Grey matter differences in bipolar disorder: a meta-analysis of voxel-based morphometry studies

Psychedelic Drugs in Mental Disorders: Current Clinical Scope and Deep Learning-Based Advanced Perspectives

Mental disorders are a representative type of brain disorder, including anxiety, major depressive depression (MDD), and autism spectrum disorder (ASD), that are caused by multiple etiologies, including genetic heterogeneity, epigenetic dysregulation, and aberrant morphological and biochemical conditions. Psychedelic drugs such as psilocybin and lysergic acid diethylamide (LSD) have been renewed as fascinating treatment options and have gradually demonstrated potential therapeutic effects in mental disorders. However, the multifaceted conditions of psychiatric disorders resulting from individuality, complex genetic interplay, and intricate neural circuits impact the systemic pharmacology of psychedelics, which disturbs the integration of mechanisms that may result in dissimilar medicinal efficiency. The precise prescription of psychedelic drugs remains unclear, and advanced approaches are needed to optimize drug development. Here, recent studies demonstrating the diverse pharmacological effects of psychedelics in mental disorders are reviewed, and emerging perspectives on structural function, the microbiota-gut-brain axis, and the transcriptome are discussed. Moreover, the applicability of deep learning is highlighted for the development of drugs on the basis of big data. These approaches may provide insight into pharmacological mechanisms and interindividual factors to enhance drug discovery and development for advanced precision medicine.

Associations of alcohol and tobacco use with psychotic, depressive and developmental disorders revealed via multimodal neuroimaging

People affected by psychotic, depressive and developmental disorders are at a higher risk for alcohol and tobacco use. However, the further associations between alcohol/tobacco use and symptoms/cognition in these disorders remain unexplored. We identified multimodal brain networks involving alcohol use (n = 707) and tobacco use (n = 281) via supervised multimodal fusion and evaluated if these networks affected symptoms and cognition in people with psychotic (schizophrenia/schizoaffective disorder/bipolar, n = 178/134/143), depressive (major depressive disorder, n = 260) and developmental (autism spectrum disorder/attention deficit hyperactivity disorder, n = 421/346) disorders. Alcohol and tobacco use scores were used as references to guide functional and structural imaging fusion to identify alcohol/tobacco use associated multimodal patterns. Correlation analyses between the extracted brain features and symptoms or cognition were performed to evaluate the relationships between alcohol/tobacco use with symptoms/cognition in 6 psychiatric disorders. Results showed that (1) the default mode network (DMN) and salience network (SN) were associated with alcohol use, whereas the DMN and fronto-limbic network (FLN) were associated with tobacco use; (2) the DMN and fronto-basal ganglia (FBG) related to alcohol/tobacco use were correlated with symptom and cognition in psychosis; (3) the middle temporal cortex related to alcohol/tobacco use was associated with cognition in depression; (4) the DMN related to alcohol/tobacco use was related to symptom, whereas the SN and limbic system (LB) were related to cognition in developmental disorders. In summary, alcohol and tobacco use were associated with structural and functional abnormalities in DMN, SN and FLN and had significant associations with cognition and symptoms in psychotic, depressive and developmental disorders likely via different brain networks. Further understanding of these relationships may assist clinicians in the development of future approaches to improve symptoms and cognition among psychotic, depressive and developmental disorders.

Right ventrolateral and left dorsolateral 10 Hz transcranial magnetic stimulation as an add-on treatment for bipolar I and II depression: a double-blind, randomised, three-arm, sham-controlled study

OBJECTIVES

Despite the clinical importance of bipolar depression (BDE), effective treatment options are still limited. Transcranial magnetic stimulation (rTMS) has proven of moderate efficacy in major depression, but the evidence remains inconclusive for BDE.

METHODS

A 4-week, double-blind, randomised, parallel-group, sham-controlled study (trial ID ISRCTN77188420) explored the benefits of 10 Hz MRI-guided right ventrolateral (RVL) rTMS and left dorsolateral (LDL) rTMS as add-on treatments for BDE. Outcome measures included changes in the Montgomery-Åsberg Depression Rating Scale (MADRS) score, self-assessment, response and remission rates, and side effects.

RESULTS

Sixty patients were randomly assigned to study groups, and forty-six completed the double-blind phase. The mean change from baseline to Week 4 in MADRS was greater in both active groups compared to the sham, yet differences did not achieve significance (RVL vs sham: -4.50, 95%CI -10.63 to 1.64, p = 0.3; LDL vs sham: -4.07, 95%CI -10.24 to 2.10, p = 0.4). None of the other outcome measures yielded significant results.

CONCLUSIONS

While not demonstrating the superiority of either 10 Hz rTMS over sham, with the limited sample size, we can not rule out a moderate yet clinically meaningful effect. Further well-powered studies are essential to elucidate the role of rTMS in managing BDE.

Frequency and imaging correlates of neuropsychiatric symptoms in Progressive Supranuclear Palsy

Neuropsychiatric symptoms are intrinsic to Progressive Supranuclear Palsy (PSP) and a spoonful of studies investigated their imaging correlates. Describe (I) the frequency and severity of neuropsychiatric symptoms in PSP and (II) their structural imaging correlates. Twenty-six PSP patients underwent Neuropsychiatric Inventory (NPI) and brain 3D T1-weighted MRI. Spearman's rho with Bonferroni correction was used to investigate correlations between NPI scores and volumes of gray matter regions. More than 80% of patients presented at least one behavioral symptom of any severity. The most frequent and severe were depression/dysphoria, apathy, and irritability/lability. Significant relationships were found between the severity of irritability and right pars opercularis volume (p < 0.001) as well as between the frequency of agitation/aggression and left lateral occipital volume (p < 0.001). Depression, apathy, and irritability are the most common neuropsychiatric symptoms in PSP. Moreover, we found a relationship between specific positive symptoms as irritability and agitation/aggression and greater volume of the right pars opercularis cortex and lower volume of the left occipital cortex, respectively, which deserve further investigations.

The Risk for Schizophrenia-Bipolar Spectrum: Does the Apple Fall Close to the Tree? A Narrative Review

Schizophrenia (SCZ) and bipolar disorder (BD) are severe psychiatric disorders that share clinical features and several risk genes. Important information about their genetic underpinnings arises from intermediate phenotypes (IPs), quantifiable biological traits that are more prevalent in unaffected relatives (RELs) of patients compared to the general population and co-segregate with the disorders. Within IPs, neuropsychological functions and neuroimaging measures have the potential to provide useful insight into the pathophysiology of SCZ and BD. In this context, the present narrative review provides a comprehensive overview of the available evidence on deficits in neuropsychological functions and neuroimaging alterations in unaffected relatives of SCZ (SCZ-RELs) and BD (BD-RELs). Overall, deficits in cognitive functions including intelligence, memory, attention, executive functions, and social cognition could be considered IPs for SCZ. Although the picture for cognitive alterations in BD-RELs is less defined, BD-RELs seem to present worse performances compared to controls in executive functioning, including adaptable thinking, planning, self-monitoring, self-control, and working memory. Among neuroimaging markers, SCZ-RELs appear to be characterized by structural and functional alterations in the cortico-striatal-thalamic network, while BD risk seems to be associated with abnormalities in the prefrontal, temporal, thalamic, and limbic regions. In conclusion, SCZ-RELs and BD-RELs present a pattern of cognitive and neuroimaging alterations that lie between patients and healthy individuals. Similar abnormalities in SCZ-RELs and BD-RELs may be the phenotypic expression of the shared genetic mechanisms underlying both disorders, while the specificities in neuropsychological and neuroimaging profiles may be associated with the differential symptom expression in the two disorders.

Mania-related effects on structural brain changes in bipolar disorder - a narrative review of the evidence

Cross-sectional neuroimaging studies show that bipolar disorder is associated with structural brain abnormalities, predominantly observed in prefrontal and temporal cortex, cingulate gyrus, and subcortical regions. However, longitudinal studies are needed to elucidate whether these abnormalities presage disease onset or are consequences of disease processes, and to identify potential contributing factors. Here, we narratively review and summarize longitudinal structural magnetic resonance imaging studies that relate imaging outcomes to manic episodes. First, we conclude that longitudinal brain imaging studies suggest an association of bipolar disorder with aberrant brain changes, including both deviant decreases and increases in morphometric measures. Second, we conclude that manic episodes have been related to accelerated cortical volume and thickness decreases, with the most consistent findings occurring in prefrontal brain areas. Importantly, evidence also suggests that in contrast to healthy controls, who in general show age-related cortical decline, brain metrics remain stable or increase during euthymic periods in bipolar disorder patients, potentially reflecting structural recovering mechanisms. The findings stress the importance of preventing manic episodes. We further propose a model of prefrontal cortical trajectories in relation to the occurrence of manic episodes. Finally, we discuss potential mechanisms at play, remaining limitations, and future directions.

