of similarity, to analyze the morphological similarity of amygdala-ventral prefrontal pathways. Data drawn from the Leipzig Study for Mind-Body-Emotion Interactions dataset showed that younger adults (20 to 35 y of age) with low trait anxiety, in contrast to trait-anxious individuals, had consistently similar morphological configurations in their left amygdala-ventral prefrontal pathways. Additional tests on an independent sample of older adults (60 to 75 y of age) validated this finding. Our study reveals a generalizable pattern of brain-anxiety association that is embedded within the shared geometries between fiber tract morphology and trait anxiety data.

Structural connectome-based prediction of trait anxiety

Neurobiological research on anxiety has shown that trait-anxious individuals may be characterized by weaker structural connectivity of the amygdala-prefrontal circuitry, representing a reduced capacity for efficient communication between the two brain regions. However, comparison of available studies has been inconsistent, possibly related to factors such as aging that influences both trait anxiety and structural connectivity of the brain. To help clarify the nature of brain-anxiety relationship, we applied a connectome-based predictive modeling framework on 148 diffusion-weighted imaging data from the Leipzig Study for Mind-Body Emotion Interactions dataset and identified multivariate patterns of whole-brain structural connectivity that predicted trait anxiety. Results showed that networks predictive of trait anxiety differed across age groups. Specifically, an isolated negative network, which shared overlapping features with the amygdala-prefrontal circuitry, was found in younger adults (20-30 years of age), whereas a widespread positive network highlighted by frontotemporal and frontolimbic connectivity was identified when both younger and older adults (20-80 years of age) were examined. No predictive network was observed when only older adults (30-80 years of age) were considered. Our findings highlight an important age-dependent effect on the structural connectome-based prediction of trait anxiety, supporting ongoing efforts to develop potential neural biomarkers of anxiety.

Reduced cortical volume of the default mode network in adolescents with generalized anxiety disorder

BACKGROUND

Widespread structural alterations have been shown to be implicated in individuals with generalized anxiety disorder (GAD). However, there have been inconsistent findings in cortical volume (CV) differences. Most structural neuroimaging studies looking at GAD used region-based approach with relatively small sample sizes, let alone be specific to adolescents with GAD. We believe this is the first study to look at CV measures using a network-based approach in a larger sample of adolescents with GAD. The goal of the current study was to focus on three different brain networks (i.e., Limbic, Frontoparietal, and Default Mode Network [DMN]) in adolescents with GAD.

METHOD

The study involved 81 adolescents with GAD and 112 typically developing (TD) comparison individuals matched on age (15.98 and 15.63 respective means), sex (42F/39M and 45F/67M), and IQ (101.90 and 103.94 respective means). Participants underwent structural MRI. Freesurfer was used to estimate CV (both network-specific and region-specific within networks) and region-specific sub-cortical volume measures. Multivariate analysis of covariance (MANCOVA; with sex, age, IQ, and intracranial volume [ICV] as potential covariates) was used to estimate group differences.

RESULTS

We found significantly lower CV for the DMN in adolescents with GAD, compared with TD individuals. Adolescents with GAD also showed significantly lower hemispheric mean CV of the default-mode regions (particularly the prefrontal and temporal regions) and the hippocampus, compared with TD individuals.

CONCLUSION

The current findings suggest structural alterations in adolescents with GAD. These structural alterations will need to be addressed when implementing and developing treatments for patients with GAD.

Transdiagnostic role of glutamate and white matter damage in neuropsychiatric disorders: A Systematic Review

Neuropsychiatric disorders including generalized anxiety disorder (GAD), obsessive-compulsive disorder (OCD), major depressive disorder (MDD), bipolar disorder (BD), and schizophrenia (SZ) have been considered distinct categories of diseases despite their overlapping characteristics and symptomatology. We aimed to provide an in-depth review elucidating the role of glutamate/Glx and white matter (WM) abnormalities in these disorders from a transdiagnostic perspective. The PubMed online database was searched for studies published between 2010 and 2021. After careful screening, 401 studies were included. The findings point to decreased levels of glutamate in the Anterior Cingulate Cortex in both SZ and BD, whereas Glx is elevated in the Hippocampus in SZ and MDD. With regard to WM abnormalities, the Corpus Callosum and superior Longitudinal Fascicle were the most consistently identified brain regions showing decreased fractional anisotropy (FA) across all the reviewed disorders, except GAD. Additionally, the Uncinate Fasciculus displayed decreased FA in all disorders, except OCD. Decreased FA was also found in the inferior Longitudinal Fasciculus, inferior Fronto-Occipital Fasciculus, Thalamic Radiation, and Corona Radiata in SZ, BD, and MDD. Decreased FA in the Fornix and Corticospinal Tract were found in BD and SZ patients. The Cingulum and Anterior Limb of Internal Capsule exhibited decreased FA in MDD and SZ patients. The results suggest a gradual increase in severity from GAD to SZ defined by the number of brain regions with WM abnormality which may be partially caused by abnormal glutamate levels. WM damage could thus be considered a potential marker of some of the main neuropsychiatric disorders.

A dynamic relation between whole-brain white matter microstructural integrity and anxiety symptoms in preadolescent females with pathological anxiety

Pathological anxiety typically emerges during preadolescence and has been linked to alterations in white matter (WM) pathways. Because myelination is critical for efficient neuronal communication, characterizing associations between WM microstructure and symptoms may provide insights into pathophysiological mechanisms associated with childhood pathological anxiety. This longitudinal study examined 182 girls enrolled between the ages of 9-11 that were treatment-naïve at study entry: healthy controls (n = 49), subthreshold-anxiety disorders (AD) (n = 82), or meeting DSM-5 criteria for generalized, social, and/or separation ADs (n = 51), as determined through structured clinical interview. Anxiety severity was assessed with the Clinical Global Impression Scale and Screen for Child Anxiety and Related Emotional Disorders (SCARED). Participants (n = 182) underwent clinical, behavioral, and diffusion tensor imaging (DTI) assessments at study entry, and those with pathological anxiety (subthreshold-AD and AD, n = 133) were followed longitudinally for up to 3 additional years. Cross-sectional ANCOVAs (182 scans) examining control, subthreshold-AD, and AD participants found no significant relations between anxiety and DTI measurements. However, in longitudinal analyses of girls with pathological anxiety (343 scans), linear mixed-effects models demonstrated that increases in anxiety symptoms (SCARED scores) were associated with reductions in whole-brain fractional anisotropy, independent of age (Std. β (95% CI) = -0.06 (-0.09 to -0.03), F(1, 46.24) = 11.90, P = 0.001). Using a longitudinal approach, this study identified a dynamic, within-participant relation between whole-brain WM microstructural integrity and anxiety in girls with pathological anxiety. Given the importance of WM microstructure in modulating neural communication, this finding suggests the possibility that WM development could be a viable target in the treatment of anxiety-related psychopathology.

Larger bilateral amygdalar volumes are associated with affective loss experiences

Affective loss (AL) (i.e., bereavement, relationship breakup) is a stressful life event leading to a heightened risk of developing a psychiatric disorder, for example, depression and anxiety disorder. These disorders have been associated with altered subcortical brain volumes. Little is known though, how AL in healthy subjects is linked to subcortical volumes. In a study with 196 healthy young adults, we probed the association between AL across the individual entire life span, assessed via the List of Threatening Experiences Questionnaire, and magnetic resonance imaging brain gray matter volumes (a priori selected: bilateral amygdalae, hippocampi, thalami; exploratory analyses: nuclei accumbens, caudate, putamina), segmented by use of volBrain. AL was defined as death of a first-degree relative/spouse, close relative/friend, and breakup of a marriage or steady relationship. AL was associated with larger bilateral amygdalar volumes and, after taking into account the total number of ALs, with smaller right hippocampal volumes, both irrespective of sex. Exploratory analyses of striatal volumes yielded an association of AL with larger right nucleus accumbens volumes in men, and increased caudate volumes after the loss of a first-degree relative irrespective of sex. Our data suggest that AL engenders alterations in limbic structures that likely involve processes of chronic stress and amygdala- and hippocampus-dependent fear conditioning, and resemble those observed in general anxiety disorder, childhood maltreatment, and major depressive disorder. Our exploratory findings of striatal volume alterations hint at a modulation of reward processing by AL.

