Insular subdivisions functional connectivity dysfunction within major depressive disorder

Seed-based resting-state connectivity as a neurosignature in fibromyalgia and depression: a narrative systematic review

Background

Major depressive disorder (MDD) often co-occur with fibromyalgia (FM), and both conditions have been associated with impaired resting state functional connectivity (rs-FC). The present systematic review aims to summarize the evidence on rs-FC in individuals with MDD and FM compared with healthy controls and explore overlapping connectivity patterns and their relationships with clinical symptoms.

Methods

A systematic search of the EMBASE, PubMed, Scopus and ScienceDirect databases was conducted according to PRISMA guidelines. Studies were included that addressed rs-FC using seed-based analysis in MDD and FM patients compared to HC. Methodological quality and risk of bias were assessed using a 13-point checklist adapted from previous neuroimaging meta-analyzes.

Results

A total of 33 articles were included in the analysis (17 with MDD and 16 with FM). The sample comprised 1,877 individuals, including 947 patients and 930 controls, with a mean age of 39.83 years. The seeds were categorized into six neural networks. Shared disruptions across MDD and FM studies have been identified in key circuits, including decreased connectivity between the insula and anterior cingulate cortex (ACC), middle frontal gyrus (MFG), superior frontal gyrus (SFG), and putamen. Increased FC was observed between the dorsolateral prefrontal cortex (DLPFC) and ACC, as well as between the thalamus and precuneus. Decreased insula-ACC connectivity correlated with greater pain intensity and catastrophizing in FM and with more severe depressive symptoms in MDD. Unique patterns of rs-FC were also observed: FM-specific changes involved the periaqueductal gray, hypothalamus, and thalamus, indicating impaired pain modulation and emotional processing. In contrast, MDD-specific changes were primarily observed in the reward, salience, and default mode networks, reflecting impaired emotional regulation. The studies showed considerable heterogeneity in the selection of seeds and study designs, which limits the feasibility of meta-analyses and underlines the need for standardized methods.

Findings

This study provides information about overlapping and distinct neural mechanisms in FM and MDD, suggesting potentially the presence of a potential neurosignature that reflects shared disruptions in pain and emotion regulation networks while highlighting unique pathways underlying their respective pathophysiology.

Reduced microstructural white matter integrity is associated with the severity of physical symptoms in functional neurological disorder

BACKGROUND

Functional neurological disorder (FND) is linked to functional changes in brain networks without an underlying brain lesion. However, the dichotomy between functional and structural changes has been challenged by research suggesting that not only functional but also anatomical alterations in the gray and white matter may underlie a subset of symptoms. This study aimed to characterize white matter microstructural integrity and its association with patient-reported and clinician-rated physical symptoms' severity in a large sample of FND patients.

METHODS

Diffusion-weighted imaging data were collected from 85 FND patients with mixed symptoms and 75 healthy controls (HCs), together with illness duration, clinician-rated (S-FMDRS & CGI), and patient-reported (SF-36) symptom severity. Microstructural integrity was computed based on probabilistic tractography using the Desikan-Killiany parcellation.

RESULTS

Compared to HCs, patients with FND presented widespread reduced microstructural integrity stemming from regions such as the right lateral orbitofrontal cortex, insula, putamen, and superior temporal regions. After adjusting for depression and anxiety, these differences were no longer significant. Within-group analysis revealed that reduced microstructural integrity, particularly in the left precuneus and left superior parietal cortex, was strongly correlated with both patient-reported and clinician-evaluated severity of physical symptoms in FND patients.

CONCLUSION

Patients with FND present widespread reduced microstructural integrity in the brain, predominantly originating from temporoparietal, paralimbic and associated regions involved in emotion regulation and body awareness. These changes seem to be partly explained by comorbid mood disorders and the severity of physical symptoms, suggesting a plasticity phenomenon rather than trait biomarkers, which warrants further investigation in longitudinal study designs.

Functional Connectivity Changes Associated With Depression in Dementia With Lewy Bodies

OBJECTIVES

Depressive symptoms are frequent in the early stages of dementia with Lewy bodies (DLB), and more than half of DLB patients would have a history of depression. Our study sought to investigate the functional connectivity (FC) changes associated with depressive symptoms in prodromal to mild DLB patients compared with controls.

METHODS

MRI data were collected from 66 DLB patients and 18 controls. Depression was evaluated with the Mini International Neuropsychiatric Interview. Resting-state FC (rsFC) was investigated with the CONN toolbox using a seed-based approach and both regression and comparison analyses.

RESULTS

Correlations were found between the depression scores and the rsFC between fronto-temporal and primary visual areas in DLB patients (p < 0.05, FDR corrected). Depressed DLB patients also showed decreased rsFC within the salience network (SN), increased rsFC between the default mode network (DMN) and the language network (LN) and decreased rsFC between the cerebellar network (CN) and the fronto-parietal network (FPN) compared to non-depressed DLB patients (p < 0.05, uncorrected). Comparison analyses between antidepressant-treated and non-treated DLB patients highlighted FC changes in treated patients involving the SN, the DMN, the FPN and the dorsal attentional network (p < 0.05, uncorrected).

CONCLUSIONS

Our findings revealed that depressive symptoms would especially be associated with rsFC changes between fronto-temporal and primary visual areas in DLB patients. Such alterations could contribute to difficulties in regulating emotions, processing biases towards negative stimuli, and self-focused ruminations.

TRIAL REGISTRATION

This study is part of the cohort study AlphaLewyMA (https://clinicaltrials.gov/ct2/show/NCT01876459).

Cognitive and clinical dimensions of structural and functional insula alterations in patients with depression: a resting-state fMRI study

Aim: Depression is characterized by pervasive cognitive and emotional disturbances, yet the neural mechanisms underlying these deficits remain incompletely understood. Method: This study utilized multimodal neuroimaging, including resting-state functional MRI and structural T1-weighted imaging, alongside the MATRICS Consensus Cognitive Battery (MCCB) and the Hamilton Depression Rating Scale (HAMD), to delineate the structural and functional alterations in the insula in first-episode, medication-naïve patients with depression. Result: Compared to matched healthy controls, patients with depression exhibited significant reductions in gray matter density in the left insula, which were robustly associated with impairments in reasoning and problem-solving abilities. Mediation analyses revealed that insular gray matter density mediated the relationship between depressive symptom severity and cognitive deficits, emphasizing the insula's critical role in linking emotional and cognitive dysfunctions. Furthermore, functional connectivity analyses identified disrupted insula-medial prefrontal cortex circuits, highlighting their contribution to the pathophysiology of depression. Conclusion: These findings underscore the insula's dual role as a structural and functional hub in depression, advancing our understanding of the neural substrates of cognitive dysfunction and informing potential targets for intervention.

Exploring causal association between functional/structural connectivity and major depression disorder: A bidirectional Mendelian randomization study

OBJECTIVES

Prior observational studies have suggested a correlation between major depressive disorder (MDD) and communication imbalances within the resting-state brain network (RSN), but the causal relationship remains unclear. This research uses Mendelian randomization (MR) analysis to explore the potential causal effects between functional connectivity (FC), structural connectivity (SC) and MDD.

METHODS

Two-sample bidirectional MR analysis was employed in this study. Inverse variance weighted (IVW) was used to explore the causal relationship between the FC/SC and MDD, with various methods such as MR-Egger to conduct sensitivity analyses.

RESULTS

The IVW analysis results showed that higher genetic predicted dorsal attention network FC, limbic network SC, and dorsal attention network SC were associated with an increased risk of MDD (β: 15.08, 95%CI: 5.89-24.27, p = 0.001; β: 3.79, 95%CI: -0.22-7.8, p = 0.034; β: 9.89, 95%CI: 0.88-18.90, p = 0.031). Reverse MR analysis demonstrated that a genetically predicted elevated risk of MDD was associated with reduced frontal parietal network FC (β: -0.00046, p = 0.041).

CONCLUSIONS

The study suggests a causal relationship between the FC and SC within specific RSNs and the risk of MDD. Abnormalities in the dorsal attention network FC/SC and the limbic network SC were risk factors for MDD. The FC abnormality of the frontal parietal network may be the downstream influence following the MDD onset. Further investigation is needed to determine the potential utility of these neuroimaging markers in the prevention of MDD or the evaluation of treatment efficacy.

Connectivity of the insular subdivisions differentiates posttraumatic headache-associated from nonheadache-associated mild traumatic brain injury: an arterial spin labelling study

OBJECTIVE

The insula is an important part of the posttraumatic headache (PTH) attributed to mild traumatic brain injury (mTBI) neuropathological activity pattern. It is composed of functionally different subdivisions and each of which plays different role in PTH neuropathology.

METHODS

Ninety-four mTBI patients were included in this study. Based on perfusion imaging data obtained from arterial spin labelling (ASL) perfusion magnetic resonance imaging (MRI), this study evaluated the insular subregion perfusion-based functional connectivity (FC) and its correlation with clinical characteristic parameters in patients with PTH after mTBI and non-headache mTBI patients.

