Anisotropic kernels for coordinate-based meta-analyses of neuroimaging studies

Chemotherapy-induced grey matter abnormalities in cancer survivors: a voxel-wise neuroimaging meta-analysis

BACKGROUND

Findings regarding chemotherapy-induced grey matter abnormalities are heterogeneous, and no meta-analysis has quantitatively assessed brain structural alterations in cancer survivors treated with chemotherapy.

PURPOSE

To investigate the grey matter abnormalities in non-CNS (central nervous system) cancer survivors treated with chemotherapy using Anisotropic Effect Size Signed Differential Mapping (AES-SDM) software.

METHOD

We identified studies published up to Sep 2018 that compared grey matter in non-CNS cancer survivors treated with chemotherapy (CT+, 10 data sets including 433 individuals) and cancer survivors not treated with chemotherapy (CT-, 7 data sets including 210 individuals) or healthy controls (HC, 3 data sets including 407 individuals) using whole-brain VBM. We used statistical maps from the studies included where available and reported peak coordinates otherwise.

RESULTS

Compared with both CT- and HC, the CT + groups exhibited a reduced grey matter volume (GMV), mainly in the prefrontal and anterior cingulate cortex (ACC) and right fusiform gyrus (FG). A smaller GMV in the FG and prefrontal cortex were found in the CT + compared with the CT-groups and in the CT + groups with impaired cognition. GMV in two areas was positively associated with the time since chemotherapy.

CONCLUSIONS

The present results suggest that non-CNS cancer survivors treated with chemotherapy exhibit grey matter abnormalities in the brain, especially in the prefrontal and ACC cortex. Grey matter volume changes after chemotherapy may contribute to cognitive impairments in cancer survivors that can be observed after chemotherapy.

Obesity is associated with reduced orbitofrontal cortex volume: A coordinate-based meta-analysis

Neural models of obesity vary in their focus upon prefrontal and striatal differences. Animal and human studies suggest that differential functioning of the orbitofrontal cortex is associated with obesity. However, meta-analyses of functional neuroimaging studies have not found a clear relationship between the orbitofrontal cortex and obesity. Meta-analyses of structural imaging studies of obesity have shown mixed findings with regards to an association with reduced orbitofrontal cortex gray matter volume. To clarify these findings, we conducted a meta-analysis of 25 voxel-based morphometry studies, and found that greater body mass index is associated with decreased gray matter volume in the right orbitofrontal cortex (Brodmanns' areas 10 and 11), where family-wise corrected p < .05, N = 7,612. Use of the right orbitofrontal cortex as a seed in a Neurosynth Network Coactivation analysis showed that this region is associated with activity in the left frontal medial cortex, left temporal lobe, right precuneus cortex, posterior division of the left middle temporal gyrus, and right frontal pole. When Neurosynth Network Coactivation results were submitted as regions of interest in the Human Connectome Project data, we found that greater body mass index was associated with greater activity in left frontal medial cortex response to the Gambling Task, where p < .05, although this did not survive Bonferroni-correction. Our findings highlight the importance of the orbitofrontal cortex structure and functioning in neural models of obesity. Exploratory analyses suggest more studies are needed that examine the functional significance of reduced orbitofrontal cortex gray matter volume in obesity, and the effect of age and weight changes on this relationship using longitudinal designs.

Hunger and BMI modulate neural responses to sweet stimuli: fMRI meta-analysis

OBJECTIVE

Consuming sweet foods, even when sated, can lead to unwanted weight gain. Contextual factors, such as longer time fasting, subjective hunger, and body mass index (BMI), may increase the likelihood of overeating. Nevertheless, the neural mechanisms underlying these moderating influences on energy intake are poorly understood.

METHODS

We conducted both categorical meta-analysis and meta-regression of factors modulating neural responses to sweet stimuli, using data from 30 functional magnetic resonance imaging (fMRI) articles incorporating 39 experiments (N = 995) carried out between 2006 and 2019.

RESULTS

Responses to sweet stimuli were associated with increased activity in regions associated with taste, sensory integration, and reward processing. These taste-evoked responses were modulated by context. Longer fasts were associated with higher posterior cerebellar, thalamic, and striatal activity. Greater self-reported hunger was associated with higher medial orbitofrontal cortex (OFC), dorsal striatum, and amygdala activity and lower posterior cerebellar activity. Higher BMI was associated with higher posterior cerebellar and insular activity.

CONCLUSIONS

Variations in fasting time, self-reported hunger, and BMI are contexts associated with differential sweet stimulus responses in regions associated with reward processing and homeostatic regulation. These results are broadly consistent with a hierarchical model of taste processing. Hunger, but not fasting or BMI, was associated with sweet stimulus-related OFC activity. Our findings extend existing models of taste processing to include posterior cerebellar regions that are associated with moderating effects of both state (fast length and self-reported hunger) and trait (BMI) variables.

Cortical thickness in Parkinson disease: A coordinate-based meta-analysis

BACKGROUND

A growing number of studies have used surface-based morphometry (SBM) analyses to investigate gray matter cortical thickness (CTh) abnormalities in Parkinson disease (PD). However, the results across studies are inconsistent and have not been systematically reviewed. A clear picture of CTh alterations in PD remains lacked. Coordinate-based meta-analysis (CBMA) is a powerful tool to quantitatively integrate the results of individual voxel-based neuroimaging studies to identify the functional or structural neural substrates of particular neuropsychiatric disorders. Recently, CBMA has been updated for integrating SBM studies.

METHODS

The online databases PubMed, Embase, Web of Science, China National Knowledge Infrastructure (CNKI), WanFang, and SinoMed were comprehensively searched without language limitations from the database inception to February 2, 2020. We will include all SBM studies that compared regional CTh between patients with idiopathic PD and healthy control subjects at the whole-cortex level using Seed-based d Mapping with Permutation of Subject Images (SDM-PSI). In addition to the main CBMA, we will conduct several supplementary analyses to test the robustness of the results, such as jackknife analyses, subgroup analyses, heterogeneity analyses, publication bias analyses, and meta-regression analyses.

RESULTS

This CBMA will offer the latest evidence of CTh alterations in PD.

CONCLUSIONS

Consistent and robust evidence of CTh alterations will feature brain morphometry of PD and may facilitate biomarker development.

PROSPERO REGISTRATION NUMBER

CRD42020148775.

Gray matter alterations in restless legs syndrome: A coordinate-based meta-analysis

BACKGROUND

Voxel-based morphometry (VBM) is an objective structural magnetic resonance imaging (MRI) technique which allows researchers to investigate group-level differences in regional gray matter (GM) volume or density over the whole brain. In the last decade, VBM studies in restless leg syndrome (RLS) have exhibited inconsistent and conflicting findings.

METHODS

Studies will be identified through a computerized literature search of the following databases: PubMed, Web of Science, and Embase until October 1, 2018 and updated on March 1, 2020. This protocol will be performed in accordance with the Preferred Reporting Items for Systematic review and Meta-Analysis Protocols (PRISMA-P). In addition, we will follow the recent guidelines and recommendations for coordinate-based meta-analysis (CBMA). This CBMA will be performed with the seed-based d mapping with permutation of subject images (SDM-PSI) software.

RESULTS

This CBMA will offer the latest evidence of GM alterations in RLS.

CONCLUSIONS

To our knowledge, this will be the first CBMA that pooled VBM findings in RLS. This quantitative evidence of GM alterations will characterize brain morphometry of RLS.

PROSPERO REGISTRATION NUMBER

CRD42018117014.

Is there a reliable brain morphological signature for migraine?