The Value of Neuroimaging Techniques in the Translation and Transdiagnostic Validation of Psychiatric Diagnoses - Selective Review

Psychiatric diagnosis has long been perceived as more of an art than a science since its foundations lie within the observation, and the self-report of the patients themselves and objective diagnostic biomarkers are lacking. Furthermore, the diagnostic tools in use not only stray away from the conventional medical framework but also remain invalidated with evidence-based concepts. However, neuroscience, as a source of valid objective knowledge has initiated the process of a paradigm shift underlined by the main concept of psychiatric disorders being "brain disorders". It is also a bridge closing the explanatory gap among the different fields of medicine via the translation of the knowledge within a multidisciplinary framework. The contemporary neuroimaging methods, such as fMRI provide researchers with an entirely new set of tools to reform the current status quo by creating an opportunity to define and validate objective biomarkers that can be translated into clinical practice. Combining multiple neuroimaging techniques with the knowledge of the role of genetic factors, neurochemical imbalance and neuroinflammatory processes in the etiopathophysiology of psychiatric disorders is a step towards a comprehensive biological explanation of psychiatric disorders and a final differentiation of psychiatry as a well-founded medical science. In addition, the neuroscientific knowledge gained thus far suggests a necessity for directional change to exploring multidisciplinary concepts, such as multiple causality and dimensionality of psychiatric symptoms and disorders. A concomitant viewpoint transition of the notion of validity in psychiatry with a focus on an integrative validatory approach may facilitate the building of a collaborative bridge above the wall existing between the scientific fields analyzing the mind and those studying the brain.

White matter structural network disturbances in first-episode, drug-naïve adolescents with generalized anxiety disorder

BACKGROUND

Previous studies have suggested that individuals with generalized anxiety disorder (GAD) would show inefficient whole-brain communication and dysconnectivity in the fronto-parietal-subcortical sub-networks in the white matter (WM) structural network. However, these hypotheses have yet to be tested.

METHODS

Individual WM structural networks were constructed based on diffusion MRI data and deterministic tractography in 34 first-episode, medication-naïve adolescents with GAD and 27 healthy controls (HCs). Graph theory was applied to investigate the topological organization alterations of the structural network.

RESULTS

GAD patients showed disrupted small-world configurations (i.e., increased path length and decreased clustering coefficient) and hub organization (i.e., less connection strength in the feeder and local connections). A decreased connection strength was found in a GAD-related sub-network (mainly involving the frontal-subcortical circuits), which was able to distinguish GAD patients from HCs with higher accuracy (area under the curve of 0.96, sensitivity of 94%, specificity of 89%) than clinical scores and other topological alternations.

LIMITATIONS

The current study just compared GAD patients with HCs based on a small sample, leaving whether the alternations found here are specific to GAD still an open question. Future studies are recommended to recruit patients with other anxiety disorders (e.g., social anxiety disorder) and/or comorbid mood disorders to identify the GAD-specific WM alterations using a larger sample.

CONCLUSIONS

Our findings highlight the disruption of the topological organization of the whole-brain WM structural network (especially the frontal-subcortical circuits) in GAD, and suggest the potential of using structural connectivity of the GAD-related sub-network as a biomarker for GAD patients.

Aberrant amplitude low-frequency fluctuation (ALFF) and regional homogeneity (ReHo) in generalized anxiety disorder (GAD) and their roles in predicting treatment remission

Background

Generalized anxiety disorder (GAD) is a common affective disorder characterized by comprehensive anxiety with dysregulation of brain activity which can be reflected by functional magnetic resonance imaging (f-MRI). We aimed to examine abnormal aberrant amplitude low-frequency fluctuation (ALFF) and regional homogeneity (ReHo) in GAD and evaluate their ability to predict treatment remission.

Methods

Using resting-state fMRI (Rs-fMRI), we examined ALFF and ReHo in 30 GAD patients and 30 healthy control (HC) participants. Using on DEPASF4.3 Advanced Edition, voxel-based two-sample t-test analysis was performed on the ALFF and ReHo maps to compare GAD to HC groups, and to compare remitters (n=9) and non-remitters (n=21). Pearson's correlation analysis was used to explore the relationship between baseline Hamilton Anxiety Rating Scale (HAM-A) scores/illness duration and mean ALFF/ReHo values. The severity of GAD symptoms was rated with HAM-A. Remission was defined as HAM-A ≤7 by week 8.

Results

Compared to the HC group, GAD patients showed lower ALFF in the right postcentral and right precentral gyrus; lower ReHo in the right precentral, right postcentral, and left precentral gyrus; and higher ReHo in the left posterior cingulate cortex. ALFF values for left postcentral gyrus was negatively correlated with baseline HAM-A, while that of the middle frontal gyrus was positively correlated with baseline HAM-A scores. ReHo value of the left postcentral gyrus was negatively correlated with baseline HAM-A, while that of the right middle frontal gyrus was positively correlated with baseline HAM-A scores. ALFF of the right frontal_superior_orbital and right frontal-medial-orbital cortex was positively correlated with illness duration. ReHo of the left supplementary motor area cortex was negatively correlated with illness duration. Remitters showed higher ALFF in the left hippocampus and higher ReHo value in the right postcentral cortex compared to nonremitters.

Conclusions

These results suggest that altered regional brain activity and local synchronization may be related to the pathophysiology of GAD and have certain value in predicting remission in treatment.

Parsing differences in amygdala volume among individuals with and without social and generalized anxiety disorders across the lifespan

Structural differences in the amygdala (AMG) are implicated in anxiety and observed among individuals with generalized (GAD) and social anxiety (SAD) disorders. Findings have been mixed, perhaps because studies rarely examine differences between GAD and SAD, test comorbidity, or examine age-related differences. We tested AMG volume differences among a sample of adults and youth with/without SAD and GAD. Participants (N = 242; ages 7-60 years) completed an MRI scan, diagnostic interviews, and anxiety symptom measures. Groups were formed from diagnostic interviews: 1) Typically developing (TD; n = 91); 2) GAD (n = 53); 3) SAD (n = 35); and 4) comorbid SAD/GAD (n = 63). We used analysis of covariance with a bonferroni correction to examine group differences in AMG volume. The SAD and comorbid SAD/GAD groups exhibited increased bilateral AMG volume compared to the TD group. GAD and TD groups did not differ from each other in AMG size. The SAD, but not the comorbid SAD/GAD group, displayed greater right AMG size relative to the GAD group. SAD and comorbid SAD/GAD groups did not differ from the GAD group in left AMG volume. SAD and SAD/GAD groups did not exhibit different bilateral AMG size. Linear regression analyses demonstrated that greater social anxiety but not generalized anxiety symptom severity was associated with enlarged AMG volume. Age was not associated with AMG volume and nor did age moderate any group or symptom effects. Future longitudinal studies should examine whether larger AMG volume is a unique biomarker for SAD across the lifespan.

Disrupted dynamic local brain functional connectivity patterns in generalized anxiety disorder

Previous studies have reported abnormalities in static brain activity and connectivity in patients with generalized anxiety disorder (GAD). However, the dynamic patterns of brain connectivity in patients with GAD have not been fully explored. In this study, we aimed to investigate the dynamic local brain functional connectivity in patients with GAD using dynamic regional phase synchrony (DRePS), a newly developed method for assessing intrinsic dynamic local functional connectivity. Seventy-four patients with GAD and 74 healthy controls (HCs) were enrolled and underwent resting-state functional magnetic resonance imaging. Compared to the HCs, patients with GAD exhibited decreased DRePS values in the bilateral caudate, left hippocampus, left anterior insula, left inferior frontal gyrus, and right fusiform gyrus extending to inferior temporal gyrus. The DRePS value of the left hippocampus was negatively correlated with the Hamilton Anxiety Rating Scale scores. Moreover, these abnormal DRePS patterns could be used to distinguish patients with GAD from HCs in an independent sample (18 patients with GAD and 21 HCs). Our findings provide further evidence on brain dysfunction in GAD from the perspective of the dynamic behaviour of local connections, suggesting that patients with GAD may have an insufficient brain adaptation. This study provides new insights into the neurocognitive mechanism of GAD and could potentially inform the diagnosis and treatment of this disease. Future studies on GAD could benefit from combining the DRePS method with task-related functional magnetic resonance imaging and non-invasive brain stimulation.

