Resting-state functional connectivity of the amygdala and longitudinal changes in depression severity in adolescent depression

Neural Correlates of Irritability and Potential Moderating Effects of Inhibitory Control

Background

Irritability affects up to 20% of youth and is a primary reason for referral to pediatric mental health clinics. Irritability is thought to be associated with disruptions in processing of reward, threat, and cognitive control; however, empirical study of these associations at both the behavioral and neural level have yielded equivocal findings that may be driven by small sample sizes and differences in study design. Associations between irritability and brain connectivity between cognitive control and reward- or threat-processing circuits remain understudied. Furthermore, better inhibitory control has been linked to lower irritability and differential neural functioning among irritable youth, suggesting that good inhibitory control may serve as a protective factor.

Methods

We hypothesized that higher irritability scores would be associated with less positive (or negative) connectivity between cognitive control and threat-processing circuits and between cognitive control and reward-processing circuits in the Healthy Brain Network dataset (release 10.0; N = 4135). We also hypothesized that these associations would be moderated by inhibitory control such that weaker associations between irritability and connectivity would be detected in youths with better than with worse inhibitory control. Regression models were used to test whether associations between irritability and between-network connectivity were moderated by inhibitory control.

Results

Counter to our hypothesis, we detected higher irritability associated with reduced connectivity between threat- and reward-processing and cognitive control networks only in 5- to 9-year-old boys. Inhibitory control did not moderate associations of irritability with between-network connectivity.

Conclusions

Exploratory findings indicate that reduced between-network connectivity may underlie difficulty regulating negative emotions, leading to greater irritability.

Neuroimaging findings of adolescent depression: A review by the Research Domain Criteria (RDoC) framework

This review examines neuroimaging studies on adolescent depression (AD) within the Research Domain Criteria (RDoC) framework, focusing on fMRI, DTI, and EEG findings. The research highlights disrupted connectivity in several neural networks-such as the affective, reward processing, cognitive control, and default mode networks-that underpin emotional and cognitive dysfunctions in AD. Notably, hypoconnectivity in the affective and cognitive control networks correlates with deficits in emotional processing and executive functioning, while hyperactivity in the default mode network relates to excessive self-referential thoughts. Additionally, blunted reward responses and frontal-striatal connectivity are discussed alongside the therapeutic potential of cognitive behavioral therapy (CBT) to modulate these dysfunctional circuits. Despite these insights, variability in findings due to small sample sizes and diverse methodologies suggests a need for further research to validate neuroimaging biomarkers for treatment efficacy and to explore less studied treatments like ECT and TMS in this population. This review underscores the importance of integrating neuroimaging findings to enhance understanding and treatment of AD.

Altered resting-state functional connectivity of amygdala subregions in adults with subthreshold depression after aerobic exercise

Aerobic exercise has been proved to reduce the risk of major depression in subthreshold depression (StD) individuals effectively, yet previous studies ignored the different functions of amygdala subregions. In this study, 44 StD individuals and 34 healthy controls (HCs) underwent resting-state functional magnetic resonance imaging before and after eight weeks of aerobic exercise respectively. Transverse and longitudinal analyses were conducted based on the seed-based functional connectivity (FC) analysis between amygdala subregions and the whole brain of the two groups. The transverse analyses showed that compared to HCs, StD individuals showed abnormal FC between the right dorsal amygdala (DA) and right superior frontal gyrus, the left medial amygdala (MA) and left gyrus rectus, right caudate, as well as the right ventrolateral amygdala (VA) and right angular gyrus before the exercise intervention, while increased FC between the right DA and left supramarginal gyrus after the exercise intervention. The longitudinal analysis showed decreased FC between the left DA and left caudate, left middle frontal gyrus, while increased FC between the right MA and posterior central gyrus in StD individuals after exercise intervention. As for HCs, the DA showed FC differences with the insula, frontal lobe, parietal lobe, temporal lobe and thalamus. The MA showed FC differences with the central posterior gyrus, occipital lobe and thalamus. The VA showed FC differences with the calcarine cortex and parietal lobe. The findings demonstrated the alleviative effect of aerobic exercise on depression from the perspective of brain function.

Early environmental influences on the orbito-frontal cortex function and its effects on behavior

Early-life adversity during pre- and early post-natal phases can impact brain development and lead to maladaptive changes in executive function related behaviors. This increases the risk for a range of psychopathologies and physical diseases. Importantly, exposure to adversities during these periods is also linked to alterations in the orbito-frontal cortex (OFC) which is a key player in these executive functions. The OFC thus appears to be a central node in this association between early life stress and disease risk. Gaining a clear, and detailed understanding of the association between early life stress, OFC function, and executive function, as well as the underlying mechanisms mediating this association is relevant to inform potential therapeutic interventions. In this paper, we begin by reviewing evidence linking early life adversities to 1) alterations in behaviors regulated by the OFC and 2) changes in OFC anatomy and function. We then present insights into the underlying mechanisms for these changes, stemming from early life adversity models, and highlight important future directions for this line of research.

Loss of PV Interneurons in the BLA May Contribute to Altered Network and Behavioral States in Chronically Epileptic Mice

Psychiatric disorders, including anxiety and depression, are highly comorbid in people with epilepsy. However, the mechanisms mediating the shared pathophysiology are currently unknown. There is considerable evidence implicating the basolateral amygdala (BLA) in the network communication of anxiety and fear, a process demonstrated to involve parvalbumin-positive (PV) interneurons. The loss of PV interneurons has been well described in the hippocampus of chronically epileptic mice and in postmortem human tissue of patients with temporal lobe epilepsy (TLE). We hypothesize that a loss of PV interneurons in the BLA may contribute to comorbid mood disorders in epilepsy. To test this hypothesis, we employed a ventral intrahippocampal kainic acid model of TLE in mice, which exhibits profound behavioral deficits associated with chronic epilepsy. We demonstrate a loss of PV interneurons and dysfunction of the remaining PV interneurons in the BLA of chronically epileptic mice. Furthermore, we demonstrate altered principal neuron function and impaired coordination of BLA network and behavioral states in chronically epileptic mice. To determine whether the loss of PV interneurons contributes to these altered network and behavioral states, we partially ablated PV interneurons in the BLA by stereotaxically injecting AAV-Flex-DTA into the BLA of PV-Cre mice. Loss of PV interneurons in the BLA is sufficient to alter behavioral states, such as increasing avoidance behaviors and impairing fear learning. These data suggest that compromised inhibition in the BLA in chronically epileptic mice may contribute to behavioral deficits, suggesting a novel mechanism contributing to comorbid anxiety and epilepsy.

Boosting Psychotherapy With Noninvasive Brain Stimulation: The Whys and Wherefores of Modulating Neural Plasticity to Promote Therapeutic Change

The phenomenon of neural plasticity pertains to the intrinsic capacity of neurons to undergo structural and functional reconfiguration through learning and experiential interaction with the environment. These changes could manifest themselves not only as a consequence of various life experiences but also following therapeutic interventions, including the application of noninvasive brain stimulation (NIBS) and psychotherapy. As standalone therapies, both NIBS and psychotherapy have demonstrated their efficacy in the amelioration of psychiatric disorders' symptoms, with a certain variability in terms of effect sizes and duration. Consequently, scholars suggested the convenience of integrating the two interventions into a multimodal treatment to boost and prolong the therapeutic outcomes. Such an approach is still in its infancy, and the physiological underpinnings substantiating the effectiveness and utility of combined interventions are still to be clarified. Therefore, this opinion paper aims to provide a theoretical framework consisting of compelling arguments as to why adding NIBS to psychotherapy can promote therapeutic change. Namely, we will discuss the physiological effects of the two interventions, thus providing a rationale to explain the potential advantages of a combined approach.

Shared and unique lifetime stressor characteristics and network connectivity predict adolescent anxiety and depression

Background

Exposure to major life stressors and aberrant functional connectivity have been linked to anxiety and depression, especially during adolescence. However, whether specific characteristics of life stressors and functional network connectivity act together to differentially predict anxiety and depression symptoms remains unclear.

Methods

We utilized baseline lifetime stressor exposure and resting-state functional magnetic resonance imaging data in a longitudinal sample of 107 adolescents enriched for anxiety and depressive disorders. We examined five stressor characteristics: physical danger, interpersonal loss, humiliation, entrapment, and role change/disruption. Anxiety and depression symptoms were assessed at baseline, 6-month and 12-month follow-ups. Linear mixed-effect models tested if lifetime severity of these stressor characteristics, functional connectivity within and between frontoparietal, default, and ventral attention networks, and their interactions differentially predicted anxiety and depression symptoms at two 6-month follow-ups.