Predominant polarity as a neurobiological specifier in bipolar disorder: Evidence from a multimodal neuroimaging study

BACKGROUND

While predominant (PP) and onset polarity (OP) have considerable clinical and treatment implications in bipolar disorder (BD), the neurobiological underpinnings of PP and OP from a radiological perspective remain largely unknown. The main objective of this study is to investigate the neuroanatomical profile of polarity subphenotypes (PP and OP) in euthymic BD patients, using a standardized multimodal neuroimaging protocol to evaluate regional gray matter (GM) volumes, cortical thickness, as well as white matter (WM) integrity of major projection, commissural and association tracts.

METHODS

Forty-two euthymic BD patients stratified for PP and OP and 42 healthy controls (HC) were included in this computational neuroimaging study to comprehensively characterize gray and white matter alterations. Univariate analyses of covariance (ANCOVAs) were conducted with Bonferroni corrections for each MRI modality and Cohen's d effect sizes were calculated for group comparisons.

RESULTS

Phenotype-associated cortical thickness abnormalities and volumetric alterations were identified, but no WM changes ascertained. Specifically, we found a main effect of OP on GM volume of left middle frontal gyrus and of OP and PP (either or both) on cortical thickness of various regions previously implicated in BD, i.e. inferior frontal gyrus-pars opercularis (left) and pars orbitalis (bilateral), left lateral orbitofrontal gyrus, bilateral medial segment of the superior frontal gyrus, left planum polare, right anterior cingulate gyrus, left anterior and posterior insula, bilateral frontal operculum (both OP and PP); left anterior and posterior orbitofrontal gyrus, left transverse temporal gyrus, right posterior insula (only OP); and right medial frontal cortex (only PP). Based on the magnitude of differences on pairwise comparisons, we found a large effect of OP on cortical thickness in a single region (left anterior orbitofrontal gyrus) (OP-M > OP-D), while PP subgroups showed large or medium effect size differences in cortical thickness (PP-M > PP-D) in a wider array of regions (right medial frontal cortex, left frontal operculum, left inferior frontal gyrus-pars opercularis, bilateral medial segment of the superior frontal gyrus). For most regions, PP-D patients showed the greatest decreases in cortical thickness compared to HC while PP-M showed the smallest, with PP-U showing an "unspecified" pattern mostly lying in-between PP-D and PP-M.

CONCLUSIONS

Our multimodal imaging findings suggest specific polarity BD subgroups with compromised cortical thickness; we recorded a greater impact of PP on brain structure compared to OP, which provides additional evidence that PP can be considered as a neurobiological specifier in BD.

Why lithium should be used in patients with bipolar disorder? A scoping review and an expert opinion paper

INTRODUCTION

Lithium treatment is considered the gold standard for the long-term management of bipolar disorder and recurrent unipolar depression. It is also extremely effective in other psychiatric conditions characterized by impulsivity and aggression, and for the prevention of suicidal behaviours.

AREAS COVERED

This paper provides a scoping review and an expert commentary regarding the use of lithium in adult patients. Available information about efficacy, tolerability, dosing, and switching is analyzed, and the strategies that may be most useful in real-world clinical settings are highlighted.

EXPERT OPINION

Lithium is effective on different domains of bipolar disorder, including the long-term prevention of recurrences of affective episodes, management of acute mania as well as in the prophylaxis of all affective episodes. Lithium has been defined a 'forgotten drug,' since its use in routine clinical practice has been declined over the last 20 or 30 years. Reasons for this trend include lack of adequate training on the management of lithium side effects. Considering its efficacy, use of lithium in ordinary clinical practice should be promoted. Several strategies, such as using slow-release formulations, can be easily implemented in order to minimize lithium side effects and improve its tolerability profile.

Correlations between peripheral levels of inflammatory mediators and frontolimbic structures in bipolar disorder: an exploratory analysis

BACKGROUND

Altered peripheral immune/inflammatory system and brain volumetric changes have been implicated in the pathophysiology of bipolar disorder (BD). This study aimed to evaluate how peripheral levels of cytokines are related to volumetric brain changes in euthymic patients with BD.

METHODS

Euthymic patients with BD (n = 21) and healthy controls (n = 22) were enrolled in this exploratory study. Blood samples were collected on the same day of clinical assessment and neuroimaging. Cytokines were measured through cytometric bead array method. Neuroimaging data were acquired using a sagittal three-dimensional magnetic resonance imaging T1-weighted fast field echo sequence and was processed using FreeSurfer.

RESULTS

Compared to controls, BD patients had significantly lower volumes in the cingulate, medial-orbitofrontal (MOF) and parahippocampal regions. We found a negative correlation between right MOF volume and interferon-gamma levels (β = -0.431, P = .049) and a positive correlation between interleukin-10 levels and left posterior cingulate volume (β = 0.457, P = .048).

CONCLUSION

Our results support the involvement of inflammatory pathways in structural brain changes in BD.

Functional and structural brain differences in bipolar disorder: a multimodal meta-analysis of neuroimaging studies

BACKGROUND

Numerous studies of resting-state functional imaging and voxel-based morphometry (VBM) have revealed differences in specific brain regions of patients with bipolar disorder (BD), but the results have been inconsistent.

METHODS

A whole-brain voxel-wise meta-analysis was conducted on resting-state functional imaging and VBM studies that compared differences between patients with BD and healthy controls using Seed-based d Mapping with Permutation of Subject Images software.

RESULTS

A systematic literature search identified 51 functional imaging studies (1842 BD and 2190 controls) and 83 VBM studies (2790 BD and 3690 controls). Overall, patients with BD displayed increased resting-state functional activity in the left middle frontal gyrus, right inferior frontal gyrus (IFG) extending to the right insula, right superior frontal gyrus and bilateral striatum, as well as decreased resting-state functional activity in the left middle temporal gyrus extending to the left superior temporal gyrus and post-central gyrus, left cerebellum, and bilateral precuneus. The meta-analysis of VBM showed that patients with BD displayed decreased VBM in the right IFG extending to the right insula, temporal pole and superior temporal gyrus, left superior temporal gyrus extending to the left insula, temporal pole, and IFG, anterior cingulate cortex, left superior frontal gyrus (medial prefrontal cortex), left thalamus, and right fusiform gyrus.

CONCLUSIONS

The multimodal meta-analyses suggested that BD showed similar patterns of aberrant brain activity and structure in the insula extending to the temporal cortex, fronto-striatal-thalamic, and default-mode network regions, which provide useful insights for understanding the underlying pathophysiology of BD.

Neural correlates of N-back task performance and proposal for corresponding neuromodulation targets in psychiatric and neurodevelopmental disorders

AIM

Working memory (WM) deficit represents the most common cognitive impairment in psychiatric and neurodevelopmental disorders, making the identification of its neural substrates a crucial step towards the conceptualization of restorative interventions. We present a meta-analysis focusing on neural activations associated with the most commonly used task to measure WM, the N-back task, in patients with schizophrenia, depressive disorder, bipolar disorder, and attention-deficit/hyperactivity disorder. Showing qualitative similarities and differences in WM processing between patients and healthy controls, we propose possible targets for cognitive enhancement approaches.

METHODS

Selected studies, following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines, were analyzed through the activation likelihood estimate statistical framework, with subsequent generation of disorder-specific N-back activation maps.

RESULTS

Despite similar WM deficits shared across all disorders, results highlighted different brain activation patterns for each disorder compared with healthy controls. In general, results showed brain activity in frontal, parietal, subcortical, and cerebellar regions; however, reduced engagement of specific nodes of the fronto-parietal network emerged in patients compared with healthy controls. In particular, neither bipolar nor depressive disorders showed detectable activations in the dorsolateral prefrontal cortices, while their parietal activation patterns were lateralized to the left and right hemispheres, respectively. On the other hand, patients with attention-deficit/hyperactivity disorder showed a lack of activation in the left parietal lobe, whereas patients with schizophrenia showed lower activity over the left prefrontal cortex.

CONCLUSION

These results, together with biophysical modeling, were then used to discuss the design of future disorder-specific cognitive enhancement interventions based on noninvasive brain stimulation.

Decreased cortical gyrification in patients with bipolar disorder

BACKGROUND

An aberrant neural connectivity has been known to be associated with bipolar disorder (BD). Local gyrification may reflect the early neural development of cortical connectivity and has been studied as a possible endophenotype of psychiatric disorders. This study aimed to investigate differences in the local gyrification index (LGI) in each cortical region between patients with BD and healthy controls (HCs).