Maternal Prenatal Stress Is Associated With Altered Uncinate Fasciculus Microstructure in Premature Neonates

BACKGROUND

Maternal prenatal stress exposure (PNSE) increases risk for adverse psychiatric and behavioral outcomes in offspring. The biological basis for this elevated risk is poorly understood but may involve alterations to the neurodevelopmental trajectory of white matter tracts within the limbic system, particularly the uncinate fasciculus. Additionally, preterm birth is associated with both impaired white matter development and adverse developmental outcomes. In this study we hypothesized that higher maternal PNSE was associated with altered uncinate fasciculus microstructure in offspring.

METHODS

In this study, 251 preterm infants (132 male, 119 female) (median gestational age = 30.29 weeks [range, 23.57-32.86 weeks]) underwent brain magnetic resonance imaging including diffusion-weighted imaging around term-equivalent age (median = 42.43 weeks [range, 37.86-45.71 weeks]). Measures of white matter microstructure were calculated for the uncinate fasciculus and the inferior longitudinal fasciculus, a control tract that we hypothesized was not associated with maternal PNSE. Multiple regressions were used to investigate the relationship among maternal trait anxiety scores, stressful life events, and white matter microstructure indices in the neonatal brain.

RESULTS

Adjusting for gestational age at birth, postmenstrual age at scan, maternal age, socioeconomic status, sex, and number of days on parenteral nutrition, higher stressful life events scores were associated with higher axial diffusivity (β = .177, q = .007), radial diffusivity (β = .133, q = .026), and mean diffusivity (β = .149, q = .012) in the left uncinate fasciculus, and higher axial diffusivity (β = .142, q = .026) in the right uncinate fasciculus.

CONCLUSIONS

These findings suggest that PNSE is associated with altered development of specific frontolimbic pathways in preterm neonates as early as term-equivalent age.

Abnormal dynamic functional connectivity density in patients with generalized anxiety disorder

BACKGROUND

Numerous studies have revealed the abnormal static functional connectivity (FC) among different brain regions in patients with generalized anxiety disorder (GAD). However, little is known about the dynamic changes of FC in patients with GAD.

METHODS

This study investigated the whole-brain dynamic changes of FC in patients with GAD by combining global FC density (FCD) and sliding window correlation analyses. The standard deviation of dynamic FCD (dFCD) was calculated to evaluate its temporal variability along time. Support vector regression was then employed to predict the symptom severity of patients based on abnormal dynamic connectivity patterns.

RESULTS

The abnormal dFCD variability between 81 GAD patients and 80 healthy controls showed that the patients had higher dFCD variability in the bilateral dorsomedial prefrontal cortex (dmPFC) and left hippocampus while lower dFCD variability in the right postcentral gyrus. The abnormal dFCD variability of the left dmPFC is an important feature for anxiety prediction.

LIMITATIONS

The selection of sliding window length remains controversial, and most of our patients have been treated with medications. Future studies are expected to rule out the potential confounding effects from applying different parameters of the sliding window and recruiting large samples of medication-free patients.

CONCLUSION

The altered patterns of time-varying brain connectivity in the frontolimbic and sensorimotor areas may reflect abnormal dynamic neural communication between these regions and other regions of the brain, which may deepen our understanding of the disease.

Task MRI-Based Functional Brain Network of Anxiety

Magnetic resonance imaging (MRI) is a good tool for researchers to understand the biological mechanisms and pathophysiology of the brain due to the translational characteristics of MRI methods. For the psychiatric illness, this kind of mental disorders usually have minor alterations when compared to traditional neurological disorders. Therefore the functional study, such as functional connectivity, would play a significant role for understanding the pathophysiology of mental disorders. This chapter would focus on the discussion of task MRI-based functional network studies in anxiety. For social anxiety disorder, the limbic system, such as the temporal lobe, amygdala, and hippocampus, would show alterations in the functional connectivity with frontal regions, such as anterior cingulate, prefrontal, and orbitofrontal cortices. PD has anterior cingulate cortex-amygdala alterations in fear conditioning, frontoparietal alterations in attention network task, and limbic-prefrontal alterations in emotional task. A similar amygdala-based aberrant functional connectivity in specific phobia is observed. The mesocorticolimbic and limbic-prefrontal functional alterations are found in generalized anxiety disorder. The major components of task MRI-based functional connectivity in anxiety include limbic and frontal regions which might play a vital role for the origination of anxiety under different scenarios and tasks.

White Matter-Based Structural Brain Network of Anxiety

Anxiety disorders are characterized by excessive fear and anxiety and related behavioral disturbances. Because diffusion tensor imaging is sensitive to detect subtle pathology of the brain, it has been used to characterize differences in white matter microstructure for a broad spectrum of psychiatric disorders. The neurobiological underpinnings of a trait anxiety seem to be associated with the uncinate fasciculus, a major pathway between the amygdala and orbitofrontal cortex. Apparent WM micro-alterations in patients with panic disorder are present in diverse and widespread regions, although alterations vary in terms of clinical symptom severity and comorbidities. Social anxiety disorder is associated with structural dysconnectivity in a fronto-limbic network consistent with reduced fractional anisotropy values in uncinate fasciculus and inferior longitudinal fasciculus. The pathogenesis of obsessive-compulsive disorder may include abnormal findings in not only the fronto-striato-thalamic circuit but also the posterior and temporal regions of forceps major and cingulum bundle. Studies of white matter status in anxiety revealed overlapping patterns of front-cortical and fronto-limbic changes with uncinate fasciculus and cingulum alterations a frequent component.

The Relationship Between the Uncinate Fasciculus and Anxious Temperament Is Evolutionarily Conserved and Sexually Dimorphic

BACKGROUND

Anxious temperament (AT) is an early-life heritable trait that predisposes individuals to develop anxiety and depressive disorders. Our previous work in preadolescent children suggests alterations in the uncinate fasciculus (UF), the white matter tract that connects prefrontal with limbic regions, in boys with anxiety disorders. Here, using a nonhuman primate model of AT, we tested whether this sexually dimorphic finding is evolutionarily conserved and examined the extent to which heritable and environmental influences contribute to UF microstructure.

METHODS

Diffusion tensor images were collected in 581 young rhesus monkeys (1.89 ± 0.77 years old; 43.9% female). Using tract-based analyses, we assessed the relationship among AT, UF microstructure (as measured with fractional anisotropy), and sex. Heritability of tract microstructure was determined using oligogenic linkage analysis of this large multigenerational pedigree.

RESULTS

We predicted and found a negative relation between AT and UF fractional anisotropy in male but not female monkeys (AT × sex; p = .032, 1-tailed). Additionally, heritability analyses revealed that variation in UF fractional anisotropy was largely due to nonheritable factors (h² = 0.185, p = .077).

CONCLUSIONS

These results demonstrate a cross-species, male-specific relation between UF microstructure and anxiety and provide a potential substrate for anxiety-related prefrontal-limbic dysregulation. The heritability analyses point to the importance of environmental influences on UF microstructure, which could be important in mediating the nonheritable components of pathological anxiety. These findings have the potential to guide new treatment strategies for childhood anxiety disorders and further support the use of nonhuman primates as a translational model to discover mechanisms underlying the development of anxiety.