Voxel-based morphometry (VBM) is a popular non-invasive magnetic resonance imaging technique to investigate brain gray matter (GM) differences between groups. Recently, two VBM studies in migraine have been published in The Journal of Headache and Pain. Reviewing the two and those previous published VBM studies, we found considerable variations of the results. Spatially diverse brain regions with decreased and increased GM alterations and null findings have been reported. It is interesting to know whether there is a reliable brain morphological signature for migraine. Coordinate-based meta-analysis (CBMA) is increasingly used to quantitatively pool individual neuroimaging studies to identify consistent and reliable findings. Several CBMA have been conducted, however, their results were inconsistent. The algorithms for CBMA have evolved and more eligible VBM studies in migraine have been published. We therefore conducted an updated CBMA using the latest algorithms for CBMA, seed-based d mapping with permutation of subject images (SDM-PSI). The present CBMA of 32 VBM studies (41 datasets comprising 1252 patients and 1025 healthy controls) found no evidence of consistent GM alterations in migraine. Sensitivity analysis, subgroup meta-analyses, and meta-regression analyses revealed that the result was robust. This negative result indicates that there is no reliable brain morphological signature for migraine. VBM investigations in migraine remain a heterogeneous field. Many potential confounding factors, such as underpowered sample sizes, variations in demographic and clinical characteristics, and differences in MRI scanners, head coils, scanning parameters, preprocessing procedures, and statistical strategies may cause the inconsistences of the results. Future VBM studies are warranted to enroll well-characterized and homogeneous subtype samples with appropriate sample sizes, comprehensively assess comorbidities and medication status, and use well-validated and standardized imaging protocols and processing and analysis pipelines to produce robust and replicable results in migraine.

Neural signatures of conditioning, extinction learning, and extinction recall in posttraumatic stress disorder: a meta-analysis of functional magnetic resonance imaging studies

BACKGROUND

Establishing neurobiological markers of posttraumatic stress disorder (PTSD) is essential to aid in diagnosis and treatment development. Fear processing deficits are central to PTSD, and their neural signatures may be used as such markers.

METHODS

Here, we conducted a meta-analysis of seven Pavlovian fear conditioning fMRI studies comparing 156 patients with PTSD and 148 trauma-exposed healthy controls (TEHC) using seed-based d-mapping, to contrast neural correlates of experimental phases, namely conditioning, extinction learning, and extinction recall.

RESULTS

Patients with PTSD, as compared to TEHCs, exhibited increased activation in the anterior hippocampus (extending to the amygdala) and medial prefrontal cortex during conditioning; in the anterior hippocampus-amygdala regions during extinction learning; and in the anterior hippocampus-amygdala and medial prefrontal areas during extinction recall. Yet, patients with PTSD have shown an overall decreased activation in the thalamus during all phases in this meta-analysis.

CONCLUSION

Findings from this metanalysis suggest that PTSD is characterized by increased activation in areas related to salience and threat, and lower activation in the thalamus, a key relay hub between subcortical areas. If replicated, these fear network alterations may serve as objective diagnostic markers for PTSD, and potential targets for novel treatment development, including pharmacological and brain stimulation interventions. Future longitudinal studies are needed to examine whether these observed network alteration in PTSD are the cause or the consequence of PTSD.

Brain structural correlates of familial risk for mental illness: a meta-analysis of voxel-based morphometry studies in relatives of patients with psychotic or mood disorders

Schizophrenia (SCZ), bipolar disorder (BD), and major depressive disorder (MDD) are heritable psychiatric disorders with partially overlapping genetic liability. Shared and disorder-specific neurobiological abnormalities associated with familial risk for developing mental illnesses are largely unknown. We performed a meta-analysis of structural brain imaging studies in relatives of patients with SCZ, BD, and MDD to identify overlapping and discrete brain structural correlates of familial risk for mental disorders. Search for voxel-based morphometry studies in relatives of patients with SCZ, BD, and MDD in PubMed and Embase identified 33 studies with 2292 relatives and 2052 healthy controls (HC). Seed-based d Mapping software was used to investigate global differences in gray matter volumes between relatives as a group versus HC, and between those of each psychiatric disorder and HC. As a group, relatives exhibited gray matter abnormalities in left supramarginal gyrus, right striatum, right inferior frontal gyrus, left thalamus, bilateral insula, right cerebellum, and right superior frontal gyrus, compared with HC. Decreased right cerebellar gray matter was the only abnormality common to relatives of all three conditions. Subgroup analyses showed disorder-specific gray matter abnormalities in left thalamus and bilateral insula associated with risk for SCZ, in left supramarginal gyrus and right frontal regions with risk for BD, and in right striatum with risk for MDD. While decreased gray matter in right cerebellum might be a common brain structural abnormality associated with shared risk for SCZ, BD, and MDD, regional gray matter abnormalities in neocortex, thalamus, and striatum appear to be disorder-specific.

White matter disruption in obsessive-compulsive disorder revealed by meta-analysis of tract-based spatial statistics

BACKGROUND

Exploring white matter (WM) microstructural alterations is a momentous step for gaining insights about underlying mechanisms of obsessive-compulsive disorder (OCD) and improving the efficacy of therapies for this condition. Many tract-based spatial statistics (TBSS) studies have revealed abnormalities of fractional anisotropy (FA; an index of WM integrity) in OCD. However, research works have not drawn robust conclusions. Therefore, we integrated the findings of TBSS studies to identify the most consistent FA changes in OCD using meta-analytical approach.

METHODS

Online databases were systematically searched for all TBSS studies comparing FA between patients with OCD and controls. A coordinate-based meta-analysis was performed using anisotropic effect size version of the seed-based d mapping software. Meanwhile, meta-regression was used to explore the potential association of clinical characteristics with regional FA abnormalities.

RESULTS

Our meta-analysis included 488 OCD patients and 519 controls across 17 datasets. FA reductions were identified in the genu of the corpus callosum and the left orbitofrontal WM in OCD patients relative to controls. Metaregression analyses showed that the FA in the left orbitofrontal WM was negatively and independently correlated with symptom severity and illness duration in patients with OCD.

CONCLUSIONS

The current study provides a quantitative overview of TBSS findings in OCD and demonstrates the most prominent and replicable WM abnormalities in OCD are in the anterior part of the brain including interhemispheric connection and orbitofrontal region. Additionally, our findings suggest that FA reduction in the orbitofrontal WM might be a potential biomarker in predicting disease severity and progression in patients with OCD.

Altered white matter microarchitecture in Parkinson's disease: a voxel-based meta-analysis of diffusion tensor imaging studies

This study aimed to define the most consistent white matter microarchitecture pattern in Parkinson's disease (PD) reflected by fractional anisotropy (FA), addressing clinical profiles and methodology-related heterogeneity. Web-based publication databases were searched to conduct a meta-analysis of whole-brain diffusion tensor imaging studies comparing PD with healthy controls (HC) using the anisotropic effect size-signed differential mapping. A total of 808 patients with PD and 760 HC coming from 27 databases were finally included. Subgroup analyses were conducted considering heterogeneity with respect to medication status, disease stage, analysis methods, and the number of diffusion directions in acquisition. Compared with HC, patients with PD had decreased FA in the left middle cerebellar peduncle, corpus callosum (CC), left inferior fronto-occipital fasciculus, and right inferior longitudinal fasciculus. Most of the main results remained unchanged in subgroup meta-analyses of medicated patients, early stage patients, voxel-based analysis, and acquisition with 30 diffusion directions. The subgroup meta-analysis of medication-free patients showed FA decrease in the right olfactory cortex. The cerebellum and CC, associated with typical motor impairment, showed the most consistent FA decreases in PD. Medication status, analysis approaches, and the number of diffusion directions have an important impact on the findings, needing careful evaluation in future meta-analyses.

Voxel-wise meta-analysis of structural changes in gray matter of Parkinson's disease patients with mild cognitive impairment

Evidence from previous voxel-based morphometry (VBM) studies indicates that widespread brain regions are involved in Parkinson’s disease with mild cognitive impairment (PD-MCI). However, the spatial localization reported for gray matter (GM) abnormalities is heterogeneous. The aim of the present study was to quantitatively integrate studies on GM abnormalities observed in PD-MCI in order to determine whether a pattern exists. Eligible whole-brain VBM studies were identified by a systematic search of articles in PubMed and EMBASE databases spanning from 1995 to January 1, 2019. A meta-analysis was performed to investigate regional GM abnormalities in PD-MCI. The anisotropic effect size version of seed-based d mapping (AES-SDM) meta-analysis was conducted to explore the GMV differences of PD-MCI compared with PD patients with normal cognitive function (PD-NC). A total of 12 studies comprising 243 PD-MCI patients and 326 PD-NC were included in the meta-analysis. PD-MCI patients showed a robust GM decrease in the left insula and left superior temporal gyrus. Moreover, meta-regression analysis demonstrated that age, PD duration and stage, and Unified Parkinson’s Disease Rating Scale III and Mini-Mental State Examination scores might be partly correlated with the GM abnormalities observed in PD-MCI patients. The convergent findings of this quantitative meta-analysis revealed a characteristic neuroanatomical pattern in PD-MCI. The findings provide some evidence that MCI in PD may result in the breakdown of the insula and temporal gyrus, which may serve as specific regions of interest for further investigations.