METHODS

LGI values, as measured using FreeSurfer software, were compared between 61 patients with BD and 183 HCs. The values were also compared between patients with BD type I and type II as a sub-group analysis. Furthermore, we evaluated whether there was a correlation between LGI values and illness duration or depressive symptom severity in patients with BD.

RESULTS

Patients with BD showed significant hypogyria in various cortical regions, including the left inferior frontal gyrus (pars opercularis), precentral gyrus, postcentral gyrus, superior temporal cortex, insula, right entorhinal cortex, and both transverse temporal cortices, compared to HCs after the Bonferroni correction (p < 0.05/66, 0.000758). LGI was not associated with clinical factors such as illness duration, depressive symptom severity, and lithium treatment. No significant differences in cortical gyrification according to the BD subtype were found.

CONCLUSIONS

BD appears to be characterized by a significant regionally localized hypogyria, in various cortical areas. This abnormality may be a structural and developmental endophenotype marking the risk for BD, and it might help to clarify the etiology of BD.

Neuroimaging Studies of Brain Structure in Older Adults with Bipolar Disorder: A Review

Bipolar disorder (BD) is a common mood disorder that can have severe consequences during later life, including suffering and impairment due to mood and cognitive symptoms, elevated risk for dementia and an especially high risk for suicide. Greater understanding of the brain circuitry differences involved in older adults with BD (OABD) in later life and their relationship to aging processes is required to improve outcomes of OABD. The current literature on gray and white matter findings, from high resolution structural and diffusion-weighted magnetic resonance imaging (MRI) studies, has shown that BD in younger age groups is associated with gray matter reductions within cortical and subcortical brain regions that subserve emotion processing and regulation, as well as reduced structural integrity of white matter tracts connecting these brain regions. While fewer neuroimaging studies have focused on OABD, it does appear that many of the structural brain differences found in younger samples are present in OABD. There is also initial suggestion that there are additional brain differences, for at least a subset of OABD, that may result from more pronounced gray and white matter declines with age that may contribute to adverse outcomes. Preclinical and clinical data supporting neuro-plastic and -protective effects of mood-stabilizing medications, suggest that treatments may reverse and/or prevent the progression of brain changes thereby reducing symptoms. Future neuroimaging research implementing longitudinal designs, and large-scale, multi-site initiatives with detailed clinical and treatment data, holds promise for reducing suffering, cognitive dysfunction and suicide in OABD.

Lithium increases cortical and subcortical volumes in subjects with bipolar disorder

Bipolar disorder (BD) is a highly variable and burdensome disease for patients and caregivers. A BD diagnosis almost triples the likelihood of developing dementia as the disease progresses. Neurocognitive reserve appears to be one of the most important influences on lifelong functional outcomes and quality of life in BD. Though several prior studies have assessed the effects of lithium on regional gray and white matter volumes in this population, representative cohorts are typically middle-aged, have a more severe pathology, and are not as commonly assessed in the depressive phase (which represents the majority of most patients' lifespans outside of remission). Here we have shown that positive adaptations with lithium can be observed throughout the brain after only six weeks of monotherapy at low-therapeutic serum levels. Importantly, these results remove some confounders seen in prior studies (patients were treatment free at time of enrollment and mostly treatment naïve). This cohort also includes underrepresented demographics in the literature (young adult patients, mostly bipolar II, and exclusively in the depressed phase). These findings bolster the extensive body of evidence in support of long-term lithium therapy in BD, furthering the possibility of its expanded use to wider demographics.

Peripheral inflammatory markers associated with brain volume reduction in patients with bipolar I disorder

BACKGROUND

Neuroinflammation and brain structural abnormalities are found in bipolar disorder (BD). Elevated levels of cytokines and chemokines have been detected in the serum and cerebrospinal fluid of patients with BD. This study investigated the association between peripheral inflammatory markers and brain subregion volumes in BD patients.

METHODS

Euthymic patients with bipolar I disorder (BD-I) aged 20-45 years underwent whole-brain magnetic resonance imaging. Plasma levels of monocyte chemoattractant protein-1 (MCP-1), chitinase-3-like protein 1 (also known as YKL-40), fractalkine (FKN), soluble tumour necrosis factor receptor-1 (sTNF-R1), interleukin-1β, and transforming growth factor-β1 were measured on the day of neuroimaging. Clinical data were obtained from medical records and interviewing patients and reliable others.

RESULTS

We recruited 31 patients with a mean age of 29.5 years. In multivariate regression analysis, plasma level YKL-40, a chemokine, was the most common inflammatory marker among these measurements displaying significantly negative association with the volume of various brain subareas across the frontal, temporal, and parietal lobes. Higher YKL-40 and sTNF-R1 levels were both significantly associated with lower volumes of the left anterior cingulum, left frontal lobe, right superior temporal gyrus, and supramarginal gyrus. A greater number of total lifetime mood episodes were also associated with smaller volumes of the right caudate nucleus and bilateral frontal lobes.

CONCLUSIONS

The volume of brain regions known to be relevant to BD-I may be diminished in relation to higher plasma level of YKL-40, sTNF-R1, and more lifetime mood episodes. Macrophage and macrophage-like cells may be involved in brain volume reduction among BD-I patients.

Cell-type-specific genes associated with cortical structural abnormalities in pediatric bipolar disorder

Background

Pediatric bipolar disorder (PBD) has been proven to be related to abnormal brain structural connectivity, but how the abnormalities in PBD correlate with gene expression is debated.

Objective

This study aims at identification of cell-type-specific gene modules based on cortical structural differences in PBD.

Methods

Morphometric similarity networks (MSN) were computed as a marker of interareal cortical connectivity based on MRI data from 102 participants (59 patients and 43 controls). Partial least squares (PLS) regression was used to calculate MSN differences related to transcriptomic data in AHBA. The biological processes and cortical cell types associated with this gene expression profile were determined by gene enrichment tools.

Results

MSN analysis results demonstrated differences of cortical structure between individuals diagnosed with PBD and healthy control participants. MSN differences were spatially correlated with the PBD-related weighted genes. The weighted genes were enriched for "trans-synaptic signaling" and "regulation of ion transport", and showed significant specific expression in excitatory and inhibitory neurons.

Conclusions

This study identified the genes that contributed to structural network aberrations in PBD. It was found that transcriptional changes of excitatory and inhibitory neurons might be associated with abnormal brain structural connectivity in PBD.

Rethinking "aggression" and impulsivity in bipolar disorder: Risk, clinical and brain circuitry features

BACKGROUND

Elevated aggression and impulsivity are implicated in Bipolar Disorder (BD); however, relationships between these behavioral constructs have not been clarified, which can lead to misconceptions with negative consequences including stigma and adverse outcomes including suicide. The study aimed to clarify brain-based distinctions between the two constructs and their associations to risk factors, symptoms and suicide thoughts and behaviors.

METHODS

Self-rated Brown-Goodwin Aggression (BGA) and Barratt Impulsiveness Scale (BIS) scores were compared between adults with BD (n = 38, 74% female) and healthy controls (HC, n = 29, 64% female). Relationships were examined between BGA and BIS with childhood trauma questionnaire (CTQ), mood, comorbidities, and magnetic resonance imaging gray matter volume (GMV) assessments.

RESULTS

In BD, BGA and BIS total scores were both elevated and associated with childhood maltreatment (CM), particularly emotional CM, depression, substance use disorders (SUDs) and suicide attempts (SAs). BGA scores were increased by items corresponding to dysregulation of emotional and social behavior and associated with elevated mood states and suicide ideation and GMV decreases in bilateral orbitofrontal cortex and left posterior insula brain regions, previously associated with these behaviors and clinical features. BIS motor impulsiveness scores were associated with GMV decreases in anterior cingulate cortex implicated in mood and behavioral dyscontrol.

LIMITATIONS

modest sample size, self-reports CONCLUSIONS: The findings suggest separable brain-based domains of dysfunction in BD of motor impulsiveness versus emotionally dysregulated feelings that are primarily self-directed. Both domains are associated with suicide behavior and modifiable risk factors of CM, depression and SUDs that could be targeted for prevention.

Serum levels of olanzapine are associated with acute cognitive effects in bipolar disorder

Bipolar (BPD) patients have deficits in cognition, but there are still controversies about the effects of some medications on their cognitive performance. Here, we investigated the relationship between cognition in terms of executive functions, memory, and attention in both first-episode medication-naive BPD patients and BPD patients taking olanzapine. Forty-one healthy controls, 40 unmedicated drug-naive BPD patients, and 34 BPD patients who took only olanzapine were recruited for the study. Cognitive performance was assessed using the Flanker test, Stroop test, and Corsi-block test. Bayesian multivariate regression analysis was run considering maximum robustness to avoid bias and to predict the outcomes. Our results revealed that unmedicated medication-naive BPD patients performed worse than healthy controls and the olanzapine group in some tasks. Additionally, BPD patients who took olanzapine had better cognitive performance than healthy controls and unmedicated BPD patients. The acute cognitive effects were predicted by olanzapine dosage and serum levels (i.e., large effects). The potential pro-cognitive effects of olanzapine in BPD patients should be carefully interpreted by considering various other clinical variables. We expect that our findings will contribute to further research in this area, with the goal of helping other researchers, patients, and the population.

