Bilateral Amygdala Volumes Research Articles

Nonclinical psychotic-like experiences and schizotypy dimensions: Associations with hippocampal subfield and amygdala volumes.

Schizotypy and psychotic‐like experiences (PLE) form part of the wider psychosis continuum and may have brain structural correlates in nonclinical cohorts. This study aimed to compare the effects of differential schizotypy dimensions, PLE, and their interaction on hippocampal subfields and amygdala volumes in the absence of clinical psychopathology. In a cohort of 367 psychiatrically healthy individuals, we assessed schizotypal traits using the Oxford‐Liverpool Inventory of Life Experiences (O‐LIFE) and PLE using the short form of the Prodromal Questionnaire (PQ‐16). Based on high‐resolution structural MRI scans, we used automated segmentation to estimate volumes of limbic structures. Sex and total intracranial volume (Step 1), PLE and schizotypy dimensions (Step 2), and their interaction terms (Step 3) were entered as regressors for bilateral amygdala and hippocampal subfield volumes in hierarchical multiple linear regression models. Positive schizotypy, but not PLE, was negatively associated with left amygdala and subiculum volumes. O‐LIFE Impulsive Nonconformity, as well as the two‐way interaction between positive schizotypy and PLE, were associated with larger left subiculum volumes. None of the estimators for right hemispheric hippocampal subfield volumes survived correction for multiple comparisons. Our findings support differential associations of hippocampus subfield volumes with trait dimensions rather than PLE, and support overlap and interactions between psychometric positive schizotypy and PLE. In a healthy cohort without current psychosis risk syndromes, the positive association between PLE and hippocampal subfield volume occurred at a high expression of positive schizotypy. Further studies combining stable, transient, and genetic parameters are required.

Prospective association of maternal psychosocial stress in pregnancy with newborn hippocampal volume and implications for infant social-emotional development

Maternal psychosocial stress during pregnancy can impact the developing fetal brain and influence offspring mental health. In this context, animal studies have identified the hippocampus and amygdala as key brain regions of interest, however, evidence in humans is sparse. We, therefore, examined the associations between maternal prenatal psychosocial stress, newborn hippocampal and amygdala volumes, and child social-emotional development.In a sample of 86 mother-child dyads, maternal perceived stress was assessed serially in early, mid and late pregnancy. Following birth, newborn (aged 5–64 postnatal days, mean: 25.8 ± 12.9) hippocampal and amygdala volume was assessed using structural magnetic resonance imaging. Infant social-emotional developmental milestones were assessed at 6- and 12-months age using the Bayley-III.After adjusting for covariates, maternal perceived stress during pregnancy was inversely associated with newborn left hippocampal volume (β = −0.26, p = .019), but not with right hippocampal (β = −0.170, p = .121) or bilateral amygdala volumes (ps > .5). Furthermore, newborn left hippocampal volume was positively associated with infant social-emotional development across the first year of postnatal life (B = 0.01, p = .011). Maternal perceived stress was indirectly associated with infant social-emotional development via newborn left hippocampal volume (B = −0.34, 95% CIBC [-0.97, −0.01]), suggesting mediation.This study provides prospective evidence in humans linking maternal psychosocial stress in pregnancy with newborn hippocampal volume and subsequent infant social-emotional development across the first year of life. These findings highlight the importance of maternal psychosocial state during pregnancy as a target amenable to interventions to prevent or attenuate its potentially unfavorable neural and behavioral consequences in the offspring.

A Diagnosis and Biotype Comparison Across the Psychosis Spectrum: Investigating Volume and Shape Amygdala-Hippocampal Differences from the B-SNIP Study.