RESULTS

The insular subregions of mTBI + PTH (mTBI patients with PTH) and mTBI-PTH (mTBI patients without PTH) group had positive perfusion-based functional connections with other insular nuclei and adjacent discrete cortical regions. Compared with mTBI-PTH group, significantly increased resting-state perfusion-based FC between the anterior insula (AI) and middle cingulate cortex (MCC)/Rolandic operculum (ROL), between posterior insula (PI) and supplementary motor area (SMA), and decreased perfusion-based FC between PI and thalamus were found in mTBI + PTH group. Changes in the perfusion-based FC of the left posterior insula/dorsal anterior insula with the thalamus/MCC were significant correlated with headache characteristics.

CONCLUSIONS

Our findings provide new ASL-based evidence for changes in the perfusion-based FC of the insular subregion in PTH patients attributed to mTBI and the association with headache features, revealing the possibility of potential neuroplasticity after PTH. These findings may contribute to early diagnosis of the disease and follow-up of disease progression.

Emotional processing impairments in patients with insula lesions following stroke

Functional imaging has helped to understand the role of the human insula as a major processing network for integrating input with the current state of the body. However, these studies remain at a correlative level. Studies that have examined insula damage show lesion-specific performance deficits. Case reports have provided anecdotal evidence for deficits following insula damage, but group lesion studies offer a number of advances in providing evidence for functional representation of the insula. We conducted a systematic literature search to review group studies of patients with insula damage after stroke and identified 23 studies that tested emotional processing performance in these patients. Eight of these studies assessed emotional processing of visual (most commonly IAPS), auditory (e.g., prosody), somatosensory (emotional touch) and autonomic function (heart rate variability). Fifteen other studies looked at social processing, including emotional face recognition, gaming tasks and tests of empathy. Overall, there was a bias towards testing only patients with right-hemispheric lesions, making it difficult to consider hemisphere specificity. Although many studies included an overlay of lesion maps to characterise their patients, most did not differentiate lesion statistics between insula subunits and/or applied voxel-based associations between lesion location and impairment. This is probably due to small group sizes, which limit statistical comparisons. We conclude that multicentre analyses of lesion studies with comparable patients and performance tests are needed to definitively test the specific function of parts of the insula in emotional processing and social interaction.

The association between gray matter volume in the hippocampal subfield and antidepressant efficacy mediated by abnormal dynamic functional connectivity

An abnormality of structures and functions in the hippocampus may have a key role in the pathophysiology of major depressive disorder (MDD). However, it is unclear whether structure factors of the hippocampus effectively impact antidepressant responses by hippocampal functional activity in MDD patients. We collected longitudinal data from 36 MDD patients before and after a 3-month course of antidepressant pharmacotherapy. Additionally, we obtained baseline data from 43 healthy controls matched for sex and age. Using resting-state functional magnetic resonance imaging (rs-fMRI), we estimated the dynamic functional connectivity (dFC) of the hippocampal subregions using a sliding-window method. The gray matter volume was calculated using voxel-based morphometry (VBM). The results indicated that patients with MDD exhibited significantly lower dFC of the left rostral hippocampus (rHipp.L) with the right precentral gyrus, left superior temporal gyrus and left postcentral gyrus compared to healthy controls at baseline. In MDD patients, the dFC of the rHipp.L with right precentral gyrus at baseline was correlated with both the rHipp.L volume and HAMD remission rate, and also mediated the effects of the rHipp.L volume on antidepressant performance. Our findings suggested that the interaction between hippocampal structure and functional activity might affect antidepressant performance, which provided a novel insight into the hippocampus-related neurobiological mechanism of MDD.

Specific alterations of resting-state functional connectivity in the triple network related to comorbid anxiety in major depressive disorder

The brain's default mode network (DMN) and the executive control network (ECN) switch engagement are influenced by the ventral attention network (VAN). Alterations in resting-state functional connectivity (RSFC) within this so-called triple network have been demonstrated in patients with major depressive disorder (MDD) or anxiety disorders (ADs). This study investigated alterations in the RSFC in patients with comorbid MDD and ADs to better understand the pathophysiology of this prevalent group of patients. Sixty-eight participants (52.9% male, mean age 35.3 years), consisting of 25 patients with comorbid MDD and ADs (MDD + AD), 20 patients with MDD only (MDD) and 23 healthy controls (HCs) were investigated clinically and with 3T resting-state fMRI. RSFC utilizing a seed-based approach within the three networks belonging to the triple network was compared between the groups. Compared with HC, MDD + AD showed significantly reduced RSFC between the ECN and the VAN, the DMN and the VAN and within the ECN. No differences could be found for the MDD group compared with both other groups. Furthermore, symptom severity and medication status did not affect RSFC values. The results of this study show a distinct set of alterations of RSFC for patients with comorbid MDD and AD compared with HCs. This set of dysfunctions might be related to less adequate switching between the DMN and the ECN as well as poorer functioning of the ECN. This might contribute to additional difficulties in engaging and utilizing consciously controlled emotional regulation strategies.

Modulating the default mode network: Antidepressant efficacy of transcutaneous electrical cranial-auricular acupoints stimulation targeting the insula

BACKGROUND

Transcutaneous electrical cranial-auricular acupoint stimulation (TECAS) is a novel non-invasive therapy for major depressive disorder (MDD) that stimulates acupoints innervated by the trigeminal and auricular vagus nerves. However, there are few neuroimaging studies involving the TECAS for the treatment of MDD. Therefore, this study aimed to investigate the treatment response and neurological effects of TECAS using resting-state functional magnetic resonance imaging (rs-fMRI).

METHOD

A total of 34 patients with mild-to-moderate MDD and 34 demographically matched healthy controls (HCs) were recruited. After an eight-week treatment the primary outcome was clinical response, defined as a baseline-to-endpoint ≥ 50 % reduction in the 17-item Hamilton Depression Rating Scale (HAMD-17). The low-frequency fluctuations (ALFF) method were used to investigate the brain abnormalities of MDD patients and HCs, and altered brain networks were analyzed between pre- and post-treatment using seed-based functional connectivity (FC) analysis.

RESULTS

We found no significant differences in terms of gender, age, and years of education between the two groups. After treatment, the response rate was 58.82 %. Compared to HCs, MDD patients showed lower ALFF values in the left insula(t = -4.298,P < 0.005), the insula-based FC revealed in the right middle frontal gyrus (MFG)/ right superior frontal gyrus, orbital part (ORBsupmed) (t = -5.29,P < 0.005) and the right anterior cingulate gyrus (ACC)were decreased (t = -6.08,P < 0.005). Furthermore, Compared to pre-treatment, abnormal FC values in the ACC /orbital superior frontal gyrus (SFG) (t = 3.42,P < 0.005) and left superior frontal gyrus (SFG)/ supplement motor area (SMA) were enhanced (t = 3.34,P < 0.005).

CONCLUSION

TECAS exhibits antidepressant efficacy, particularly influencing the insula-based functional connections within the Default Mode Network (DMN) related to emotion processing in individuals with MDD.

Disorganized Functional Connectivity of Anterior Insular Subnetworks in Adults with Executive Dysfunction after Trauma Exposure

There is increasing evidence that major trauma can adversely affect the brain and cognition. In some cases, trauma may lead to deficits in executive function (EF). The anterior insula may be a causal outflow hub acting to coordinate EF-related brain networks. To clarify the neural underpinnings of EF deficits (EFD) after trauma, we performed a resting-state functional magnetic resonance imaging (rs-fMRI) study of anterior insular subnetworks in adults who have lost their only child. A total of 167 participants completed various psychological and cognitive assessments to assess EF-related deficits. Correlations were computed between abnormal connectivity and cognitive/post-traumatic stress symptoms. The results showed abnormal anterior insular subregion connectivity in the default mode network (DMN), prefrontal lobe, and cerebellum lobe in participants with EFD. No correlation was found between abnormal connectivity and cognitive/post-traumatic stress symptoms in participants with EFD. These results suggest that excessive connections between the insula and DMN could contribute to EFD after trauma. Overall, this study provides novel references into the neural mechanisms of EF status after trauma exposure.

Shared and specific neurobiology in bipolar disorder and unipolar disorder: Evidence based on the connectome gradient and a transcriptome-connectome association study

BACKGROUND

Distinguishing bipolar disorder (BD) and unipolar disorder (UD) remains challenging. To identify the common and diagnosis-specific neuropathological alterations and their potential molecular mechanisms in patients with UD and BD (with a current depressive episode).

METHODS

Resting-state functional magnetic resonance imaging was obtained from 279 participants (95 BD patients, 107 UD patients and 77 health controls). Connectome gradients analysis was performed to explore the shared and diagnosis-specific gradient alterations in BD and UD. The Allen Human Brain Atlas data was used to explore the potential gene mechanisms of the gradient alterations.

RESULTS

BD and UD had shared hierarchical disorganisation, including downgrading and contraction from the unimodal sensory networks (vision and sensorimotor) to the transmodal cognitive networks (limbic, frontoparietal, dorsal attention, and default) (all P < 0.05, FDR corrected) in gradient 1 and gradient 2. The BD patients had specific connectome gradient dysfunction in the subcortical network. Moreover, the hierarchical disorganisation was closely correlated with profiles of gene expression specific to the neuroglial cells in the prefrontal cortex in BD and UD, while the most correlated gene ontology biological processes and function were concentrated in synaptic signalling, calcium ion binding, and transmembrane transporter activity.