Results

Greater lifetime severity of physical danger and humiliation predicted higher anxiety symptoms. Greater lifetime entrapment severity predicted higher anxiety and depression symptoms. After including within- and between-network functional connectivity and other predictive characteristics, only the effects of lifetime entrapment severity remained significant. Lifetime entrapment severity more strongly predicted anxiety symptoms in youth with higher default network connectivity. Greater functional connectivity between frontoparietal and default networks predicted increased depression symptoms.

Conclusions

Our study is the first to use lifetime severity of distinct stressor characteristics and resting-state functional connectivity jointly to predict adolescent anxiety and depression symptoms. These results imply certain stressor characteristics and functional connectivity metrics as specific predictors of anxiety or depression and highlight entrapment as a shared predictor for anxiety and depression.

The effects of adverse life events on brain development in the ABCD study®: a propensity-weighted analysis

Longitudinal studies of the effects of adversity on human brain development are complicated by the association of stressful events with confounding variables. To counter this bias, we apply a propensity-weighted analysis of the first two years of The Adolescent Brain Cognitive DevelopmentSM (ABCD) Study® data, employing a machine learning analysis weighted by individuals' propensity to experience adversity. Data included 338 resting-state functional connections from 7190 youth (46% female), divided into a training group (80%) and an independent testing group (20%). Propensity scores were computed using 390 variables to balance across two-year adverse life event exposures. Using elastic net regularization with and without inverse propensity weighting, we developed linear models in which changes in functional connectivity of brain connections during the two-year period served as predictors of the number of adverse events experienced during that same period. Haufe's method was applied to forward-transform the backward prediction models. We also tested whether brain changes associated with adverse events correlated with concomitant changes in internalizing or externalizing behaviors or to academic achievement. In the propensity-weighted analysis, brain development significantly predicted the number of adverse events experienced during that period in both the training group (ρ = 0.14, p < 0.001) and the independent testing group (ρ = 0.10, p < 0.001). The predictor indicated a general pattern of decreased functional connectivity between large-scale networks and subcortical brain regions, particularly for cingulo-opercular and sensorimotor networks. These network-to-subcortical functional connectivity decreases inversely associated with the development of internalizing symptoms, suggesting adverse events promoted adaptive brain changes that may buffer against stress-related psychopathology. However, these same functional connections were also associated with poorer grades at the two-year follow-up. Although cortical-subcortical brain developmental responses to adversity potentially shield against stress-induced mood and anxiety disorders, they may be detrimental to other domains such as academic success.

Revisiting Resting-State Functional Connectivity of the Amygdala and Subgenual Anterior Cingulate Cortex in Adolescents and Adults With Depression

BACKGROUND

Adolescent depression is a growing public health concern, and neuroimaging offers a promising approach to its pathology. We focused on the functional connectivity of the amygdala and subgenual anterior cingulate cortex (sgACC), which is theoretically important in major depressive disorder (MDD), but empirical evidence has remained inconsistent. This discrepancy is likely due to the limited statistical power of small sample sizes.

METHODS

We rigorously examined sgACC-amygdala connectivity in adolescents and adults with depression using data from the Healthy Brain Network (n = 321; 170 female), the ABCD (Adolescent Brain Cognitive Development) Study (n = 141; 56 female), the Boston Adolescent Neuroimaging of Depression and Anxiety study (n = 108; 75 female), and the REST-meta-MDD project (n = 1436; 880 female). Linear mixed models, Bayesian factor analyses, and meta-analysis were used to assess connectivity.

RESULTS

Our analyses revealed that sgACC-amygdala connectivity in adolescents with MDD was comparable to that in healthy control individuals, whereas adults with recurrent MDD exhibited reduced connectivity. Resampling analysis demonstrated that small sample sizes (i.e., n < 30 MDD cases) tend to inflate effects, potentially leading to misinterpretations.

CONCLUSIONS

These findings clarify the state of sgACC-amygdala connectivity in MDD and underscore the importance of refining neurocognitive models separately for adolescents and adults. The study also highlights the necessity for large-scale replication studies to ensure robust and reliable findings.

The Effects of Adverse Life Events on Brain Development in the ABCD Study®: A Propensity-weighted Analysis

Longitudinal studies of the effects of adversity on human brain development are complicated by the association of stressful events with confounding variables. To counter this bias, we apply a propensity-weighted analysis of the first two years of The Adolescent Brain Cognitive DevelopmentSM (ABCD) Study® data, employing a machine learning analysis weighted by individuals' propensity to experience adversity. Data included 338 resting-state functional connections from 7190 youth (46% female), divided into a training group (80%) and an independent testing group (20%). Propensity scores were computed using 390 variables to balance across two-year adverse life event exposures. Using elastic net regularization with and without inverse propensity weighting, we developed linear models in which changes in functional connectivity of brain connections during the two-year period served as predictors of the number of adverse events experienced during that same period. Haufe's method was applied to forward-transform the backward prediction models. We also tested whether brain changes associated with adverse events correlated with concomitant changes in internalizing or externalizing behaviors or to academic achievement. In the propensity-weighted analysis, brain development significantly predicted the number of adverse events experienced during that period in both the training group (ρ=0.14, p<0.001) and the independent testing group (ρ=0.10, p<0.001). The predictor indicated a general pattern of decreased functional connectivity between large-scale networks and subcortical brain regions, particularly for cingulo-opercular and sensorimotor networks. These network-to-subcortical functional connectivity decreases inversely associated with the development of internalizing symptoms, suggesting adverse events promoted adaptive brain changes that may buffer against stress-related psychopathology. However, these same functional connections were also associated with poorer grades at the two-year follow-up. Although cortical-subcortical brain developmental responses to adversity potentially shield against stress-induced mood and anxiety disorders, they may be detrimental to other domains such as academic success.

Longitudinal development of resting-state functional connectivity in adolescents with and without internalizing disorders

Longitudinal studies using resting-state functional magnetic resonance imaging (rs-fMRI) focused on adolescent internalizing psychopathology are scarce and have mostly investigated standardized treatment effects on functional connectivity (FC) of the full amygdala. The role of amygdala subregions and large resting-state networks had yet to be elucidated, and treatment is in practice often personalized. Here, longitudinal FC development of amygdala subregions and whole-brain networks are investigated in a clinically representative sample. Treatment-naïve adolescents with clinical depression and comorbid anxiety who started care-as-usual (n = 23; INT) and healthy controls (n = 24; HC) participated in rs-fMRI scans and questionnaires at baseline (before treatment) and after three months. Changes between and within groups over time in FC of the laterobasal amygdala (LBA), centromedial amygdala (CMA) and whole-brain networks derived from independent component analysis (ICA) were investigated. Groups differed significantly in FC development of the right LBA to the postcentral gyrus and the left LBA to the frontal pole. Within INT, FC to the frontal pole and postcentral gyrus changed over time while changes in FC of the right LBA were also linked to symptom change. No significant interactions were observed when considering FC from CMA bilateral seeds or within ICA-derived networks. Results in this cohort suggest divergent longitudinal development of FC from bilateral LBA subregions in adolescents with internalizing disorders compared to healthy peers, possibly reflecting nonspecific treatment effects. Moreover, associations were found with symptom change. These results highlight the importance of differentiation of amygdala subregions in neuroimaging research in adolescents.

Identifying individual brain development using multimodality brain network

The cortical development of our brains is in a hierarchical manner and promotes the emergence of large-scale functional hierarchy. However, under interindividual heterogenicity, how the spatiotemporal features of brain networks reflect brain development and mental health remains unclear. Here we collect both resting-state electroencephalography and functional magnetic resonance imaging data from the Child Mind Institute Biobank to demonstrate that during brain growth, the global dynamic patterns of brain states become more active and the dominant networks shift from sensory to higher-level networks; the individual functional network patterns become more similar to that of adults and their spatial coupling tends to be invariable. Furthermore, the properties of multimodality brain networks are sufficiently robust to identify healthy brain age and mental disorders at specific ages. Therefore, multimodality brain networks provide new insights into the functional development of the brain and a more reliable and reasonable approach for age prediction and individual diagnosis.