Brain-based Biotypes for psychotic disorders have been developed as part of the B-SNIP consortium to create neurobiologically distinct subgroups within idiopathic psychosis, independent from traditional phenomenological diagnostic methods. In the current study, we aimed to validate the Biotype model by assessing differences in volume and shape of the amygdala and hippocampus contrasting traditional clinical diagnoses with Biotype classification. A total of 811 participants from 6 sites were included: probands with schizophrenia (n = 199), schizoaffective disorder (n = 122), psychotic bipolar disorder with psychosis (n = 160), and healthy controls (n = 330). Biotype classification, previously developed using cognitive and electrophysiological data and K-means clustering, was used to categorize psychosis probands into 3 Biotypes, with Biotype-1 (B-1) showing reduced neural salience and severe cognitive impairment. MAGeT-Brain segmentation was used to determine amygdala and hippocampal volumetric data and shape deformations. When using Biotype classification, B-1 showed the strongest reductions in amygdala-hippocampal volume and the most widespread shape abnormalities. Using clinical diagnosis, probands with schizophrenia and schizoaffective disorder showed the most significant reductions of amygdala and hippocampal volumes and the most abnormal hippocampal shape compared with healthy controls. Biotype classification provided the strongest neuroanatomical differences compared with conventional DSM diagnoses, with the best discrimination seen using bilateral amygdala and right hippocampal volumes in B-1. These findings characterize amygdala and hippocampal volumetric and shape abnormalities across the psychosis spectrum. Grouping individuals by Biotype showed greater between-group discrimination, suggesting a promising approach and a favorable target for characterizing biological heterogeneity across the psychosis spectrum.

Dispositional Negative Emotionality in Childhood and Adolescence Predicts Structural Variation in the Amygdala and Caudal Anterior Cingulate During Early Adulthood: Theoretically and Empirically Based Tests.

Substantial evidence implicates the amygdala and related structures in the processing of negative emotions. Furthermore, neuroimaging evidence suggests that variations in amygdala volumes are related to trait-like individual differences in neuroticism/negative emotionality, although many questions remain about the nature of such associations. We conducted planned tests of the directional prediction that dispositional negative emotionality measured at 10-17years using parent and youth ratings on the Child and Adolescent Dispositions Scale (CADS) would predict larger volumes of the amygdala in adulthood and conducted exploratory tests of associations with other regions implicated in emotion processing. Participants were 433 twins strategically selected for neuroimaging during wave 2 from wave 1 of the Tennessee Twins Study (TTS) by oversampling on internalizing and/or externalizing psychopathology risk. Controlling for age, sex, race-ethnicity, handedness, scanner, and total brain volume, youth-rated negative emotionality positively predicted bilateral amygdala volumes after correction for multiple testing. Each unit difference of one standard deviation (SD) in negative emotionality was associated with a .12 SD unit difference in larger volumes of both amygdalae. Parent-rated negative emotionality predicted greater thickness of the left caudal/dorsal anterior cingulate cortex (β = 0.28). Associations of brain structure with negative emotionality were not moderated by sex. These results are striking because dispositions assessed at 10-17years of age were predictive of grey matter volumes measured 12-13years later in adulthood. Future longitudinal studies should examine the timing of amygdala/cingulate associations with dispositional negative emotionality to determine when these associations emerge during development.

Neonatal amygdala volumes and the development of self-regulation from early infancy to toddlerhood.