CONCLUSION

These findings reveal the shared and diagnosis-specific neurobiological mechanism underlying BD and UD patients, which advances our understanding of the neuromechanisms of these disorders.

Changes in brain functional networks in remitted major depressive disorder: a six-month follow-up study

BACKGROUND

Patients with remitted major depressive disorder (rMDD) show abnormal functional connectivity of the central executive network (CEN), salience networks (SN) and default mode network (DMN). It is unclear how these change during remission, or whether changes are related to function.

METHODS

Three spatial networks in 17 patients with rMDD were compared between baseline and the six-month follow-up, and to 22 healthy controls. Correlations between these changes and psychosocial functioning were also assessed.

RESULTS

In the CEN, patients at baseline had abnormal functional connectivity in the right anterior cingulate, right dorsolateral prefrontal cortex (DLPFC) and inferior parietal lobule (IPL) compare with HCs. There were functional connection differences in the right DLPFC and left IPL at baseline during follow-up. Abnormal connectivity in the right DLPFC and medial prefrontal cortex (mPFC) were found at follow-up. In the SN, patients at baseline had abnormal functional connectivity in the insula, left anterior cingulate, left IPL, and right precuneus; compared with baseline, patients had higher connectivity in the right DLPFC at follow-up. In the DMN, patients at baseline had abnormal functional connectivity in the right mPFC. Resting-state functional connectivity of the IPL and DLPFC in the CEN correlated with psychosocial functioning.

CONCLUSIONS

At six-month follow-up, the CEN still showed abnormal functional connectivity in those with rMDD, while anomalies in the SN and DMN has disappeared. Resting-state functional connectivity of the CEN during early rMDD is associated with psychosocial function.

CLINICAL TRIALS REGISTRATION

Pharmacotherapy and Psychotherapy for MDD after Remission on Psychology and Neuroimaging. https://www.

CLINICALTRIALS

gov/ , registration number: NCT01831440 (15/4/2013).

Abnormal voxel-wise whole-brain functional connectivity in first-episode, drug-naïve adolescents with major depression disorder

Major depression disorder (MDD) is one of the most common psychiatric disorders. Previous studies have demonstrated structural and functional abnormalities in adult depression. However, the neurobiology of adolescent depression has not been fully understood. The aim of this study was to investigate the intrinsic dysconnectivity pattern of voxel-level whole-brain functional networks in first-episode, drug-naïve adolescents with MDD. Resting-state functional magnetic resonance imaging data were acquired from 66 depressed adolescents and 47 matched healthy controls. Voxel-wise degree centrality (DC) analysis was performed to identify voxels that showed altered whole-brain functional connectivity (FC) with other voxels. We further conducted seed-based FC analysis to investigate in more detail the connectivity patterns of the identified DC changes. The relationship between altered DC and clinical variables in depressed adolescents was also analyzed. Compared with controls, depressed adolescents showed lower DC in the bilateral hippocampus, left superior temporal gyrus and right insula. Seed-based analysis revealed that depressed adolescents, relative to controls, showed hypoconnectivity between the hippocampus to the medial prefrontal regions and right precuneus. Furthermore, the DC values in the bilateral hippocampus were correlated with the Hamilton Depression Rating Scale score and duration of disease (all P < 0.05, false discovery rate corrected). Our study indicates abnormal intrinsic dysconnectivity patterns of whole-brain functional networks in drug-naïve, first-episode adolescents with MDD, and abnormal DC in the hippocampus may affect the association of prefrontal-hippocampus circuit. These findings may provide new insights into the pathophysiology of adolescent-onset MDD.

Alterations of insular dynamic functional connectivity and psychological characteristics in unmedicated bipolar depression patients with a recent suicide attempt

BACKGROUND

Mounting evidence showed that insula contributed to the neurobiological mechanism of suicidal behaviors in bipolar disorder (BD). However, no studies have analyzed the dynamic functional connectivity (dFC) of insular Mubregions and its association with personality traits in BD with suicidal behaviors. Therefore, we investigated the alterations of dFC variability in insular subregions and personality characteristics in BD patients with a recent suicide attempt (SA).

METHODS

Thirty unmedicated BD patients with SA, 38 patients without SA (NSA) and 35 demographically matched healthy controls (HCs) were included. The sliding-window analysis was used to evaluate whole-brain dFC for each insular subregion seed. We assessed between-group differences of psychological characteristics on the Minnesota Multiphasic Personality Inventory-2. Finally, a multivariate regression model was adopted to predict the severity of suicidality.

RESULTS

Compared to NSA and HCs, the SA group exhibited decreased dFC variability values between the left dorsal anterior insula and the left anterior cerebellum. These dFC variability values could also be utilized to predict the severity of suicidality (r = 0.456, p = 0.031), while static functional connectivity values were not appropriate for this prediction. Besides, the SA group scored significantly higher on the schizophrenia clinical scales (p < 0.001) compared with the NSA group.

CONCLUSIONS

Our findings indicated that the dysfunction of insula-cerebellum connectivity may underlie the neural basis of SA in BD patients, and highlighted the dFC variability values could be considered a neuromarker for predictive models of the severity of suicidality. Moreover, the psychiatric features may increase the vulnerability of suicidal behavior.

Decreased functional connectivity in patients with major depressive disorder and a history of childhood traumatization through experiences of abuse

BACKGROUND

Childhood trauma (CT) increases vulnerability for the development of major depressive disorder (MDD). Alterations in resting-state functional connectivity (RSFC) have frequently been reported for MDD. These alterations may be much more prominent in depressive patients with a history of CT. The present study aims to compare RSFC in different brain networks of patients with MDD and CT (MDD+CT) vs. MDD and no CT compared to healthy controls.

METHODS

45 patients (22 with CT) were compared to 23 age-and-gender-matched healthy control subjects. Demographic parameters, severity of MDD, severity of CT and comorbid anxiety disorders were assessed. For assessment of RSFC alterations, a seed-based approach within five well-established RSFC networks was used.

RESULTS

CT in MDD patients predicts severity of comorbid anxiety. A significant decrease in in-between network RSFC-values of MDD patients compared to controls was found in the network pairs of default mode network (DMN) - dorsal attention network (DAN), ventral attention network (VAN) - DMN and DAN - affective network (AN). MDD+CT patients presented more aberrant RSFC than MDD-CT patients. MDD scores predicted the decrease in RSFC for MDD patients. Higher Childhood Trauma Questionnaire (CTQ) scores are linked to reduced functional connectivity (FC) between DMN - DAN.

CONCLUSIONS

Our study shows reduced RSFC in MDD patients for DMN - DAN, VAN - DMN, DAN - AN and MDD+CT patients presented more aberrant RSFC so that we suspect CT to be a considerable factor in the etiology of MDD. Through dysregulated neural circuits, CT is likely to contribute to a distinct MDD pathophysiology.

Distinct patterns of functional brain network integration between treatment-resistant depression and non treatment-resistant depression: A resting-state functional magnetic resonance imaging study

BACKGROUND

Previous neuroimaging has paid little attention to the differences in brain network integration between patients with treatment-resistant depression(TRD) and non-TRD (nTRD), and the relationship between their impaired brain network integration and clinical symptoms has not been elucidated.

METHOD

Eighty one major depressive disorder (MDD) patients (40 in TRD, 41 in nTRD) and 40 healthy controls (HCs) were enrolled for the functional magnetic resonance imaging (fMRI) scans. A seed-based functional connectivity (FC) method was used to investigate the brain network abnormalities of default mode network (DMN), affective network (AN), salience network (SN) and cognitive control network (CCN) for the MDD. Finally, the correlation was analyzed between the abnormal FCs and 17-item Hamilton Rating Scale for Depression scale (HAMD-17) scores.

RESULTS

Compared with the HC group, the FCs in DMN, AN, SN, CCN were altered in both the TRD and nTRD groups. Compared with the nTRD group, FC alterations in the AN and CCN were more abnormal in the TRD group, and the FC alterations were generally decreased at the SN in the TRD group. In addition, the FC values of right dorsolateral prefrontal cortices and left caudate nucleus in the TRD group and the FC values of right subgenual anterior cingulate cortex and left middle temporal gyrus in the nTRD group were positively correlated with HAMD-17 scale scores.

CONCLUSIONS

Abnormal FCs are present in four brain networks (DMN, AN, SN, CCN) in both the TRD and nTRD groups. Except of DMN, FCs in AN, SN and CCN maybe underlay the neurobiological mechanism in differentiating TRD from nTRD.

Disrupted interhemispheric coordination of sensory-motor networks and insula in major depressive disorder

Objective

Prior researches have identified distinct differences in neuroimaging characteristics between healthy controls (HCs) and patients with major depressive disorder (MDD). However, the correlations between homotopic connectivity and clinical characteristics in patients with MDD have yet to be fully understood. The present study aimed to investigate common and unique patterns of homotopic connectivity and their relationships with clinical characteristics in patients with MDD.