Amygdala fMRI-A Critical Appraisal of the Extant Literature

Even before the advent of fMRI, the amygdala occupied a central space in the affective neurosciences. Yet this amygdala-centred view on emotion processing gained even wider acceptance after the inception of fMRI in the early 1990s, a landmark that triggered a goldrush of fMRI studies targeting the amygdala in vivo. Initially, this amygdala fMRI research was mostly confined to task-activation studies measuring the magnitude of the amygdala's response to emotional stimuli. Later, interest began to shift more towards the study of the amygdala's resting-state functional connectivity and task-based psychophysiological interactions. Later still, the test-retest reliability of amygdala fMRI came under closer scrutiny, while at the same time, amygdala-based real-time fMRI neurofeedback gained widespread popularity. Each of these major subdomains of amygdala fMRI research has left its marks on the field of affective neuroscience at large. The purpose of this review is to provide a critical assessment of this literature. By integrating the insights garnered by these research branches, we aim to answer the question: What part (if any) can amygdala fMRI still play within the current landscape of affective neuroscience? Our findings show that serious questions can be raised with regard to both the reliability and validity of amygdala fMRI. These conclusions force us to cast doubt on the continued viability of amygdala fMRI as a core pilar of the affective neurosciences.

Intracranial Directed Connectivity Links Subregions of the Prefrontal Cortex to Major Depression

Understanding the neural basis of major depressive disorder (MDD) is vital to guiding neuromodulatory treatments. The available evidence supports the hypothesis that MDD is fundamentally a disease of cortical disinhibition, where breakdowns of inhibitory neural systems lead to diminished emotion regulation and intrusive ruminations. Recent research also points towards network changes in the brain, especially within the prefrontal cortex (PFC), as primary sources of MDD etiology. However, due to limitations in spatiotemporal resolution and clinical opportunities for intracranial recordings, this hypothesis has not been directly tested. We recorded intracranial EEG from the dorsolateral (dlPFC), orbitofrontal (OFC), and anterior cingulate cortices (ACC) in neurosurgical patients with MDD. We measured daily fluctuations in self-reported depression severity alongside directed connectivity between these PFC subregions. We focused primarily on delta oscillations (1-3 Hz), which have been linked to GABAergic inhibitory control and intracortical communication. Depression symptoms worsened when connectivity within the left vs. right PFC became imbalanced. In the left hemisphere, all directed connectivity towards the ACC, from the dlPFC and OFC, was positively correlated with depression severity. In the right hemisphere, directed connectivity between the OFC and dlPFC increased with depression severity as well. This is the first evidence that delta oscillations flowing between prefrontal subregions transiently increase intensity when people are experiencing more negative mood. These findings support the overarching hypothesis that MDD worsens with prefrontal disinhibition.

Characteristics of oxyhemoglobin during the verbal fluency task in subthreshold depression: A multi-channel near-infrared spectroscopy study

OBJECTIVE

Subthreshold depression is an essential precursor and risk factor for major depressive disorder, and its accurate identification and timely intervention are important for reducing the prevalence of major depressive disorder. Therefore, we used functional near-infrared spectroscopic imaging (fNIRS) to explore the characteristics of the brain neural activity of college students with subthreshold depression in the verbal fluency task.

METHODS

A total of 72 subthreshold depressed college students (SDs) and 67 healthy college students (HCs) were recruited, and all subjects were subjected to a verbal fluency task (VFT) while a 53-channel fNIRS device was used to collect the subjects' cerebral blood oxygenation signals.

RESULTS

The results of the independent samples t-test showed that the mean oxyhemoglobin in the right dorsolateral prefrontal (ch34, ch42, ch45) and Broca's area (ch51, ch53) of SDs was lower than that of HCs. The peak oxygenated hemoglobin of SDs was lower in the right dorsolateral prefrontal (ch34) and Broca's area (ch51, ch53).The brain functional connectivity strength was lower than that of HCs. Correlation analysis showed that the left DLPFC and Broca's area were significantly negatively correlated with the depression level.

CONCLUSION

SDs showed abnormally low, inadequate levels of brain activation and weak frontotemporal brain functional connectivity. The right DLPFC has a higher sensitivity for the differentiation of depressive symptoms and is suitable as a biomarker for the presence of depressive symptoms. Dysfunction in Broca's area can be used both as a marker of depressive symptoms and as a biomarker, indicating the severity of depressive symptoms.

Abnormal intrinsic brain functional network dynamics in first-episode drug-naïve adolescent major depressive disorder

BACKGROUND

Alterations in brain functional connectivity (FC) have been frequently reported in adolescent major depressive disorder (MDD). However, there are few studies of dynamic FC analysis, which can provide information about fluctuations in neural activity related to cognition and behavior. The goal of the present study was therefore to investigate the dynamic aspects of FC in adolescent MDD patients.

METHODS

Resting-state functional magnetic resonance imaging data were acquired from 94 adolescents with MDD and 78 healthy controls. Independent component analysis, a sliding-window approach, and graph-theory methods were used to investigate the potential differences in dynamic FC properties between the adolescent MDD patients and controls.

RESULTS

Three main FC states were identified, State 1 which was predominant, and State 2 and State 3 which occurred less frequently. Adolescent MDD patients spent significantly more time in the weakly-connected and relatively highly-modularized State 1, spent significantly less time in the strongly-connected and low-modularized State 2, and had significantly higher variability of both global and local efficiency, compared to the controls. Classification of patients with adolescent MDD was most readily performed based on State 1 which exhibited disrupted intra- and inter-network FC involving multiple functional networks.

CONCLUSIONS

Our study suggests local segregation and global integration impairments and segregation-integration imbalance of functional networks in adolescent MDD patients from the perspectives of dynamic FC. These findings may provide new insights into the neurobiology of adolescent MDD.

Socioeconomic factors, sleep timing and duration, and amygdala resting-state functional connectivity in children

Introduction

Reduced sleep health has been consistently linked with increased negative emotion in children. While sleep characteristics have been associated with neural function in adults and adolescents, much less is known about these associations in children while considering socioeconomic context. In this study, we examined the associations among socioeconomic factors, sleep duration and timing, and resting-state functional connectivity (rsFC) of the amygdala in children.

Methods

Participants were typically-developing 5- to 9-year-olds from socioeconomically diverse families (61% female; N = 94). Parents reported on children's weekday and weekend bedtimes and wake-up times, which were used to compute sleep duration and midpoint. Analyses focused on amygdala-anterior cingulate cortex (ACC) connectivity followed by amygdala-whole brain connectivity.

Results

Lower family income-to-needs ratio and parental education were significantly associated with later weekday and weekend sleep timing and shorter weekday sleep duration. Shorter weekday sleep duration was associated with decreased amygdala-ACC and amygdala-insula connectivity. Later weekend sleep midpoint was associated with decreased amygdala-paracingulate cortex and amygdala-postcentral gyrus connectivity. Socioeconomic factors were indirectly associated with connectivity in these circuits via sleep duration and timing.

Discussion

These results suggest that socioeconomic disadvantage may interfere with both sleep duration and timing, in turn possibly altering amygdala connectivity in emotion processing and regulation circuits in children. Effective strategies supporting family economic conditions may have benefits for sleep health and brain development in children.

Associations between perceived parenting, brain activity and connectivity, and depression symptoms in Brazilian adolescents

In adolescence, parental care is associated with lower depression symptoms whereas parental overprotection is associated with greater depression symptoms, effects which may be mediated by adolescent brain activity and connectivity. The present study examined associations between perceived parenting, brain activity and connectivity, and depression symptoms in adolescents from Brazil, a middle-income country (MIC). Analyses included 100 adolescents who underwent functional magnetic resonance imaging scanning while completing a face matching task. Parental care and overprotection were associated with adolescent depression symptoms in expected directions. We also found that parental care and overprotection were associated with amygdala connectivity with several brain regions; however, amygdala activity was not associated with parenting and neither activity or connectivity mediated the association between parenting and depression symptoms. Results identify how parenting influences brain function and depression symptoms in youth from a MIC.

Weakened effective connectivity between salience network and default mode network during resting state in adolescent depression

Adolescent major depressive disorder (MDD) is associated with altered resting-state connectivity between the default mode network (DMN) and the salience network (SN), which are involved in self-referential processing and detecting and filtering salient stimuli, respectively. Using spectral dynamical causal modelling, we investigated the effective connectivity and input sensitivity between key nodes of these networks in 30 adolescents with MDD and 32 healthy controls while undergoing resting-state fMRI. We found that the DMN received weaker inhibition from the SN and that the medial prefrontal cortex and the anterior cingulate cortex showed reduced self-inhibition in MDD, making them more prone to external influences. Moreover, we found that selective serotonin reuptake inhibitor (SSRI) intake was associated with decreased and increased self-inhibition of the SN and DMN, respectively, in patients. Our findings suggest that adolescent MDD is characterized by a hierarchical imbalance between the DMN and the SN, which could affect the integration of emotional and self-related information. We propose that SSRIs may help restore network function by modulating excitatory/inhibitory balance in the DMN and the SN. Our study highlights the potential of prefrontal-amygdala interactions as a biomarker and a therapeutic target for adolescent depression.