Shared gray matter alterations in individuals with diverse behavioral addictions: A voxel-wise meta-analysis

BACKGROUND AND AIMS

Numerous studies on behavioral addictions (BAs) have reported gray matter (GM) alterations in multiple brain regions by using voxel-based morphometry (VBM). However, findings are poorly replicated and it remains elusive whether distinct addictive behaviors are underpinned by shared abnormalities. In this meta-analysis, we integrated VBM studies on different BAs to investigate common GM abnormalities in individuals with BAs.

METHODS

Numerous studies on behavioral addictions (BAs) have reported gray matter (GM) alterations in multiple brain regions by using voxel-based morphometry (VBM). However, findings are poorly replicated and it remains elusive whether distinct addictive behaviors are underpinned by shared abnormalities. In this meta-analysis, we integrated VBM studies on different BAs to investigate common GM abnormalities in individuals with BAs.

RESULTS

Twenty studies including 505 individuals with BAs and 564 healthy controls met the inclusion criteria. Compared with healthy controls, individuals with BAs showed GM atrophy in the left anterior cingulate (extending to the left medial superior frontal gyrus and bilateral orbitofrontal gyrus), right putamen and right supplementary motor area. Subgroup analysis found heterogeneity in gender and subtypes of BAs. Meta-regression revealed that GM decreases in the left anterior cingulate and right supplementary motor area were positively correlated with addictive severity. Higher impulsivity was associated with smaller volume of the left anterior cingulate.

DISCUSSION AND CONCLUSIONS

Our findings on BAs were mainly derived from internet gaming disorder (IGD) and pathological gambling (PG) studies, preliminarily suggesting that GM atrophy in the prefrontal and striatal areas might be a common structural biomarker of BAs.

Large-scale network dysfunction in the acute state compared to the remitted state of bipolar disorder: A meta-analysis of resting-state functional connectivity

Background

Bipolar disorder (BD) is a mental disorder characterized by mood fluctuations between an acute episodic state of either mania or depression and a clinically remitted state. Dysfunction of large-scale intrinsic brain networks has been demonstrated in this disorder, but it remains unknown whether those network alterations are related to different states.

Methods

In the present study, we performed a meta-analysis of whole-brain seed-based resting-state functional connectivity (rsFC) studies in BD patients to compare the intrinsic function of brain networks between episodic and remitted states. Thirty-nine seed-based voxel-wise rsFC datasets from thirty publications (1047 BD patients vs 1081 controls) were included in the meta-analysis. Seeds were categorized into networks by their locations within a priori functional networks. Seed-based d mapping analysis of between-state effects identified brain systems in which different states were associated with increased connectivity or decreased connectivity within and between each seed network.

Findings

We found that BD patients presented decreased connectivity within the affective network (AN) in acute episodes but not in the remitted state of the illness. Similar decreased connectivity within the default-mode network (DMN) was also found in the acute state, but it was replaced by increased connectivity in the remitted state. In addition, different patterns of between-network dysconnectivity were observed between the acute and remitted states.

Interpretation

This study is the first to identify different patterns of intrinsic function in large-scale brain networks between the acute and remitted states of BD through meta-analysis. The findings suggest that a shift in network function between the acute and remitted states may be related to distinct emotional and cognitive dysfunctions in BD, which may have important implications for identifying clinically relevant biomarkers to guide alternative treatment strategies for BD patients during active episodes or remission.

Funding

This study was supported by grants from the National Natural Science Foundation of China (81171488, 81671669 and 81820108018) and by a Sichuan Provincial Youth Grant (2017JQ0001).

White Matter Abnormalities in Anorexia Nervosa: Psychoradiologic Evidence From Meta-Analysis of Diffusion Tensor Imaging Studies Using Tract Based Spatial Statistics

Background: Anorexia nervosa (AN) is a debilitating illness whose neural basis remains unclear. Studies using tract-based spatial statistics (TBSS) with diffusion tensor imaging (DTI) have demonstrated differences in white matter (WM) microarchitecture in AN, but the findings are inconclusive and controversial.

Objectives: To identify the most consistent WM abnormalities among previous TBSS studies of differences in WM microarchitecture in AN.

Methods: By systematically searching online databases, a total of 11 datasets were identified, including 245 patients with AN and 246 healthy controls (HC). We used Seed-based d Mapping to analyze fractional anisotropy (FA) differences between AN patients and HC, and performed meta-regression analysis to explore the effects of clinical characteristics on WM abnormalities in AN.

Results: The pooled results of all AN patients showed robustly lower FA in the corpus callosum (CC) and the cingulum compared to HC. These two regions preserved significance in the sensitivity analysis as well as in all subgroup analyses. Fiber tracking showed that the WM tracts primarily involved were the body of the CC and the cingulum bundle. Meta-regression analysis revealed that the body mass index and mean age were not linearly correlated with the lower FA.

Conclusions: The most consistent WM microstructural differences in AN were in the interhemispheric connections and limbic association fibers. These common “targets” advance our understanding of the complex neural mechanisms underlying the puzzling symptoms of AN, and may help in developing early treatment approaches.

Grey matter volume alterations in trigeminal neuralgia: A systematic review and meta-analysis of voxel-based morphometry studies

In recent decades, a growing number of structural neuroimaging studies of grey matter (GM) in trigeminal neuralgia (TN) have reported inconsistent alterations. We carried out a systematic review and meta-analysis to identify consistent and replicable GM volume abnormalities using effect-size signed differential mapping (ES-SDM). Furthermore, we conducted a meta-regression to explore the potential effects of clinical characteristics on GM volume alterations in patients with TN. A total of 13 studies with 15 datasets, representing 407 TN patients and 376 healthy individuals, were included in the present study. The results revealed that TN patients had GM volume abnormalities mainly in the basal ganglia, including the putamen, nucleus accumbens (NAc), caudate nucleus and amygdala, as well as the cingulate cortex (CC), thalamus, insula and superior temporal gyrus (STG). The meta-regression analysis showed that verbal rating scale (VRS) scores were negatively correlated with decreased GM volume in the left striatum and that illness duration was negatively correlated with decreased GM volume in the left STG and left insula. These results provide a thorough profile of GM volume alterations in TN patients and constitute robust evidence that aberrant GM volumes in the brain regions regulating and moderating sensory-motor and affective processing may play an important role in the pathophysiology of TN.

Failure of activation of striatum during the performance of executive function tasks in adult patients with bipolar disorder

BACKGROUND

Although numerous studies have used functional neuroimaging to identify executive dysfunction in patients with bipolar disorder (BD), the findings are not consistent. The aim of this meta-analysis is to identify the most reliable functional anomalies in BD patients during performance of Executive Function (EF) tasks.

METHODS

A web-based search was performed on publication databases to identify functional magnetic resonance imaging studies of BD patients performing EF tasks and a voxel-based meta-analytic method known as anisotropic Effect Size Signed Differential Mapping (ES-SDM) was used to identify brain regions which showed anomalous activity in BD patients compared with healthy controls (HC).

RESULTS

Twenty datasets consisting of 463 BD patients and 484 HC were included. Compared with HC, BD patients showed significant hypo-activation or failure of activation in the left striatum (p = 0.00007), supplementary motor area (BA 6, p = 0.00037), precentral gyrus (BA 6, p = 0.0014) and cerebellum (BA 37, p = 0.0019), and hyper-activation in the left gyrus rectus (BA 11, p ≈ 0) and right middle temporal gyrus (BA 22, p = 0.00031) during performance of EF tasks. Sensitivity and subgroup analyses showed that the anomaly of left striatum is consistent across studies and present in both euthymic and BD I patients.

CONCLUSIONS

Patients with BD consistently showed abnormal activation in the cortico-striatal system during performance of EF tasks compared with HC. Failure of activation of the striatum may be a reliable marker for impairment in performance of especially inhibition tasks by patients with BD.