Objective: At the broadest level, self-regulation (SR) refers to a range of separate, but interrelated, processes (e.g., working memory, inhibition, and emotion regulation) central for the regulation of cognition, emotion, and behavior that contribute to a plethora of health and mental health outcomes. SR skills develop rapidly in early childhood, but their neurobiological underpinnings are not yet well understood. The amygdala is one key structure in negative emotion generation that may disrupt SR. In the current study, we investigated the associations between neonatal amygdala volumes and mother-reported and observed child SR during the first 3 years of life. We expected that larger neonatal amygdala volumes would be related to poorer SR in children. Method: We measured amygdala volumes from magnetic resonance imaging (MRI) performed at age M = 3.7 ± 1.0. We examined the associations between the amygdala volumes corrected for intracranial volume (ICV) and (a) parent-reported indicators of SR at 6, 12, and 24 months (N = 102) and (b) observed task-based indicators of SR (working memory and inhibitory control) at 30 months of age in a smaller subset of participants (N = 80). Results: Bilateral neonatal amygdala volumes predicted poorer working memory at 30 months in girls, whereas no association was detected between amygdalae and inhibitory control or parent-reported SR. The left amygdala by sex interaction survived correction for multiple comparisons. Conclusions: Neonatal amygdala volume is associated with working memory, particularly among girls, and the association is observed earlier than in prior studies. Moreover, our findings suggest that the neural correlates for parent-reported, compared to observed early life SR, may differ. (PsycInfo Database Record (c) 2021 APA, all rights reserved).

The modulating impact of cigarette smoking on brain structure in panic disorder: a voxel-based morphometry study.

Cigarette smoking increases the likelihood of developing anxiety disorders, among them panic disorder (PD). While brain structures altered by smoking partly overlap with morphological changes identified in PD, the modulating impact of smoking as a potential confounder on structural alterations in PD has not yet been addressed. In total, 143 PD patients (71 smokers) and 178 healthy controls (62 smokers) participated in a multicenter magnetic resonance imaging (MRI) study. T1-weighted images were used to examine brain structural alterations using voxel-based morphometry in a priori defined regions of the defensive system network. PD was associated with gray matter volume reductions in the amygdala and hippocampus. This difference was driven by non-smokers and absent in smoking subjects. Bilateral amygdala volumes were reduced with increasing health burden (neither PD nor smoking > either PD or smoking > both PD and smoking). As smoking can narrow or diminish commonly observed structural abnormalities in PD, the effect of smoking should be considered in MRI studies focusing on patients with pathological forms of fear and anxiety. Future studies are needed to determine if smoking may increase the risk for subsequent psychopathology via brain functional or structural alterations.

Amygdala subnuclei volume in bipolar spectrum disorders: Insights from diffusion-based subsegmentation and a high-risk design.

Amygdala abnormalities are widely documented in bipolar spectrum disorders (BSD). Amygdala volume typically is measured after BSD onset; thus, it is not known whether amygdala abnormalities predict BSD risk or relate to the disorder. Additionally, past literature often treated the amygdala as a homogeneous structure, and did not consider its distinct subnuclei and their differential connectivity to other brain regions. To address these issues, we used a behavioral high‐risk design and diffusion‐based subsegmentation to examine amygdala subnuclei among medication‐free individuals with, and at risk for, BSD. The behavioral high‐risk design (N = 114) included low‐risk (N = 37), high‐risk (N = 47), and BSD groups (N = 30). Diffusion‐based subsegmentation of the amygdala was conducted to determine whether amygdala volume differences related to particular subnuclei. Individuals with a BSD diagnosis showed greater whole, bilateral amygdala volume compared to Low‐Risk individuals. Examination of subnuclei revealed that the BSD group had larger volumes compared to the High‐Risk group in both the left medial and central subnuclei, and showed larger volume in the right lateral subnucleus compared to the Low‐Risk group. Within the BSD group, specific amygdala subnuclei volumes related to time since first episode onset and number of lifetime episodes. Taken together, whole amygdala volume analyses replicated past findings of enlargement in BSD, but did not detect abnormalities in the high‐risk group. Examination of subnuclei volumes detected differences in volume between the high‐risk and BSD groups that were missed in the whole amygdala volume. Results have implications for understanding amygdala abnormalities among individuals with, and at risk for, a BSD.

A Preliminary Investigation of the Effects of a Western Diet on Hippocampal Volume in Children.