Amantadine exerts anxiolytic like effect in mice: Evidences for the involvement of nitrergic and GABAergic signaling pathways

Amantadine is a glutamatergic antagonist that works by inhibiting the NMDA receptor. Besides the inhibition of NMDA receptors amantadine also stabilizes the glutamatergic system and protects the neurons against the NMDA toxicity. Amantadine treatment also reduces the production of NO and metabolism of GABA. Therefore amantadine modulates glutamate, GABA and NO which are known to be implicated in the pathogenesis of anxiety and related behavior. The present study was designed to investigate the anxiolytic like effect of amantadine in mice. Nitrergic and GABAergic signaling influence in the anxiolytic like effect of amantadine was also studied. Amantadine (25, 50 and 75 mg/kg, i.p.) was administered and the anxiety related behavior was determined using light and dark box (LDB) and elevated plus maze (EPM) methods. Further, the effect of various treatments on the whole brain glutamate, nitrite and GABA levels were also determined. The results obtained demonstrated that the amantadine (50 mg/kg, i.p.) exerted anxiolytic like effect in mice and reduced the levels of glutamate, nitrite and GABA in the brain of mice as compared to control. Further, the influence of NO and GABA in the anxiolytic like effect of the amantadine was also determined. The results obtained demonstrated that NO donor counteracted while NO inhibitor potentiated the anxiolytic like effect of amantadine in mice. Also the combined treatment of amantadine (25 mg/kg, i.p.) and diazepam (1 mg/kg, i.p.) did not affect the anxiety related behavior, brain GABA and nitrite level of mice but reduced the levels the brain glutamate levels significantly as compared to amantadine (25 mg/kg, i.p.) and diazepam (1 mg/kg, i.p.) treated mice. Thus, amantadine exerted anxiolytic like effect in mice and the anxiolytic like effect of amantadine was modulated by nitrergic and GABAergic signaling pathway.

Systematic review and meta-analyses of neural structural and functional differences in generalized anxiety disorder and healthy controls using magnetic resonance imaging

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PFC-amygdala FC is altered in GAD, indicating top-down processing deficits.

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GAD had reduced activity for emotion regulation and working memory in the culmen.

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Salience, default, and central executive nodes have altered structure and function.

Objective

To compare structure, functional connectivity (FC) and task-based neural differences in subjects with generalized anxiety disorder (GAD) compared to healthy controls (HC).

Methods

The Embase, Ovid Medline, PsycINFO, Scopus, and Web of Science databases were searched from inception until March 12, 2018. Two reviewers independently screened titles, abstracts, and full-text articles. Data were extracted from records directly contrasting GAD and HC that included structure (connectivity and local indices such as volume, etc.), FC, or task-based magnetic resonance imaging data. Meta-analyses were conducted, as applicable, using AES-SDM software.

Results

The literature search produced 4,645 total records, of which 85 met the inclusion criteria for the systematic review. Records included structural (n = 35), FC (n = 33), and task-based (n = 42) findings. Meta-analyses were conducted on voxel-based morphometry and task-based results.

Discussion

The systematic review confirms and extends findings from previous reviews. Although few whole-brain resting state studies were conducted, key nodes of resting state networks have altered physiology: the hippocampus (default network), ACC and amygdala (salience network), have reduced volume, and the dlPFC (central executive network) and ACC have reduced FC with the amygdala in GAD. Nodes in the sensorimotor network are also altered with greater pre- and postcentral volume, reduced supplementary motor area volume, and reduced FC in anterior and increased FC in posterior cerebellum.

Conclusions

Despite limitations due to sample size, the meta-analyses highly agree with the systematic review and provide evidence of widely distributed neural differences in subjects with GAD, compared to HC. Further research optimized for meta-analyses would greatly improve large-scale comparisons.

Anxiety in transition: Neuroendocrine mechanisms supporting the development of anxiety pathology in adolescence and young adulthood

Adolescence marks a key developmental window during which emotion dysregulation increases, along with risk for the onset of anxiety and other affect-related pathologies. Although emotion dysregulation and related pathologies normatively decline during the transition into adulthood, this does not occur for a sizable minority of individuals. Finally, sex differences in anxiety emerge during adolescence, with females developing a 2-fold increase in risk relative to males. Unfortunately, a neurobiological model of the mechanisms that cause these changes during adolescence has yet to be proposed. In the present work, we first provide brief reviews of relevant literature. Next, we outline a dual-mechanism model focused on (i) the influence of pubertal testosterone on key emotion-regulation circuitry (i.e., orbitofrontal cortex-amygdala coupling) and (ii) myelination of the fiber bundles connecting such circuitry (i.e., uncinate fasciculus). The proposed model offers a set of specific, testable hypotheses that will hopefully spur much needed cross-disciplinary research.

Individualized prediction of dispositional worry using white matter connectivity

BACKGROUND

Excessive worry is a defining feature of generalized anxiety disorder and is present in a wide range of other psychiatric conditions. Therefore, individualized predictions of worry propensity could be highly relevant in clinical practice, with respect to the assessment of worry symptom severity at the individual level.

METHODS

We applied a multivariate machine learning approach to predict dispositional worry based on microstructural integrity of white matter (WM) tracts.

RESULTS

We demonstrated that the machine learning model was able to decode individual dispositional worry scores from microstructural properties in widely distributed WM tracts (mean absolute error = 10.46, p < 0.001; root mean squared error = 12.82, p < 0.001; prediction R2 = 0.17, p < 0.001). WM tracts that contributed to worry prediction included the posterior limb of internal capsule, anterior corona radiate, and cerebral peduncle, as well as the corticolimbic pathways (e.g. uncinate fasciculus, cingulum, and fornix) already known to be critical for emotion processing and regulation.

CONCLUSIONS

The current work thus elucidates potential neuromarkers for clinical assessment of worry symptoms across a wide range of psychiatric disorders. In addition, the identification of widely distributed pathways underlying worry propensity serves to better improve the understanding of the neurobiological mechanisms associated with worry.

Altered Uncinate Fasciculus Microstructure in Childhood Anxiety Disorders in Boys But Not Girls

OBJECTIVE

Anxiety disorders are common, can result in lifelong suffering, and frequently begin before adolescence. Evidence from adults suggests that altered prefrontal-limbic connectivity is a pathophysiological feature of anxiety disorders. More specifically, in adults with anxiety disorders, decreased fractional anisotropy (FA), a measure of white matter integrity, has been observed in the uncinate fasciculus, the major tract that connects limbic and prefrontal regions. Because of the early onset of anxiety disorders and the increased incidence in anxiety disorders in females during their reproductive years, it is important to understand whether the reduction in uncinate fasciculus FA exists in children with anxiety disorders and the extent to which this alteration is sex related. To address these issues, the authors assessed FA in the uncinate fasciculus in unmedicated boys and girls with anxiety disorders.

METHODS

FA measures were derived from diffusion tensor images that were acquired from 98 unmedicated children (ages 8-12); 52 met criteria for generalized anxiety disorder, separation anxiety disorder, social anxiety disorder, or anxiety disorder not otherwise specified, and 46 were matched control subjects.

RESULTS

Tract-based results demonstrated that children with anxiety disorders have significant reductions in uncinate fasciculus FA. A significant sex-by-group interaction and post hoc testing revealed that this effect was evident only in boys. No other main effects or sex-by-group interactions were found for other white matter tracts.

CONCLUSIONS

These findings provide evidence of uncinate fasciculus white matter alterations in boys with anxiety disorders. The data demonstrate that anxiety disorder-related alterations in prefrontal-limbic structural connectivity are present early in life, are not related to psychotropic medication exposure, and are sex specific. Building on these findings, future research has the potential to provide insights into the genesis and sexual dimorphism of the pathophysiology that leads to anxiety disorders, as well as to identify sex-specific early-life treatment targets.

Comparison of structural connectivity in Parkinson's disease with depressive symptoms versus non-depressed: a diffusion MRI connectometry study

ABSTRACTObjective:Research on psychobiological markers of Parkinson's disease (PD) remains a hot topic. Non-motor symptoms such as depression and REM sleep behavior disorder (RBD) each attribute to a particular neurodegenerative cluster in PD, and might enlighten the way for early prediction/detection of PD. The neuropathology of mood disturbances remains unclear. In fact, a few studies have investigated depression using diffusion magnetic resonance imaging (diffusion MRI).