A Multimodal Meta-Analysis of Structural and Functional Changes in the Brain of Tinnitus

Brain imaging studies of tinnitus patients have revealed marked changes in brain structure and function, but there are inconsistencies in those findings. In this meta-analysis, we investigated concurrence across studies to clarify those abnormalities in brain structure and function in tinnitus. Neuroimaging studies published up to December 6, 2019 were searched in the PubMed, Web of Science, EMBASE, and Cochrane Library databases, Chinese Nation Knowledge Infrastructure, Chinese Biomedical Literature Database, the Chongqing VIP, and Wanfang Database. Study selection, quality assessment, and data extraction were performed by two independent researchers. Anisotropic effect size signed differential mapping (AES-SDM) was used to perform a multimodal analysis of available studies reporting whole-brain structural or functional data in tinnitus patients. There were 14 studies that met the inclusion criteria. The structural dataset comprised 242 tinnitus patients and 217 matched healthy subjects (HS), while the functional dataset included 130 tinnitus patients and 140 matched HS. Our analysis revealed structural alterations in the superior temporal gyrus, middle temporal gyrus (MTG), angular gyrus, caudate nucleus, superior frontal gyrus, and supplementary motor area, as well as functional differences in the MTG, middle occipital gyrus, precuneus, and right inferior parietal (excluding supramarginal and angular) gyri. The multimodal analysis revealed significant differences in the right MTG of tinnitus patients relative to HS. These findings suggest the involvement of the cortico-striatal circuits in the neuropathology of tinnitus.

Structural and functional alterations in the brain gray matter among first-degree relatives of schizophrenia patients: A multimodal meta-analysis of fMRI and VBM studies

OBJECTIVE

We conducted a multimodal coordinate-based meta-analysis (CBMA) to investigate structural and functional brain alterations in first-degree relatives of schizophrenia patients (FRs).

METHODS

We conducted a systematic literature search from electronic databases to find studies that examined differences between FRs and healthy controls using whole-brain functional magnetic resonance imaging (fMRI) or voxel-based morphometry (VBM). A CBMA of 30 fMRI (754 FRs; 959 controls) and 11 VBM (885 FRs; 775 controls) datasets were conducted using the anisotropic effect-size version of signed differential mapping. Further, we conducted separate meta-analyses about functional alterations in different cognitive tasks: social cognition, executive functioning, working memory, and inhibitory control.

RESULTS

FRs showed higher fMRI activation in the right frontal gyrus during cognitive tasks than healthy controls. In VBM studies, there were no differences in gray matter density between FRs and healthy controls. Furthermore, multi-modal meta-analysis obtained no differences between FRs and healthy controls. By utilizing the BrainMap database, we showed that the brain region which showed functional alterations in FRs (i) overlapped only slightly with the brain regions that were affected in the meta-analysis of schizophrenia patients and (ii) correlated positively with the brain regions that exhibited increased activity during cognitive tasks in healthy individuals.

CONCLUSIONS

Based on this meta-analysis, FRs may exhibit only minor functional alterations in the brain during cognitive tasks, and the alterations are much more restricted and only slightly overlapping with the regions that are affected in schizophrenia patients. The familial risk did not relate to structural alterations in the gray matter.

Modality-specific overlaps in brain structure and function in obsessive-compulsive disorder: Multimodal meta-analysis of case-control MRI studies

Neuroimaging research has shown that patients with obsessive-compulsive disorder (OCD) may present brain structural and functional alterations, but the results across imaging modalities and task paradigms are difficult to reconcile. Are the same brain systems that are structurally different in OCD patients also involved in executive function and emotional processing? To answer this, we conducted separate meta-analyses of voxel-based morphometry studies, executive function functional magnetic resonance imaging (fMRI) studies, and emotional processing fMRI studies. Next, with a multimodal approach (conjunction analysis), we identified the common alterations across meta-analyses. Patients presented increased gray matter volume and hyperactivation in the putamen, but the putamen subregions affected differed depending on the psychological process. Left posterior/dorsal putamen showed hyperactivation during executive processing tasks, while predominantly right anterior/ventral putamen showed hyperactivation during emotional processing tasks. Interestingly, age was significantly associated with increased right putamen volume. Finally, the left dorsolateral prefrontal cortex was hyperactive in both functional domains. Our findings highlight task-specific correlates of brain structure and function in OCD and help integrate a growing literature.

Abnormalities of intrinsic regional brain activity in first-episode and chronic schizophrenia: a meta-analysis of resting-state functional MRI

BACKGROUND

Resting-state functional MRI (fMRI) studies have provided much evidence for abnormal intrinsic brain activity in schizophrenia, but results have been inconsistent.

METHODS

We conducted a meta-analysis of whole-brain, resting-state fMRI studies that explored differences in amplitude of low-frequency fluctuation (ALFF) between people with schizophrenia (including first episode and chronic) and healthy controls.

RESULTS

A systematic literature search identified 24 studies comparing a total of 1249 people with schizophrenia and 1179 healthy controls. Overall, patients with schizophrenia displayed decreased ALFF in the bilateral postcentral gyrus, bilateral precuneus, left inferior parietal gyri and right occipital lobe, and increased ALFF in the right putamen, right inferior frontal gyrus, left inferior temporal gyrus and right anterior cingulate cortex. In the subgroup analysis, patients with first-episode schizophrenia demonstrated decreased ALFF in the bilateral inferior parietal gyri, right precuneus and left medial prefrontal cortex, and increased ALFF in the bilateral putamen and bilateral occipital gyrus. Patients with chronic schizophrenia showed decreased ALFF in the bilateral postcentral gyrus, left precuneus and right occipital gyrus, and increased ALFF in the bilateral inferior frontal gyri, bilateral superior frontal gyrus, left amygdala, left inferior temporal gyrus, right anterior cingulate cortex and left insula.

LIMITATIONS

The small sample size of our subgroup analysis, predominantly Asian samples, processing steps and publication bias could have limited the accuracy of the results.

CONCLUSION

Our comprehensive meta-analysis suggests that findings of aberrant regional intrinsic brain activity during the initial stages of schizophrenia, and much more widespread damage with the progression of disease, may contribute to our understanding of the progressive pathophysiology of schizophrenia.

Adverse Effects of Cannabis Use on Neurocognitive Functioning: A Systematic Review of Meta- Analytic Studies

Objective: As the perceived risk of cannabis use continues to decline among youths and access continues to increase, it has become more important to synthesize the rapidly growing literature on the effects of cannabis on neurocognition. Hundreds of studies examining associations between cannabis use and neurocognitive functioning have been published in recent decades. However, results often differ across individual studies, particularly when sample sizes are small. Meta-analytic methods help to make sense of this literature and have been increasingly applied to studies on cannabis use and neurocognition. Methods: A systematic literature search using the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines was conducted to identify peer-reviewed meta-analyses of neurocognitive or functional neuroimaging data that examined associations between cannabis use and non-acute effects on neurocognitive functioning (n = 8). Results: Current findings suggest that regular healthy cannabis users, regardless of age, display poorer neurocognitive functioning relative to nonusers of small to medium effect sizes across many neurocognitive domains, as well as functional brain alterations when compared to non-users. Adverse effects are not uniform across neurocognitive domains and evidence for adolescent-onset users having poorer neurocognitive outcomes remains equivocal based on these studies. However, less is known about cannabis effects on neurocognition among clinical samples, as findings from specific clinical samples revealed mixed results. Conclusions: Meta-analyses have played an important role in helping to grasp the totality of results from a large body of literature on cannabis effects on neurocognition, yet more research (particularly large-scale longitudinal studies) is needed to identify critical periods or patterns of use that are more likely to result in negative outcomes.

Altered Gray Matter Volume in Patients With Type 1 Diabetes Mellitus

Background and Purpose: Many imaging studies have reported structure alterations in patients with type 1 diabetes mellitus (T1DM) by using voxel-based morphometry (VBM). Nevertheless, the results reported were inconsistent and had not been reviewed quantitatively. Accordingly, the quantitative meta-analysis which including VBM studies of patients with T1DM was conducted. Materials and Methods: The gray matter volume alterations in patients with T1DM was estimated by using the software seed-based d mapping. Meantime, the meta-regression was applied to detect the effects of some demographics and clinical characteristics. Results: Six studies were finally included, which with 6 datasets comprising 414 T1DM patients and 216 healthy controls. The pooled meta-analyses detected that patients with T1DM showed robustly increased gray matter volume in the left dorsolateral superior frontal gyrus and middle frontal gyrus and a decreased gray matter volume in the right lingual gyrus, cerebellum, precuneus, the left inferior temporal gyrus, and middle temporal gyrus. The meta-regression showed that the mean age, the female patient's ratio, duration of illness and HbAlc% for T1DM patients were not linearly related with gray matter alterations. Conclusion: This meta-analysis demonstrates that gray matter volume decreases in T1DM patients were mainly locates in the cortical regions and cerebellum.