Introduction: Over the course of the 20th century, there has been a sharp increase in the consumption of saturated fat and refined sugars. This so-called “western diet” (WD) has been extensively linked to biological alterations and associated functional deficits in the hippocampus of animals. However, the effects of a WD on the human hippocampus are less well-characterized. This preliminary study aimed to extend prior animal work by investigating the effects of a WD on hippocampal volume in children.Methods: Twenty-one healthy children (ages 5–9) completed a structural T1-weighted magnetic resonance imaging scan. Bilateral hippocampal volumes (as regions-of-interest) and bilateral amygdala volumes (as medial temporal lobe control regions-of-interest) were calculated. WD variables were derived from the parent-completed Youth/Adolescent Food Frequency Questionnaire. Specifically, variables were calculated as percent of daily calories consumed from sugars, fats, or a combination of these (WD).Results: While the relationships between overall WD consumption and bilateral hippocampal volumes were not significant, increased fat consumption was significantly related to decreased left hippocampal volume. Sugar consumption was not related to hippocampal size. Control region volumes were not related to any diet variables.Discussion: This study is the first to directly link diet—specifically fat consumption—to decreased left hippocampal volume in children. This extends previous work showing smaller left hippocampal volume related to obesity in pediatric samples. Though preliminary, findings represent an important step toward understanding the impact of diet on child brain development.

Volume changes of subcortical structures in patients with post-hepatitis B cirrhosis: A magnetic resonance imaging study.

To investigate volume changes of subcortical structures in patients with post-hepatitis B cirrhosis. Thirty patients with post-hepatitis B cirrhosis (the cirrhosis group) and 24 age- and sex-matched healthy controls (the control group) were enrolled in this prospective study. All subjects underwent neuropsychological tests, blood biochemical determinations, and cerebral MRI. Volumes of 18 selected subcortical structures were automatically segmented and analyzed by the FreeSurfer. In the cirrhosis group, the relationships between abnormal subcortical volumes and clinical index or neurocognitive performance were investigated. The relationships between globus pallidus volumes and pallidal hyperintensity were also examined. Compared with the healthy controls, patients with post-hepatitis B cirrhosis displayed smaller bilateral putamen, amygdala, and nucleus accumbens volumes and larger bilateral globus pallidus volumes (P<0.001 or P=0.001). In the cirrhosis group, the volumes of left putamen and amygdala were negatively correlated with the number connection test-A (NCT-A)(left putamen r=-0.410, P=0.034; left amygdala r=-0.439, P=0.022), and the volumes of bilateral globus pallidus were positively correlated with pallidal index (PI) (left globus pallidus r=0.889, P<0.001; right globus pallidus r=0.900, P<0.001). Abnormalities of subcortical volumes appear bilaterally symmetrical in patients with post-hepatitis B cirrhosis. Atrophy of left putamen and amygdala might contribute to poor neurocognitive performance, and the manganese deposition might contribute to the increased globus pallidus volumes in patients with post-hepatitis B cirrhosis.

Structure related to function: prefrontal surface area has an indirect effect on the relationship between amygdala volume and trait neuroticism.

Trait neuroticism refers to individual differences in negative emotional response to threat, frustration, or loss, operationally defined by elevated levels of irritability, anger, sadness, anxiety, worry, hostility, self-consciousness, and vulnerability to mental and physical difficulties. While functional studies have been fairly consistent when identifying regions associated with neuroticism during emotional stimuli, structural imagining studies do not tend to find a relationship between amygdala volume and trait neuroticism. There is a great deal of functional evidence that frontoparietal areas are related to the amygdala, and to emotional reactivity more generally, as a function of their involvement in emotion regulation. Specifically, top-down emotion appraisal and expression appear to involve parts of the dorsolateral and dorsomedial prefrontal cortices, which operate at least in part via the indirect modulation of the amygdala. It was hypothesized that cortical surface area and cortical thickness in regions associated with emotion appraisal/expression and emotional attention (i.e., superior frontal and rostral middle frontal gyri, respectively) would have an indirect effect on the relationship between amygdala volume and self-reported neuroticism (respectively), potentially explaining the inconsistency in the structural literature. In sample of 1106 adults, superior frontal and rostral middle frontal gyri, as parcellated by Freesurfer, were examined as potentially restricting variance in a model of indirect effects, which may elucidate the overall relationship between cortical and subcortical gray matter volume and trait neuroticism. Results indicated that, despite no association between bilateral amygdala volume and trait neuroticism, when right superior frontal surface area was entered into the model of indirect effects, a significant relationship between amygdala volume and trait neuroticism emerged. Two of the three remaining models indicated that cortical surface area had an indirect effect on the relationship between amygdala volume and trait neuroticism. These findings highlight the relationship between structural and functional neuroimaging studies. Specifically, the results indicate that when volume is related to behavior, individual differences in higher-order cortical regions, particularly surface area, may help to better understand the relationship between emotion and subcortical gray matter volume.