METHOD

Diffusion MRI of PD patients without comorbid RBD was used to assess whether microstructural abnormalities are detectable in the brain of 40 PD patients with depression compared to 19 patients without depression. Diffusion MRI connectometry was used to carry out group analysis between age- and gender-matched PD patients with and without depressive symptoms. Diffusion MRI connectometry is based on spin distribution function, which quantifies the density of diffusing water and is a sensitive and specific analytical method to psychological differences between groups.

RESULTS

A significant difference (FDR = 0.016129) was observed in the left and right uncinate fasciculi, left and right inferior longitudinal fasciculi, left and right fornices, left inferior fronto-occipital fasciculus, right corticospinal tract, genu of corpus callosum, and middle cerebellar peduncle.

CONCLUSION

These results suggest the prominent circuits involved in emotion recognition, particularly negative emotions, might be impaired in comorbid depressive symptoms in PD.

Fear Network Model in Panic Disorder: The Past and the Future

The core concept for pathophysiology in panic disorder (PD) is the fear network model (FNM). The alterations in FNM might be linked with disturbances in the autonomic nervous system (ANS), which is a common phenomenon in PD. The traditional FNM included the frontal and limbic regions, which were dysregulated in the feedback mechanism for cognitive control of frontal lobe over the primitive response of limbic system. The exaggerated responses of limbic system are also associated with dysregulation in the neurotransmitter system. The neuroimaging studies also corresponded to FNM concept. However, more extended areas of FNM have been discovered in recent imaging studies, such as sensory regions of occipital, parietal cortex and temporal cortex and insula. The insula might integrate the filtered sensory information via thalamus from the visuospatial and other sensory modalities related to occipital, parietal and temporal lobes. In this review article, the traditional and advanced FNM would be discussed. I would also focus on the current evidences of insula, temporal, parietal and occipital lobes in the pathophysiology. In addition, the white matter and functional connectome studies would be reviewed to support the concept of advanced FNM. An emerging dysregulation model of fronto-limbic-insula and temporooccipito-parietal areas might be revealed according to the combined results of recent neuroimaging studies. The future delineation of advanced FNM model can be beneficial from more extensive and advanced studies focusing on the additional sensory regions of occipital, parietal and temporal cortex to confirm the role of advanced FNM in the pathophysiology of PD.

The Role of miR-150 in Stress-Induced Anxiety-Like Behavior in Mice

Stress plays a crucial role in several psychiatric disorders, including anxiety. However, the underlying mechanisms remain poorly understood. Here, we used acute stress (AS) and chronic restraint stress (CRS) models to develop anxiety-like behavior and investigate the role of miR-150 in the hippocampi of mice. Corticosterone levels as well as glutamate receptors in the hippocampus were evaluated. We found that anxiety-like behavior was induced after either AS or CRS, as determined by the open-field test (OFT) and elevated plus-maze test (EPM). Increased corticosterone levels were observed in the blood of AS and CRS groups, while the expression of miR-150 mRNA in the hippocampus was significantly decreased. The expressions of GluN2A, GluR1, GluR2, and V-Glut2 in the hippocampus were decreased after either AS or CRS. Hippocampal GAD67 expression was increased by AS but not CRS, and GluN2B expression was decreased by CRS but not AS. Adult miR-150 knockout mice showed anxiety-like behavior, as assessed by the OFT and EPM. The expressions of GluN2A, GluN2B, GluR1, and GluR2 were also downregulated, but the expression of V-Glut2 was upregulated in the hippocampi of miR-150 knockout mice compared with wild-type mice. Interestingly, we found that the miR-150 knockout mice showed decreased dendrite lengths, dendrite branchings, and numbers of dendrite spines in the hippocampus compared with wild-type mice. These results suggest that miR-150 may influence the synaptic plasticity of the hippocampus and play a significant role in stress-induced anxiety-like behavior in adult mice.

Genetics of generalized anxiety disorder and related traits

This review serves as a systematic guide to the genetics of generalized anxiety disorder (GAD) and further focuses on anxiety-relevant endophenotypes, such as pathological worry fear of uncertainty, and neuroticism. We inspect clinical genetic evidence for the familialityl heritability of GAD and cross-disorder phenotypes based on family and twin studies. Recent advances of linkage studies, genome-wide association studies, and candidate gene studies (eg, 5-HTT, 5-HT1A, MAOA, BDNF) are outlined. Functional and structural neuroimaging and neurophysiological readouts relating to peripheral stress markers and psychophysiology are further integrated, building a multilevel disease framework. We explore etiologic factors in gene-environment interaction approaches investigating childhood trauma, environmental adversity, and stressful life events in relation to selected candidate genes (5-HTT, NPSR1, COMT, MAOA, CRHR1, RGS2), Additionally, the pharmacogenetics of selective serotonin reuptake inhibitor/serotonin-norepinephrine reuptake inhibitor treatment are summarized (5-HTT, 5-HT2A, COMT, CRHR1). Finally, GAD and trait anxiety research challenges and perspectives in the field of genetics, including epigenetics, are discussed.

Brain structural changes in late-life generalized anxiety disorder

Late-life Generalized Anxiety Disorder (GAD) is relatively understudied and the underlying structural and functional neuroanatomy has received little attention. In this study, we compare the brain structural characteristics in white and gray matter in 31 non-anxious older adults and 28 late-life GAD participants. Gray matter indices (cortical thickness and volume) were measured using FreeSurfer parcellation and segmentation, and mean diffusivity was obtained through Diffusion Tensor Imaging (DTI). We assessed both macroscopic white matter changes [using white matter hyperintensity (WMH) burden] and microscopic white matter integrity [using fractional anisotropy (FA)]. No differences in macro- or microscopic white matter integrity were found between GAD and non-anxious controls (HC). GAD participants had lower cortical thickness in the orbitofrontal cortex (OFC), inferior frontal gyrus, and pregenual anterior cingulate cortex (ACC). Higher worry severity was associated with gray matter changes in OFC, ACC and the putamen. The results did not survive the multiple comparison correction, but the effect sizes indicate a moderate effect. The study suggests that late-life GAD is associated with gray matter changes in areas involved in emotion regulation, more so than with white matter changes. We conclude that anxiety-related chronic hypercortisolemia may have a dissociative effect on gray and white matter integrity.

Neurogenetic plasticity and sex influence the link between corticolimbic structural connectivity and trait anxiety

Corticolimbic pathways connecting the amygdala and ventral prefrontal cortex (vPFC) are linked with trait anxiety, but it remains unclear what potential genetic moderators contribute to this association. We sought to address this by examining the inter-individual variability in neuroplasticity as modeled by a functional polymorphism (rs6265) in the human gene for brain derived neurotrophic factor (BDNF). Amygdala-vPFC pathway fractional anisotropy (FA) from 669 diffusion magnetic resonance images was used to examine associations with trait anxiety as a function of rs6265 genotype. We first replicated the inverse correlation between trait anxiety and amygdala-vPFC pathway FA in women. Furthermore, we found a moderating influence of rs6265 genotype such that the association between trait anxiety and right amygdala-vPFC pathway FA was strongest in women carrying the Met allele, which is linked with decreased activity-dependent neuroplasticity. Results indicate that the microstructural integrity of pathways supporting communication between the amygdala and vPFC help shape the expression of trait anxiety in women, and that this association is further modulated by genetically driven variability in neuroplasticity.