Central mechanisms of itch: A systematic literature review and meta-analysis

In recent years, studying the central mechanism of itch has gained momentum. However, a proper meta-analysis has not been conducted in this domain. In this study, we tried to respond to this need. A systematic search and a meta-analysis were carried out to estimate the central mechanism of itch. The itch matrix comprises the thalamus and the parietal, secondary somatosensory, insular and cingulate cortices. We have shown that the basal ganglia (BG) play an important role in itch reduction. Finally, we explored itch processing in AD patients and observed that the itch matrix in these patients was different. In conclusion, this is the first meta-analysis on the central mechanisms of itch perception and processing. Our study demonstrated that different modalities of itch induction can produce a common pattern of activity in the brain and provided further insights into understanding the underlying nature of itch central perception.

Impairments of large-scale functional networks in attention-deficit/hyperactivity disorder: a meta-analysis of resting-state functional connectivity

Altered resting-state functional connectivity (rsFC) has been noted in large-scale functional networks in attention-deficit/hyperactivity disorder (ADHD). However, identifying consistent abnormalities of functional networks is difficult due to varied methods and results across studies. To integrate rsFC alterations and search for coherent patterns of intrinsic functional network impairments in ADHD, this research conducts a coordinate-based meta-analysis of voxel-wise seed-based rsFC studies comparing rsFC between ADHD patients and healthy controls. A total of 25 datasets from 21 studies including 700 ADHD patients and 580 controls were analyzed. We extracted the coordinates of seeds and between-group effects. Each seed was then categorized into a seed-network by its location within priori 7-network parcellations. Then, pooled meta-analyses were conducted for the default mode network (DMN), frontoparietal network (FPN) and affective network (AN) separately, but not for the ventral attention network (VAN), dorsal attention network (DAN), somatosensory network (SSN) and visual network due to a lack of primary studies. The results showed that ADHD was characterized by hyperconnectivity between the FPN and regions of the DMN and AN as well as hypoconnectivity between the FPN and regions of the VAN and SSN. These findings not only support the triple-network model of pathophysiology associated with ADHD but also extend this model by highlighting the involvement of the SSN and AN in the mechanisms of network interactions that may account for motor hyperactivity and impulsive symptoms.

Rumination and the default mode network: Meta-analysis of brain imaging studies and implications for depression

Rumination is strongly and consistently correlated with depression. Although multiple studies have explored the neural correlates of rumination, findings have been inconsistent and the mechanisms underlying rumination remain elusive. Functional brain imaging studies have identified areas in the default mode network (DMN) that appear to be critically involved in ruminative processes. However, a meta-analysis to synthesize the findings of brain regions underlying rumination is currently lacking. Here, we conducted a meta-analysis consisting of experimental tasks that investigate rumination by using Signed Differential Mapping of 14 fMRI studies comprising 286 healthy participants. Furthermore, rather than treat the DMN as a unitary network, we examined the contribution of three DMN subsystems to rumination. Results confirm the suspected association between rumination and DMN activation, specifically implicating the DMN core regions and the dorsal medial prefrontal cortex subsystem. Based on these findings, we suggest a hypothesis of how DMN regions support rumination and present the implications of this model for treating major depressive disorder characterized by rumination.

Systematic review and meta-analyses of neural structural and functional differences in generalized anxiety disorder and healthy controls using magnetic resonance imaging

•

PFC-amygdala FC is altered in GAD, indicating top-down processing deficits.

•

GAD had reduced activity for emotion regulation and working memory in the culmen.

•

Salience, default, and central executive nodes have altered structure and function.

Objective

To compare structure, functional connectivity (FC) and task-based neural differences in subjects with generalized anxiety disorder (GAD) compared to healthy controls (HC).

Methods

The Embase, Ovid Medline, PsycINFO, Scopus, and Web of Science databases were searched from inception until March 12, 2018. Two reviewers independently screened titles, abstracts, and full-text articles. Data were extracted from records directly contrasting GAD and HC that included structure (connectivity and local indices such as volume, etc.), FC, or task-based magnetic resonance imaging data. Meta-analyses were conducted, as applicable, using AES-SDM software.

Results

The literature search produced 4,645 total records, of which 85 met the inclusion criteria for the systematic review. Records included structural (n = 35), FC (n = 33), and task-based (n = 42) findings. Meta-analyses were conducted on voxel-based morphometry and task-based results.

Discussion

The systematic review confirms and extends findings from previous reviews. Although few whole-brain resting state studies were conducted, key nodes of resting state networks have altered physiology: the hippocampus (default network), ACC and amygdala (salience network), have reduced volume, and the dlPFC (central executive network) and ACC have reduced FC with the amygdala in GAD. Nodes in the sensorimotor network are also altered with greater pre- and postcentral volume, reduced supplementary motor area volume, and reduced FC in anterior and increased FC in posterior cerebellum.

Conclusions

Despite limitations due to sample size, the meta-analyses highly agree with the systematic review and provide evidence of widely distributed neural differences in subjects with GAD, compared to HC. Further research optimized for meta-analyses would greatly improve large-scale comparisons.

Meta-analyses of the functional neural alterations in subjects with Internet gaming disorder: Similarities and differences across different paradigms

Internet gaming disorder (IGD) has become a global public health concern due to its increasing prevalence and potential negative consequences. Researchers have sought to identify which brain regions are associated with this disorder. However, inconsistent results have been reported among studies due to the heterogeneity of paradigms and subjects. The present research aimed to combine the results of individual studies to provide a more coherent and powerful explanation. By selecting 40 studies utilizing a qualified whole-brain analysis, we performed a comprehensive series of meta-analyses that employed seed-based d mapping. We divided the existing experimental paradigms into 3 categories: game-related cue-reactivity, executive control, and risk-reward-related decision-making tasks. We divided all studies into three subgroups according to their paradigms. In cue-reactivity tasks, patients with IGD exhibited significant hyperactivation in the bilateral precuneus and bilateral cingulate and significant hypoactivation in the insula, but there were no differences in the striatum. In executive control tasks, patients with IGD displayed significant hyperactivation in the right superior temporal gyrus, bilateral precuneus, bilateral cingulate, and insula and hypoactivation in the left inferior frontal gyrus. In risky decision-making paradigms, IGD patients exhibited significant hyperactivation in the left striatum, right inferior frontal gyrus, and insula and hypoactivation in the left superior frontal gyrus, left inferior frontal gyrus, and right precentral gyrus. Our study aimed to discover the similarities among all studies and to explore the uniqueness of the different paradigms. This study further confirmed the critical role of reward circuitry and executive control circuitry in IGD but not under all conditions.

Reorganization of the brain in spinal cord injury: a meta-analysis of functional MRI studies

PURPOSE

Reorganization of the brain is considered the key mechanism of functional recovery in patients after spinal cord injury (SCI). This meta-analysis assessed abnormal brain activation in SCI patients to understand the pattern of reorganization in the brain after SCI.

METHODS

Functional magnetic resonance imaging (fMRI) studies that compared SCI patients with controls and were published before August 30, 2018, were extracted from the PubMed, Web of Science, and EMBASE databases. Voxel-wise whole-brain meta-analysis and region-of-interest meta-analysis of group differences were separately performed. Then, meta-regression analysis was conducted with several clinical characteristics as regressors.

RESULTS

Sixteen studies that met the inclusion criteria were identified. Compared with control individuals, SCI patients showed increased activation in the sensorimotor cortex in both whole-brain and region-of-interest (ROI) analyses. In addition, whole-brain meta-analysis revealed increased activation in the cerebellum, and this increase was positively correlated with lesion level and injury severity.

CONCLUSION

Our results demonstrated that reorganization occurred mainly in the sensorimotor system of the brain after SCI, implying that brain functions involved in sensorimotor demands can still be preserved in this condition. These findings provide opportunities for future studies in terms of therapeutic strategies and prognosis assessment.

