Voxel-based morphometry study of the insular cortex in bipolar depression

Brain structural and functional alterations related to anxiety in allergic asthma

Psychiatric disorders are common in patients with allergic asthma, and they can have a significant impact on their quality of life and disease control. Recent studies have suggested that there may be potential immune-brain communication mechanisms in asthma, which can activate inflammatory responses in different brain areas, leading to structural and functional alterations and behavioral changes. However, the precise mechanisms underlying these alterations remain unclear. In this paper, we comprehensively review the relevant research on asthma-induced brain structural and functional alterations that lead to the initiation and promotion of anxiety. We summarize the possible pathways for peripheral inflammation to affect the brain's structure and function. Our review highlights the importance of addressing neuropsychiatric disorders in the clinical guidelines of asthma, to improve the quality of life of these patients. We suggest that a better understanding of the mechanisms underlying psychiatric comorbidities in asthma could lead to the development of more effective treatments for these patients.

Altered striatal functional connectivity and structural dysconnectivity in individuals with bipolar disorder: A resting state magnetic resonance imaging study

OBJECTIVE

Bipolar disorder (BD) is a mood swing illness characterized by episodes ranging from depressive lows to manic highs. Although the specific origin of BD is unknown, genetics, environment, and changes in brain structure and chemistry may all have a role. Through magnetic resonance imaging (MRI) evaluations, this study looked into functional abnormalities involving the striatum between BD group and healthy controls (HC), compared the whole-brain gray matter (GM) morphological patterns between the groups and see whether functional connectivity has its underlying structural basis.

MATERIALS AND METHODS

We applied sliding windows to functional magnetic resonance imaging (fMRI) data from 49 BD patients and 44 HCs to generate temporal correlations maps to determine strength and variability of the striatum-to-whole-brain-network functional connectivity (FC) in each window whilst also employing voxel-based morphometry (VBM) to high-resolution structural MRI data to uncover structural differences between the groups.

RESULTS

Our analyses revealed increased striatal connectivity in three consecutive windows 69, 70, and 71 (180, 182, and 184 s) in individuals with BD (p < 0.05; Bonferroni corrected) in fMRI images. Moreover, the VBM findings of structural images showed gray matter (GM) deficits in the left precentral gyrus and middle frontal gyrus of the BD patients (p = 0.001, uncorrected) when compared to HCs. Variability of striatal connectivity did not reveal significant differences between the groups.

CONCLUSION

These findings revealed that BD was associated with a weakening of the precentral gyrus and middle frontal gyrus, also implying that bipolar illness may be linked to striatal functional brain alterations.

Age-dependent brain morphometry in Major Depressive disorder

BACKGROUND

Major depressive disorder (MDD) is a complex disorder that affects nearly 264 million people worldwide. Structural brain abnormalities in multiple neuroanatomical networks have been implicated in the etiology of MDD, but the degree to which MDD affects brain structure during early to late adulthood is unclear.

METHODS

We examined morphometry of brain regions commonly implicated in MDD, including the amygdala, hippocampus, anterior cingulate gyrus, lateral orbitofrontal gyrus, subgenual cortex, and insular cortex subregions, from early to late adulthood. Harmonized measures for gray matter (GM) volume and cortical thickness of each region were estimated cross-sectionally for 305 healthy controls (CTLs) and 247 individuals with MDD (MDDs), collated from four research cohorts. We modeled the nonlinear associations of age with GM volume and cortical thickness using generalized additive modeling and tested for age-dependent group differences.

RESULTS

Overall, all investigated regions exhibited smaller GM volume and thinner cortical measures with increasing age. Compared to age matched CTLs, MDDs had thicker cortices and greater GM volume from early adulthood until early middle age (average 35 years), but thinner cortices and smaller GM volume during and after middle age in the lateral orbital gyrus and all insular subregions. Deviations of the MDD and CTL models for both GM volume and cortical thickness in these regions started as early as age 18.

CONCLUSIONS

The analyses revealed that brain morphometry differences between MDDs and CTLs are dependent on age and brain region. The significant age-by-group interactions in the lateral orbital frontal gyrus and insular subregions make these regions potential targets for future longitudinal studies of MDD.