Anxiety-related experience-dependent white matter structural differences in adolescence: A monozygotic twin difference approach

Anxiety is linked to deficits in structural and functional connectivity between limbic structures and pre-frontal cortices. We employed a monozygotic (MZ) twin difference design to examine the relationship between structural characteristics of the uncinate fasciculus (UF) measured by Diffusion Tensor Imaging (DTI) and anxiety symptoms in a sample of N = 100 monozygotic (genetically identical), adolescent twins. The MZ difference design allowed us focus on environmental factors that vary within twin pairs while controlling for genetic and environmental factors shared by twin pairs. Twins aged 13-18 years reported on symptoms of generalized anxiety and social phobia prior to participating in a neuroimaging visit. Regions of interest from the JHU ICBM atlas, including uncinate fasciculus and sagittal stratum as a control tract, were registered to the study template. We incorporated multiple diffusion tensor measures to characterize the white matter differences. Within twin pairs, the more anxious twin exhibited decreased fractional anisotropy (t = -2.22, p = 0.032) and axial diffusivity (t = -2.38, p = 0.022) in the left UF compared to the less anxious twin, controlling for age and gender. This study demonstrated the feasibility and advantages of adopting the MZ twin design for DTI measures in neuroimaging research.

A comparison of structural connectivity in anxious depression versus non-anxious depression

BACKGROUND

Major depressive disorder (MDD) and anxiety disorders are highly co-morbid. Research has shown conflicting evidence for white matter alteration and amygdala volume reduction in mood and anxiety disorders. To date, no studies have examined differences in structural connectivity between anxious depressed and non-anxious depressed individuals. This study compared fractional anisotropy (FA) and density of selected white matter tracts and amygdala volume between anxious depressed and non-anxious depressed individuals.

METHODS

64- direction DTI and T1 scans were collected from 110 unmedicated subjects with MDD, 39 of whom had a co-morbid anxiety disorder diagnosis. Region of interest (ROI) and tractography methods were performed to calculate amygdala volume and FA in the uncinate fasciculus, respectively. Diffusion connectometry was performed to identify whole brain group differences in white matter health. Correlations were computed between biological and clinical measures.

RESULTS

Tractography and ROI analyses showed no significant differences between bilateral FA values or bilateral amygdala volumes when comparing the anxious depressed and non-anxious depressed groups. The diffusion connectometry analysis showed no significant differences in anisotropy between the groups. Furthermore, there were no significant relationships between MRI-based and clinical measures.

CONCLUSION

The lack of group differences could indicate that structural connectivity and amygdalae volumes of those with anxious-depression are not significantly altered by a co-morbid anxiety disorder. Improving understanding of anxiety co-morbid with MDD would facilitate development of treatments that more accurately target the underlying networks.

Spontaneous alterations of regional brain activity in patients with adult generalized anxiety disorder

OBJECTIVE

We aimed to examine how spontaneous brain activity might be related to the pathophysiology of generalized anxiety disorder (GAD).

PATIENTS AND METHODS

Using resting-state functional MRI, we examined spontaneous regional brain activity in 31 GAD patients (mean age, 36.87±9.16 years) and 36 healthy control participants (mean age, 39.53±8.83 years) matched for age, education, and sex from December 2014 to October 2015. We performed a two-sample t-test on the voxel-based analysis of the regional homogeneity (ReHo) maps. We used Pearson correlation analysis to compare scores from the Hamilton Anxiety Rating Scale, Hamilton Depression Rating Scale, State-Trait Anxiety Scale-Trait Scale, and mean ReHo values.

RESULTS

We found abnormal spontaneous activity in multiple regions of brain in GAD patients, especially in the sensorimotor cortex and emotional regions. GAD patients showed decreased ReHo values in the right orbital middle frontal gyrus, left anterior cingulate cortex, right middle frontal gyrus, and bilateral supplementary motor areas, with increased ReHo values in the left middle temporal gyrus, left superior temporal gyrus, and right superior occipital gyrus. The ReHo value of the left middle temporal gyrus correlated positively with the Hamilton Anxiety Rating Scale scores.

CONCLUSION

These results suggest that altered local synchronization of spontaneous brain activity may be related to the pathophysiology of GAD.

Anxiety Patients Show Reduced Working Memory Related dlPFC Activation During Safety and Threat

BACKGROUND

Anxiety patients exhibit deficits in cognitive tasks that require prefrontal control of attention, including those that tap working memory (WM). However, it is unclear whether these deficits reflect threat-related processes or symptoms of the disorder. Here, we distinguish between these hypotheses by determining the effect of shock threat versus safety on the neural substrates of WM performance in anxiety patients and healthy controls.

METHODS

Patients, diagnosed with generalized and/or social anxiety disorder, and controls performed blocks of an N-back WM task during periods of safety and threat of shock. We recorded blood-oxygen-level dependent (BOLD) activity during the task, and investigated the effect of clinical anxiety (patients vs. controls) and threat on WM load-related BOLD activation.

RESULTS

Behaviorally, patients showed an overall impairment in both accuracy and reaction time compared to controls, independent of threat. At the neural level, patients showed less WM load-related activation in the dorsolateral prefrontal cortex, a region critical for cognitive control. In addition, patients showed less WM load-related deactivation in the ventromedial prefrontal cortex and posterior cingulate cortex, which are regions of the default mode network. Most importantly, these effects were not modulated by threat.

CONCLUSIONS

This work suggests that the cognitive deficits seen in anxiety patients may represent a key component of clinical anxiety, rather than a consequence of threat.

The Inverse Relationship between the Microstructural Variability of Amygdala-Prefrontal Pathways and Trait Anxiety Is Moderated by Sex

Anxiety impacts the quality of everyday life and may facilitate the development of affective disorders, possibly through concurrent alterations in neural circuitry. Findings from multimodal neuroimaging studies suggest that trait-anxious individuals may have a reduced capacity for efficient communication between the amygdala and the ventral prefrontal cortex (vPFC). A diffusion-weighted imaging protocol with 61 directions was used to identify lateral and medial amygdala-vPFC white matter pathways. The structural integrity of both pathways was inversely correlated with self-reported levels of trait anxiety. When this mask from our first dataset was then applied to an independent validation dataset, both pathways again showed a consistent inverse relationship with trait anxiety. Importantly, a moderating effect of sex was found, demonstrating that the observed brain-anxiety relationship was stronger in females. These data reveal a potential neuroanatomical mediator of previously documented functional alterations in amygdala-prefrontal connectivity that is associated with trait anxiety, which might prove informative for future studies of psychopathology.

Associations between Neuropsychiatric Symptoms and Cerebral Amyloid Deposition in Cognitively Impaired Elderly People

BACKGROUND

Neuropsychiatric symptoms, also known as behavioral and psychological symptoms of dementia (BPSD), affect the majority of patients with dementia, and result in a greater cognitive and functional impairment.

OBJECTIVE

To investigate associations between BPSD and amyloid cerebral deposition as measured by 18F-Florbetapir-PET quantitative uptake in elderly subjects with and without cognitive impairment.

METHODS

Participants with cognitive impairment [mild cognitive impairment (MCI) or Alzheimer's disease (AD)] and healthy controls (HC) from the ADNI cohort (Alzheimer Disease Neuroimaging Initiative) who underwent an 18F-florbetapir PET scan between May 2010 and March 2014 were included. Clinical assessments included the Clinical Dementia Rating, the Mini-Mental State Examination (MMSE), and the Neuropsychiatric Inventory. Freesurfer software was used to extract PET counts based on T1-based structural ROI (frontal, cingulate, parietal, and temporal). Spearman's partial correlation scores between BPSD severity and regional amyloid uptake were calculated.

RESULTS

Data for 657 participants [age = 72.6 (7.19); MMSE = 27.4 (2.67)] were analyzed, including 230 HC [age = 73.1 (6.02); MMSE = 29 (1.21)], 308 MCI [age = 71.5 (7.44); MMSE = 28.0 (1.75)], and 119 AD subjects [age = 74.7 (8.05); MMSE = 23.1 (2.08)]. Considering all diagnostic groups together, positive significant correlations were found between anxiety and 18F-florbetapir uptake in the frontal (r = 0.102; p = 0.009), cingulate (r = 0.083; p = 0.034), and global cerebral uptake (r = 0.099; p = 0.011); between irritability and frontal (r = 0.089; p = 0.023), cingulate (r = 0.085; p = 0.030), parietal (r = 0.087; p = 0.025), and global cerebral uptake (r = 0.093; p = 0.017); in the MCI subgroup, between anxiety and frontal (r = 0.126; p = 0.03) and global uptake (r = 0.14; p = 0.013); in the AD subgroup, between irritability and parietal uptake (r = 0.201; p = 0.03).