A comparative evaluation of bilateral hippocampus and amygdala volumes with ADC values in pediatric primary idiopathic partial epilepsy patients

Amac: Temporal nobetlerin yaklasik %70'i hipokampal nobetlerdir ve genellikle amigdala nobetleri ile birliktedir. Bu bolgede meydana gelen nobetler genellikle kompleks parsiyel nobetlerdir.Calismamizin amaci, rutin kraniyal MRG'de patolojisi olmayan 0-18 yas arasindaki idiyopatik parsiyel epilepsi hastalarinda hipokampus ve amigdala hacminde anlamli bir degisiklik olup olmadigini belirlemek ve hastalarin hipokampus ile amigdala ADC degerlerini kontrol grubu ile karsilastimali olarak degerlendirmektir. Yontemler: Yapilan olgu-kontrol calismasinda 2014 ve 2017 yillari arasinda hastanemize basvuran, 1-18 yas arasinda olup, EEG ve klinik bulgulariyla idiyopatik parsiyel epilepsi tanisi alan 27 hasta ile 20 kontrol grubu karsilastirildi. Kontrol grubu olarak, benzer yaslarda olup hastanemize bas agrisi ve bas donmesi gibi nonspesifik sikâyetlerle basvuran ve kraniyal MRG cekilen 20 cocuk degerlendirildi. Calisma ve kontrol grubunda bilinen konjenital hastalik oykusu olan, edinsel norodejeneratif hastalik geciren, intrakraniyal enfeksiyon ya da perinatal etkilenme oykusu bulunan ve intrakraniyal kitlesi olan cocuklar calismaya dâhil edilmemistir Cizimler, volumetrik olcumler ve ADC olcumleri iki ayri degerlendirici tarafindan yapildilar (Biri nororadyolog, digeri radyoloji arastirma gorevlisi). Bulgular: Kontrol grubu ile karsilastirildiginda, calisma grubunda hipokampus ve amigdala volumlerinde azalma izlenmekle beraber sonuclar sadece sol hipokampus icin anlamliydi. ADC degerlerinin karsilastirilimasinda calisma grubunun ADC degerleri kontrol grubuna kiyasla artmis olmakla birlikte bulgular sadece sol amigdala icin istatistiksel olarak anlamliydi. Sonuc: Calismamizda, idiyopatik parsiyel epilepsi tanisi alanlarda, hipokampus ve amigdala volumlerinin, nobet odagina bagli olarak ipsilateral azalmis oldugunu bulduk. Ayni zamanda, ipsilateral amigdalada ADC degerlerinde artis oldugunu bulduk.

Larger Amygdala Volume Mediates the Association Between Prenatal Maternal Stress and Higher Levels of Externalizing Behaviors: Sex Specific Effects in Project Ice Storm.