Methods

We recruited 42 patients diagnosed with MDD and 42 HCs. We collected a range of clinical variables, as well as exploratory eye movement (EEM), event-related potentials (ERPs) and resting-state functional magnetic resonance imaging (rs-fMRI) data. The data were analyzed using correlation analysis, support vector machine (SVM), and voxel-mirrored homotopic connectivity (VMHC).

Results

Compared with HCs, patients with MDD showed decreased VMHC in the insula, and increased VMHC in the cerebellum 8/vermis 8/vermis 9 and superior/middle occipital gyrus. SVM analysis using VMHC values in the cerebellum 8/vermis 8/vermis 9 and insula, or VMHC values in the superior/middle occipital gyrus and insula as inputs can distinguish HCs and patients with MDD with high accuracy, sensitivity, and specificity.

Conclusion

The study demonstrated that decreased VMHC in the insula and increased VMHC values in the sensory-motor networks may be a distinctive neurobiological feature for patients with MDD, which could potentially serve as imaging markers to discriminate HCs and patients with MDD.

Contrasting the amygdala activity and functional connectivity profile between antidepressant-free participants with major depressive disorder and healthy controls: A systematic review of comparative fMRI studies

Functional neuroimaging research suggests that the amygdala is implicated in the pathophysiology of major depressive disorder (MDD). This systematic review aimed to identify consistently reported amygdala activity and functional connectivity (FC) abnormalities in antidepressant-free participants with MDD as compared to healthy controls at baseline (i.e., before treatment initiation or experimental manipulation). A search for relevant published studies and registered clinical trials was conducted through OVID (MEDLINE, PsycINFO, and Embase) and ClinicalTrials.gov with an end date of March 7th, 2022. Fifty published studies and two registered clinical trials were included in this review. Participants with MDD frequently exhibited amygdala hyperactivity in response to negative stimuli, abnormal event-related amygdala-anterior cingulate cortex (ACC) FC, and abnormal resting-state amygdala FC with the insula and the prefrontal, temporal, and parietal cortices. Decreased resting-state FC was consistently found between the amygdala and the orbitofrontal cortex, striatum, cerebellum, and middle/inferior frontal gyri. Due to the limited number of studies examining resting-state amygdala activity and FC with specific subregions of interest, including those within the ACC, further investigation is warranted.

Anterior default mode network and posterior insular connectivity is predictive of depressive symptom reduction following serial ketamine infusion

BACKGROUND

Ketamine is a rapidly-acting antidepressant treatment with robust response rates. Previous studies have reported that serial ketamine therapy modulates resting state functional connectivity in several large-scale networks, though it remains unknown whether variations in brain structure, function, and connectivity impact subsequent treatment success. We used a data-driven approach to determine whether pretreatment multimodal neuroimaging measures predict changes along symptom dimensions of depression following serial ketamine infusion.

METHODS

Patients with depression (n = 60) received structural, resting state functional, and diffusion MRI scans before treatment. Depressive symptoms were assessed using the 17-item Hamilton Depression Rating Scale (HDRS-17), the Inventory of Depressive Symptomatology (IDS-C), and the Rumination Response Scale (RRS) before and 24 h after patients received four (0.5 mg/kg) infusions of racemic ketamine over 2 weeks. Nineteen unaffected controls were assessed at similar timepoints. Random forest regression models predicted symptom changes using pretreatment multimodal neuroimaging and demographic measures.

RESULTS

Two HDRS-17 subscales, the HDRS-6 and core mood and anhedonia (CMA) symptoms, and the RRS: reflection (RRSR) scale were predicted significantly with 19, 27, and 1% variance explained, respectively. Increased right medial prefrontal cortex/anterior cingulate and posterior insula (PoI) and lower kurtosis of the superior longitudinal fasciculus predicted reduced HDRS-6 and CMA symptoms following treatment. RRSR change was predicted by global connectivity of the left posterior cingulate, left insula, and right superior parietal lobule.

CONCLUSIONS

Our findings support that connectivity of the anterior default mode network and PoI may serve as potential biomarkers of antidepressant outcomes for core depressive symptoms.

Resting-state functional connectivity correlates of anxiety co-morbidity in major depressive disorder

Major depressive disorder (MDD) is frequently co-morbid with anxiety disorders. The co-morbid state has poorer functional outcomes and greater resistance to first line treatments, highlighting the need for novel treatment targets. This systematic review examined differences in resting-state brain connectivity associated with anxiety comorbidity in young- and middle-aged adults with MDD, with the aim of identifying novel targets for neuromodulation treatments, as these treatments are thought to work partly by altering dysfunctional connectivity pathways. Twenty-one studies met inclusion criteria, including a total of 1292 people with MDD. Only two studies included people with MDD and formally diagnosed co-morbid anxiety disorders; the remainder included people with MDD with dimensional anxiety measurement. The quality of most studies was judged as fair. Results were heterogeneous, partly due to a focus on a small set of connectivity relationships within individual studies. There was evidence for dysconnectivity between the amygdala and other brain networks in co-morbid anxiety, and an indication that abnormalities of default mode network connectivity may play an underappreciated role in this condition.

Multiple-Network Alterations in Major Depressive Disorder With Gastrointestinal Symptoms at Rest Revealed by Global Functional Connectivity Analysis

Objective

Gastrointestinal (GI) symptoms are prominent in major depressive disorder (MDD) and bring patients lots of complaints and troubles. We aimed to explore whether there were some distinctive brain image alterations in MDD with GI symptoms, which could be used to distinguish MDD with GI symptoms from those without GI symptoms and healthy controls (HCs).

Methods

A total of 35 outpatients with GI symptoms, 17 outpatients without GI symptoms, and 28 HCs were recruited. All the participants were scanned by a resting-state functional magnetic resonance imaging. Imaging data were analyzed with the global functional connectivity (GFC) and support vector machine methods.

Results

MDD with GI symptoms showed decreased GFC in the left superior medial prefrontal cortex (MPFC) compared with MDD without GI symptoms. Compared with HCs, MDD with GI symptoms showed decreased GFC in the bilateral middle temporal pole (MTP) and left posterior cingulate cortex/precuneus (PCC/Pcu), and increased GFC in the right insula and bilateral thalamus. SVM analysis showed that an accuracy was 78.85% in differentiating MDD with GI symptoms from MDD without GI symptoms by using the GFC of the left superior MPFC. A combination of GFC of the left PCC/Pcu and bilateral MTP exhibited the highest accuracy (87.30%) in differentiating patients with MDD with GI symptoms from HCs.

Conclusion

MDD with GI symptoms showed abnormal GFC in multiple networks, including the default mode network and cortico-limbic mood-regulating circuit. Using abnormal GFC might work well to discriminate MDD with GI symptoms from MDD without GI symptoms and HCs.

Subregion-specific, modality-dependent and timescale-sensitive hippocampal connectivity alterations in patients with first-episode, drug-naïve major depression disorder

BACKGROUND

Despite accumulating evidence for the hippocampus as a key dysfunctional node in major depressive disorder (MDD), previous findings are controversial possibly due to heterogeneous and small clinical samples, complicated hippocampal structure, and different imaging modalities and analytical methods.

METHODS

We collected structural and resting-state functional MRI data from 100 first-episode, drug-naïve MDD patients and 99 healthy controls. A subset of the participants (34 patients and 33 controls) also completed a battery of neuropsychological tests and childhood trauma questionnaires. Seed-based morphological and functional (static and dynamic) connectivity were calculated for ten hippocampal subregions, followed by analyses of dynamic functional connectivity states (k-means clustering), connectivity cross-modality relationships (cosine similarity), and connectivity associations with clinical and neuropsychological variables (Spearman correlation).

RESULTS

Between-group comparisons revealed abnormal hippocampal connectivity in the patients that depended on 1) hippocampal subdivisions: the cornu ammonis (CA) was the most seriously affected subregion, in particular the right CA1 for functional connectivity alterations; 2) imaging modality: morphological connectivity revealed seldom and sporadic alterations with different lobes, while functional connectivity identified numerous and convergent alterations with prefrontal regions; and 3) time scale: dynamic functional connectivity was more sensitive than static functional connectivity, in particular in revealing alterations between the right CA1 and contralateral prefrontal cortex. Among the 34 patients, functional connectivity alterations of the CA1 were related to the history of childhood trauma in the patients.

LIMITATIONS

Only a subset of the patients completed the neuropsychological tests, which may cause underestimation of cognitive relevance of hippocampal connectivity alterations.

CONCLUSIONS

Disrupted hippocampal CA1 functional connectivity plays key roles in the pathophysiology of MDD and may act as a potential diagnostic biomarker for the disease.

Sustained attention alterations in major depressive disorder: A review of fMRI studies employing Go/No-Go and CPT tasks

BACKGROUND

Major depressive disorder (MDD) is a severe psychiatric condition characterized by selective cognitive dysfunctions. In this regard, functional Magnetic Resonance Imaging (fMRI) studies showed, both at resting state and during tasks, alterations in the brain functional networks involved in cognitive processes in MDD patients compared to controls. Among those, it seems that the attention network may have a role in the disease pathophysiology. Therefore, in this review we aim at summarizing the current fMRI evidence investigating sustained attention in MDD patients.