Neural Correlates of Verbal Working Memory: An fMRI Meta-Analysis

Verbal Working memory (vWM) capacity measures the ability to maintain and manipulate verbal information for a short period of time. The specific neural correlates of this construct are still a matter of debate. The aim of this study was to conduct a coordinate-based meta-analysis of 42 fMRI studies on visual vWM in healthy subjects (n = 795, males = 459, females = 325, unknown = 11; age range: 18-75). The studies were obtained after an exhaustive literature search on PubMed, Scopus, Web of Science, and Brainmap database. We analyzed regional activation differences during fMRI tasks with the anisotropic effect-size version of seed-based d mapping software (ES-SDM). The results were further validated by performing jackknife sensitivity analyses and heterogeneity analyses. We investigated the effect of numerous relevant influencing factors by fitting corresponding linear regression models. We isolated consistent activation in a network containing fronto-parietal areas, right cerebellum, and basal ganglia structures. Regarding lateralization, the results pointed toward a bilateral frontal activation, a left-lateralization of parietal regions and a right-lateralization of the cerebellum, indicating that the left-hemisphere concept of vWM should be reconsidered. We also isolated activation in regions important for response inhibition, emphasizing the role of attentional control in vWM. Moreover, we found a significant influence of mean reaction time, load, and age on activation associated with vWM. Activation in left medial frontal gyrus, left precentral gyrus, and left precentral gyrus turned out to be positively associated with mean reaction time whereas load was associated with activation across the PFC, fusiform gyrus, parietal cortex, and parts of the cerebellum. In the latter case activation was mainly detectable in both hemispheres whereas the influence of age became manifest predominantly in the left hemisphere. This led us to conclude that future vWM studies should take these factors into consideration.

Regional gray matter reductions associated with mild cognitive impairment in Parkinson's disease: A meta-analysis of voxel-based morphometry studies

Mild cognitive impairment (MCI) is inconclusively associated with regional gray matter (GM) abnormalities in Parkinson's disease (PD). We aimed to quantitatively evaluate whole-brain voxel-based morphometry (VBM) studies that have investigated brain GM changes in PD patients with MCI (PD-MCI). Seed-based d Mapping, a well-validated coordinate-based meta-analytic approach, was utilized. We included 20 VBM studies that reported 22 datasets containing 504 patients with PD-MCI and 554 PD patients without MCI (PD-NCI). The most reliable finding identified in this meta-analysis was that patients with PD-MCI exhibited greater GM atrophy in the left anterior insula than those with PD-NCI. Our findings further suggest that several moderators (age, gender, educational level, disease stage, severity of motor disability, and the severity of cognitive impairments) in PD-MCI individuals, as well as scanner field-strength, may drive heterogeneous GM changes across studies. GM abnormalities in the anterior insula, an important cognitive hub involved in switching between neural networks, contribute to understanding the neural substrates of MCI in PD, which may serve as a biomarker of PD-MCI.

No reliable gray matter changes in essential tremor

BACKGROUND

Voxel-based morphometry (VBM) has been used to study human brain gray matter (GM) alterations in essential tremor (ET) for over one decade. However, the literature revealed heterogeneous findings.

METHODS

We therefore conducted a coordinate-based meta-analysis to synthesize the VBM studies to examine which brain regions show the most reliable GM alterations in patients with ET relative to healthy controls.

RESULTS

A total of 16 original VBM studies, comprising 387 patients with ET and 355 healthy controls, were included in this meta-analysis. This quantitative meta-analysis revealed no evidence of robust and reliable alterations in regional brain GM structures in ET. Meta-regression analyses indicate that many moderators (e.g., MR field strength, statistical methodology, age, onset age, gender, illness severity, illness duration, and family history) account for some of the heterogeneity in GM across studies.

CONCLUSIONS

High heterogeneity in GM alterations across studies may reflect true heterogeneity in ET regarding the clinic, etiology, and pathology, as well as possibly the VBM methodological variations. Currently, this heterogeneity limits the use of VBM as a reliable tool to distinguish ET from healthy controls. In order to improve reproducibility of VBM results in ET, future research may benefit from increasing the sample size, comprehensively subtyping ET phenotypes, and using well-designed and standardized imaging acquisition and analytical protocols. Furthermore, data sharing should be considered as a high priority.

Altered Resting-State Functional Activity in Medication-Naive Patients With First-Episode Major Depression Disorder vs. Healthy Control: A Quantitative Meta-Analysis

Background: There is an urgent need for a meta-analysis that characterizes the brain states of major depression disorder (MDD) patients and potentially provides reliable biomarkers, because heterogeneity in the results of resting-state functional neuroimaging has been observed between studies, with some patients not showing the consistent changes, or even opposite patterns. Thus, we evaluated consistent regional brain activity alterations in medication-naive patients with first-episode unipolar MDD and compared the results with those in healthy controls (HCs).

Methods: A systematic database search was conducted (in PubMed, Ovid, and Web of Knowledge) between January 1984 and July 2016 to select resting-state functional activity studies with a voxel-wise analysis in MDD. We used anisotropic effect size-signed differential mapping to perform a whole-brain meta-analysis, comparing functional alterations between first-episode medication-naive unipolar MDD patients and HCs by integrating the studies. In addition, subgroup meta-analysis was conducted to control for the MRI analysis method. Moreover, the meta-regression analyses were performed to examine the potential effects of mean age, education duration, illness duration, and severity of depressive symptoms.

Results: A total of 12 studies were included, comparing 313 MDD patients with 283 HCs. The pooled and subgroup meta-analysis found that the MDD patients showed hyperactivity in the left parahippocampal gyrus, left supplementary motor area, left amygdala, left hippocampus, and left middle frontal gyrus (MFG; orbital part), and hypoactivity in the left lingual gyrus, left middle occipital gyrus, right cuneus cortex, right MFG (orbital part), and left cerebellum. In the meta-regression analyses, the mean illness duration was positively associated with hyper-activation in the left parahippocampal gyrus and hypoactivation in the hemispheric lobule IV/V of the left cerebellum.

Conclusions: This meta-analysis indicated that MDD patients had significant and robust resting-state brain activity alteration in amygdala, left hippocampus and other regions, which implicated this finding in the pathophysiology of cognitive and emotional impairment in MDD patients.

Neural signatures of the risk for bipolar disorder: A meta-analysis of structural and functional neuroimaging studies

OBJECTIVE

Widespread functional and structural alterations in the brain have been extensively reported in unaffected relatives (RELs) of patients with bipolar disorder (BD) who are at genetic risk for BD. A sufficiently powered meta-analysis of structural (sMRI) and functional magnetic resonance imaging (fMRI) alterations in RELs is still lacking.

METHODS

Functional and structural magnetic resonance imaging studies investigating RELs and healthy controls (HCs) published by July 2017 were included in the meta-analyses. Study procedures were conducted in accordance with the Meta-analysis Of Observational Studies in Epidemiology (MOOSE) guidelines. Random-effects coordinate-based meta-analyses were performed across all the studies per imaging modality using Seed-based d Mapping (SDM). For fMRI studies, meta-analyses were calculated for each task type. For sMRI studies, regional volumetric changes-analyses were estimated using R. Finally, multimodal meta-analyses of structural and functional abnormalities were performed.

RESULTS

Sixty-nine imaging studies (2195 RELs and 3169 HCs) were included in the meta-analyses. RELs showed hyperactivation in the fronto-striatal regions as well as parietal hypoactivation during cognition. Also, activation was increased in the amygdala during emotional processing and in the orbitofrontal cortex during reward, respectively. Frontal and superior temporal cortex were hypertrophic in RELs. The right inferior frontal gyrus (rIFG) showed both increased activation during cognitive tasks and greater volume in RELs.

CONCLUSIONS

Our findings demonstrate that increased brain volume and activation are present in RELs and may represent intermediate phenotypes for the disorder. Furthermore, some neural changes including increased rIFG volume may be associated with the resilience to BD.

Grey matter alterations in obesity: A meta-analysis of whole-brain studies

Obesity is a major problem in the modern world causing a higher risk for various cerebrovascular diseases causing a profound individual and societal burden. The neurobiological foundation bears potential to understand the complex interaction of individual differences in brain structure and function and ingestive behaviour. This systematic review was performed on the current evidence of structural abnormalities in grey matter volume (GMV) in patients with obesity based on studies published until December 2017, which were selected through search in PubMed, CENTER (Cochrane Library), PsycINFO, Web of Science, and Ovid MEDLINE. Ten studies were included; all of them included patients with obesity and provided a whole-brain analysis of grey matter (GM) distribution. Our findings confirmed the most consistent GM reductions in patients with obesity in the left, middle, and right inferior frontal gyrus (including the insula), the left middle temporal cortex, the left precentral gyrus, and the cerebellum. On the other hand, increased GMV in patients with obesity were found in the left cuneus, left middle frontal gyrus, left inferior occipital gyrus, and corpus callosum.