Introduction: The amygdala is a brain structure involved in emotional regulation. Studies have shown that larger amygdala volumes are associated with behavioral disorders. Prenatal maternal depression is associated with structural changes in the amygdala, which in turn, is predictive of an increase in behavioral problems. Girls may be particularly vulnerable. However, it is not known whether disaster-related prenatal maternal stress (PNMS), or which aspect of the maternal stress experience (i.e., objective hardship, subjective distress, and cognitive appraisal), influences amygdala volumes. Nor is it known whether amygdala volumes mediate the effect of PNMS on behavioral problems in girls and boys.Aims: To assess whether aspects of PNMS are associated with amygdala volume, to determine whether timing of exposure moderates the effect, and to test whether amygdala volume mediates the association between PNMS and internalizing and externalizing problems in 11½ year old children exposed in utero, to varying levels of disaster-related PNMS.Methods: Bilateral amygdala volumes (AGV) and total brain volume (TBV) were acquired using magnetic resonance imaging, from 35 boys and 33 girls whose mothers were pregnant during the January 1998 Quebec Ice Storm. The mothers' disaster-related stress was assessed in June 1998. Child internalizing and externalizing problems were assessed at 11½ years using the Child Behavior Checklist (CBCL). Hierarchical regression analyses and mediation analyses were conducted on boys and girls separately, controlling for perinatal and postnatal factors.Results: In boys, subjective distress was associated with larger right AGV/TBV when mothers where exposed during late pregnancy, which in turn explained higher levels of externalizing behavior. However, when adjusting for postnatal factors, the effect was no longer significant. In girls, later gestational exposure to the ice storm was associated with larger AGV/TBV, but here, higher levels of objective PNMS were associated with more externalizing problems, which was, in part, mediated by larger AGV/TBV. No effects were detected on internalizing behaviors.Conclusion: These results suggest that the effects of PNMS on amygdala development and externalizing symptoms, as assessed in boys and girls in early adolescence, can be influenced by the timing of the stress in pregnancy, and the particular aspect of the mother's stress experience.

Cerebellar, limbic, and midbrain volume alterations in sudden unexpected death in epilepsy.

The processes underlying sudden unexpected death in epilepsy (SUDEP) remain elusive, but centrally mediated cardiovascular or respiratory collapse is suspected. Volume changes in brain areas mediating recovery from extreme cardiorespiratory challenges may indicate failure mechanisms and allow prospective identification of SUDEP risk. We retrospectively imaged SUDEP cases (n=25), patients comparable for age, sex, epilepsy syndrome, localization, and disease duration who were high-risk (n=25) or low-risk (n=23), and age- and sex-matched healthy controls (n=25) with identical high-resolution T1-weighted scans. Regional gray matter volume, determined by voxel-based morphometry, and segmentation-derived structure sizes were compared across groups, controlling for total intracranial volume, age, and sex. Substantial bilateral gray matter loss appeared in SUDEP cases in the medial and lateral cerebellum. This was less prominent in high-risk subjects and absent in low-risk subjects. The periaqueductal gray, left posterior and medial thalamus, left hippocampus, and bilateral posterior cingulate also showed volume loss in SUDEP. High-risk subjects showed left thalamic volume reductions to a lesser extent. Bilateral amygdala, entorhinal, and parahippocampal volumes increased in SUDEP and high-risk patients, with the subcallosal cortex enlarged in SUDEP only. Disease duration correlated negatively with parahippocampal volume. Volumes of the bilateral anterior insula and midbrain in SUDEP cases were larger the closer to SUDEP from magnetic resonance imaging. SUDEP victims show significant tissue loss in areas essential for cardiorespiratory recovery and enhanced volumes in areas that trigger hypotension or impede respiratory patterning. Those changes may shed light on SUDEP pathogenesis and prospectively detect patterns identifying those at risk.

Callous and uncaring traits are associated with reductions in amygdala volume among youths with varying levels of conduct problems.