METHODS

We conducted a search on PubMed on case-control studies on MDD employing fMRI acquisitions during Go/No-Go and continuous performance tasks. A total of 12 studies have been included in the review.

RESULTS

Overall, the majority of fMRI studies reported quantitative alterations in the response to attentive tasks in selective brain regions, including the prefrontal cortex, the cingulate cortex, the temporal and parietal lobes, the insula and the precuneus, which are key nodes of the attention, the executive, and the default mode networks.

LIMITATIONS

The heterogeneity in the study designs, fMRI acquisition techniques and processing methods have limited the generalizability of the results.

CONCLUSIONS

The results from the included studies showed the presence of alterations in the activation patterns of regions involved in sustained attention in MDD, which are in line with current evidence and seemed to explain some of the key symptoms of depression. However, given the paucity and heterogeneity of studies available, it may be worthwhile to continue investigating the attentional domain in MDD with ad-hoc study designs to retrieve more robust evidence.

BMRMI Reduces Depressive Rumination Possibly through Improving Abnormal FC of Dorsal ACC

Rumination is a common symptom of major depressive disorder (MDD) and has been characterized as a vulnerability factor for the onset or recurrence of MDD. However, the neurobiological mechanisms underlying rumination and appropriate treatment strategies remain unclear. In the current study, we used resting-state functional magnetic resonance imaging to investigate the effects of body-mind relaxation meditation induction (BMRMI) intervention in MDD with rumination. To this aim, we have recruited 25 MDD and 24 healthy controls (HCs). Changes in functional connectivity (FC) of the anterior cingulate cortex (ACC) subregion and the scores of clinical measurements were examined using correlation analysis. At baseline, MDD showed stronger FC between the right dorsal ACC (dACC) and right superior frontal gyrus than did the HC group. Compared to baseline, the HC group showed a significantly enhanced FC between the right dACC and right superior frontal gyrus, and the MDD group demonstrated a significantly weaker FC between the left dACC and right middle frontal gyrus (MFG) after the intervention. Furthermore, the FC between the right dACC and right superior frontal gyrus was positively associated with rumination scores across all participants at baseline. The above results indicate that BMRMI may regulate self-referential processing and cognitive function through modulating FC of the dACC in MDD with rumination.

C-reactive protein is related to a distinct set of alterations in resting-state functional connectivity contributing to a differential pathophysiology of major depressive disorder

BACKGROUND

Several studies in major depressive disorder (MDD) have found inflammation, especially C-reactive protein (CRP), to be consistently associated with MDD and network dysfunction. The aim was to investigate whether CRP is linked to a distinct set of resting-state functional connectivity (RSFC) alterations.

METHODS

For this reason, we investigated the effects of diagnosis and elevated blood plasma CRP levels on the RSFC in 63 participants (40 females, mean age 31.4 years) of which were 27 patients with a primary diagnosis of MDD and 36 healthy control-subjects (HC), utilizing a seed-based approach within five well-established RSFC networks obtained using fMRI.

RESULTS

Of the ten network pairs examined, five showed increased between-network RSFC-values unambiguously connected either to a diagnosis of MDD or elevated CRP levels. For elevated CRP levels, increased RSFC between DMN and AN was found. Patients showed increased RSFC within DMN areas and between the DMN and ECN and VAN, ECN and AN and AN and DAN.

CONCLUSIONS

The results of this study show dysregulated neural circuits specifically connected to elevated plasma CRP levels and independent of other alterations of RSFC in MDD. This dysfunction in neural circuits might in turn result in a certain immune-inflammatory subtype of MDD.

Alteration of whole-brain amplitude of low-frequency fluctuation and degree centrality in patients with mild to moderate depression: A resting-state functional magnetic resonance imaging study

BACKGROUND

Mild to moderate depressive disorder has a high risk of progressing to major depressive disorder.

METHODS

Low-frequency amplitude and degree centrality were calculated to compare 49 patients with mild to moderate depression and 21 matched healthy controls. Correlation analysis was conducted to explore the correlation between the amplitude of low-frequency fluctuation (ALFF) and the degree centrality (DC) of altered brain region and the scores of clinical scale. Receiver operating characteristic (ROC) curves were further analyzed to evaluate the predictive value of above altered ALFF and DC areas as image markers for mild to moderate depression.

RESULTS

Compared with healthy controls, patients with mild to moderate depression had lower ALFF values in the left precuneus and posterior cingulate gyrus [voxel p < 0.005, cluster p < 0.05, Gaussian random field correction (GRF) corrected] and lower DC values in the left insula (voxel p < 0.005, cluster p < 0.05, GRF corrected). There was a significant negative correlation between DC in the left insula and scale scores of Zung's Depression Scale (ZungSDS), Beck Self-Rating Depression Scale (BDI), Toronto Alexithymia Scale (TAS26), and Ruminative Thinking Response Scale (RRS_SUM, RRS_REFLECTION, RRS_DEPR). Finally, ROC analysis showed that the ALFF of the left precuneus and posterior cingulate gyrus had a sensitivity of 61.9% and a specificity of 79.6%, and the DC of the left insula had a sensitivity of 81% and a specificity of 85.7% in differentiating mild to moderate depression from healthy controls.

CONCLUSION

Intrinsic abnormality of the brain was mainly located in the precuneus and insular in patients with mild to moderate depression, which provides insight into potential neurological mechanisms.

Structural covariance pattern abnormalities of insula in major depressive disorder: A CAN-BIND study report

BACKGROUND AND METHODS

Investigation of the insula may inform understanding of the etiopathogenesis of major depressive disorder (MDD). In the present study, we introduced a novel gray matter volume (GMV) based structural covariance technique, and applied it to a multi-centre study of insular subregions of 157 patients with MDD and 93 healthy controls from the Canadian Biomarker Integration Network in Depression (CAN-BIND, https://www.canbind.ca/). Specifically, we divided the unilateral insula into three subregions, and investigated their coupling with whole-brain GMV-based structural brain networks (SBNs). We compared between-group difference of the structural coupling patterns between the insular subregions and SBNs.

RESULTS

The insula was divided into three subregions, including an anterior one, a superior-posterior one and an inferior-posterior one. In the comparison between MDD patients and controls we found that patients' right anterior insula showed increased inter-network coupling with the default mode network, and it showed decreased inter-network coupling with the central executive network; whereas patients' right ventral-posterior insula showed decreased inter-network coupling with the default mode network, and it showed increased inter-network coupling with the central executive network. We also demonstrated that patients' loading parameters of the right ventral-posterior insular structural covariance negatively correlated with their suicidal ideation scores; and controls' loading parameters of the right ventral-posterior insular structural covariance positively correlated with their motor and psychomotor speed scores, whereas these phenomena were not found in patients. Additionally, we did not find significant inter-network coupling between the whole-brain SBNs, including salience network, default mode network, and central executive network.

CONCLUSIONS

Our work proposed a novel technique to investigate the structural covariance coupling between large-scale structural covariance networks, and provided further evidence that MDD is a system-level disorder that shows disrupted structural coupling between brain networks.

Shared and distinct brain fMRI response during performance of working memory tasks in adult patients with schizophrenia and major depressive disorder

Working memory (WM) impairments are common features of psychiatric disorders. A systematic meta-analysis was performed to determine common and disorder-specific brain fMRI response during performance of WM tasks in patients with SZ and patients with MDD relative to healthy controls (HC). Thirty-four published fMRI studies of WM in patients with SZ and 18 published fMRI studies of WM in patients with MDD, including relevant HC, were included in the meta-analysis. In both SZ and MDD there was common stronger fMRI response in right medial prefrontal cortex (MPFC) and bilateral anterior cingulate cortex (ACC), which are part of the default mode network (DMN). The effects were of greater magnitude in SZ than MDD, especially in prefrontal-temporal-cingulate-striatal-cerebellar regions. In addition, a disorder-specific weaker fMRI response was observed in right middle frontal gyrus (MFG) in MDD, relative to HC. For both SZ and MDD a significant correlation was observed between the severity of clinical symptoms and lateralized fMRI response relative to HC. These findings indicate that there may be common and distinct anomalies in brain function underlying deficits in WM in SZ and MDD, which may serve as a potential functional neuroimaging-based diagnostic biomarker with value in supporting clinical diagnosis, measuring illness severity and assessing the efficacy of treatments for SZ and MDD at the brain level.

Sub-regional anterior cingulate cortex functional connectivity revealed default network subsystem dysfunction in patients with major depressive disorder

BACKGROUND

Major depressive disorder (MDD) is a prevalent mental disorder characterized by impairments in affect, behaviour and cognition. Previous studies have indicated that the anterior cingulate cortex (ACC) may play an essential role in the pathophysiology of depression. In this study, we systematically identified changes in functional connectivity (FC) for ACC subdivisions that manifest in MDD and further investigated the relationship between these changes and the clinical symptoms of depression.