CONCLUSION

Anxiety and irritability are associated with greater amyloid deposition in the neurodegenerative process leading to AD.

Clinically Anxious Individuals Show Disrupted Feedback between Inferior Frontal Gyrus and Prefrontal-Limbic Control Circuit

Clinical anxiety is associated with generalization of conditioned fear, in which innocuous stimuli elicit alarm. Using Pavlovian fear conditioning (electric shock), we quantify generalization as the degree to which subjects' neurobiological responses track perceptual similarity gradients to a conditioned stimulus. Previous studies show that the ventromedial prefrontal cortex (vmPFC) inversely and ventral tegmental area directly track the gradient of perceptual similarity to the conditioned stimulus in healthy individuals, whereas clinically anxious individuals fail to discriminate. Here, we extend this work by identifying specific functional roles within the prefrontal-limbic circuit. We analyzed fMRI time-series acquired from 57 human subjects during a fear generalization task using entropic measures of circuit-wide regulation and feedback (power spectrum scale invariance/autocorrelation), in combination with structural (diffusion MRI-probabilistic tractography) and functional (stochastic dynamic causal modeling) measures of prefrontal-limbic connectivity within the circuit. Group comparison and correlations with anxiety severity across 57 subjects revealed dysregulatory dynamic signatures within the inferior frontal gyrus (IFG), which our prior work has linked to impaired feedback within the circuit. Bayesian model selection then identified a fully connected prefrontal-limbic model comprising the IFG, vmPFC, and amygdala. Dysregulatory IFG dynamics were associated with weaker reciprocal excitatory connectivity between the IFG and the vmPFC. The vmPFC exhibited inhibitory influence on the amygdala. Our current results, combined with our previous work across a threat-perception spectrum of 137 subjects and a meta-analysis of 366 fMRI studies, dissociate distinct roles for three prefrontal-limbic regions, wherein the IFG provides evaluation of stimulus meaning, which then informs the vmPFC in inhibiting the amygdala.

SIGNIFICANCE STATEMENT

Affective neuroscience has generally treated prefrontal regions (orbitofrontal cortex, dorsolateral prefrontal cortex, inferior frontal gyrus, ventromedial prefrontal cortex) equivalently as inhibitory components of the prefrontal-limbic system. Yet research across the anxiety spectrum suggests that the inferior frontal gyrus may have a more complex role in emotion regulation, as this region shows abnormal function in disorders of both hyperarousal and hypoarousal. Using entropic measures of circuit-wide regulation and feedback, in combination with measures of structural and functional connectivity, we dissociate distinct roles for three prefrontal-limbic regions, wherein the inferior frontal gyrus provides evaluation of stimulus meaning, which then informs the ventromedial prefrontal cortex in inhibiting the amygdala. This reconfiguration coheres with studies of conceptual disambiguation also implicating the inferior frontal gyrus.

Early life stress and the anxious brain: evidence for a neural mechanism linking childhood emotional maltreatment to anxiety in adulthood

BACKGROUND

Childhood emotional maltreatment (CEM) increases the likelihood of developing an anxiety disorder in adulthood, but the neural processes underlying conferment of this risk have not been established. Here, we test the potential for neuroimaging the adult brain to inform understanding of the mechanism linking CEM to adult anxiety symptoms.

METHOD

One hundred eighty-two adults (148 females, 34 males) with a normal-to-clinical range of anxiety symptoms underwent structural and functional magnetic resonance imaging while completing an emotion-processing paradigm with facial expressions of fear, anger, and happiness. Participants completed self-report measures of CEM and current anxiety symptoms. Voxelwise mediation analyses on gray-matter volumes and activation to each emotion condition were used to identify candidate brain mechanisms relating CEM to anxiety in adulthood.

RESULTS

During processing of fear and anger faces, greater amygdala and less right dorsolateral prefrontal (dlPFC) activation partially mediated the positive relationship between CEM and anxiety symptoms. Greater right posterior insula activation to fear also partially mediated this relationship, as did greater ventral anterior cingulate (ACC) and less dorsal ACC activation to anger. Responses to happy faces in these regions did not mediate the CEM-anxiety relationship. Smaller right dlPFC gray-matter volumes also partially mediated the CEM-anxiety relationship.

CONCLUSIONS

Activation patterns of the adult brain demonstrate the potential to inform mechanistic accounts of the CEM conferment of anxiety symptoms. Results support the hypothesis that exaggerated limbic activation to negative valence facial emotions links CEM to anxiety symptoms, which may be consequent to a breakdown of cortical regulatory processes.

Differential alterations of resting-state functional connectivity in generalized anxiety disorder and panic disorder

Generalized anxiety disorder (GAD) and panic disorder (PD) are most common anxiety disorders with high lifetime prevalence while the pathophysiology and disease-specific alterations still remain largely unclear. Few studies have taken a whole-brain perspective in the functional connectivity (FC) analysis of these two disorders in resting state. It limits the ability to identify regionally and psychopathologically specific network abnormalities with their subsequent use as diagnostic marker and novel treatment strategy. The whole brain FC using a novel FC metric was compared, that is, scaled correlation, which they demonstrated to be a reliable FC statistics, but have higher statistical power in two-sample t-test of whole brain FC analysis. About 21 GAD and 18 PD patients were compared with 22 matched control subjects during resting-state, respectively. It was found that GAD patients demonstrated increased FC between hippocampus/parahippocampus and fusiform gyrus among the most significantly changed FC, while PD was mainly associated with greater FC between somatosensory cortex and thalamus. Besides such regional specificity, it was observed that psychopathological specificity in that the disrupted FC pattern in PD and GAD correlated with their respective symptom severity. The findings suggested that the increased FC between hippocampus/parahippocampus and fusiform gyrus in GAD were mainly associated with a fear generalization related neural circuit, while the greater FC between somatosensory cortex and thalamus in PD were more likely linked to interoceptive processing. Due to the observed regional and psychopathological specificity, their findings bear important clinical implications for the potential treatment strategy.

FKBP5 is associated with amygdala volume in the human brain and mood state: A voxel-based morphometry (VBM) study

The present study was to investigate the effects of 6 FK506 binding protein 51 (FKBP5) single nucleotide polymorphisms (SNPs) on brain structure using voxel-based morphometry (VBM) and the psychological tests to psychological stress. We genotyped 112 healthy controls with respect to 6 SNPs (rs) of FKBP5. We examined the Beck Depression Inventory and the State (STAI-S) and Trait (STAI-T) versions of the Spielberger Anxiety Inventory and the Profile of Mood States (POMS) to evaluate mood. The right amygdala was larger in subjects with the minor allele (C) of rs3800373 and rs992105 and the minor allele (T) of rs1360780. The right middle orbitofrontal region in those with the minor allele (C) of rs3800373 and the right inferior orbitofrontal region in those with the minor allele (T) of rs9470080 was larger. Both the amygdala volumes were associated significantly with FKBP5 SNPs. We found significant relationships between factors in POMS and the right and left amygdala and left insula. Our results suggest that FKBP5 SNPs are associated with the alternations of volumes in right amygdala and the right middle and inferior orbitofrontal region. Genetic variants of FKBP5 may be associated with depressive and anxiety state via differential effects on amygdala and orbitofrontal region.