Longitudinal Structural Brain Changes in Bipolar Disorder: A Multicenter Neuroimaging Study of 1232 Individuals by the ENIGMA Bipolar Disorder Working Group

BACKGROUND

Bipolar disorder (BD) is associated with cortical and subcortical structural brain abnormalities. It is unclear whether such alterations progressively change over time, and how this is related to the number of mood episodes. To address this question, we analyzed a large and diverse international sample with longitudinal magnetic resonance imaging (MRI) and clinical data to examine structural brain changes over time in BD.

METHODS

Longitudinal structural MRI and clinical data from the ENIGMA (Enhancing Neuro Imaging Genetics through Meta Analysis) BD Working Group, including 307 patients with BD and 925 healthy control subjects, were collected from 14 sites worldwide. Male and female participants, aged 40 ± 17 years, underwent MRI at 2 time points. Cortical thickness, surface area, and subcortical volumes were estimated using FreeSurfer. Annualized change rates for each imaging phenotype were compared between patients with BD and healthy control subjects. Within patients, we related brain change rates to the number of mood episodes between time points and tested for effects of demographic and clinical variables.

RESULTS

Compared with healthy control subjects, patients with BD showed faster enlargement of ventricular volumes and slower thinning of the fusiform and parahippocampal cortex (0.18 <d < 0.22). More (hypo)manic episodes were associated with faster cortical thinning, primarily in the prefrontal cortex.

CONCLUSIONS

In the hitherto largest longitudinal MRI study on BD, we did not detect accelerated cortical thinning but noted faster ventricular enlargements in BD. However, abnormal frontocortical thinning was observed in association with frequent manic episodes. Our study yields insights into disease progression in BD and highlights the importance of mania prevention in BD treatment.

Cortical thickness abnormalities in patients with bipolar disorder: A systematic review and meta-analysis

BACKGROUND

An increasing number of neuroimaging studies report alterations of cortical thickness (CT) related to the neuropathology of bipolar disorder (BD). We provide here a whole-brain vertex-wise meta-analysis, which may help improve the spatial precision of these identifications.

METHODS

A comprehensive meta-analysis was performed to investigate the differences in CT between patients with BD and healthy controls (HCs) by using a newly developed mask for CT analysis in seed-based d mapping (SDM) meta-analytic software. We used meta-regression to explore the effects of demographics and clinical characteristics on CT. This meta-review was conducted in accordance with PRISMA guideline.

RESULTS

We identified 21 studies meeting criteria for the systematic review, of which 11 were eligible for meta-analysis. The meta-analysis comprising 649 BD patients and 818 HCs showed significant cortical thinning in the left insula extending to left Rolandic operculum and Heschl gyrus, the orbital part of left inferior frontal gyrus (IFG), the medial part of left superior frontal gyrus (SFG) as well as bilateral anterior cingulate cortex (ACC) in BD. In meta-regression analyses, mean patient age was negatively correlated with reduced CT in the left insula.

LIMITATIONS

All enrolled studies were cross-sectional; we could not explore the potential effects of medication and mood states due to the limited data.

CONCLUSIONS

Our results suggest that BD patients have significantly thinner frontoinsular cortex than HCs, and the results may be helpful in revealing specific neuroimaging biomarkers of BD patients.

Common and specific patterns of functional and structural brain alterations in schizophrenia and bipolar disorder: a multimodal voxel-based meta-analysis

BACKGROUND

Schizophrenia and bipolar disorder have been linked to alterations in the functional activity and grey matter volume of some brain areas, reflected in impaired regional homogeneity and aberrant voxel-based morphometry. However, because of variable findings and methods used across studies, identifying patterns of brain alteration in schizophrenia and bipolar disorder has been difficult.

METHODS

We conducted a meta-analysis of differences in regional homogeneity and voxel-based morphometry between patients and healthy controls for schizophrenia and bipolar disorder separately, using seed-based d mapping.

RESULTS

We included 45 publications on regional homogeneity (26 in schizophrenia and 19 in bipolar disorder) and 190 publications on voxel-based morphometry (120 in schizophrenia and 70 in bipolar disorder). Patients with schizophrenia showed increased regional homogeneity in the frontal cortex and striatum and the supplementary motor area; they showed decreased regional homogeneity in the insula, primary sensory cortex (visual and auditory cortices) and sensorimotor cortex. Patients with bipolar disorder showed increased regional homogeneity in the frontal cortex and striatum; they showed decreased regional homogeneity in the insula. Patients with schizophrenia showed decreased grey matter volume in the superior temporal gyrus, inferior frontal gyrus, cingulate cortex and cerebellum. Patients with bipolar disorder showed decreased grey matter volume in the insula, cingulate cortex, frontal cortex and thalamus. Overlap analysis showed that patients with schizophrenia displayed decreased regional homogeneity and grey matter volume in the left insula and left superior temporal gyrus; patients with bipolar disorder displayed decreased regional homogeneity and grey matter volume in the left insula.

LIMITATIONS

The small sample size for our subgroup analysis (unmedicated versus medicated patients and substantial heterogeneity in the results for some regions could limit the interpretability and generalizability of the results.

CONCLUSION

Patients with schizophrenia and bipolar disorder shared a common pattern of regional functional and structural alterations in the insula and frontal cortex. Patients with schizophrenia showed more widespread functional and structural impairment, most prominently in the primary sensory motor areas.

Shared and distinct changes in local dynamic functional connectivity patterns in major depressive and bipolar depressive disorders

BACKGROUND

Distinguishing bipolar depressive disorder (BDD) from major depressive disorder (MDD) solely relying on clinical clues is a challenge. Evidence in neuroimaging have revealed potential neurological markers for the differential diagnosis.

METHODS

We aimed to characterize common and specific alterations in the dynamic local functional connectivity pattern in BDD and MDD by using the dynamic regional phase synchrony (DRePS), a newly developed method for assessing intrinsic dynamic local functional connectivity. A total of 98 patients with MDD and 56 patients with BDD patients, and 97 age-, gender-, and education-matched healthy controls (HC) were included and underwent the resting-state functional magnetic resonance imaging.

RESULTS

Compared with HC, patients with two disorders shared decreased DRePS value in the bilateral orbitofrontal cortex (OFC) extends to insula, the right insula extends to hippocampus, the left hippocampus, the right inferior frontal gyrus (IFG), the left thalamus extends to caudate, the right caudate, the bilateral superior frontal gyrus (SFG), and the right medial frontal gyrus (MFG). Furthermore, patients with MDD exhibited specific decreased DRePS value in the left caudate. Moreover, voxel signals in these regions during the support vector machine analysis contributed to the classification of the two diagnoses.

CONCLUSIONS

Our findings provided new insight into the neural mechanism of patients with MDD and BDD and could potentially inform the diagnosis and the treatment of this disease.

Obesity and Cerebral Blood Flow in the Reward Circuitry of Youth With Bipolar Disorder

BACKGROUND

Bipolar disorder (BD) is associated with elevated body mass index (BMI) and increased rates of obesity. Obesity among individuals with BD is associated with more severe course of illness. Motivated by previous research on BD and BMI in youth as well as brain findings in the reward circuit, the current study investigates differences in cerebral blood flow (CBF) in youth BD with and without comorbid overweight/obesity (OW/OB).

METHODS

Participants consisted of youth, ages 13-20 years, including BD with OW/OB (BDOW/OB; n = 25), BD with normal weight (BDNW; n = 55), and normal-weight healthy controls (HC; n = 61). High-resolution T1-weighted and pseudo-continuous arterial spin labeling images were acquired using 3 Tesla magnetic resonance imaging. CBF differences were assessed using both region of interest and whole-brain voxel-wise approaches.

RESULTS

Voxel-wise analysis revealed significantly higher CBF in reward-associated regions in the BDNW group relative to the HC and BDOW/OB groups. CBF did not differ between the HC and BDOW/OB groups. There were no significant region of interest findings.

CONCLUSIONS

The current study identified distinct CBF levels relating to BMI in BD in the reward circuit, which may relate to underlying differences in cerebral metabolism, compensatory effects, and/or BD severity. Future neuroimaging studies are warranted to examine for changes in the CBF-OW/OB link over time and in relation to treatment.