Insula activity in resting-state differentiates bipolar from unipolar depression: a systematic review and meta-analysis

Symptomatic overlap of depressive episodes in bipolar disorder (BD) and major depressive disorder (MDD) is a major diagnostic and therapeutic problem. Mania in medical history remains the only reliable distinguishing marker which is problematic given that episodes of depression compared to episodes of mania are more frequent and predominantly present at the beginning of BD. Resting-state functional magnetic resonance imaging (rs-fMRI) is a non-invasive, task-free, and well-tolerated method that may provide diagnostic markers acquired from spontaneous neural activity. Previous rs-fMRI studies focused on differentiating BD from MDD depression were inconsistent in their findings due to low sample power, heterogeneity of compared samples, and diversity of analytical methods. This meta-analysis investigated resting-state activity differences in BD and MDD depression using activation likelihood estimation. PubMed, Web of Science, Scopus and Google Scholar databases were searched for whole-brain rs-fMRI studies which compared MDD and BD currently depressed patients between Jan 2000 and August 2020. Ten studies were included, representing 234 BD and 296 MDD patients. The meta-analysis found increased activity in the left insula and adjacent area in MDD compared to BD. The finding suggests that the insula is involved in neural activity patterns during resting-state that can be potentially used as a biomarker differentiating both disorders.

Bipolar Mood State Reflected in Functional Connectivity of the Hate Circuit: A Resting-State Functional Magnetic Resonance Imaging Study

BACKGROUND

Previous studies suggested bipolar disorder caused an aberrant alteration in the insular, putamen, and left superior frontal gyrus, which are the main components of the hate circuit. However, the relationship between the hate circuit and the pathophysiologic substrate underlying different phases of bipolar disorder remain unclear. In this study, we aimed to identify group differences of resting-state functional connectivity within the hate circuit in healthy controls (HCs) and bipolar patients in different mood states.

METHODS

Resting-state functional magnetic resonance imaging of the brain were acquired from 54 HCs and 81 patients with bipolar disorder including 20 with bipolar mania (BM), 35 with bipolar depression (BD), and 26 with bipolar euthymia (BE). We selected bilateral insula (L.INS and R.INS), bilateral putamen (L.PUT and R.PUT), and left superior frontal gyrus (L.SFGd) as seed regions, and conducted the seed-based functional connectivity analysis to identify group differences of connectivity strength within the hate circuit. Spearman correlations were performed to evaluate the relationship between the hate circuit and manic/depressive symptoms.

RESULTS

Significant group differences of connectivity strength within the hate circuit were found in links of the R.INS-L.SFGd, R.PUT-L.SFGd, and L.INS- R.PUT after false discovery rate was corrected. The BM group showed an opposite hate circuit pattern to BD, BE, and HCs. The BD group showed decreased hate circuit connectivity in the L.INS-R.PUT compared with the BE group. No significant difference was detected among BD, BE, and HCs. Furthermore, functional connectivity of the R.INS-L.SFGd and R.PUT-L.SFGd were positively correlated with manic symptoms, while the L.INS- R.PUT was negatively correlated with depressive symptoms.

CONCLUSIONS

Our preliminary findings suggest that altered functional connectivity of the hate circuit in different mood phases may be related to state markers and underpin the neuropathological basis of bipolar disorder.

Structural imaging biomarkers for bipolar disorder: Meta-analyses of whole-brain voxel-based morphometry studies

BACKGROUND

Bipolar disorder (BD) is a common and destructive psychiatric illness worldwide. Although it is known that BD is associated with morphological abnormalities of the brain, the regions implicated in BD remain unclear. Therefore, we aimed to update current knowledge on potential structural imaging biomarkers of BD.

METHODS

Studies published up to January 31, 2018, were identified by a comprehensive literature search of PubMed, EBSCO, and BrainMap voxel-based morphometry (VBM) database. Whole-brain VBM studies that examined gray matter (GM) abnormalities of group comparisons between BD and healthy controls (HC) and reported results as coordinates in a standard reference space were included. Different meta-analyses were performed by activation likelihood estimation (ALE) algorithm.

RESULTS

A total of 46 studies with 56 experiments, including 1720 subjects and 268 foci were included. Seven different meta-analyses were calculated separately across experiments reporting decreased or increased GM volume among BD, BDΙ, BD-adults, and BD-youths groups. Fifteen regions of significantly different GM volume between four groups and HC were identified. There were extensive GM deficits in the prefrontal and temporal cortex, and enlargements in the putamen, cingulate cortex, and precuneus.

CONCLUSIONS

The results revealed that the thinning of prefrontal cortex was a key region in the pathophysiology of BD. The enlargement of the cingulate cortex may be implicated in a compensatory mechanism. It underscored important differences between BD-adults and BD-youths and specific biomarkers of three subgroups.