METHODS

Sub-regional ACC FC was estimated in 41 first-episode medication-naïve MDD patients compared to 43 healthy controls. The relationships between depressive symptom severity and aberrant FC of ACC subdivisions were investigated. In addition, we conducted a meta-analysis to generate the distributions of MDD-related abnormal regions from previously reported results and compared them to FC deficits revealed in this study.

RESULTS

In MDD patients, the subgenual and perigenual ACC demonstrated decreased FC with the posterior regions of the default network (DN), including the posterior inferior parietal lobule and posterior cingulate cortex. FC of these regions was negatively associated with the Automatic Thoughts Questionnaire scores and largely overlapped with previously reported abnormal regions. In addition, reduced FC between the caudal ACC and precuneus was negatively correlated with the Hamilton Anxiety Scale scores. We also found increased FC between the rostral ACC and dorsal medial prefrontal cortex.

CONCLUSIONS

Our findings confirmed that functional interaction changes in different ACC sub-regions are specific and associated with distinct symptoms of depression. Our findings provide new insights into the role of ACC sub-regions and DN in the pathophysiology of MDD.

Functional connectivity dysfunction of insular subdivisions in cognitive impairment after acute mild traumatic brain injury

Purpose

This study aimed to investigate the early functional connectivity alterations between insula subdivisions and other cortical regions in patients with acute mild traumatic brain injury (mTBI) and subsequently to explore the relationship between functional connectivity changes of insula subdivisions with other cortical regions and cognitive function.

Methods

Fifty-three mTBI patients and 37 age-, gender- and education level- matched healthy controls were included in this study. All participants obtained resting state functional magnetic resonance imaging (rs-fMRI) and clinical and neuropsychological evaluations (Montreal cognitive assessment, MoCA) at the acute stage. Functional connectivity alterations of insula subdivisions and correlations with MoCA were further explored by seed-voxel functional connectivity.

Results

Compared with healthy controls, patients with acute mTBI showed significantly decreased functional connectivity between the L-vAI and the left middle temporal gyrus and right superior frontal gyrus and significantly decreased functional connectivity between the R-vAI and the right middle frontal gyrus and right hippocampus. While significantly decreased functional connectivity were observed between the L-dAI and the right superior frontal gyrus. In addition, significantly increased functional connectivity was observed between the R-PI and the left inferior frontal gyrus. Furthermore, the mTBI group demonstrated positive correlations between performances in orientation and insula and middle temporal gyrus and superior frontal gyrus and middle frontal gyrus functional connectivities. Abstraction scores for mTBI patients positively correlated with functional connectivity between insula and middle frontal gyrus.

Conclusions

The present study demonstrated functional connectivity dysfunction of insula subdivisions and correlations between these alterations and cognitive performance, which provide a novel insight into the neurophysiological mechanism of cognitive impairment in patients with mTBI at the acute stage.

Differential functional connectivity of insular subdivisions in de novo Parkinson's disease with mild cognitive impairment

The insula, consisting of functionally diverse subdivisions, plays a significant role in Parkinson's disease (PD)-related cognitive disorders. However, the functional connectivity (FC) patterns of insular subdivisions in PD remain unclear. Our aim is to investigate the changes in FC patterns of insular subdivisions and their relationships with cognitive domains. Three groups of participants were recruited in this study, including PD patients with mild cognitive impairment (PD-MCI, n = 25), PD patients with normal cognition (PD-NC, n = 13), and healthy controls (HCs, n = 17). Resting-state functional magnetic resonance imaging (rs-fMRI) was used to investigate the FC in insular subdivisions of the three groups. Moreover, all participants underwent a neuropsychological battery to assess cognition so that the relationship between altered FC and cognitive performance could be elucidated. Compared with the PD-NC group, the PD-MCI group exhibited increased FC between the left dorsal anterior insular (dAI) and the right superior parietal gyrus (SPG), and altered FC was negatively correlated with memory and executive function. Compared with the HC group, the PD-MCI group showed significantly increased FC between the right dAI and the right median cingulate and paracingulate gyri (DCG), and altered FC was positively related to attention/working memory, visuospatial function, and language. Our findings highlighted the different abnormal FC patterns of insular subdivisions in PD patients with different cognitive abilities. Furthermore, dysfunction of the dAI may partly contribute to the decline in executive function and memory in early drug-naïve PD patients.

The Association Between Insular Subdivisions Functional Connectivity and Suicide Attempt in Adolescents and Young Adults with Major Depressive Disorder

Previous studies demonstrated the possible involvement of insula in suicide owing to depression. However, the function of insula in young depressed patients with suicide attempt (SA) remains to be revealed. This study aimed to explore the association between resting-state functional connectivity (FC) of insula and SA in young depressed patients. Fifty-eight adolescents and young adults with major depressive disorder, including 22 with a history of at least one SA (SA group) and 36 without a history of SA (NSA group) were scanned with a 3.0T functional magnetic resonance imaging system, and the resting-state functional magnetic resonance imaging data was extracted. Whole brain resting-state FC of insular subdivisions were compared between the two groups. Significantly increased FC of the left posterior insula with the orbital part of left inferior frontal gyrus, the right supplementary motor area and the bilateral paracentral lobule extending to the bilateral middle cingulate cortex was observed in the SA group compared with the NSA group. In addition, the orbital part of left superior frontal gyrus in the SA group exhibited significantly increased FC with the right posterior insula compared with the NSA group. However, no significant correlation was found between the insular subdivisions FC and different clinical variables in two groups. The present study highlighted the disruptions of the resting-state FC of the posterior insula with the orbitofrontal cortex and a series of motor cortices, and added incremental value to the knowledge of the neural mechanism underlying SA in young depressed patients.

Dysfunction of anterior insula in the non- affected hemisphere in patients with post- stroke depression: A resting-state fMRI study

BACKGROUND:

Post-stroke depression (PSD) is a consequential neuropsychiatric sequela that occurs after stroke. However, the pathophysiology of PSD are not well understood yet.

OBJECTIVE:

To explore alterations in functional connectivity (FC) between anterior insula and fronto-cortical and other subcortical regions in the non-affected hemisphere in patients with PSD compared to without PSD and healthy control.

METHODS:

Resting-state FC was estimated between the anterior insula and cortical and subcortical brain regions in the non-affected hemisphere in 13 patients with PSD, 12 patients without PSD, and 13 healthy controls. The severity of depressive mood was measured by the Beck Depression Inventory (BDI)-II.

RESULTS:

Patients with PSD showed significant differences in FC scores between the anterior insula and the superior frontal, middle frontal, and orbitofrontal gyrus in the non-affected hemisphere than healthy control or patients without PSD (P< 0.05). In post-hoc, patients with PSD showed higher FC scores between the anterior insula and the superior frontal region than patients without PSD (P< 0.05). Furthermore, alterations in FC of the superior frontal, middle frontal, and orbitofrontal gyrus were positively correlated with depression severity, as measured with the BDI-II (P< 0.001).

Altered Insular Subregional Connectivity Associated With Cognitions for Distinguishing the Spectrum of Pre-clinical Alzheimer's Disease

Background: Subjective cognitive decline (SCD) and amnestic mild cognitive impairment (aMCI) are regarded as part of the pre-clinical Alzheimer's disease (AD) spectrum. The insular subregional networks are thought to have diverse intrinsic connectivity patterns that are involved in cognitive and emotional processing. We set out to investigate convergent and divergent altered connectivity patterns of the insular subregions across the spectrum of pre-clinical AD and evaluated how well these patterns can differentiate the pre-clinical AD spectrum.

Method: Functional connectivity (FC) analyses in insular subnetworks were carried out among 38 patients with SCD, 56 patients with aMCI, and 55 normal controls (CNs). Logistic regression analyses were used to construct models for aMCI and CN, as well as SCD and CN classification. Finally, we conducted correlation analyses to measure the relationship between FCs of altered insular subnetworks and cognition.

Results: Patients with SCD presented with reduced FC in the bilateral cerebellum posterior lobe and increased FC in the medial frontal gyrus and the middle temporal gyrus. On the other hand, patients with aMCI largely presented with decreased FC in the bilateral inferior parietal lobule, the cerebellum posterior lobe, and the anterior cingulate cortex, as well as increased FC in the medial and inferior frontal gyrus, and the middle and superior temporal gyrus. Logistic regression analyses indicated that a model composed of FCs among altered insular subnetworks in patients with SCD was able to appropriately classify 83.9% of patients with SCD and CN, with an area under the receiver operating characteristic (ROC) curve (AUC) of 0.876, 81.6% sensitivity, and 81.8% specificity. A model consisting of altered insular subnetwork FCs in patients with aMCI was able to appropriately classify 86.5% of the patients with aMCI and CNs, with an AUC of 0.887, 80.4% sensitivity, and 83.6% specificity. Furthermore, some of the FCs among altered insular subnetworks were significantly correlated with episodic memory and executive function.

Conclusions: Patients with SCD and aMCI are likely to share similar convergent and divergent altered intrinsic FC patterns of insular subnetworks as the pre-clinical AD spectrum, and presented with abnormalities among subnetworks. Based on these abnormalities, individuals can be correctly differentiated in the pre-clinical AD spectrum. These results suggest that alterations in insular subnetworks can be utilized as a potential biomarker to aid in conducting a clinical diagnosis of the spectrum of pre-clinical AD.