Functional neuroanatomy of mania

Mania, the diagnostic hallmark of bipolar disorder, is an episodic disturbance of mood, sleep, behavior, and perception. Improved understanding of the neurobiology of mania is expected to allow for novel avenues to address current challenges in its diagnosis and treatment. Previous research focusing on the impairment of functional neuronal circuits and brain networks has resulted in heterogenous findings, possibly due to a focus on bipolar disorder and its several phases, rather than on the unique context of mania. Here we present a comprehensive overview of the evidence regarding the functional neuroanatomy of mania. Our interpretation of the best available evidence is consistent with a convergent model of lateralized circuit dysfunction in mania, with hypoactivity of the ventral prefrontal cortex in the right hemisphere, and hyperactivity of the amygdala, basal ganglia, and anterior cingulate cortex in the left hemisphere of the brain. Clarification of dysfunctional neuroanatomic substrates of mania may contribute not only to improve understanding of the neurobiology of bipolar disorder overall, but also highlights potential avenues for new circuit-based therapeutic approaches in the treatment of mania.

Focusing on Comorbidity-A Novel Meta-Analytic Approach and Protocol to Disentangle the Specific Neuroanatomy of Co-occurring Mental Disorders

BACKGROUND

In mental health, comorbidities are the norm rather than the exception. However, current meta-analytic methods for summarizing the neural correlates of mental disorders do not consider comorbidities, reducing them to a source of noise and bias rather than benefitting from their valuable information.

OBJECTIVES

We describe and validate a novel neuroimaging meta-analytic approach that focuses on comorbidities. In addition, we present the protocol for a meta-analysis of all major mental disorders and their comorbidities.

METHODS

The novel approach consists of a modification of Seed-based d Mapping-with Permutation of Subject Images (SDM-PSI) in which the linear models have no intercept. As in previous SDM meta-analyses, the dependent variable is the brain anatomical difference between patients and controls in a voxel. However, there is no primary disorder, and the independent variables are the percentages of patients with each disorder and each pair of potentially comorbid disorders. We use simulations to validate and provide an example of this novel approach, which correctly disentangled the abnormalities associated with each disorder and comorbidity. We then describe a protocol for conducting the new meta-analysis of all major mental disorders and their comorbidities. Specifically, we will include all voxel-based morphometry (VBM) studies of mental disorders for which a meta-analysis has already been published, including at least 10 studies. We will use the novel approach to analyze all included studies in two separate single linear models, one for children/adolescents and one for adults.

DISCUSSION

The novel approach is a valid method to focus on comorbidities. The meta-analysis will yield a comprehensive atlas of the neuroanatomy of all major mental disorders and their comorbidities, which we hope might help develop potential diagnostic and therapeutic tools.

OUP accepted manuscript

Genetic variants in the human leukocyte antigen and killer cell immunoglobulin-like receptor regions have been associated with many brain-related diseases, but how they shape brain structure and function remains unclear. To identify the genetic variants in HLA and KIR genes associated with human brain phenotypes, we performed a genetic association study of ∼30 000 European unrelated individuals using brain MRI phenotypes generated by the UK Biobank (UKB). We identified 15 HLA alleles in HLA class I and class II genes significantly associated with at least one brain MRI-based phenotypes (P < 5 × 10⁻⁸). These associations converged on several main haplotypes within the HLA. In particular, the human leukocyte antigen alleles within an ancestral haplotype 8.1 were associated with multiple MRI measures, including grey matter volume, cortical thickness (TH) and diffusion MRI (dMRI) metrics. These alleles have been strongly associated with schizophrenia. Additionally, associations were identified between HLA-DRB1*04∼DQA1*03:01∼DQB1*03:02 and isotropic volume fraction of diffusion MRI in multiple white matter tracts. This haplotype has been reported to be associated with Parkinson’s disease. These findings suggest shared genetic associations between brain MRI biomarkers and brain-related diseases. Additionally, we identified 169 associations between the complement component 4 (C4) gene and imaging phenotypes. We found that C4 gene copy number was associated with cortical TH and dMRI metrics. No KIR gene copy numbers were associated with image-derived phenotypes at genome-wide threshold. To address the multiple testing burden in the phenome-wide association study, we performed a multi-trait association analysis using trait-based association test that uses extended Simes procedure and identified MRI image-specific associations. This study contributes to insight into how critical immune genes affect brain-related traits as well as the development of neurological and neuropsychiatric disorders.

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.

Changing the Cortical Conductor's Tempo: Neuromodulation of the Claustrum

The claustrum is a thin sheet of neurons that is densely connected to many cortical regions and has been implicated in numerous high-order brain functions. Such brain functions arise from brain states that are influenced by neuromodulatory pathways from the cholinergic basal forebrain, dopaminergic substantia nigra and ventral tegmental area, and serotonergic raphe. Recent revelations that the claustrum receives dense input from these structures have inspired investigation of state-dependent control of the claustrum. Here, we review neuromodulation in the claustrum-from anatomical connectivity to behavioral manipulations-to inform future analyses of claustral function.

Lithium prevents grey matter atrophy in patients with bipolar disorder: an international multicenter study

BACKGROUND

Lithium (Li) is the gold standard treatment for bipolar disorder (BD). However, its mechanisms of action remain unknown but include neurotrophic effects. We here investigated the influence of Li on cortical and local grey matter (GM) volumes in a large international sample of patients with BD and healthy controls (HC).

METHODS

We analyzed high-resolution T1-weighted structural magnetic resonance imaging scans of 271 patients with BD type I (120 undergoing Li) and 316 HC. Cortical and local GM volumes were compared using voxel-wise approaches with voxel-based morphometry and SIENAX using FSL. We used multiple linear regression models to test the influence of Li on cortical and local GM volumes, taking into account potential confounding factors such as a history of alcohol misuse.

RESULTS

Patients taking Li had greater cortical GM volume than patients without. Patients undergoing Li had greater regional GM volumes in the right middle frontal gyrus, the right anterior cingulate gyrus, and the left fusiform gyrus in comparison with patients not taking Li.

CONCLUSIONS

Our results in a large multicentric sample support the hypothesis that Li could exert neurotrophic and neuroprotective effects limiting pathological GM atrophy in key brain regions associated with BD.

Clinical and neuroimaging correlates of cardiorespiratory fitness in adolescents with bipolar disorder

INTRODUCTION

Cardiovascular disease (CVD) is exceedingly prevalent, and occurs prematurely in individuals with bipolar disorder (BD). Cardiorespiratory fitness (CRF), arguably the most important modifiable CVD risk factor, is also associated with brain structure and function. There is a gap in knowledge regarding CRF in BD, particularly in relation to brain structure.

METHODS

Adolescents with BD (n = 54) and healthy controls (HC; n = 53) completed semi-structured diagnostic interviews, self-report questionnaires, and 20 minutes of cardiorespiratory exercise at 60-80% of estimated maximum heart rate (HR) on a bicycle ergometer. Average power (watts/kg) within this HR range served as a previously validated proxy for CRF. Brain magnetic resonance imaging (MRI) structural analysis was done using FreeSurfer. Analyses controlled for age and sex.

RESULTS

CRF was significantly lower in BD vs HC (0.91 ± 0.32 vs 1.01 ± 0.30, p = 0.03, F = 4.66, df=1, η² =0.04). Within BD, greater depression symptoms were associated with lower CRF (P = .02), and greater physical activity (PA) was associated with greater CRF (P < .001). In multivariable analyses, there were significant main effects of diagnosis (HC>BD; P = .03) and sex (M > F; P < .001) on power. Significant predictors of power within BD included male sex (P = .02) and PA (P = .002) but not depression symptoms (P = .29). Significant diagnosis by CRF interaction effects was found in frontal, parietal, and occipital cortical regions.

CONCLUSION

CRF was reduced among adolescents with BD, particularly women, related in part to depression symptoms and inactivity and was differentially associated with regional brain structure. Studies seeking to improve CRF as a means of reducing psychiatric symptoms of BD are warranted.

Cerebral glucose metabolism in bipolar disorder: A voxel-based meta-analysis of positron emission tomography studies

BACKGROUND

Previous positron emission tomography studies have reported the changes of cerebral glucose metabolism in bipolar disorder. However, the findings across studies remain controversial, containing differing results.

METHODS

A systematic literature search of the PubMed, Embase, Cochrane Library, and Web of Science databases was conducted. We conducted a voxel-wide meta-analysis of cerebral glucose metabolism studies, using the seed-based mapping approach, in patients with bipolar disorder (BD).

