BackgroundResting-state functional magnetic resonance imaging studies using a regional homogeneity (ReHo) method have reported that amnestic mild cognitive impairment (aMCI) was associated with abnormalities in local functional connectivity. However, their results were not conclusive.MethodsSeed-based d Mapping was used to conduct a coordinate-based meta-analysis to identify consistent ReHo alterations in aMCI.ResultsWe identified 10 studies with 11 datasets suitable for inclusion, including 378 patients with aMCI and 435 healthy controls. This meta-analysis identified significant ReHo alterations in patients with aMCI relative to healthy controls, mainly within the default mode network (DMN) (bilateral posterior cingulate cortex [PCC], right angular gyrus, bilateral middle temporal gyri, and left parahippocampal gyrus/hippocampus), executive control network (right superior parietal lobule and dorsolateral prefrontal cortex), visual network (right lingual gyrus and left middle occipital gyrus), and sensorimotor network (right paracentral lobule/supplementary motor area, right postcentral gyrus and left posterior insula). Significant heterogeneity of ReHo alterations in the bilateral PCC, left parahippocampal gyrus/hippocampus, and right superior parietal lobule/angular gyrus was observed. Exploratory meta-regression analyses indicated that general cognitive function, gender distribution, age, and education level partially contributed to this heterogeneity.ConclusionsThis study provides provisional evidence that aMCI is associated with abnormal ReHo within the DMN, executive control network, visual network, and sensorimotor network. These local functional connectivity alterations suggest coexistence of functional deficits and compensation in these networks. These findings contribute to the modeling of brain functional connectomes and to a better understanding of the neural substrates of aMCI. Confounding factors merit much attention and warrant future investigations.Electronic supplementary materialThe online version of this article (10.1186/s40035-018-0134-8) contains supplementary material, which is available to authorized users.

Voxel-based morphometry (VBM) studies have provided cumulative evidence of gray matter (GM) atrophy in patients with Parkinson's disease with dementia (PDD) relative to healthy controls (HC). However, not all the studies reported entirely consistent findings. A systematic search for VBM studies of PDD patients and HC subjects published in PubMed and Embase databases from January 2000 to June 2012 was conducted. Meta-analysis was performed by using a newly improved voxel-based meta-analytic technique, effect size signed differential mapping, to quantitatively explore the GM abnormalities between PDD patients and HC subjects. A total of 6 cross-sectional VBM studies involving 105 PDD patients and 131 HC subjects met the inclusion criteria. Considerable regional GM decrease was detected in the medial temporal lobe (MTL) and basal ganglia. The findings of the present study remained largely unchanged in the entire brain jackknife sensitivity analyses. Meta-regression showed dementia severity correlated with the left MTL. The present meta-analysis provided evidence of PDD-related GM atrophy, which suggested MTL and basal ganglia were implicated in PDD. This finding could give us further insight about the pathophysiological basis revealed by structure abnormalities in PDD.

Voxel-based morphometry (VBM) studies have provided cumulative evidence of gray matter (GM) atrophy in patients with progressive supranuclear palsy (PSP) relative to healthy controls (HC). However, not all findings have been entirely concordant. Herein, we performed a quantitative meta-analysis study in order to consistently quantify GM anomalies in PSP. We conducted a systematic search for VBM studies of PSP patients and HC using PubMed and Embase databases from January 2000 to May 2012. Meta-analysis of these VBM studies was performed using a newly improved voxel-based meta-analytic technique, effect-size signed differential mapping. A total of 9 cross-sectional VBM studies that involved 143 PSP patients and 216 HC subjects met the inclusion criteria. Considerable regional GM volume decrease was detected in the thalamus, basal ganglia, midbrain, insular cortex, and frontal cortex. These findings remained largely unchanged following jackknife sensitivity analyses. The present meta-analysis provided evidence of PSP-specific GM atrophy. This finding might help contribute to our understanding of the neurobiological basis underlying PSP.

Brain 18F-fluorodeoxyglucose positron emission tomography (FDG-PET) has been utilized to monitor disease conversion from amnestic mild cognitive impairment (aMCI) to Alzheimer’s dementia (AD). However, the conversion patterns of FDG-PET metabolism across studies are not conclusive. We conducted a voxel-wise meta-analysis using Seed-based d Mapping that included 10 baseline voxel-wise FDG-PET comparisons between 93 aMCI converters and 129 aMCI non-converters from nine longitudinal studies. The most robust and reliable metabolic alterations that predicted conversion from aMCI to AD were localized in the left posterior cingulate cortex (PCC)/precuneus. Furthermore, meta-regression analyses indicated that baseline mean age and severity of cognitive impairment, and follow-up duration were significant moderators for metabolic alterations in aMCI converters. Our study revealed hypometabolism in the left PCC/precuneus as an early feature in the development of AD. This finding has important implications in understanding the neural substrates for AD conversion and could serve as a potential imaging biomarker for early detection of AD as well as for tracking disease progression at the predementia stage.Electronic supplementary materialThe online version of this article (10.1186/s40035-018-0114-z) contains supplementary material, which is available to authorized users.

Many studies have applied arterial spin labeling (ASL) to characterize cerebral perfusion patterns of Alzheimer's disease (AD). However, findings across studies are not conclusive. A quantitatively voxel-wise meta-analysis to pool the resting-state ASL studies that measure regional cerebral blood flow (rCBF) alterations in AD was conducted to identify the most consistent and replicable perfusion pattern using seed-based d mapping. The meta-analysis, including 17 ASL studies encompassing 327 AD patients and 357 healthy controls, demonstrated that decreased rCBF in AD patients relative to healthy controls were consistently identified in the bilateral posterior cingulate cortices (PCC)/precuneus, bilateral inferior parietal lobules (IPLs), and left dorsolateral prefrontal cortex. The meta-regression analysis showed that more severe cognitive impairment in the AD samples correlated with greater decreases of rCBF in the bilateral PCC and left IPL. This study characterizes an aberrant ASL-rCBF perfusion pattern of AD involving the posterior default mode network and executive network, which are implicated in its pathophysiology and hold promise for developing imaging biomarkers.