Restoration of psychosocial functioning in remitted major depressive disorder patients: A 1-year longitudinal study

BACKGROUND

The recovery of psychosocial functioning is an important treatment goal for patients with depression. The aim of the present study is to investigate psychosocial functioning restoration 1 year after major depressive disorder (MDD) remission.

METHODS

Depression symptoms and psychosocial functioning were assessed in 167 remitted MDD patients at baseline, as well as 1, 2, 6, 9, and 12 months following remission, according to the Hamilton Depression Scale (HAMD-17) and Generic Quality of Life Inventory (GQOLI-74).

RESULTS

Of the 167 MDD patients, 85 completed the final evaluation at 1 year, 32 relapsed, and 50 dropped out. The total relapse rate over 1 year was 27%. A rapid increase in psychosocial functioning was found in the first 2 months after remission in the non-relapse group. In the non-relapse group, psychosocial functioning was higher at 2 months than at baseline. At baseline and 2 months, psychosocial functioning was lower in the relapse group patients compared to those in the non-relapse group.

CONCLUSIONS

Patients with MDD showed continuous improvement in psychosocial functioning during the first year after remission, though psychosocial functioning in the relapse group remained the same during the first two months, suggesting possible further relapse.

The concurrent disturbance of dynamic functional and structural brain connectome in major depressive disorder: the prefronto-insular pathway

BACKGROUND

Robust evidence has shown that abnormal function networks, particularly the salience network (SN), are observed in depressed patients. Although white matter structural connectivity may predict time-varying functional connectivity, including symptom phenotype, in psychiatric disorders, there is still a gap in elucidating the concurrent dynamic functional and structural connectivity profiles of the SN in depressed patients.

METHODS

We measured static and dynamic functional connectivity (FC) of the SN using resting-state fMRI BOLD time series in 76 subjects (21 with major depressive disorder (MDD), 27 with bipolar depression (BD), and 28 healthy controls (HC)). Hamilton Depression Scale total score was used to measure depression severity. Furthermore, we investigated the concurrent structural connectivity using diffusion kurtosis imaging (DKI)-based tractography.

RESULTS

Our findings suggested that in the presence of MDD, both structural and dynamic (but not static) FC were reduced in the SN, particularly affecting the left prefronto-insular pathways (L.aPFC-L.insula). MDD patients showed decreased connectivity variability within the SN compared with HC. The aberrant dynamic FC in the prefronto-insular pathways of the SN related to severity of depressive symptoms in MDD. Furthermore, compared with BD patients, those with MDD showed significantly decreased dynamic FC in the left prefronto-parietal system (L.aPFC-lateral parietal cortex).

LIMITATIONS

The generalizability of our findings is, to some extent, constrained by the small sample size.

CONCLUSIONS

The integrity of SN connectivity, particularly the prefronto-insular pathway, appears to be a crucial signature of MDD. The perturbed dynamic interaction of SN with prefrontal regions may underlie the clinical severity in depressed patients.

Effects of Serial Ketamine Infusions on Corticolimbic Functional Connectivity in Major Depression

BACKGROUND

Ketamine is a highly effective antidepressant for patients with treatment-resistant major depressive disorder (MDD). Resting-state functional magnetic resonance imaging studies show disruptions of functional connectivity (FC) between limbic regions and resting-state networks (RSNs) in MDD, including the default mode network, central executive network (CEN), and salience network (SN). Here, we investigated whether serial ketamine treatments change FC between limbic structures and RSNs.

METHODS

Patients with MDD (n = 44) were scanned at baseline (time 1 [T1]) and 24 hours after the first (T2) and fourth (T3) infusions of ketamine. Healthy control subjects (n = 50) were scanned at baseline, with a subgroup (n = 17) being rescanned at 2 weeks. Limbic regions included the amygdala and hippocampus, and RSNs included the default mode network, CEN, and SN.

RESULTS

Ketamine increased right amygdala FC to the right CEN (p = .05), decreased amygdala FC to the left CEN (p = .005) at T2 versus T1 (p = .015), which then increased at T3 versus T2 (p = .002), and decreased left amygdala FC to the SN (p = .016). Decreased left amygdala to SN FC at T2 predicted improvements in anxiety at T3 (p = .006). Ketamine increased right hippocampus FC to the left CEN (p = .001), and this change at T2 predicted decreased anhedonia at T3 (p = .005).

CONCLUSIONS

Ketamine modulates FC between limbic regions and RSNs implicated in MDD. Increases in FC between limbic regions and the CEN suggest that ketamine may be involved in restoring top-down control of emotion processing. FC decreases between the left amygdala and SN suggest that ketamine may ameliorate MDD-related dysconnectivity in these circuits. Early FC changes between limbic regions and RSNs may be predictive of clinical improvements.

Alterations in functional brain networks in depressed patients with a suicide attempt history

Suicide is a major challenge in public health and is strongly associated with major depressive disorder (MDD). Despite recent neuroimaging developments, the neural correlates of suicide behavior in patients with MDD remain unclear. Independent component analysis (ICA) for neuroimaging data allows the identification of functional brain networks without prior regions of interest and may help to identify neurobiological markers of specific disorders. Using ICA, we investigated the differences in resting-state brain networks in patients with MDD who had or did not have a history of suicide attempts and in healthy controls (HCs). Suicidal depressed (SD) patients, non-suicidal depressed (NSD) patients, and HCs significantly differed from each other in the pattern of connectivity of multiple functional networks, network synchronization, and functional network connectivity (FNC). The patient groups had a decreased network synchronization in the insular, cerebellum, basal ganglia, thalamus, operculum, frontoparietal cortices, and sensory cortices relative to the HCs. The decreased FNC between these networks (insular-default mode network and insular-cerebellum) was found in the SD group compared to the NSD and HC groups. These differences were not related to illness duration and medication status differences between SD and NSD. Furthermore, the degree of FNC in these networks was associated with the suicide ideation and stress level. Our results demonstrated that widespread but discrete network changes in brain networks and their interconnectivity was associated with suicide attempts in patients with MDD. Our results suggest that the neural basis underlying the psychopathology of attempted suicide in patients with MDD involves multiple brain networks and their interaction.

Hormone levels are related to functional compensation in prolactinomas: A resting-state fMRI study

Prolactinomas are tumors of the pituitary gland, which overproduces prolactin leading to dramatic fluctuations of endogenous hormone levels throughout the body. While it is not fully understood how endogenous hormone disorders affect a patient's brain, it is well known that fluctuating hormone levels can have negative neuropsychological effects. Using resting-state functional magnetic resonance imaging (rs-fMRI), we investigated whole-brain functional connectivity (FC) and its relationship with hormone levels in prolactinomas. By performing seed-based FC analyses, we compared FC metrics between 33 prolactinoma patients and 31 healthy controls matched for age, sex, and hand dominance. We then carried out a partial correlation analysis to examine the relationship between FC metrics and hormone levels. Compared to healthy controls, prolactinoma patients showed significantly increased thalamocortical and cerebellar-cerebral FC. Endogenous hormone levels were also positively correlated with increased FC metrics, and these hormone-FC relationships exhibited sex differences in prolactinoma patients. Our study is the first to reveal altered FC patterns in prolactinomas and to quantify the hormone-FC relationships. These results indicate the importance of endogenous hormones on functional compensation of the brain in patients with prolactinomas.

Affective Modulation after High-Intensity Exercise Is Associated with Prolonged Amygdalar-Insular Functional Connectivity Increase

Acute moderate exercise has been shown to induce prolonged changes in functional connectivity (FC) within affect and reward networks. The influence of different exercise intensities on FC has not yet been explored. Twenty-five male athletes underwent 30 min of “low”- (35% < lactate threshold (LT)) and “high”- (20% > LT) intensity exercise bouts on a treadmill. Resting-state fMRI was acquired at 3 Tesla before and after exercise, together with the Positive and Negative Affect Scale (PANAS). Data of 22 subjects (3 dropouts) were analyzed using the FSL feat pipeline and a seed-to-network-based analysis with the bilateral amygdala as the seed region for determining associated FC changes in the “emotional brain.” Data were analyzed using a repeated measures ANOVA. Comparisons between pre- and post-exercise were analyzed using a one-sample t-test, and a paired t-test was used for the comparison between “low” and “high” exercise conditions (nonparametric randomization approach, results reported at p < 0.05). Both exercise interventions induced significant increases in the PANAS positive affect scale. There was a significant interaction effect of amygdalar FC to the right anterior insula, and this amygdalar-insular FC correlated significantly with the PANAS positive affect scale (r = 0.47, p = 0.048) in the “high”-intensity exercise condition. Our findings suggest that mood changes after exercise are associated with prolonged alterations in amygdalar-insular FC and occur in an exercise intensity-dependent manner.