Brain grey-matter volume alteration in adult patients with bipolar disorder under different conditions: a voxel-based meta-analysis

BACKGROUND

The literature on grey-matter volume alterations in bipolar disorder is heterogeneous in its findings.

METHODS

Using effect-size differential mapping, we conducted a meta-analysis of grey-matter volume alterations in patients with bipolar disorder compared with healthy controls.

RESULTS

We analyzed data from 50 studies that included 1843 patients with bipolar disorder and 2289 controls. Findings revealed lower grey-matter volumes in the bilateral superior frontal gyri, left anterior cingulate cortex and right insula in patients with bipolar disorder and in patients with bipolar disorder type I. Patients with bipolar disorder in the euthymic and depressive phases had spatially distinct regions of altered grey-matter volume. Meta-regression revealed that the proportion of female patients with bipolar disorder or bipolar disorder type I was negatively correlated with regional grey-matter alteration in the right insula; the proportion of patients with bipolar disorder or bipolar disorder type I taking lithium was positively correlated with regional grey-matter alterations in the left anterior cingulate/paracingulate gyri; and the proportion of patients taking antipsychotic medications was negatively correlated with alterations in the anterior cingulate/paracingulate gyri.

LIMITATIONS

This study was cross-sectional; analysis techniques, patient characteristics and clinical variables in the included studies were heterogeneous.

CONCLUSION

Structural grey-matter abnormalities in patients with bipolar disorder and bipolar disorder type I were mainly in the prefrontal cortex and insula. Patients' mood state might affect grey-matter alterations. Abnormalities in regional grey-matter volume could be correlated with patients' specific demographic and clinical features.

Uncontrolled eating: a unifying heritable trait linked with obesity, overeating, personality and the brain

Many eating-related psychological constructs have been proposed to explain obesity and overeating. However, these constructs, including food addiction, disinhibition, hedonic hunger, emotional eating, binge eating and the like all have similar definitions, emphasizing loss of control over intake. As questionnaires measuring the constructs correlate strongly (r > 0.5) with each other, we propose that these constructs should be reconsidered to be part of a single broad phenotype: uncontrolled eating. Such an approach enables reviewing and meta-analysing evidence obtained with each individual questionnaire. Here, we describe robust associations between uncontrolled eating, body mass index (BMI), food intake, personality traits and brain systems. Reviewing cross-sectional and longitudinal data, we show that uncontrolled eating is phenotypically and genetically intertwined with BMI and food intake. We also review evidence on how three psychological constructs are linked with uncontrolled eating: lower cognitive control, higher negative affect and a curvilinear association with reward sensitivity. Uncontrolled eating mediates all three constructs' associations with BMI and food intake. Finally, we review and meta-analyse brain systems possibly subserving uncontrolled eating: namely, (i) the dopamine mesolimbic circuit associated with reward sensitivity, (ii) frontal cognitive networks sustaining dietary self-control and (iii) the hypothalamus-pituitary-adrenal axis, amygdala and hippocampus supporting stress reactivity. While there are limits to the explanatory and predictive power of the uncontrolled eating phenotype, we conclude that treating different eating-related constructs as a single concept, uncontrolled eating, enables drawing robust conclusions on the relationship between food intake and BMI, psychological variables and brain structure and function.

Atrophy in midbrain & cerebral/cerebellar pedunculi is characteristic for progressive supranuclear palsy - A double-validation whole-brain meta-analysis

OBJECTIVE

Progressive supranuclear palsy (PSP) is an atypical parkinsonian syndrome characterized by vertical gaze palsy and postural instability. Midbrain atrophy is suggested as a hallmark, but it has not been validated systematically in whole-brain imaging.

METHODS

We conducted whole-brain meta-analyses identifying disease-related atrophy in structural MRI. Eighteen studies were identified (N = 315 PSP, 393 controls) and separated into gray or white matter analyses (15/12). All patients were diagnosed according to the National Institute of Neurological Disorders and Stroke and the Society for PSP (NINDS-SPSP criteria, Litvan et al. (1996a)), which are now considered as PSP-Richardson syndrome (Höglinger et al., 2017). With overlay analyses, we double-validated two meta-analytical algorithms: anatomical likelihood estimation and seed-based D mapping. Additionally, we conducted region-of-interest effect size meta-analyses on radiological biomarkers and subtraction analyses differentiating PSP from Parkinson's disease.

RESULTS

Whole brain meta-analyses revealed consistent gray matter atrophy in bilateral thalamus, anterior insulae, midbrain, and left caudate nucleus. White matter alterations were consistently detected in bilateral superior/middle cerebellar pedunculi, cerebral pedunculi, and midbrain atrophy. Region-of-interest meta-analyses demonstrated that midbrain metrics generally perform very well in distinguishing PSP from other parkinsonian syndromes with strong effect sizes. Subtraction analyses identified the midbrain as differentiating between PSP and Parkinson's disease.

CONCLUSIONS

Our meta-analyses identify gray matter atrophy of the midbrain and white matter atrophy of the cerebral/cerebellar pedunculi and midbrain as characteristic for PSP. Results support the incorporation of structural MRI data, and particularly these structures, into the revised PSP diagnostic criteria.

Alterations in resting-state local functional connectivity in obsessive-compulsive disorder

BACKGROUND

Obsessive-compulsive disorder (OCD) is increasingly conceptualized as a brain connectivity disorder. Recently, abnormalities in remote resting-state functional connectivity (FC) have been well demonstrated in the frontoparietal areas that linked impairments in large-scale intrinsic brain networks with aberrant fronto-striatal interactions. Beyond the remote FC abnormalities in OCD, many studies using regional homogeneity (ReHo) analysis have reported local FC alterations. However, their results were not entirely consistent.

METHODS

We conducted a voxel-wise meta-analysis of ReHo studies to identify consistent local FC abnormalities in patients with OCD. A seed-based d mapping approach was used.

RESULTS

Eight studies that compared 200 patients with OCD and 187 healthy controls were included. Increased ReHo in the lateral orbitofrontal cortices and dorsomedial prefrontal cortices bilaterally, and decreased ReHo in the fusiform gyri bilaterally were the most consistent and reliable findings in patients with OCD relative to healthy controls.

LIMITATIONS

The number of available studies included in the meta-analysis was relatively small. Many potential confounds on changes in ReHo warrant further attention.

CONCLUSIONS

These regions are critically implicated in the pathophysiology of OCD. Our findings in local FC alterations are complementary to the abnormalities in remote FC in OCD, contributing to the modeling of brain functional connectomes in OCD.

Aberrant brain regional homogeneity in first-episode drug-naïve patients with major depressive disorder: A voxel-wise meta-analysis

BACKGROUND

Resting-state functional magnetic resonance imaging studies have reported aberrant brain regional homogeneity (ReHo) in patients with major depressive disorder (MDD). However, the findings across studies were confounded by medication status and different depressive episodes.

METHODS

A systematic literature search of the PubMed, Embase, and Web of Science databases was conducted. We conducted a quantitative voxel-wise meta-analysis of ReHo studies, using the Seed-based d Mapping approach, in first-episode drug-naïve patients with MDD.

RESULTS

We identified 10 studies with 12 datasets suitable for inclusion, consisting of 402 first-episode drug-naïve patients with MDD and 330 healthy controls. The most consistent and robust findings were that patients with MDD relative to healthy controls exhibited increased ReHo in the left hippocampus and decreased ReHo in the left orbitofrontal cortex.

LIMITATIONS

The patient samples included in our meta-analysis were all Chinese, thus limiting the applicability of the present findings to other populations.

CONCLUSIONS

ReHo alterations in these brain regions are likely to reflect the core disease-related functional abnormalities, which are implicated in emotional dysregulation and cognitive impairment that are seen in the early stage of MDD. These findings contribute to a better understanding of the neurobiological underpinnings of MDD, and the left hippocampus and orbitofrontal cortex could serve as specific regions of interest for further investigations.

Meta-analytic Evidence for the Plurality of Mechanisms in Transdiagnostic Structural MRI Studies of Hallucination Status

BACKGROUND

Hallucinations are transmodal and transdiagnostic phenomena, occurring across sensory modalities and presenting in psychiatric, neurodegenerative, neurological, and non-clinical populations. Despite their cross-category occurrence, little empirical work has directly compared between-group neural correlates of hallucinations.