Transdiagnostic and diagnosis-specific dynamic functional connectivity anchored in the right anterior insula in major depressive disorder and bipolar depression

Dysfunctional and abnormal functional connectivity in the right anterior insula (rAI) may underlie the pathophysiology of depression episode in bipolar disorder (BD) and of major depressive disorder (MDD). In this study, we examined the dynamic functional connectivity (dFC) of the rAI of 30 patients with BD, 30 patients with MDD, and 30 healthy controls. In the functional separation of rAI, the right dorsal AI (rdAI) and ventral AI (rvAI) were defined as seed regions. Sliding-window correlation of rAI subregions was implemented to measure the variance of dFC. BD and MDD shared abnormality in dFC, such as the decreased dFC between the rvAI and right ventrolateral prefrontal cortex. Others were disorder-specific and included MDD-related increases in dFC between the rvAI and right precuneus, temporal pole, and left dorsolateral prefrontal cortex. This observation is in stark contrast to BD-related increases in the dFC between the rdAI and left inferior parietal lobule and right middle occipital gyrus. The abnormal dFC of rAI shared by BD and MDD supports the importance of rAI in the common pathophysiology of these disorders. Meanwhile, disorder-specific abnormalities that attribute to the dorsal and ventral divisions of rAI can be used as biomarkers to differentiate BD from MDD.

Abnormal Resting-State Functional Connectivity of Insular Subregions and Disrupted Correlation with Working Memory in Adults with Attention Deficit/Hyperactivity Disorder

OBJECTIVES

Executive function (EF) deficits are major impairments in adults with attention deficit/hyperactivity disorder (ADHD). Previous studies have shown that the insula is involved in cognitive and EFs. However, the insula is highly heterogeneous in function, and few studies have focused on functional networks which related to specific insular subregions in adults with ADHD. We explored the functional networks of the insular subregions [anterior insula (AI), mid-insula (MI), and posterior insula (PI)]. Furthermore, their correlations with self-ratings of ecological EFs, including inhibition, shifting, and working memory were investigated.

METHODS

Resting-state functional magnetic resonance imaging data in 28 adults with ADHD and 30 matched healthy controls (HCs) were analyzed. The seed-based resting-state functional connectivity (RSFC) of the insular subregions was evaluated. We also investigated their associations with the Behavior Rating Inventory of Executive Function-Adult Version (BRIEF-A) inhibition, working memory, and shifting factor scores.

RESULTS

Compared with HCs, adults with ADHD showed altered RSFC of the AI, with the precuneus, precentral gyrus, and inferior temporal gyrus extended to the middle temporal gyrus, lingual gyrus, and superior occipital gyrus, respectively. There were no significant differences in RSFC of the MI and PI between the two groups. Within the HC group, working memory scores were associated with the RSFC of AI with precuneus and temporal gyrus. However, there was no correlation between these variables in the ADHD group.

CONCLUSION

The study evaluated RSFC patterns of the insular subregions in adults with ADHD for the first time. Altered RSFC of the AI which is a crucial region of salience network (SN) and part of regions in default mode network (DMN), were detected in adults with ADHD in both results with and without global signal regression (GSR), suggesting that disrupted SN-DMN functional connectivity may be involved in EF impairments in adults with ADHD, especially with respect to working memory. Deficits of the AI which is involved in salient stimuli allocation, might be associated with the pathophysiology of ADHD. The inconsistent results of MI and PI between analyses with and without GSR need further exploration.

Altered intrinsic regional brain activity in female asthmatics with or without depressive symptoms: A resting-state functional magnetic resonance imaging study

BACKGROUND

Previous studies have suggested that asthma patients are more susceptible to anxiety or depression and have more specifically elevated depressive symptomology. These psychological factors are associated with anatomical brain changes. However, little is known about alterations in spontaneous brain activity in asthma patients with depressive symptoms. Here we hypothesized that asthma patients exhibit an altered regional spontaneous brain activity, which may contribute to their increased susceptibility to depression and poor perception of asthma symptoms. The purpose of this study was to examine spontaneous brain activity in female asthma patients using resting-state functional magnetic resonance imaging (rs-fMRI).

METHODS

Eleven asthmatics without depressive symptoms (ASs), 14 asthmatics with depressive symptoms (ADs), and 15 age- and education-matched healthy controls (HCs) completed rs-fMRI. The regional homogeneity (ReHo) value was calculated based on rs-fMRI to assess local signal synchrony strength and compared among the groups. Correlation analyses were conducted between both ReHo values and clinical parameters.

RESULT

Compared with HCs, ASs showed a significantly increased ReHo in the right insula; whereas ADs showed a significantly decreased ReHo in the right insula, which positively correlated with nocturnal symptom score in the Asthma Control Test (r = 0.562, P = 0.036). No significant correlation was observed between the total ACT scores and right insula activities (r = 0.263, P = 0.364).

CONCLUSION

Decreased ReHo in the right insula may play an important role in depressive symptoms and abnormal asthma symptom perception.