RESULTS

We identified 7 studies suitable for inclusion, which included a total of 126 individuals with BD and 160 healthy controls. The most consistent and robust findings were an increase in cerebral glucose metabolism in the right precentral gyrus and a decrease in the left superior temporal gyrus, left middle temporal gyrus, and cerebellum. Additionally, the sex distribution and illness duration had significant moderating effects on cerebral glucose metabolism alterations.

CONCLUSIONS

Cerebral glucose metabolism alterations in these brain regions are likely to reflect the disease-related functional abnormalities such as emotion and cognition. These findings contribute to a better understanding of the neurobiological underpinnings of bipolar disorder.

LIMITATIONS

This study was done at a study level and cannot be addressed at the patient level. Subgroup analysis of BD I and BD II is not possible due to limited literature data.

Out of control: An altered parieto-occipital-cerebellar network for impulsivity in bipolar disorder

Bipolar disorder is an affective disorder characterized by rapid fluctuations in mood ranging from episodes of depression to mania, as well as by increased impulsivity. Previous studies investigated the neural substrates of bipolar disorder mainly using univariate methods, with a particular focus on the neural circuitry underlying emotion regulation difficulties. In the present study, capitalizing on an innovative whole-brain multivariate method to structural analysis known as Source-based Morphometry, we investigated the neural substrates of bipolar disorder and their relation with impulsivity, assessed with both self-report measures and performance-based tasks. Structural images from 46 patients with diagnosis of bipolar disorder and 60 healthy controls were analysed. Compared to healthy controls, patients showed decreased gray matter concentration in a parietal-occipital-cerebellar network. Notably, the lower the gray matter concentration in this circuit, the higher the self-reported impulsivity. In conclusion, we provided new evidence of an altered brain network in bipolar disorder patients related to their abnormal impulsivity. Taken together, these findings extend our understanding of the neural and symptomatic characterization of bipolar disorder.

Preservation of Gray Matter Volume in Early Stage of Bipolar Disorder: A Case for Early Intervention: Préservation du volume de matière grise au stade précoce du trouble bipolaire: un cas pour intervention précoce

OBJECTIVE

It has been proposed that different stages of the bipolar disorder might have distinct neurobiological changes. However, the evidence for this has not been consistent, as the studies in early stages of the illness are limited by small sample sizes. The purpose of this study was to investigate the gray matter volume changes in bipolar patients who recently recovered from their first episode of mania (FEM).

METHODS

Using a whole-brain voxel-based analysis, we compared the regional gray matter volumes of 61 bipolar patients who have recovered from their FEM in the past 3 months with 43 age- and gender-matched healthy participants. We also performed a series of subgroup analyses to determine the effects of hospitalization during the FEM, history of depressive episodes, and exposure to lithium.

RESULTS

No statistically significant difference was found between gray matter volumes of FEM patients and healthy participants, even at a more liberal threshold (P < 0.001, uncorrected for multiple comparisons). Voxel-based subgroup analyses did not reveal significant gray matter differences except for a trend toward decreased gray matter volume in left lateral occipital cortex (P < 0.001, uncorrected) in patients with a previous history of depression.

CONCLUSION

This study represents the largest structural neuroimaging investigation of FEM published to date. Early stage of bipolar disorder was not found to be associated with significant gray matter volume changes. Our findings suggest that there might be a window of opportunity for early intervention strategies to prevent or delay neuroprogression in bipolar disorder.

Genetic variants in the bipolar disorder risk locus SYNE1 that affect CPG2 expression and protein function

Bipolar disorder (BD) is a common mood disorder characterized by recurrent episodes of mania and depression. Both genetic and environmental factors have been implicated in BD etiology, but the biological underpinnings remain elusive. Recently, genome-wide association studies (GWAS) of neuropsychiatric disorders have identified a risk locus for BD containing the SYNE1 gene, a large gene encoding multiple proteins. The BD association signal spans, almost exclusively, the part of SYNE1 encoding CPG2, a brain-specific protein localized to excitatory postsynaptic sites, where it regulates glutamate receptor internalization. Here we show that CPG2 protein levels are significantly decreased in postmortem brain tissue from BD patients, as compared to control subjects, as well as schizophrenia and depression patients. We identify genetic variants within the postmortem brains that map to the CPG2 promoter region, and show that they negatively affect gene expression. We also identify missense single nucleotide polymorphisms (SNPs) in CPG2 coding regions that affect CPG2 expression, localization, and synaptic function. Our findings link genetic variation in the CPG2 region of SYNE1 with a mechanism for glutamatergic synapse dysfunction that could underlie susceptibility to BD in some individuals. Few GWAS hits in human genetics for neuropsychiatric disorders to date have afforded such mechanistic clues. Further, the potential for genetic distinction of susceptibility to BD from other neuropsychiatric disorders with overlapping clinical traits holds promise for improved diagnostics and treatment of this devastating illness.

Specific Gray Matter Volume Changes of the Brain in Unipolar and Bipolar Depression

To identify the common and specific structural basis of bipolar depression (BD) and unipolar depression (UD) is crucial for clinical diagnosis. In this study, a total of 85 participants, including 22 BD patients, 36 UD patients, and 27 healthy controls, were enrolled. A voxel-based morphology method was used to identify the common and specific changes of the gray matter volume (GMV) to determine the structural basis. Significant differences in GMV were found among the three groups. Compared with healthy controls, UD patients showed decreased GMV in the orbital part of the left inferior frontal gyrus, whereas BD patients showed decreased GMV in the orbital part of the left middle frontal gyrus. Compared with BD, UD patients have increased GMV in the left supramarginal gyrus and middle temporal gyrus. Our results revealed different structural changes in UD and BD patients suggesting BD and UD have different neurophysiological underpinnings. Our study contributes toward the biological determination of morphometric changes, which could help to discriminate between UD and BD.

Altered functional activity in bipolar disorder: A comprehensive review from a large-scale network perspective

BACKGROUND

Growing literature continues to identify brain regions that are functionally altered in bipolar disorder. However, precise functional network correlates of bipolar disorder have yet to be determined due to inconsistent results. The overview of neurological alterations from a large-scale network perspective may provide more comprehensive results and elucidate the neuropathology of bipolar disorder. Here, we critically review recent neuroimaging research on bipolar disorder using a network-based approach.

METHODS

A systematic search was conducted on studies published from 2009 through 2019 in PubMed and Google Scholar. Articles that utilized functional magnetic resonance imaging technique to examine altered functional activity of major regions belonging to a large-scale brain network in bipolar disorder were selected.

RESULTS

A total of 49 studies were reviewed. Within-network hypoconnectivity was reported in bipolar disorder at rest among the default mode, salience, and central executive networks. In contrast, when performing a cognitive task, hyperconnectivity among the central executive network was found. Internetwork functional connectivity in the brain of bipolar disorder was greater between the salience and default mode networks, while reduced between the salience and central executive networks at rest, compared to control.

CONCLUSION

This systematic review suggests disruption in the functional activity of large-scale brain networks at rest as well as during a task stimuli in bipolar disorder. Disrupted intra- and internetwork functional connectivity that are also associated with clinical symptoms suggest altered functional connectivity of and between large-scale networks plays an important role in the pathophysiology of bipolar disorder.

Degenerative dementias: Alterations of emotions and mood disorders

Degenerative dementias such as Alzheimer's disease and frontotemporal dementia result in distinct alterations in emotional processing, emotional experiences, and mood. The neuropathology of these dementias extends to structures involved in emotional processing, including the basolateral limbic network (orbitofrontal cortex, anterior temporal lobe, amygdala, and thalamus), the insula, and ventromedial frontal lobe. Depression is the most common emotion and mood disorder affecting patients with Alzheimer's disease. The onset of depression can be a prodromal sign of this dementia. Anxiety can also be present early in the course of Alzheimer's disease and especially among patients with early-onset forms of the disease. In contrast, patients with behavioral variant frontotemporal dementia demonstrate hypoemotionality, deficits in the recognition of emotion, and decreased psychophysiological reactivity to emotional stimuli. They typically have a disproportionate impairment in emotional and cognitive empathy. One other unique feature of behavioral variant frontotemporal dementia is the frequent occurrence of bipolar disorder. The management strategies for these alterations of emotion and mood in degenerative dementias primarily involve the judicious use of the psychiatric armamentarium of medications.