Disruption of resting-state functional connectivity of right posterior insula in adolescents and young adults with major depressive disorder

BACKGROUND

The neural basis of Major Depressive Disorder (MDD) which is a clinical syndrome characterized by emotional and cognitive impairments is poorly understood. Accumulating evidence has suggested that the insula is an important substrate underlying the mechanism of MDD. This study aimed to examine the disrupted resting-state brain regional function in insula and to further investigate the associated resting-state functional connectivity (rs-FC) of insula underlie the MDD in adolescents and young adults.

METHODS

We employed 3.0T resting-state functional magnetic resonance imaging (rs-fMRI) to acquire data from 76 adolescents and young adults with MDD and 44 age and sex matched healthy control subjects. We employed a regional Amplitude of Low-Frequency Fluctuation (ALFF) analysis to explore local intrinsic neural oscillation alterations in insula and an ALFF-based functional connectivity (FC) approach to detect the potential changes in remote connectivity with insula in adolescents and young adults with MDD.

RESULTS

By applying ALFF analysis, significantly decreased activities were detected in bilateral insula, and in particular in right anterior insular gyrus (MNI; ROI1: 42, 24, -3), right posterior insular gyrus (Montreal Neurological Institute, MNI; ROI2: 36, -9, 15) and left anterior insular gyrus (MNI; ROI3: -36, 12, 9) in patients with MDD compared to the healthy controls (p < 0.05, 1000 permutations, TFCE corrected). With ROI2 as the seed in the subsequent ALFF-based rs-FC analysis, patients with MDD were observed to have significantly reduced FC with bilateral middle occipital gyrus, lingual gyrus, calcarine, postcentral gyrus, precentral gyrus, supramarginal area, superior temporal gyrus and middle cingulate gyrus as compared to the healthy controls (p < 0.05, 1000 permutations, TFCE corrected). No significant differences of FC were detected between the patients and healthy controls when using ROI1 and ROI3 as the seeds. We found no correlations between ALFF or rs-FC values and the severity of depression as estimated by Hamilton Depression Rating Scale (HAM-D).

LIMITATIONS

Clinical information were limited and no significant correlations were found between imaging variables and HAM-D scores, which reduces the power to interpret the present findings. A cross-sectional design was employed in this study so that it is not possible to know whether the abnormal ALFF or altered brain FC of insula reflects a state or trait effect in young people with MDD.

CONCLUSIONS

This study highlights the regional/network interaction abnormalities of insula in adolescents and young adults with MDD, and could provide further insight into understanding the neural pathomechanism of MDD in young patients.

Social anxiety, posterior insula activation, and autonomic response during self-initiated action in a Cyberball game

BACKGROUND

An earlier study characterized the neural correlates of self-initiated actions in a Cyberball game in healthy individuals. It remains unclear how social anxiety may influence these neural processes.

METHODS

We examined regional activations to self-initiated actions in 25 adults with low and 25 with high social anxiety (LA and HA, respectively). Skin conductance was recorded concurrently with fMRI. We followed published routines in the analyses of imaging and skin conductance data.

RESULTS

We hypothesized that HA as compared to LA individuals would demonstrate increased cortical limbic activations during self-initiated actions (tossing or T > receiving or R trials, to control for motor activities) in social exclusion (EX) vs. fair game (FG) scenario. At a corrected threshold, HA as compared with LA group showed increases in bilateral posterior insula activation during T vs. R trials in EX as compared to FG. Further, HA as compared to LA showed higher skin conductance response to tossing trials during EX as compared to FG.

LIMITATIONS

With a limited sample size, we did not examine potential sex effects. Further, we cannot rule out the effects of depression on the findings.

CONCLUSIONS

Together, the results suggest that individuals with more severe social anxiety engaged the somatosensory insula to a greater extent and exhibited higher physiological arousal when initiating ball toss during social exclusion in the Cyberball game. Posterior insula response to self-initiated action may represent a biomarker of social anxiety. It remains to be investigated whether interventions to decrease physiological arousal may alleviate social anxiety.

Frequency-Dependent Spatial Distribution of Functional Hubs in the Human Brain and Alterations in Major Depressive Disorder

Alterations in large-scale brain intrinsic functional connectivity (FC), i.e., coherence between fluctuations of ongoing activity, have been implicated in major depressive disorder (MDD). Yet, little is known about the frequency-dependent alterations of FC in MDD. We calculated frequency specific degree centrality (DC) – a measure of overall FC of a brain region – within 10 distinct frequency sub-bands accessible from the full range of resting-state fMRI BOLD fluctuations (i.e., 0.01–0.25 Hz) in 24 healthy controls and 24 MDD patients. In healthy controls, results reveal a frequency-specific spatial distribution of highly connected brain regions – i.e., hubs – which play a fundamental role in information integration in the brain. MDD patients exhibited significant deviations from the healthy DC patterns, with decreased overall connectedness of widespread regions, in a frequency-specific manner. Decreased DC in MDD patients was observed predominantly in the occipital cortex at low frequencies (0.01–0.1 Hz), in the middle cingulate cortex, sensorimotor cortex, lateral parietal cortex, and the precuneus at middle frequencies (0.1–0.175 Hz), and in the anterior cingulate cortex at high frequencies (0.175–0.25 Hz). Additionally, decreased DC of distinct parts of the insula was observed across low, middle, and high frequency bands. Frequency-specific alterations in the DC of the temporal, insular, and lateral parietal cortices correlated with symptom severity. Importantly, our results indicate that frequency-resolved analysis within the full range of frequencies accessible from the BOLD signal – also including higher frequencies (>0.1 Hz) – reveals unique information about brain organization and its changes, which can otherwise be overlooked.

Regional cerebral metabolism alterations affect resting-state functional connectivity in major depressive disorder

Background

¹⁸F-FDG positron emission tomography (PET) is a reliable technique to quantify regional neural glucose metabolism even with major depressive disorder (MDD) heterogeneous features. Previous study proposed that in the resting-state (RS), pairs of brain regions whose regional glucose metabolic rates were significantly correlated were functionally associated. This synchronicity indicates a neuronal metabolic and functional interaction in high energy efficient brain regions. In this study, a multimode method was used to identify the RS-FC patterns based on regional metabolism changes, and to observe its relationship with the severity of depressive symptoms in MDD patients.

Methods

The study enrolled 11 medication-naive MDD patients and 14 healthy subjects. All participants received a static ¹⁸F-FDG PET brain scan and a resting-state functional magnetic resonance imaging (RS-fMRI) scan. SPM5 software was used to compare brain metabolism in MDD patients with that in healthy controls, and designated regions with a change in metabolism as regions of interest (ROIs). The glucose metabolism-based regional RS-FC Z values were compared between groups. Then group independent component analysis (ICA) was used to identify the abnormal connectivity nodes in the intrinsic function networks. Finally, the correlation between abnormal RS-FC Z values and the severity of depressive symptoms was evaluated.

Results

Patients with MDD had reduced glucose metabolism in the putamen, claustrum, insular, inferior frontal gyrus, and supramarginal gyrus. The metabolic reduction regions impaired functional connectivity (FC) to key hubs, such as the Inferior frontal gyrus (pars triangular), angular gyrus, calcarine sulcus, middle frontal gyrus (MFG), located in dorsolateral prefrontal cortex (DLPFC)/parietal lobe, salience network (SN), primary visual cortex (V1), and language network respectively. There was no correlation between aberrant connectivity and the severity of clinical symptoms.

Conclusions

This research puts forward a possibility that focal neural activity alteration may share RS-FC dysfunction and be susceptible to hubs in the functional network in MDD. In particular, the metabolism and function profiles of the Inferior frontal gyrus (pars triangularis) should be emphasized in future MDD studies.

Aberrant Dynamic Functional Network Connectivity and Graph Properties in Major Depressive Disorder

Major depressive disorder (MDD) is a complex mood disorder characterized by persistent and overwhelming depression. Previous studies have identified abnormalities in large scale functional brain networks in MDD, yet most of them were based on static functional connectivity. In contrast, here we explored disrupted topological organization of dynamic functional network connectivity (dFNC) in MDD based on graph theory. One hundred and eighty-two MDD patients and 218 healthy controls were included in this study, all Chinese Han people. By applying group information guided independent component analysis (GIG-ICA) to resting-state functional magnetic resonance imaging (fMRI) data, the dFNCs of each subject were estimated using a sliding window method and k-means clustering. Network properties including global efficiency, local efficiency, node strength and harmonic centrality, were calculated for each subject. Five dynamic functional states were identified, three of which demonstrated significant group differences in their percentage of state occurrence. Interestingly, MDD patients spent much more time in a weakly-connected State 2, which includes regions previously associated with self-focused thinking, a representative feature of depression. In addition, the FNCs in MDD were connected differently in different states, especially among prefrontal, sensorimotor, and cerebellum networks. MDD patients exhibited significantly reduced harmonic centrality primarily involving parietal lobule, lingual gyrus and thalamus. Moreover, three dFNCs with disrupted node properties were commonly identified in different states, and also correlated with depressive symptom severity and cognitive performance. This study is the first attempt to investigate the dynamic functional abnormalities in MDD in a Chinese population using a relatively large sample size, which provides new evidence on aberrant time-varying brain activity and its network disruptions in MDD, which might underscore the impaired cognitive functions in this mental disorder.