Negative childhood experiences alter a prefrontal-insular-motor cortical network in healthy adults: A preliminary multimodal rsfMRI-fMRI-MRS-dMRI study

Research in humans and animals has shown that negative childhood experiences (NCE) can have long-term effects on the structure and function of the brain. Alterations have been noted in grey and white matter, in the brain's resting state, on the glutamatergic system, and on neural and behavioural responses to aversive stimuli. These effects can be linked to psychiatric disorder such as depression and anxiety disorders that are influenced by excessive exposure to early life stressors. The aim of the current study was to investigate the effect of NCEs on these systems. Resting state functional MRI (rsfMRI), aversion task fMRI, glutamate magnetic resonance spectroscopy (MRS), and diffusion magnetic resonance imaging (dMRI) were combined with the Childhood Trauma Questionnaire (CTQ) in healthy subjects to examine the impact of NCEs on the brain. Low CTQ scores, a measure of NCEs, were related to higher resting state glutamate levels and higher resting state entropy in the medial prefrontal cortex (mPFC). CTQ scores, mPFC glutamate and entropy, correlated with neural BOLD responses to the anticipation of aversive stimuli in regions throughout the aversion-related network, with strong correlations between all measures in the motor cortex and left insula. Structural connectivity strength, measured using mean fractional anisotropy, between the mPFC and left insula correlated to aversion-related signal changes in the motor cortex. These findings highlight the impact of NCEs on multiple inter-related brain systems. In particular, they highlight the role of a prefrontal-insular-motor cortical network in the processing and responsivity to aversive stimuli and its potential adaptability by NCEs.

A network of amygdala connections predict individual differences in trait anxiety

In this study we demonstrate that the pattern of an amygdala-centric network contributes to individual differences in trait anxiety. Individual differences in trait anxiety were predicted using maximum likelihood estimates of amygdala structural connectivity to multiple brain targets derived from diffusion-tensor imaging (DTI) and probabilistic tractography on 72 participants. The prediction was performed using a stratified sixfold cross validation procedure using a regularized least square regression model. The analysis revealed a reliable network of regions predicting individual differences in trait anxiety. Higher trait anxiety was associated with stronger connections between the amygdala and dorsal anterior cingulate cortex, an area implicated in the generation of emotional reactions, and inferior temporal gyrus and paracentral lobule, areas associated with perceptual and sensory processing. In contrast, higher trait anxiety was associated with weaker connections between amygdala and regions implicated in extinction learning such as medial orbitofrontal cortex, and memory encoding and environmental context recognition, including posterior cingulate cortex and parahippocampal gyrus. Thus, trait anxiety is not only associated with reduced amygdala connectivity with prefrontal areas associated with emotion modulation, but also enhanced connectivity with sensory areas. This work provides novel anatomical insight into potential mechanisms behind information processing biases observed in disorders of emotion.

Cortico-limbic network abnormalities in individuals with current and past major depressive disorder

BACKGROUND

Brain abnormalities in fronto-temporal structures have been implicated in major depressive disorder (MDD). This study aims to identify their anatomical distribution and their relation to the time course of the disease.

METHODS

A whole-brain voxel based morphometry analysis was conducted to assess gray and white matter alterations in 56 participants with a lifetime history of MDD, including currently depressed (cMDD) and remitted patients (rMDD), and 33 matched healthy controls (HC).

RESULTS

Compared to HC, MDD participants showed increased white matter volume (WMV) in the uncinate fasciculus (UF) and decreased gray matter density (GMD) on the ventromedial prefrontal cortex (vmPFC). The increased WMV in UF was driven by both cMDD and rMDD groups and positively correlated with depression scores. The GMD decrease in the vmPFC resulted mainly from abnormalities in rMDD and was not correlated with depression scores. Finally, temporal UF and vmPFC white matter showed strong structural covariance suggesting functional interactions between these two brain regions.

LIMITATIONS

The retrospective and cross-sectional design of the study limits the generalizability of the results. Information concerning ongoing treatment did not allow the exploration of interactions between medication and observed abnormalities. The duration of the remission period could have influenced abnormalities in the subgroup of remitted patients.

CONCLUSIONS

Fronto-temporal alterations in MDD consist of alterations in a cortico-limbic network involving the ventromedial prefrontal cortex and temporal white matter tracts. State-like abnormalities in the UF survive remission and persist as trait-like abnormalities together with alteration in the vmPFC.

Neural circuits in anxiety and stress disorders: a focused review

Anxiety and stress disorders are among the most prevalent neuropsychiatric disorders. In recent years, multiple studies have examined brain regions and networks involved in anxiety symptomatology in an effort to better understand the mechanisms involved and to develop more effective treatments. However, much remains unknown regarding the specific abnormalities and interactions between networks of regions underlying anxiety disorder presentations. We examined recent neuroimaging literature that aims to identify neural mechanisms underlying anxiety, searching for patterns of neural dysfunction that might be specific to different anxiety disorder categories. Across different anxiety and stress disorders, patterns of hyperactivation in emotion-generating regions and hypoactivation in prefrontal/regulatory regions are common in the literature. Interestingly, evidence of differential patterns is also emerging, such that within a spectrum of disorders ranging from more fear-based to more anxiety-based, greater involvement of emotion-generating regions is reported in panic disorder and specific phobia, and greater involvement of prefrontal regions is reported in generalized anxiety disorder and posttraumatic stress disorder. We summarize the pertinent literature and suggest areas for continued investigation.

Glutamate level in anterior cingulate predicts anxiety in healthy humans: a magnetic resonance spectroscopy study

Anxiety, a personality dimension in healthy humans, has been found to be associated with many functional consequences such as increased distractibility and attentional bias in favour of threat-related information, along with morphological and microstructural changes in the brain. The associated metabolic/neurochemical alterations are sparsely studied. In the present magnetic resonance spectroscopy (MRS) study, we investigated the possible relationship between regional brain chemistry within anterior cingulate cortex (4-cm(3) voxel) and hippocampus (2.5-cm(3) voxel) and anxiety (measured by State-Trait Anxiety Inventory) in our subject group. In the anterior cingulate cortex, multivariate analysis of covariance showed an increase in myo-inositol and combined glutamate and glutamine levels in the high anxiety subject group as compared with the low anxiety group. In the partial correlation analysis between neurochemicals and anxiety, glutamate and combined glutamate and glutamine also showed a predictive value for anxiety. On analysing the trait anxiety sub-score separately, we found glutamate, inositol and combined glutamate and glutamine levels to be increased in the high trait anxiety group as compared with the low trait anxiety group. All three resonances also had a predictive value for trait anxiety. In the hippocampus, none of the neurochemicals showed significant difference between high and low anxiety groups. The study provides a first account of alterations in anterior cingulate cortex neurochemistry in relation to anxiety in healthy subjects. The study thus contributes to the limited literature available on altered metabolism and neural mechanisms underlying sub-clinical anxiety.

Peripubertal stress-induced behavioral changes are associated with altered expression of genes involved in excitation and inhibition in the amygdala

Early-life stress is a critical risk factor for developing psychopathological alterations later in life. This early adverse environment has been modeled in rats by exposure to stress during the peripubertal period-that is, corresponding to childhood and puberty-and has been shown to lead to increased emotionality, decreased sociability and pathological aggression. The amygdala, particularly its central nucleus (CeA), is hyperactivated in this model, consistent with evidence implicating this nucleus in the regulation of social and aggressive behaviors. Here, we investigated potential changes in the gene expression of molecular markers of excitatory and inhibitory neurotransmission in the CeA. We found that peripubertal stress led to an increase in the expression of mRNA encoding NR1 (the obligatory subunit of the N-methyl D-aspartate (NMDA) receptor) but to a reduction in the level of mRNA encoding glutamic acid decarboxylase 67 (GAD67), an enzyme that is critically involved in the activity-dependent synthesis of GABA, and to an increase in the vesicular glutamate transporter 1 (VGLUT1)/vesicular GABA transporter (VGAT) ratio in the CeA. These molecular alterations were present in addition to increased novelty reactivity, sociability deficits and increased aggression. Our results also showed that the full extent of the peripubertal protocol was required for the observed behavioral and neurobiological effects because exposure during only the childhood/prepubertal period (Juvenile Stress) or the male pubertal period (Puberty Stress) was insufficient to elicit the same effects. These findings highlight peripuberty as a period in which stress can lead to long-term programming of the genes involved in excitatory and inhibitory neurotransmission in the CeA.