Roles of the medial and lateral orbitofrontal cortex in major depression and its treatment

We describe evidence for dissociable roles of the medial and lateral orbitofrontal cortex (OFC) in major depressive disorder (MDD) from structure, functional activation, functional connectivity, metabolism, and neurochemical systems. The reward-related medial orbitofrontal cortex has lower connectivity and less reward sensitivity in MDD associated with anhedonia symptoms; and the non-reward related lateral OFC has higher functional connectivity and more sensitivity to non-reward/aversive stimuli in MDD associated with negative bias symptoms. Importantly, we propose that conventional antidepressants act to normalize the hyperactive lateral (but not medial) OFC to reduce negative bias in MDD; while other treatments are needed to operate on the medial OFC to reduce anhedonia, with emerging evidence suggesting that ketamine may act in this way. The orbitofrontal cortex is the key cortical region in emotion and reward, and the current review presents much new evidence about the different ways that the medial and lateral OFC are involved in MDD.

Protocol for teen inflammation glutamate emotion research (TIGER): Toward predictors of treatment response and clinical course in depressed adolescents

Adolescent-onset depression is a prevalent and debilitating condition commonly associated with treatment refractory depression and non-response to first-line antidepressants. There are, however, no objective tests to determine who may or may not respond to antidepressants. As depressed adolescents are especially vulnerable to the lifelong consequences of ineffectively-treated depression, it is critical to identify neurobiological predictors of treatment non-response in this population. Here, we describe the scientific rationale and protocol for the Teen Inflammation Glutamate Emotion Research (TIGER) study, a prospective 18-month investigation of 160 depressed adolescents who will be assessed before and after treatment with selective serotonin reuptake inhibitors. TIGER will be using ultra-high field imaging to test the effects of acute stress and antidepressant treatment on inflammatory and glutamatergic processes hypothesized to underlie depression maintenance. Results from this work will motivate future studies testing alternative therapeutics for depressed adolescents at risk for treatment resistant depression. ClinicalTrials.gov Identifier: NCT05329441.

Major depressive disorder associated alterations in the effective connectivity of the face processing network: a systematic review

Major depressive disorder (MDD) is marked by altered processing of emotional stimuli, including facial expressions. Recent neuroimaging research has attempted to investigate how these stimuli alter the directional interactions between brain regions in those with MDD; however, methodological heterogeneity has made identifying consistent effects difficult. To address this, we systematically examined studies investigating MDD-associated differences present in effective connectivity during the processing of emotional facial expressions. We searched five databases: PsycINFO, EMBASE, PubMed, Scopus, and Web of Science, using a preregistered protocol (registration number: CRD42021271586). Of the 510 unique studies screened, 17 met our inclusion criteria. These studies identified that compared with healthy controls, participants with MDD demonstrated (1) reduced connectivity from the dorsolateral prefrontal cortex to the amygdala during the processing of negatively valenced expressions, and (2) increased inhibitory connectivity from the ventromedial prefrontal cortex to amygdala during the processing of happy facial expressions. Most studies investigating the amygdala and anterior cingulate cortex noted differences in their connectivity; however, the precise nature of these differences was inconsistent between studies. As such, commonalities observed across neuroimaging modalities warrant careful investigation to determine the specificity of these effects to particular subregions and emotional expressions. Future research examining longitudinal connectivity changes associated with treatment response may provide important insights into mechanisms underpinning therapeutic interventions, thus enabling more targeted treatment strategies.

Neighborhood Socioeconomic Disadvantage and White Matter Microstructure of the Arcuate Fasciculus and Uncinate Fasciculus in Adolescents

Background

Neighborhood- or area-level socioeconomic disadvantage is associated with neural alterations across the life span. However, few studies have examined the effects of neighborhood disadvantage on white matter microstructure during adolescence, an important period of development that coincides with increased risk for psychopathology.

Methods

In 200 adolescents (ages 13-20 years; 54.5% female, 4% nonbinary) recruited from 2 studies enriched for early adversity and depression, we examined whether neighborhood socioeconomic disadvantage derived from census tract data was related to white matter microstructure in several major white matter tracts. We also examined whether depressive symptoms and sex moderated these associations.

Results

Greater neighborhood socioeconomic disadvantage was associated with lower fractional anisotropy (FA) in the left arcuate fasciculus (β = -0.24, false discovery rate [FDR]-corrected p = .035) and right uncinate fasciculus (β = -0.32, FDR-corrected p = .002) above and beyond the effects of family-level socioeconomic status. Depressive symptoms significantly moderated the association between left arcuate fasciculus FA and both neighborhood (β = 0.17, FDR-corrected p = .026) and unemployment (β = 0.22, FDR-corrected p = .004) disadvantage such that these associations were only significant in adolescents who reported less severe depression. Sex did not moderate the association between socioeconomic disadvantage and FA in these tracts.

Conclusions

Greater neighborhood socioeconomic disadvantage, particularly poverty and educational attainment levels, was associated with lower FA in the arcuate fasciculus and uncinate fasciculus above and beyond the effects of family-level measures of socioeconomic status. These patterns were only observed in adolescents with low levels of depression, suggesting that we must be cautious about generalizing these findings to youths who struggle with mental health difficulties.

Associations between a metal mixture and infant negative affectivity: Effect modification by prenatal cortisol and infant sex

In-utero exposures interact in complex ways that influence neurodevelopment. Animal research demonstrates that fetal sex moderates the impact of joint exposure to metals and prenatal stress measures, including cortisol, on offspring socioemotional outcomes. Further research is needed in humans. We evaluated the joint association of prenatal exposures to a metal mixture and cortisol with infant negative affectivity, considering sex differences. Analyses included 226 (29% White, Non-Hispanic) mother-infant pairs with data on exposures and negative affectivity assessed using the Infant Behavior Questionnaire-Revised in 6-month-olds. Results showed that girls whose mothers had higher cortisol had significantly higher scores of Fear and Sadness with greater exposure to the mixture. Examining higher-order interactions may better elucidate the effects of prenatal exposure to metals and cortisol on socioemotional functioning.

Loss of PV interneurons in the BLA contributes to altered network and behavioral states in chronically epileptic mice

Psychiatric disorders, including anxiety and depression, are highly comorbid in people with epilepsy. However, the mechanisms mediating the shared pathophysiology are currently unknown. There is considerable evidence implicating the basolateral amygdala (BLA) in the network communication of anxiety and fear, a process demonstrated to involve parvalbumin-positive (PV) interneurons. The loss of PV interneurons has been well described in the hippocampus of chronically epileptic mice and in postmortem human tissue of patients with temporal lobe epilepsy (TLE). We hypothesize that a loss of PV interneurons in the BLA may contribute to comorbid mood disorders in epilepsy. To test this hypothesis, we employed a ventral intrahippocampal kainic acid (vIHKA) model of chronic epilepsy in mice, which exhibits profound behavioral deficits associated with chronic epilepsy. We demonstrate a loss of PV interneurons and dysfunction of remaining PV interneurons in the BLA of chronically epileptic mice. Further, we demonstrate altered principal neuron function and impaired coordination of BLA network and behavioral states in chronically epileptic mice. To determine whether these altered network and behavioral states were due to the loss of PV interneurons, we ablated a similar percentage of PV interneurons observed in chronically epileptic mice by stereotaxically injecting AAV-Flex-DTA into the BLA of PV-Cre mice. Loss of PV interneurons in the BLA is sufficient to alter behavioral states, inducing deficits in fear learning and recall of fear memories. These data suggest that compromised inhibition in the BLA in chronically epileptic mice contributes to behavioral deficits, suggesting a novel mechanism contributing to comorbid anxiety and epilepsy.

Significance Statement

Psychiatric illnesses and epilepsy are highly comorbid and negatively impact the quality of life of people with epilepsy. The pathophysiological mechanisms mediating the bidirectional relationship between mood disorders and epilepsy remain unknown and, therefore, treatment options remain inadequate. Here we demonstrate a novel mechanism, involving the loss of PV interneurons in the BLA, leading to a corruption of network and behavioral states in mice. These findings pinpoint a critical node and demonstrate a novel cellular and circuit mechanism involved in the comorbidity of psychiatric illnesses and epilepsy.