The emergence of callous unemotional (CU) traits, and associated externalizing behaviors, is believed to reflect underlying dysfunction in the amygdala. Studies of adults with CU traits or psychopathy have linked characteristic patterns of amygdala dysfunction to reduced amygdala volume, but studies in youths have not thus far found evidence of similar amygdala volume reductions. The current study examined the association between CU traits and amygdala volume by modeling CU traits and externalizing behavior as independent continuous variables, and explored the relative contributions of callous, uncaring, and unemotional traits. CU traits and externalizing behavior problems were assessed in 148 youths using the Inventory of Callous Unemotional Traits (ICU) and the Child Behavior Checklist (CBCL). For a subset of participants (n = 93), high-resolution T1-weighted images were collected and volume estimates for the amygdala were extracted. Analyses revealed that CU traits were associated with increased externalizing behaviors and decreased bilateral amygdala volume. These results were driven by the callous and uncaring sub-factors of CU traits, with unemotional traits unrelated to either externalizing behaviors or amygdala volume. Results persisted after accounting for covariation between CU traits and externalizing behaviors. Bootstrap mediation analyses indicated that CU traits mediated the relationship between reduced amygdala volume and externalizing severity. These findings provide evidence that callous-uncaring traits account for reduced amygdala volume among youths with conduct problems. These findings provide a framework for further investigation of abnormal amygdala development as a key causal pathway for the development of callous-uncaring traits and conduct problems.

Sex‐related differences in behavioral and amygdalar responses to compound facial threat cues

During face perception, we integrate facial expression and eye gaze to take advantage of their shared signals. For example, fear with averted gaze provides a congruent avoidance cue, signaling both threat presence and its location, whereas fear with direct gaze sends an incongruent cue, leaving threat location ambiguous. It has been proposed that the processing of different combinations of threat cues is mediated by dual processing routes: reflexive processing via magnocellular (M) pathway and reflective processing via parvocellular (P) pathway. Because growing evidence has identified a variety of sex differences in emotional perception, here we also investigated how M and P processing of fear and eye gaze might be modulated by observer's sex, focusing on the amygdala, a structure important to threat perception and affective appraisal. We adjusted luminance and color of face stimuli to selectively engage M or P processing and asked observers to identify emotion of the face. Female observers showed more accurate behavioral responses to faces with averted gaze and greater left amygdala reactivity both to fearful and neutral faces. Conversely, males showed greater right amygdala activation only for M-biased averted-gaze fear faces. In addition to functional reactivity differences, females had proportionately greater bilateral amygdala volumes, which positively correlated with behavioral accuracy for M-biased fear. Conversely, in males only the right amygdala volume was positively correlated with accuracy for M-biased fear faces. Our findings suggest that M and P processing of facial threat cues is modulated by functional and structural differences in the amygdalae associated with observer's sex.

Alterations in volumes and MRI features of amygdala in Chinese autistic preschoolers associated with social and behavioral deficits

To examine the amygdala volume in 2–5-year-old preschool children with autism and explore the relationship between amygdala volumes based on MRI findings and clinical features. A total of 39 cases with clinically diagnosed autism were collected. The oblique coronal T1 weighted image (T1WI) sequence was used to measure the volume of amygdala and the MRI signals were measured and analyzed. The data were compared to that of 24 age-matched healthy children and correlated to the clinical manifestations. The autism and the control groups were subject to brain scanning in 1 week after Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition (DSM-IV) review. The 39 cases, diagnosed with autism, were associated with social and behavioral deficits through clinical observation, physical and neurological examination, and assessments according to DSM IV, and the range of ABC scores in the autism group was 47–124, with an average score of 84.7 ± 24.1. Abnormal MRI signals were found in 19/78 (24.4%) amygdala in the autism group, the amygdala lesions showed punctuate or flaky low signal, slightly low signal, low to iso-signal, slightly high signal, or iso to high-signal intensity on T1 weighted three-dimendional fast low angle shot(T1FL3D) images. The right amygdala volume average was 1.088 ± 0.38 cm3, while that of the left amygdala was 1.04 ± 0.41 cm3, without any statistically significant difference (t = 0.533, p = 0.596) in the autism group. Among the 24 cases in the control group, the right amygdala volume average was 0.754 ± 0.194 cm3, while that of the left amygdala was 0.666 ± 0.252 cm3; the autism group had a significantly larger right and left amygdala volumes as compared to the age-matched typically developing group with a significant positive correlation between age and right amygdala volume (r = 0.406, p = 0.01). The preschool children with autism had significantly larger bilateral amygdala volumes as compared to age-matched typically developing children, the amygdala lesions may show abnormal signal. A relationship between age and right amygdala volume in the preschool children with autism was established.