Frontotemporal Dementia and Late-Onset Bipolar Disorder: The Many Directions of a Busy Road

It is a common pathway for patients with the behavioral variant of frontotemporal dementia (bvFTD) to be first misdiagnosed with a primary psychiatric disorder, a considerable proportion of them being diagnosed with bipolar disorder (BD). Conversely, not rarely patients presenting in late life with a first episode of mania or atypically severe depression are initially considered to have dementia before the diagnosis of late-onset BD is reached. Beyond some shared features that make these conditions particularly prone to confusion, especially in the elderly, the relationship between bvFTD and BD is far from simple. Patients with BD often have cognitive complaints as part of their psychiatric disorder but are at an increased risk of developing dementia, including FTD. Likewise, apathy and disinhibition, common features of depression and mania, respectively, are among the core features of the bvFTD syndrome, not to mention that depression may coexist with dementia. In this article, we take advantage of the current knowledge on the neurobiology of these two nosologic entities to review their historical and conceptual interplay, highlighting the clinical, genetic and neuroimaging features that may be shared by both disorders or unique to each of them.

Distinct Associations of Cognitive Impairments and Reduced Gray Matter Volumes in Remitted Patients with Schizophrenia and Bipolar Disorder

Background

Cognitive impairments are documented in schizophrenia (SZ) and bipolar disorder (BD) and may be related to gray matter volumes (GMVs). Thus, this study is aimed at exploring whether the association between cognitive impairments and GMV alterations is similar in patients with SZ and BD and understanding the underlying neurobiological mechanisms.

Methods

A total of 137 adult subjects (46 with SZ, 35 with BD, and 56 age-, sex-, and education-matched healthy controls (HC)) completed the MATRICS Consensus Cognitive Battery (MCCB) and structural magnetic resonance imaging scanning. We performed group comparisons of the cognitive impairments, the GMV alterations, and the association between them.

Results

Compared with HC, the patients with SZ and BD showed shared deficits in 4 cognitive domains (i.e., processing speed, working memory, problem solving, and social cognition) and the composite. SZ and BD had commonly decreased GMVs, mainly in the insula, superior temporal pole, amygdala, anterior cingulate, and frontal cortices (superior, middle, opercular inferior, and orbital frontal gyrus). No correlation between MCCB scores and GMVs was detected in SZ. However, for BD, working memory was relevant to the right hemisphere (i.e., right insula, amygdala, superior temporal pole, and medial and dorsolateral superior frontal gyrus). Limitations. The major limitations were that not all patients were the first-episode status and no medication.

Conclusions

The association was mainly limited to the BD group. Thus, the underlying pathophysiology of the cognitive deficits, in terms of GMV alterations, may be diverse between two disorders.

Inflammation in Bipolar Disorder (BD): Identification of new therapeutic targets

Bipolar disorder (BD) is a chronic and cyclic mental disorder, characterized by unusual mood swings between mania/hypomania and depression, raising concern in both scientific and medical communities due to its deleterious social and economic impact. Polypharmacy is the rule due to the partial effectiveness of available drugs. Disease course is often unremitting, resulting in frequent cognitive deficits over time. Despite all research efforts in identifying BD-associated molecular mechanisms, current knowledge remains limited. However, the involvement of inflammation in BD pathophysiology is increasingly consensual, with the immune system and neuroinflammation playing a key role in disease course. Evidence includes altered levels of cytokines and acute-phase proteins, pathological microglial activation, deregulation of Nrf2-Keap1 system and changes in biogenic amines neurotransmitters, whose expression is regulated by TNF-α, a pro-inflammatory cytokine highly involved in BD, pointing out inflammation as a novel and attractive therapeutic target for BD. As result, new therapeutic agents including non-steroidal anti-inflammatory drugs, N-acetylcysteine and GSK3 inhibitors have been incorporated in BD treatment. Taking into consideration the latest pre-clinical and clinical trials, in this review we discuss recent data regarding inflammation in BD, unveiling potential therapeutic approaches through direct or indirect modulation of inflammatory response.

Inflammation is associated with decreased functional connectivity of insula in unmedicated bipolar disorder

BACKGROUND

Systemic inflammation and immune dysregulation have been considered as risk factors in the pathophysiology of mood disorders including bipolar disorder (BD). Previous neuroimaging studies have demonstrated metabolic, structural and functional abnormalities in the insula in BD, proposed that the insula played an important role in BD. We herein aimed to explore neural mechanisms underlying inflammation-induced in the insular subregions functional connectivity (FC) in patients with BD.

METHODS

Brain resting-state functional magnetic resonance imaging (rs-fMRI) data were acquired from 41 patients with unmedicated BD II (current episode depressed), 68 healthy controls (HCs). Three pairs of insular seed regions were selected: the bilateral anterior insula (AI), the bilateral middle insula (MI) and the bilateral posterior insula (PI), and calculated the whole-brain FC for each subregion. Additionally, the serum levels of pro-inflammatory cytokines in patients and HCs, including IL-6 and TNF-α, were detected. Then the partial correlation coefficients between the abnormal insular subregions FC values and pro-inflammatory cytokines levels in patients with BD II depression were calculated.

RESULTS

The BD II depression group exhibited decreased FC between the right PI and the left postcentral gyrus, and increased FC between the left AI and the bilateral insula (extended to the right putamen) when compared with the HC group. Moreover, the patients with BD II depression showed higher IL-6 and TNF-α levels than HCs, and IL-6 level was negatively correlated with FC of the right PI to the left postcentral gyrus.

CONCLUSIONS

Our results demonstrated that abnormal FC between the bilateral insula, and between the insula and sensorimotor areas in BD. Moreover, disrupted FC between the insula and sensorimotor areas was associated with elevated pro-inflammatory cytokine levels of IL-6 in BD.

Distinguishing patterns of impairment on inhibitory control and general cognitive ability among bipolar with and without psychosis, schizophrenia, and schizoaffective disorder

BACKGROUND

Deficits in inhibitory control on a Stop Signal Task (SST) were previously observed to be of similar magnitude across schizophrenia, schizoaffective, and bipolar disorder with psychosis, despite variation in general cognitive ability. Understanding different patterns of performance on the SST may elucidate different pathways to the impaired inhibitory control each group displayed. Comparing nonpsychotic bipolar disorder to the psychosis groups on SST may also expand our understanding of the shared neurobiology of this illness spectrum.

METHODS

We tested schizophrenia (n = 220), schizoaffective (n = 216), bipolar disorder with (n = 192) and without psychosis (n = 67), and 280 healthy comparison participants with a SST and the Brief Assessment of Cognition in Schizophrenia (BACS), a measure of general cognitive ability.

RESULTS

All patient groups had a similar degree of impaired inhibitory control over prepotent responses. However, bipolar groups differed from schizophrenia and schizoaffective groups in showing speeded responses and inhibition errors that were not accounted for by general cognitive ability. Schizophrenia and schizoaffective groups had a broader set of deficits on inhibition and greater general cognitive deficit, which fully accounted for the inhibition deficits. No differences were found between the clinically well-matched bipolar with and without psychosis groups, including for inhibitory control or general cognitive ability.

CONCLUSIONS

We conclude that 1) while impaired inhibitory control on a SST is of similar magnitude across the schizo-bipolar spectrum, including nonpsychotic bipolar, different mechanisms may underlie the impairments, and 2) history of psychosis in bipolar disorder does not differentially impact inhibitory behavioral control or general cognitive abilities.

Changes in cortical thickness and volume of cerebellar subregions in patients with bipolar disorders

BACKGROUND

Numerous studies have suggested that structural changes in the cerebellum are implicated in the pathophysiology of bipolar disorder (BD). We aimed to investigate differences in the volume and cortical thickness of the cerebellar subregions between patients with BD and healthy controls (HCs).

METHODS

Ninety patients with BD and one hundred sixty-six HCs participated in this study and underwent T1-weighted structural magnetic resonance imaging. We analyzed the volume and cortical thickness of each cerebellar hemisphere divided into 12 subregions using T1-weighted images of participants. One-way analysis of covariance was used to evaluate differences between the groups, with age, sex, medication, and total intracranial cavity volume used as covariates.

RESULTS

The BD group had significantly increased cortical thickness of the cerebellum in all cerebellar subregions compared to the HC group. The cortical thicknesses of the whole cerebellum and each hemisphere were also significantly thicker in the BD group than in the HC group. The volume of the left lobule IX was significantly lower in patients with BD than in HCs, whereas no significant differences in the volumes were observed in the other subregions.

LIMITATIONS

Our cross-sectional design cannot provide a causal relationship between the increased cortical thickness of the cerebellum and the risk of BD.

CONCLUSIONS

We observed widespread and significant cortical thickening in all the cerebellar subregions. Our results provide evidence for the involvement of the cerebellum in BD. Further studies are required to integrate neurobiological evidence and structural brain imaging to elucidate the pathophysiology of BD.

Neural Subtypes of Euthymic Bipolar I Disorder Characterized by Emotion Regulation Circuitry

BACKGROUND

Current diagnostic strategy for bipolar disorders relies on symptomological classification. Yet, responses to both pharmacological and psychotherapeutic treatments vary widely, suggesting that underlying neuropathological differences are not well defined by current nosology. Classifying patients with bipolar disorder based on emotion regulation network (ERN) activation may account for some of the heterogeneity within the disorder.