Dynamic network characteristics of adolescents with major depressive disorder: Attention network mediates the association between anhedonia and attentional deficit

Attention deficit is a critical symptom that impairs social functioning in adolescents with major depressive disorder (MDD). In this study, we aimed to explore the dynamic neural network activity associated with attention deficits and its relationship with clinical outcomes in adolescents with MDD. We included 188 adolescents with MDD and 94 healthy controls. By combining psychophysics, resting-state electroencephalography (EEG), and functional magnetic resonance imaging (fMRI) techniques, we aimed to identify dynamic network features through the investigation of EEG microstate characteristics and related temporal network features in adolescents with MDD. At baseline, microstate analysis revealed that the occurrence of Microstate C in the patient group was lower than that in healthy controls, whereas the duration and coverage of Microstate D increased in the MDD group. Mediation analysis revealed that the probability of transition from Microstate C to D mediated anhedonia and attention deficits in the MDD group. fMRI results showed that the temporal variability of the dorsal attention network (DAN) was significantly weaker in patients with MDD than in healthy controls. Importantly, the temporal variability of DAN mediated the relationship between anhedonia and attention deficits in the patient group. After acute-stage treatment, the response prediction group (RP) showed improvement in Microstates C and D compared to the nonresponse prediction group (NRP). For resting-state fMRI data, the temporal variability of DAN was significantly higher in the RP group than in the NRP group. Overall, this study enriches our understanding of the neural mechanisms underlying attention deficits in patients with MDD and provides novel clinical biomarkers.

Systematic Review: White Matter Microstructural Organization in Adolescents With Depression

Objective

A growing body of literature has focused on the neural mechanisms of depression. Our goal was to conduct a systematic review on the white matter microstructural differences in adolescents with depressive disorders vs adolescents without depressive disorders.

Method

We searched PubMed and PsycINFO for publications on August 3, 2022 (original search conducted in July 2021). The review was registered on PROSPERO (registration number: CRD42021268200), and the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines were followed. Eligible studies were original research papers comparing diffusion tensor/spectrum imaging findings in adolescents with vs without depression (originally ages 12-19 years, later expanded to 11-21 years). Studies were excluded if they focused on depression exclusively in the context of another condition, used only dimensional depressive symptom assessment(s), or used the same dataset as another included publication.

Results

The search yielded 575 unique records, of which 14 full-text papers were included (824 adolescents with depression and 686 without depression). The following white matter regions showed significant differences in fractional anisotropy in at least 3 studies: uncinate fasciculus, cingulum, anterior corona radiata, inferior fronto-occipital fasciculus, and corpus callosum (genu and body). Most studies reported decreased, rather than increased, fractional anisotropy in adolescents with depression. Limitations include the possibility for selective reporting bias and risk of imprecision, given the small sample sizes in some studies.

Conclusion

Our systematic review suggests aberrant white matter microstructure in limbic-cortical-striatal-thalamic circuits, and the corpus callosum, in adolescents with depression. Future research should focus on developmental trajectories in depression, identifying sources of heterogeneity and integrating findings across imaging modalities.

Reactivity of the ventromedial prefrontal cortex, but not the amygdala, to negative emotion faces predicts greed personality trait

This study explored whether amygdala reactivity predicted the greed personality trait (GPT) using both task-based and resting-state functional connectivity analyses (ntotal = 452). In Cohort 1 (n = 83), task-based functional magnetic resonance imaging (t-fMRI) results from a region-of-interest (ROI) analysis revealed no direct correlation between amygdala reactivity to fearful and angry faces and GPT. Instead, whole-brain analyses revealed GPT to robustly negatively vary with activations in the right ventromedial prefrontal cortex (vmPFC), supramarginal gyrus, and angular gyrus in the contrast of fearful + angry faces > shapes. Moreover, task-based psychophysiological interaction (PPI) analyses showed that the high GPT group showed weaker functional connectivity of the vmPFC seed with a top-down control network and visual pathways when processing fearful or angry faces compared to their lower GPT counterparts. In Cohort 2, resting-state functional connectivity (rs-FC) analyses indicated stronger connectivity between the vmPFC seed and the top-down control network and visual pathways in individuals with higher GPT. Comparing the two cohorts, bilateral amygdala seeds showed weaker associations with the top-down control network in the high group via PPI analyses in Cohort 1. Yet, they exhibited distinct rs-FC patterns in Cohort 2 (e.g., positive associations of GPT with the left amygdala-top-down network FC but negative associations with the right amygdala-visual pathway FC). The study underscores the role of the vmPFC and its functional connectivity in understanding GPT, rather than amygdala reactivity.

Exploring the association between early exposure to material hardship and psychopathology through indirect effects of fronto-limbic functional connectivity during fear learning

Experiencing family material hardship has been shown to be associated with disruptions in physical and psychological development. However, the association between material hardship and functional connectivity in the fronto-limbic circuit during fear learning is unclear. A total of 161 healthy young adults aged 17-28 were recruited in our brain imaging study, using the Fear Conditioning Task to test the associations between material hardship and connectivity in fronto-limbic circuit and psychopathology. The results showed that family material hardship was linked to higher positive connectivity between the left amygdala and bilateral dorsal anterior cingulate cortex, as well as higher negative connectivity between the left hippocampus and right ventromedial prefrontal cortex. A mediation analysis showed that material hardship was associated with depression via amygdala functional connectivity (indirect effect = 0.228, P = 0.016), and also indirectly associated with aggression and anger-hostility symptoms through hippocampal connections (aggression: indirect effect = 0.057, P = 0.001; anger-hostility: indirect effect = 0.169, P = 0.048). That is, family material hardship appears to affect fronto-limbic circuits through changes in specific connectivity, and these specific changes, in turn, could lead to specific psychological symptoms. The findings have implications for designing developmentally sensitive interventions to mitigate the emergence of psychopathological symptoms.

Functional dysconnectivity in youth depression: Systematic review, meta-analysis, and network-based integration

Youth depression has been associated with heterogenous patterns of aberrant brain connectivity. To make sense of these divergent findings, we conducted a systematic review encompassing 19 resting-state fMRI seed-to-whole-brain studies (1400 participants, comprising 795 youths with major depression and 605 matched healthy controls). We incorporated separate meta-analyses of connectivity abnormalities across the levels of the most commonly seeded brain networks (default-mode and limbic networks) and, based on recent additions to the literature, an updated meta-analysis of amygdala dysconnectivity in youth depression. Our findings indicated broad and distributed findings at an anatomical level, which could not be captured by conventional meta-analyses in terms of spatial convergence. However, we were able to parse the complexity of region-to-region dysconnectivity by considering constituent regions as components of distributed canonical brain networks. This integration revealed dysconnectivity centred on central executive, default mode, salience, and limbic networks, converging with findings from the adult depression literature and suggesting similar neurobiological underpinnings of youth and adult depression.

Perceived parental depression, intrusive rumination, and internalizing problems: A three-wave longitudinal study in adolescents

Research suggests that perceiving parental depression elicits internalizing problems in adolescents, but certain studies have indicated that adolescents' internalizing problems also increase their perception of parental emotion. To further investigate the inconsistent findings about the nature of this relationship, the current study used longitudinal data to examine the causal association between adolescents' internalizing problems and the parental depression they perceived, as well as the role of intrusive rumination in the relationship. Method: In this longitudinal study, 392 adolescents who experienced the catastrophic Jiuzhaigou earthquake in 2017 were surveyed at three time points after the earthquake: 12 months (T1), 21 months (T2) and 27 months (T3). A cross-lagged panel model was used to carry out the data analysis. Results: Mutual cause-and-effect relationships were found between intrusive rumination and both perceived parental depression and internalizing problems, respectively; a unilateral causal relationship in which internalizing problems positively predicted perceived parental depression was also found. In addition, internalizing problems predicted perceived parental depression via the mediating role of intrusive rumination; similarly, intrusive rumination predicted perceived parental depression via internalizing problems. Conclusions: Internalizing problems were a risk factor for perceived parental depression, and intrusive rumination played an important role in the relationship between internalizing problems and perceived parental depression.

Subcortical volume analysis in non-suicidal self-injury adolescents: A pilot study

Given the high prevalence of non-suicidal self-injury (NSSI) among teenagers worldwide, the underlying mechanisms promoting such behavior must be urgently investigated. This study aimed to investigate neurobiological changes in the regional brain in adolescents with NSSI by comparing the volumes of the subcortical structures of 23 female adolescents with NSSI and 23 healthy controls with no history of psychiatric diagnosis or treatment. The NSSI group comprised those who underwent inpatient treatment for non-suicidal self-harm behavior at the Department of Psychiatry at Daegu Catholic University Hospital from July 1, 2018, to December 31, 2018. The control group comprised healthy adolescents from the community. We compared differences in the volume of the bilateral thalamus, caudate, putamen, hippocampus, and amygdala. All statistical analyses were conducted using SPSS Statistics Version 25. The NSSI group exhibited decreased subcortical volume in the left amygdala and marginally decreased subcortical volume in the left thalamus. Our results provide important clues about adolescent NSSI's underlying biology. Analysis of subcortical volumes between the NSSI and normal groups revealed subcortical volume differences in the left amygdala and thalamus, part of the core cerebral regions responsible for emotional processing and regulation, which may help explain the neurobiological mechanism of NSSI.