Amygdala structure and the tendency to regard the social system as legitimate and desirable

Individual variation in preferences to maintain versus change the societal status quo can manifest in the political realm by choosing leaders and policies that reinforce or undermine existing inequalities 1 . We sought to understand which individuals are likely to defend or challenge inequality in society by exploring the neuroanatomical substrates of system justification tendencies. In two independent neuroimaging studies, we observed that larger bilateral amygdala volume was positively correlated with the tendency to believe that the existing social order was legitimate and desirable. These results held for members of advantaged and disadvantaged groups (men and women, respectively). Furthermore, individuals with larger amygdala volume were less likely to participate in subsequent protest movements. We ruled out alternative explanations in terms of attitudinal extremity and political orientation per se. Exploratory whole-brain analyses suggested that system justification effects may extend to structures that are adjacent to the amygdala, including parts of the insula and the orbitofrontal cortex. These findings suggest that the amygdala may provide a neural substrate for maintaining the societal status quo, and opens avenues for further investigation into the association between system justification and other neuroanatomical regions. In two neuroimaging studies, Nam et al. find that amygdala volume is associated with individual preferences to maintain (versus change) the societal status quo.

Excess social media use in normal populations is associated with amygdala-striatal but not with prefrontal morphology

This study aims to investigate the gray matter volume (GMV) of key neural systems possibly associated with Excess Social Media Use (ESMU) in the general user population. It employs a sex-balanced case (relatively high ESMU scores) - control (relatively low ESMU scores) design with 50 random university students who have reported varying levels of ESMU. The case and control groups included 25 subjects each. Brain volumes were calculated with Voxel-Based Morphometry techniques applied to structural MRI scans. Results based on voxel-wise and region-of-interest (ROI) analyses showed that the case group had reduced GMV in the bilateral amygdala and right ventral striatum. The GMV of the bilateral amygdala and right ventral striatum negatively correlated with ESMU scores in the voxel-wise analysis. No differences or correlations in relation to prefrontal regions were observed. Using the ROI analysis, the bilateral amygdala volumes correlated with ESMU scores, and insufficient evidence regarding the ventral striatum and ESMU was obtained. It is concluded that excess social media use in the general population is associated in part with GMV reduction in the bilateral amygdala, and possibly the striatum, but not in volumetric differences in prefrontal regions.

Amygdala structure and core dimensions of the affective personality

While biological models of human personality propose that socio-affective traits and skills are rooted in the structure of the amygdala, empirical evidence remains sparse and inconsistent. Here, we used a comprehensive assessment of the affective personality and tested its association with global, local, and laterality measures of the amygdala structure. Results revealed three broad dimensions of the affective personality that were differentially related to bilateral amygdala structures. Dysfunctional and maladaptive affective traits were associated with a global size and local volume reduction of the amygdala, whereas adaptive emotional skills were linked to an increased size of the left amygdala. Furthermore, reduced asymmetry in the bilateral global amygdala volume was linked to higher affective instability and might be a potential precursor of psychiatric disorders. This study demonstrates that structural amygdala measures provide a neural basis for all major dimensions of the human personality related to adaptive and maladaptive socio-affective functioning.

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

BackgroundMajor 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. Methods64- 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. ResultsTractography 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. ConclusionThe 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.