METHODS

We performed whole-brain voxelwise meta-analyses of hallucination status across diagnoses using anisotropic effect-size seed-based d mapping (AES-SDM), and conducted a comprehensive systematic review in PubMed and Web of Science until May 2018 on other structural correlates of hallucinations, including cortical thickness and gyrification.

FINDINGS

3214 abstracts were identified. Patients with psychiatric disorders and hallucinations (eight studies) exhibited reduced gray matter (GM) in the left insula, right inferior frontal gyrus, left anterior cingulate/paracingulate gyrus, left middle temporal gyrus, and increased in the bilateral fusiform gyrus, while patients with neurodegenerative disorders with hallucinations (eight studies) showed GM decreases in the left lingual gyrus, right supramarginal gyrus/parietal operculum, left parahippocampal gyrus, left fusiform gyrus, right thalamus, and right lateral occipital gyrus. Group differences between psychiatric and neurodegenerative hallucination meta-analyses were formally confirmed using Monte Carlo randomizations to determine statistical significance, and a jackknife sensitivity analysis established the reproducibility of results across nearly all study combinations. For other structural measures (28 studies), the most consistent findings associated with hallucination status were reduced cortical thickness in temporal gyri in schizophrenia and altered hippocampal volume in Parkinson's disease and dementia. Additionally, increased severity of hallucinations in schizophrenia correlated with GM reductions within the left superior temporal gyrus, right middle temporal gyrus, bilateral supramarginal and angular gyri.

INTERPRETATION

Distinct patterns of neuroanatomical alteration characterize hallucination status in patients with psychiatric and neurodegenerative diseases, suggesting a plurality of anatomical signatures. This approach has implications for treatment, theoretical frameworks, and generates refutable predictions for hallucinations in other diseases and their occurrence within the general population.

FUNDING

None.

Cerebellar structural and functional abnormalities in first-episode and drug-naive patients with schizophrenia: A meta-analysis

Schizophrenia (SZ) is a mental disorder that involves cerebral and cerebellar abnormalities. The cerebellum plays an indispensable role in the pathophysiology of SZ. However, individual studies pertaining to the structural and resting-state functional cerebellar abnormalities in patients with SZ have been inconsistent. To make a relatively robust conclusion with little interference, such as different disease episode times and antipsychotic treatment, we conducted this meta-analysis as a first attempt to comprehensively analyze and combine studies of voxel-based morphometry (VBM), amplitude of low-frequency fluctuation (ALFF), and functional connectivity strength (FCS) in first-episode and drug-naive SZ patients, employing the Seed-based d Mapping (SDM) method. Thirteen VBM studies, eight ALFF studies, and three FCS studies involving 783 patients and 704 matched healthy controls were included. Our results showed the presence of structural and functional abnormalities within the cerebellar regions, including most superior/anterior cerebellum (lobule III-V or VI) and posterior/inferior cerebellum (lobule VIII) related to motor function, and posterior cerebellum (lobule VIIa, Crus I, and II) associated with cognition and emotion, and such anomalies might be related to illness duration and clinical symptom severity.

Resting State Abnormalities of the Default Mode Network in Mild Cognitive Impairment: A Systematic Review and Meta-Analysis

BACKGROUND

Large-scale brain networks such as the default mode network (DMN) are often disrupted in Alzheimer's disease (AD). Numerous studies have examined DMN functional connectivity in those with mild cognitive impairment (MCI), a presumed AD precursor, to discover a biomarker of AD risk. Prior reviews were qualitative or limited in scope or approach.

OBJECTIVE

We aimed to systematically and quantitatively review DMN resting state fMRI studies comparing MCI and healthy comparison (HC) groups.

METHODS

PubMed was searched for relevant articles. Study characteristics were abstracted and the number of studies showing no group difference or hyper- versus hypo-connnectivity in MCI was tallied. A voxel-wise (ES-SDM) meta-analysis was conducted to identify regional group differences.

RESULTS

Qualitatively, our review of 57 MCI versus HC comparisons suggests substantial inconsistency; 9 showed no group difference, 8 showed MCI > HC and 22 showed HC > MCI across the brain, and 18 showed regionally-mixed directions of effect. The meta-analysis of 31 studies revealed areas of significant hypo- and hyper-connectivity in MCI, including hypoconnectivity in the posterior cingulate cortex/precuneus (z = -3.1, p < 0.0001). Very few individual studies, however, showed patterns resembling the meta-analytic results. Methodological differences did not appear to explain inconsistencies.

CONCLUSIONS

The pattern of altered resting DMN function or connectivity in MCI is complex and variable across studies. To date, no index of DMN connectivity qualifies as a useful biomarker of MCI or risk for AD. Refinements to MCI diagnosis, including other biological markers, or longitudinal studies of progression to AD, might identify DMN alterations predictive of AD risk.

Psychoradiologic abnormalities of white matter in patients with bipolar disorder: diffusion tensor imaging studies using tract-based spatial statistics

BACKGROUND

An increasing number of psychoradiology studies that use tract-based spatial statistics (TBSS) of diffusion tensor imaging have reported abnormalities of white matter in patients with bipolar disorder; however, robust conclusions have proven elusive, especially considering some important clinical and demographic factors. In the present study, we performed a quantitative meta-analysis of TBSS studies to elucidate the most consistent white-matter abnormalities in patients with bipolar disorder.

METHODS

We conducted a systematic search up to May 2017 for all TBSS studies comparing fractional anisotropy (FA) between patients with bipolar disorder and healthy controls. We performed anisotropic effect size–signed differential mapping meta-analysis.

RESULTS

We identified a total of 22 data sets including 556 patients with bipolar disorder and 623 healthy controls. We found significant FA reductions in the genu and body of the corpus callosum in patients with bipolar disorder relative to healthy controls. No regions of increased FA were reported. In subgroup analyses, the FA reduction in the genu of the corpus callosum retained significance in patients with bipolar disorder type I, and the FA reduction in the body of the corpus callosum retained significance in euthymic patients with bipolar disorder. Meta-regression analysis revealed that the percentage of female patients was negatively correlated with reduced FA in the body of the corpus callosum.

LIMITATIONS

Data acquisition, patient characteristics and clinical variables in the included studies were heterogeneous. The small number of diffusion tensor imaging studies using TBSS in patients with bipolar disorder type II, as well as the lack of other clinical information, hindered the application of subgroup meta-analyses.

CONCLUSION

Our study consistently identified decreased FA in the genu and body of the corpus callosum, suggesting that interhemispheric communication may be the connectivity most affected in patients with bipolar disorder.

Comparing Region of Interest versus Voxel-Wise Diffusion Tensor Imaging Analytic Methods in Mild and Moderate Traumatic Brain Injury: A Systematic Review and Meta-Analysis

Diffusion tensor imaging is a magnetic resonance imaging technique that is uniquely capable of detecting microstructural tissue damage in mild and moderate traumatic brain injuries (TBIs). To date, it remains unknown if two common analytic techniques, region of interest (ROI) versus voxel-wise (VW) analyses, detect injury in similar locations. The purpose of this systematic review and meta-analysis was to directly compare the regions of abnormality elucidated by each method. Twenty-seven ROI and 11 VW studies met our inclusion criteria. Our ROI meta-analysis identified 11 regions, including the splenium of the corpus callosum, where fractional anisotropy (FA) was significantly decreased in TBI patients, compared with controls. Likewise, we identified higher mean diffusivity/apparent diffusivity constant in the genu, body, and splenium of the corpus callosum. Alternatively, our VW analysis identified one region of high FA in the right superior longitudinal fasciculus and seven regions of low FA, with the two largest located in the corpus callosum. High mean diffusivity and high radial diffusivity, both in the right inferior longitudinal fasciculus, also was revealed by our VW analysis. Moreover, we have shown that the magnitude of damage in the corpus callosum revealed by ROI analysis (z = -3.15) is greater than that demonstrated by VW analysis (z = -1.41). Overall, this study indicates that both ROI and VW analytic methods are sensitive to low FA in the corpus callosum; however, the ROI method has more power to detect the full extent of tissue abnormality in the corpus callosum. More research utilizing standardized methods and reporting is essential to fully characterize the extent to which ROI and VW analyses can concordantly detect other locations of pathology in mild and moderate TBI patients.