Major gender differences in relations between life stressor frequency and gray matter in adolescence and emerging adulthood

Adolescence and emerging adulthood is likely a sensitive period for the neural effects of stress due to increasing life stress, onset of stress-related disorders, and continued gray matter (GM) development. In adults, stress is associated with GM differences in the medial prefrontal cortex (mPFC), hippocampus, and amygdala, but little is known about these relations, and whether they differ by gender, during adolescence and emerging adulthood. Further, it is unknown whether dependent (self-generated) and independent (fateful) stressors have distinct associations with GM, as each have distinct relations with internalizing psychopathology. We tested relations between recent dependent and independent stressor frequency (ALEQ-R) and GM structure using MRI in a priori regions of interest (mPFC, amygdala, and hippocampus) and across the cortex in youth from the Denver/Boulder metro area ages 14-22 (N = 144). Across both genders, no effects passed multiple comparison correction (FDR q > .05). However, there were significant differences between male and female youth (FDR q < .05), with opposite relations between dependent stressor frequency and cortical GM thickness in the salience network and emotion regulation regions and with surface area in default mode network regions. These results motivate future investigations of gender differences in neural mechanisms of stress generation and reactivity. (PsycInfo Database Record (c) 2023 APA, all rights reserved).

Frontolimbic Network Topology Associated With Risk and Presence of Depression in Adolescents: A Study Using a Composite Risk Score in Brazil

BACKGROUND

There have been significant challenges in understanding functional brain connectivity associated with adolescent depression, including the need for a more comprehensive approach to defining risk, the lack of representation of participants from low- and middle-income countries, and the need for network-based approaches to model connectivity. The current study aimed to address these challenges by examining resting-state functional connectivity of frontolimbic circuitry associated with the risk and presence of depression in adolescents in Brazil.

METHODS

Adolescents in Brazil ages 14 to 16 years were classified into low-risk, high-risk, and depressed groups using a clinical assessment and composite risk score that integrates 11 sociodemographic risk variables. After excluding participants with excessive head movement, resting-state functional magnetic resonance imaging data of 126 adolescents were analyzed. We compared group differences in frontolimbic network connectivity using region of interest-to-region of interest, graph theory, and seed-based connectivity analyses. Associations between self-reported depressive symptoms and brain connectivity were also explored.

RESULTS

Adolescents with depression showed greater dorsal anterior cingulate cortex (ACC) connectivity with the orbitofrontal cortex compared with the 2 risk groups and greater dorsal ACC global efficiency than the low-risk group. Adolescents with depression also showed reduced local efficiency and a lower clustering coefficient of the subgenual ACC compared with the 2 risk groups. The high-risk group also showed a lower subgenual ACC clustering coefficient relative to the low-risk group.

CONCLUSIONS

These findings highlight altered connectivity and topology of the ACC within frontolimbic circuitry as potential neural correlates and risk factors of developing depression in adolescents in Brazil. This study broadens our understanding of the neural connectivity associated with adolescent depression in a global context.

EEG coherences of the fronto-limbic circuit between patients with major depressive disorder and healthy controls

BACKGROUND

Imaging studies found that patients with major depressive disorder (MDD) showed abnormal functional connectivity in the fronto-limbic circuit, including the prefrontal cortex (PFC), anterior cingulate cortex (ACC), and limbic system (amygdala). This study used electroencephalography (EEG) coherence as an indicator of functional connectivity in the fronto-limbic circuit and examined the group differences between the MDD group and healthy controls (HC group), and the associations between EEG coherence and depressive symptoms.

METHODS

125 and 132 participants in the MDD and HC groups have measured the symptoms of depression and anxiety, and delta, theta, alpha, and beta1-beta4 EEG coherences in the fronto-limbic circuit and examined the differences between the two groups, and the associations between the EEG coherence and depressive symptoms were examined.

RESULTS

Lower theta, alpha, beta1, beta3, and beta4 coherence in the fronto-limbic circuit and higher beta2 coherence between the PFC and limbic system in the MDD group than in the HC group. Negative correlations between delta, theta, beta1, beta3, and beta4 coherence and total depression, cognitive depression, and somatic depression; positive correlations between beta2 coherences in the PFC and limbic system, and total depression and cognitive depression scores in the MDD group.

LIMITATIONS

Whether low EEG coherence in the fronto-limbic circuit is applicable to other subtypes of MDD requires further study.

CONCLUSIONS

Low EEG coherences in the fronto-limbic circuit were related to depressive symptoms, and increased functional connectivity in the fronto-limbic circuit can be applied by neurofeedback in future studies.

A Microbial-Based Approach to Mental Health: The Potential of Probiotics in the Treatment of Depression

Probiotics are currently the subject of intensive research pursuits and also represent a multi-billion-dollar global industry given their vast potential to improve human health. In addition, mental health represents a key domain of healthcare, which currently has limited, adverse-effect prone treatment options, and probiotics may hold the potential to be a novel, customizable treatment for depression. Clinical depression is a common, potentially debilitating condition that may be amenable to a precision psychiatry-based approach utilizing probiotics. Although our understanding has not yet reached a sufficient level, this could be a therapeutic approach that can be tailored for specific individuals with their own unique set of characteristics and health issues. Scientifically, the use of probiotics as a treatment for depression has a valid basis rooted in the microbiota-gut-brain axis (MGBA) mechanisms, which play a role in the pathophysiology of depression. In theory, probiotics appear to be ideal as adjunct therapeutics for major depressive disorder (MDD) and as stand-alone therapeutics for mild MDD and may potentially revolutionize the treatment of depressive disorders. Although there is a wide range of probiotics and an almost limitless range of therapeutic combinations, this review aims to narrow the focus to the most widely commercialized and studied strains, namely Lactobacillus and Bifidobacterium, and to bring together the arguments for their usage in patients with major depressive disorder (MDD). Clinicians, scientists, and industrialists are critical stakeholders in exploring this groundbreaking concept.

Effects of a probiotic add-on treatment on fronto-limbic brain structure, function, and perfusion in depression: Secondary neuroimaging findings of a randomized controlled trial

BACKGROUND

Probiotics are suggested to improve depressive symptoms via the microbiota-gut-brain axis. We have recently shown a beneficial clinical effect of probiotic supplementation in patients with depression. Their underlying neural mechanisms remain unknown.

METHODS

A multimodal neuroimaging approach including diffusion tensor imaging, resting-state functional MRI, and arterial spin labeling was used to investigate the effects of a four-weeks probiotic supplementation on fronto-limbic brain structure, function, and perfusion and whether these effects were related to symptom changes.

RESULTS

Thirty-two patients completed both imaging assessments (18 placebo and 14 probiotics group). Probiotics maintained mean diffusivity in the left uncinate fasciculus, stabilized it in the right uncinate fasciculus, and altered resting-state functional connectivity (rsFC) between limbic structures and the temporal pole to a cluster in the precuneus. Moreover, a cluster in the left superior parietal lobule showed altered rsFC to the subcallosal cortex, the left orbitofrontal cortex, and limbic structures after probiotics. In the probiotics group, structural and functional changes were partly related to decreases in depressive symptoms.

LIMITATIONS

This study has a rather small sample size. An additional follow-up MRI session would be interesting for seeing clearer changes in the relevant brain regions as clinical effects were strongest in the follow-up.

CONCLUSION

Probiotic supplementation is suggested to prevent neuronal degeneration along the uncinate fasciculus and alter fronto-limbic rsFC, effects that are partly related to the improvement of depressive symptoms. Elucidating the neural mechanisms underlying probiotics' clinical effects on depression provide potential targets for the development of more precise probiotic treatments.