METHODS

Euthymic participants diagnosed with bipolar I disorder (n = 86) and healthy subjects (n = 80) underwent functional magnetic resonance imaging scans while engaged in emotional reappraisal of negative stimuli. After determining average regional activations in key network regions, we applied agglomerative hierarchical clustering to identify subtypes of bipolar disorder. Next, we examined relations among neural subtypes, demographic variables, and mood symptoms.

RESULTS

Analyses revealed two primary neural subtypes of euthymic bipolar I disorder participants. The first subtype, ERN cluster 1, was characterized by increased amygdala activation and slightly increased ventrolateral prefrontal and subgenual cingulate activation, whereas ERN cluster 2 was defined by decreased amygdala activation with wider-spread prefrontal activation. Cluster 1 was associated with a higher number of hospitalizations for depression (odds ratio = 1.30, 95% confidence interval = 1.02-1.64) and later onset of manic episodes (odds ratio = 1.06, 95% confidence interval = 1.00-21.13) than cluster 2. ERN clusters of healthy subjects differed from bipolar disorder clusters and were defined by differential activation of the prefrontal cortex. ERN clusters of healthy subjects, which differed from bipolar disorder clusters, were defined by differential activation of the prefrontal cortex.

CONCLUSIONS

Emotion regulation circuitry can distinguish neurobiological subtypes of bipolar disorder in the euthymic state. These subtypes, which are differentially associated with indices of illness severity and subsyndromal affective symptoms, may help to inform relapse risk and more personalized treatment approaches.

Recommendations to distinguish behavioural variant frontotemporal dementia from psychiatric disorders

The behavioural variant of frontotemporal dementia (bvFTD) is a frequent cause of early-onset dementia. The diagnosis of bvFTD remains challenging because of the limited accuracy of neuroimaging in the early disease stages and the absence of molecular biomarkers, and therefore relies predominantly on clinical assessment. BvFTD shows significant symptomatic overlap with non-degenerative primary psychiatric disorders including major depressive disorder, bipolar disorder, schizophrenia, obsessive-compulsive disorder, autism spectrum disorders and even personality disorders. To date, ∼50% of patients with bvFTD receive a prior psychiatric diagnosis, and average diagnostic delay is up to 5-6 years from symptom onset. It is also not uncommon for patients with primary psychiatric disorders to be wrongly diagnosed with bvFTD. The Neuropsychiatric International Consortium for Frontotemporal Dementia was recently established to determine the current best clinical practice and set up an international collaboration to share a common dataset for future research. The goal of the present paper was to review the existing literature on the diagnosis of bvFTD and its differential diagnosis with primary psychiatric disorders to provide consensus recommendations on the clinical assessment. A systematic literature search with a narrative review was performed to determine all bvFTD-related diagnostic evidence for the following topics: bvFTD history taking, psychiatric assessment, clinical scales, physical and neurological examination, bedside cognitive tests, neuropsychological assessment, social cognition, structural neuroimaging, functional neuroimaging, CSF and genetic testing. For each topic, responsible team members proposed a set of minimal requirements, optimal clinical recommendations, and tools requiring further research or those that should be developed. Recommendations were listed if they reached a ≥ 85% expert consensus based on an online survey among all consortium participants. New recommendations include performing at least one formal social cognition test in the standard neuropsychological battery for bvFTD. We emphasize the importance of 3D-T1 brain MRI with a standardized review protocol including validated visual atrophy rating scales, and to consider volumetric analyses if available. We clarify the role of 18F-fluorodeoxyglucose PET for the exclusion of bvFTD when normal, whereas non-specific regional metabolism abnormalities should not be over-interpreted in the case of a psychiatric differential diagnosis. We highlight the potential role of serum or CSF neurofilament light chain to differentiate bvFTD from primary psychiatric disorders. Finally, based on the increasing literature and clinical experience, the consortium determined that screening for C9orf72 mutation should be performed in all possible/probable bvFTD cases or suspected cases with strong psychiatric features.

Right-sided brain lesions predominate among patients with lesional mania: evidence from a systematic review and pooled lesion analysis

Despite claims that lesional mania is associated with right-hemisphere lesions, supporting evidence is scarce, and association with specific brain areas has not been demonstrated. Here, we aimed to test whether focal brain lesions in lesional mania are more often right- than left-sided, and if lesions converge on areas relevant to mood regulation. We thus performed a systematic literature search (PROSPERO registration CRD42016053675) on PubMed and Web-Of-Science, using terms that reflect diagnoses and structures of interest, as well as lesional mechanisms. Two researchers reviewed the articles separately according to PRISMA Guidelines, selecting reports of adult-onset hypomania, mania or mixed state following a focal brain lesion, for pooled-analyses of individual patient data. Eligible lesion images were manually traced onto the corresponding MNI space slices, and lesion topography analyzed using standard brain atlases. Using this approach, data from 211 lesional mania patients was extracted from 114 reports. Among 201 cases with focal lesions, more patients had lesions involving exclusively the right (60.7%) than exclusively the left (11.4%) hemisphere. In further analyses of 56 eligible lesion images, while findings should be considered cautiously given the potential for selection bias of published lesion images, right-sided predominance of lesions was confirmed across multiple brain regions, including the temporal lobe, fusiform gyrus and thalamus. These, and several frontal lobe areas, were also identified as preferential lesion sites in comparisons with control lesions. Such pooled-analyses, based on the most comprehensive dataset of lesional mania available to date, confirm a preferential association with right-hemisphere lesions, while suggesting that several brain areas/circuits, relevant to mood regulation, are most frequently affected.

Fractional amplitude of low-frequency fluctuations and gray matter volume alterations in patients with bipolar depression

PURPOSE

We used fractional amplitude of low-frequency fluctuations (fALFF) and gray matter volume (GMV) jointly to explore the mechanism of brain function and structure in unmedicated patients with bipolar disorder (BD).

METHODS

Thirty first episode drug-naive patients with and thirty healthy controls (HCs) were recruited in this study; All the subjects underwent Magnetic Resonance Imaging (MRI) scanning and performed the Repeatable Battery for the Assessment of Neuropsychological Status (RBANS), all the patients with MDD finished the 17-item Hamilton Depression Rating Scale (HAMD17). Data Processing and Analysis for Brain Imaging (DPABI) and SPM8 were used to find potential differences in fALFF and GMV between the two groups. A Pearson correlation model was used to analyze associations of functional and morphometric changes with clinical symptoms and cognitive tests.

RESULTS

Compared to healthy controls, the BD group had significantly reduced fALFF values in the lingual gyrus and increased fALFF values in the bilateral superior frontal gyrus and superior frontal gyrus. With regards to VBM, patients with BD showed significant GMV decreases in the bilateral superior temporal gyrus, bilateral superior frontal gyrus, right superior frontal gyrus, right parahippocampal gyrus and precuneus. Additionally, we found an overlap of brain regions focused on the left SFG. Significant negative correlations were observed between abnormal GMV values in the left SFG and vocabulary memory.

CONCLUSION

The superior frontal gyrus was the site of the most robust and reliable abnormality, with an overlap of abnormal structural and functional MRI features that play an important role in pathology in BD.

Common gray and white matter abnormalities in schizophrenia and bipolar disorder

This study aimed to investigate abnormalities in the gray matter and white matter (GM and WM, respectively) that are shared between schizophrenia (SZ) and bipolar disorder (BD). We used 3T-magnetic resonance imaging to examine patients with SZ, BD, or healthy control (HC) subjects (aged 20–50 years, N = 65 in each group). We generated modulated GM maps through voxel-based morphometry (VBM) for T1-weighted images and skeletonized fractional anisotropy, mean diffusion, and radial diffusivity maps through tract-based special statistics (TBSS) methods for diffusion tensor imaging (DTI) data. These data were analyzed using a generalized linear model with pairwise comparisons between groups with a family-wise error corrected P < 0.017. The VBM analysis revealed widespread decreases in GM volume in SZ compared to HC, but patients with BD showed GM volume deficits limited to the right thalamus and left insular lobe. The TBSS analysis showed alterations of DTI parameters in widespread WM tracts both in SZ and BD patients compared to HC. The two disorders had WM alterations in the corpus callosum, superior longitudinal fasciculus, internal capsule, external capsule, posterior thalamic radiation, and fornix. However, we observed no differences in GM volume or WM integrity between SZ and BD. The study results suggest that GM volume deficits in the thalamus and insular lobe along with widespread disruptions of WM integrity might be the common neural mechanisms underlying the pathologies of SZ and BD.