Altered structural covariance network of nucleus accumbens is modulated by illness duration and severity of symptom in depression

The differential structural covariance of nucleus accumbens (NAcc), playing a vital role in etiology and treatment, remains unclear in depression. We aimed to investigate whether structural covariance of NAcc was altered and how it was modulated by illness duration and severity of symptom measured with Hamilton Depression scale (HAMD). T1-weighted anatomical images of never-treated first-episode patients with depression (n = 195) and matched healthy controls (HCs, n = 78) were acquired. Gray matter volumes were calculated using voxel-based morphometry analysis for each subject. Then, we explored abnormal structural covariance of NAcc and how the abnormality was modulated by illness duration and severity of symptom. Patients with depression exhibited altered structural covariance of NAcc connected to key brain regions in reward system including the medial orbitofrontal cortex, amygdala, insula, parahippocampa gyrus, precuneus, thalamus, hippocampus and cerebellum. In addition, the structural covariance of the NAcc was distinctly modulated by illness duration and the severity of symptom in patients with depression. What is more, the structural covariance of the NAcc connected to hippocampus was modulated by these two factors at the same time. These results elucidate altered structural covariance of the NAcc and its distinct modulation of illness duration and severity of symptom.

Functional connectivity of the amygdala and the antidepressant and antisuicidal effects of repeated ketamine infusions in major depressive disorder

Background

Dysfunction of the amygdala is the core pathogenesis of major depressive disorder (MDD). However, it remains unclear whether ketamine treatment could modulate characteristics of amygdala-related networks. We aimed to explore the relationship between changes in the resting-state functional connectivity (RSFC) of the amygdala and the treatment of ketamine in MDD patients and to identify important neuroimaging predictors of treatment outcome.

Methods

Thirty-nine MDD patients received six subanesthetic dose infusions of ketamine. Depressive and suicidal symptoms were assessed and magnetic resonance imaging (MRI) scans were performed before and after six ketamine infusions. Forty-five healthy controls also underwent once MRI scans. Seed-based RSFC analyses were performed, focusing on the bilateral amygdala.

Results

After ketamine treatment, the RSFC between the left amygdala (LA) and the left medial superior frontal gyrus (mSFG) of MDD patients enhanced significantly, and this change was positively correlated with the reduction in depressive symptoms (r = 0.40, p = 0.012). The combination baseline RSFC of LA - right putamen and right amygdala (RA) - right putamen was related to the antidepressant and antisuicidal effects of ketamine. The combination baseline RSFC of LA - right putamen and RA - right putamen could predict the ineffective antidepressant (AUC = 0.739, p = 0.011) and antisuicidal effects of ketamine (AUC = 0.827, p = 0.001).

Conclusion

Ketamine can regulate the relevant circuits of amygdala and mSFG, and the baseline RSFC between bilateral amygdala and right putamen may be a predictor of the response of ketamine's antidepressant and antisuicidal treatment.

Clinical trial registration

https://www.chictr.org.cn/showproj.aspx?proj=20875, identifier ChiCTR-OOC-17012239.

The gut microbiota, HPA axis, and brain in adolescent-onset depression: Probiotics as a novel treatment

Stress-associated disruptions in the development of frontolimbic regions may play a critical role in the emergence of adolescent-onset depression. These regions are particularly sensitive to Hypothalamic-Pituitary-Adrenal (HPA) axis signaling. The HPA axis is hyperactive in adolescent depression, and interventions that attenuate such hyperactivity hold promise as potential treatments. The Microbiome-Gut-Brain (MGB) axis is an important pathway through which stress dysregulates HPA-axis activity and thus exerts deleterious effects on the adolescent brain. Probiotic agents, which alter the gut microbiota composition by introducing bacterial strains with beneficial physiological effects, normalize aberrant HPA-axis activity and reduce depressive symptoms in both animal studies and adult clinical trials. While the potential utility of such agents in treating or preventing adolescent depression remains largely unexplored, recent data suggest the existence of an adolescent sensitive window during which probiotics may be especially efficacious in reducing depressive symptoms compared to effects observed in adult populations. In this review, we outline evidence that probiotic use may attenuate stress effects on frontolimbic development, providing a novel means of improving depressive symptoms among adolescent populations.

Cross-lagged Relationships Between Depressive Symptoms and Altered Default Mode Network Connectivity Over the Course of Adolescence

BACKGROUND

Although the peak onset of depressive symptoms occurs during adolescence, very few studies have directly examined depression-related changes in resting-state (RS) default mode network activity during adolescence, controlling for potential neural markers of risk.

METHODS

This study used data from a longitudinal adolescent cohort to investigate age-specific, persistent (i.e., lagged), and dynamic associations between RS functional connectivity within the default mode network and depressive symptoms during adolescence using a random intercept cross-lagged panel framework. The Neuroventure sample consisted of 151 adolescents ages 12-14 at study entry without any neurological illness who were assessed three times during a 5-year follow-up with 97% follow-up across the three assessments. Depressive symptoms were measured using the depression subscale of the Brief Symptoms Inventory. RS functional magnetic resonance imaging data were collected using a 3T Siemens Magnetom Trio scanner in a single 6-minute sequence.

RESULTS

After controlling for relationships between random intercepts, future depression risk was predicted by RS couplings in the perigenual anterior cingulate cortex and anterior dorsomedial prefrontal cortex (β = -0.69, p = .014) and in the left inferior parietal lobule and anterior superior frontal gyrus (β = -0.43, p = .035). Increases in depressive symptoms at previous time points significantly predicted changes in functional connectivity between the posterior cingulate cortex and the precuneus and posterior middle temporal gyrus (β = 0.37, p = .039) and between the dorsal precuneus and posterior middle temporal gyrus (β = 0.47, p = .036).

CONCLUSIONS

This study was able to disassociate the RS brain markers of depression from those that appear to follow early-onset depression.

Exploring the course of adolescent anxiety and depression: associations with white matter tract microstructure

Cross-sectional Diffusion Tensor Imaging (DTI) studies have reported alterations in white matter (WM) microstructure in adolescents with internalizing psychopathology. Yet, longitudinal studies investigating the course of WM microstructure are lacking. This study explored WM alterations and its relation to clinical symptoms over time in adolescents with internalizing disorders. DTI scans were acquired at baseline and after three months in 22 adolescents with clinical depression and comorbid anxiety (INT), and 21 healthy peers (HC) (age: 12-18). Tract-based spatial statistics was used for three voxelwise analyses: i) changes in WM microstructure between and within the INT and HC group; ii) associations between changes in symptom severity and changes in WM microstructure within youths with INT; and iii) associations between baseline WM parameters with changes in symptom severity within youths with INT. Data did not reveal changes in WM microstructure between or within groups over three months' time nor associations between changes in WM microstructure and changes in self-reported symptoms (analyses corrected for age, gender and puberty stage). Lower baseline levels of fractional anisotropy (FA) in the right posterior corona radiata (PCR) and right cingulum were associated with a higher decrease of depressive symptoms within the INT group. Post hoc analysis of additional WM parameters in the significant FA clusters showed that higher levels of baseline mean diffusivity and radial diffusivity in the PCR were associated with a lower decrease in depressive symptoms. Baseline WM microstructure characteristics were associated with a higher decrease in depressive symptoms over time. These findings increase our understanding of neurobiological mechanisms underlying the course of internalizing disorders in adolescents.

Prediction of the trajectories of depressive symptoms among children in the adolescent brain cognitive development (ABCD) study using machine learning approach

BACKGROUND

Depression often first emerges during adolescence and evidence shows that the long-term patterns of depressive symptoms over time are heterogeneous. It is meaningful to predict the trajectory of depressive symptoms in adolescents to find early intervention targets.

METHODS

Based on the Adolescent Brain Cognitive Development Study, we included 4962 participants aged 9-10 who were followed-up for 2 years. Trajectories of depressive symptoms were identified by Latent Class Growth Analyses (LCGA). Four types of machine learning models were built to predict the identified trajectories and to obtain variables with predictive value based on the best performance model.

RESULTS

Of all participants, 536 (10.80%) were classified as increasing, 269 (5.42%) as persistently high, 433 (8.73%) as decreasing, and 3724 (75.05%) as persistently low by LCGA. Gradient Boosting Machine (GBM) model got the highest discriminant performance. Sleep quality, parental emotional state and family financial adversities were the most important predictors and three resting state functional magnetic resonance imaging functional connectivity data were also helpful to distinguish trajectories.

LIMITATION

We only have depressive symptom scores at three time points. Some valuable predictors are not specific to depression. External validation is an important next step. These predictors should not be interpreted as etiology and some variables were reported by parents/caregivers.

CONCLUSION

Using GBM combined with baseline characteristics, the trajectories of depressive symptoms with two years among adolescents aged 9-10 years can be well predicted, which might further facilitate the identification of adolescents at high risk of depressive symptoms and development of effective early interventions.

Adolescent depression and resting-state fMRI brain networks: a scoping review of longitudinal studies

The neurobiological factors associated with the emergence of major depressive disorder (MDD) in adolescence are still unclear. Previous cross-sectional studies have documented aberrant connectivity in resting-state functional magnetic resonance imaging (rs-fMRI) networks. However, whether these findings precede MDD onset has not been established. This scoping review mapped key methodological aspects and main findings of longitudinal rs-fMRI studies of MDD in adolescence. Three sets of neuroimaging methods to analyze rs-fMRI data were identified: seed-based analysis, independent component analysis, and network-based approaches. Main findings involved aberrant connectivity within and between the default mode network (DMN), the cognitive control network (CCN), and the salience network (SN). Accordingly, we utilized Menon's (2011) triple-network model for neuropsychiatric disorders to summarize key results. Adolescent MDD was associated with hyperconnectivity within the SN and between DMN and SN, as well as hypoconectivity within the CCN. These findings suggested that dysfunctional connectivity among the three main large-scale brain networks preceded MDD onset. However, there was high heterogeneity in neuroimaging methods and sampling procedures, which may limit comparisons between studies. Future studies should consider some level of harmonization for clinical instruments and neuroimaging methods.

A Double-Blind Randomized Trial to Investigate Mechanisms of Antidepressant-Related Dysfunctional Arousal in Depressed or Anxious Youth at Familial Risk for Bipolar Disorder

Antidepressants are standardly used to treat moderate to severe symptoms of depression and/or anxiety in youth but may also be associated with rare but serious psychiatric adverse events such as irritability, agitation, aggression, or suicidal ideation. Adverse events are especially common in youth with a family history of bipolar disorder (BD) who are at heightened risk for dysfunction in neurobiological systems that regulate emotion and arousal. To further understand this phenomenon, this study will examine (a) baseline risk factors associated with dysfunctional arousal in a sample of youth at high-risk for BD treated with or without an antidepressant, (b) whether antidepressant-related changes in arousal are mediated by changes in prefrontal-limbic circuitry, and (c) whether pharmacogenetic factors influence antidepressant-related changes in arousal. High-risk youth (aged 12-17 years with moderate to severe depressive and/or anxiety symptoms and at least one first-degree relative with bipolar I disorder) will be randomized to receive psychotherapy plus escitalopram or psychotherapy plus placebo. Neuroimaging and behavioral measures of arousal will be collected prior to randomization and at 4 weeks. Samples for pharmacogenetic analysis (serum escitalopram concentration, CYP2C19 metabolizer phenotype, and HTR2A and SLC6A4 genotypes) will be collected at 8 weeks. Youth will be followed for up to 16 weeks to assess change in arousal measures.

Fish oil supplementation alters emotion-generated corticolimbic functional connectivity in depressed adolescents at high-risk for bipolar I disorder: A 12-week placebo-controlled fMRI trial

OBJECTIVE

To evaluate the effects of fish oil (FO), a source of the omega-3 polyunsaturated fatty acids (n-3 PUFA), eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), on emotion-generated corticolimbic functional connectivity in depressed youth at high risk for developing bipolar I disorder.

METHODS

Thirty-nine antidepressant-free youth with a current depressive disorder diagnosis and a biological parent with bipolar I disorder were randomized to 12-week double-blind treatment with FO or placebo. At baseline and endpoint, fMRI (4 Tesla) scans were obtained while performing a continuous performance task with emotional and neutral distractors (CPT-END). Seed-to-voxel functional connectivity analyses were performed using bilateral orbitofrontal cortex (OFC) and amygdala (AMY) seeds. Measures of depression, mania, global symptom severity, and erythrocyte fatty acids were obtained.

RESULTS

Erythrocyte EPA+DHA composition increased significantly in the FO group (+47%, p ≤ 0.0001) but not in the placebo group (-10%, p = 0.11). Significant group by time interactions were found for functional connectivity between the left OFC and the left superior temporal gyrus (STG) and between the right AMY and right inferior temporal gyrus (ITG). OFC-STG connectivity increased in the FO group (p = 0.0001) and decreased in the placebo group (p = 0.0019), and AMY-ITG connectivity decreased in the FO group (p = 0.0014) and increased in the placebo group (p < 0.0001). In the FO group, but not placebo group, the decrease in AMY-ITG functional connectivity correlated with decreases in Childhood Depression Rating Scale-Revised and Clinical Global Impression-Severity Scale scores.

CONCLUSIONS

In depressed high-risk youth FO supplementation alters emotion-generated corticolimbic functional connectivity which correlates with changes in symptom severity ratings.

Cortical activation and functional connectivity during the verbal fluency task for adolescent-onset depression: A multi-channel NIRS study

OBJECTIVE

Depression disorder is accompanied by cognitive impairments. However, there is limited research focused on cognitive impairments and their neurological mechanism in adolescents with depression. The purpose of the current study is to illustrate the differences in brain activity patterns between depressed adolescents and healthy controls (HCs).

METHOD

A total of 72 adolescents with depression, as well as 74 HCs, were recruited. We utilized functional near-infrared spectroscopy (fNIRS) to monitor the concentrations of oxyhemoglobin (Oxy-Hb) in the brains of participants while they performed the verbal fluency task (VFT) to examine cognitive impairment in adolescents with depression.

RESULTS

Our study demonstrated that adolescents with depression had significantly less cortical activation in the hemodynamic responses of Oxy-Hb at channels mainly located in the prefrontal cortex (PFC) than HCs during the 60-s task period (false discovery rate (FDR)-corrected p < 0.05). The mean channel-to-channel connectivity was 0.400 for HCs (SD = 0.149) and 0.303 (SD = 0.138) for adolescents with depression, and the HC group had a higher mean channel-to-channel connectivity strength than the depression group (t = -15.586, p < 0.001). For the patient group, we found significant negative correlations between HAMD scores and mean Oxy-Hb changes in Channel 38 (r = -0.33, p < 0.01), Channel 39 (r = -0.34, p < 0.01), Channel 41 (r = -0.25, p < 0.05), Channel 42 (r = -0.28, p < 0.05), and Channel 44 (r = -0.27, p < 0.05), and these channels were mainly located in areas with little difference between groups.

CONCLUSIONS

Our study provides neurological evidence about the executive function (EF) in depressed adolescents. Adolescents with depression exhibited an abnormal activation pattern and decreased task-related functional connectivity compared to HCs. The changed Oxy-Hb concentration of PFC during VFT was not sensitive to depression symptoms.

Individual differences in amygdala volumes predict changes in functional connectivity between subcortical and cognitive control networks throughout adolescence

Adolescence is a critical period of structural and functional neural maturation among regions serving the cognitive control of emotion. Evidence suggests that this process is guided by developmental changes in amygdala and striatum structure and shifts in functional connectivity between subcortical (SC) and cognitive control (CC) networks. Herein, we investigate the extent to which such developmental shifts in structure and function reciprocally predict one another over time. 179 youth (9-15 years-old) completed annual MRI scans for three years. Amygdala and striatum volumes and connectivity within and between SC and CC resting state networks were measured for each year. We tested for reciprocal predictability of within-person and between-person changes in structure and function using random-intercept cross-lagged panel models. Within-person shifts in amygdala volumes in a given year significantly and specifically predicted deviations in SC-CC connectivity in the following year, such that an increase in volume was associated with decreased SC-CC connectivity the following year. Deviations in connectivity did not predict changes in amygdala volumes over time. Conversely, broader group-level shifts in SC-CC connectivity were predictive of subsequent deviations in striatal volumes. We did not see any cross-predictability among amygdala or striatum volumes and within-network connectivity measures. Within-person shifts in amygdala structure year-to-year robustly predicted weaker SC-CC connectivity in subsequent years, whereas broader increases in SC-CC connectivity predicted smaller striatal volumes over time. These specific structure function relationships may contribute to the development of emotional control across adolescence.

Depression in multiple system atrophy: Views on pathological, clinical and imaging aspects

Multiple system atrophy (MSA) is a common atypical parkinsonism, characterized by a varying combination of autonomic, cerebellar, and pyramidal systems. It has been noticed that the patients with MSA can be accompanied by some neuropsychiatric disorders, in particular depression. However, there is limited understanding of MSA-related depression. To bridge existing gaps, we summarized research progress on this topic and provided a new perspective regarding pathological, clinical, and imaging aspects. Firstly, we synthesized corresponding studies in order to investigate the relationship between depression and MSA from a pathological perspective. And then, from a clinical perspective, we focused on the prevalence of depression in MS patients and the comparison with other populations. Furthermore, the associations between depression and some clinical characteristics, such as life quality and gender, have been reported. The available neuroimaging studies were too sparse to draw conclusions about the radiological aspect of depression in MSA patients but we still described them in the presence of paper. Finally, we discussed some limitations and shortcomings existing in the included studies, which call for more high-quality basic research and clinical research in this field.