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European Neuropsychopharmacology : the... Nov 2013Aberrant glutamate neurotransmission has been implicated in the pathophysiology of bipolar disorder with accumulating evidence from imaging, post-mortem and pathology... (Meta-Analysis)
Meta-Analysis Review
Aberrant glutamate neurotransmission has been implicated in the pathophysiology of bipolar disorder with accumulating evidence from imaging, post-mortem and pathology studies. Studies investigating in vivo changes to the glutamatergic system have not been as consistent and warrant clarification. Studies utilizing proton-magnetic resonance spectroscopy ((1)H-MRS) have reported increased levels of combined glutamate and glutamine ("Glx"), which have been linked to impairments in N-methyl-d-aspartate (NMDA) receptor function. Similarly, neurophysiological studies utilising mismatch negativity (MMN) as an index of NMDA receptor function, have reported impairments in bipolar disorder. Here, we provide a systematic review of the literature in regards to the concentration of Glx and the magnitude of MMN in bipolar disorder. Separate meta-analyses revealed that bipolar disorder was associated with increased Glx concentration and decreased MMN-both measured frontally. The current findings corroborate previous evidence indicating that bipolar disorder is characterized by a perturbed frontal glutamate system. These observed changes in bipolar disorder might manifest as impairments in neuronal-glial interactions that lead to disrupted neuronal output and ultimately result in the characteristic neurocognitive sequelae associated with this disorder.
Topics: Bipolar Disorder; Evoked Potentials; Frontal Lobe; Glutamic Acid; Glutamine; Humans; Magnetic Resonance Spectroscopy; Protons
PubMed: 23968965
DOI: 10.1016/j.euroneuro.2013.07.007 -
The Cochrane Database of Systematic... Mar 2020Mild cognitive impairment (MCI) due to Alzheimer's disease is the symptomatic predementia phase of Alzheimer's disease dementia, characterised by cognitive and... (Meta-Analysis)
Meta-Analysis
BACKGROUND
Mild cognitive impairment (MCI) due to Alzheimer's disease is the symptomatic predementia phase of Alzheimer's disease dementia, characterised by cognitive and functional impairment not severe enough to fulfil the criteria for dementia. In clinical samples, people with amnestic MCI are at high risk of developing Alzheimer's disease dementia, with annual rates of progression from MCI to Alzheimer's disease estimated at approximately 10% to 15% compared with the base incidence rates of Alzheimer's disease dementia of 1% to 2% per year.
OBJECTIVES
To assess the diagnostic accuracy of structural magnetic resonance imaging (MRI) for the early diagnosis of dementia due to Alzheimer's disease in people with MCI versus the clinical follow-up diagnosis of Alzheimer's disease dementia as a reference standard (delayed verification). To investigate sources of heterogeneity in accuracy, such as the use of qualitative visual assessment or quantitative volumetric measurements, including manual or automatic (MRI) techniques, or the length of follow-up, and age of participants. MRI was evaluated as an add-on test in addition to clinical diagnosis of MCI to improve early diagnosis of dementia due to Alzheimer's disease in people with MCI.
SEARCH METHODS
On 29 January 2019 we searched Cochrane Dementia and Cognitive Improvement's Specialised Register and the databases, MEDLINE, Embase, BIOSIS Previews, Science Citation Index, PsycINFO, and LILACS. We also searched the reference lists of all eligible studies identified by the electronic searches.
SELECTION CRITERIA
We considered cohort studies of any size that included prospectively recruited people of any age with a diagnosis of MCI. We included studies that compared the diagnostic test accuracy of baseline structural MRI versus the clinical follow-up diagnosis of Alzheimer's disease dementia (delayed verification). We did not exclude studies on the basis of length of follow-up. We included studies that used either qualitative visual assessment or quantitative volumetric measurements of MRI to detect atrophy in the whole brain or in specific brain regions, such as the hippocampus, medial temporal lobe, lateral ventricles, entorhinal cortex, medial temporal gyrus, lateral temporal lobe, amygdala, and cortical grey matter.
DATA COLLECTION AND ANALYSIS
Four teams of two review authors each independently reviewed titles and abstracts of articles identified by the search strategy. Two teams of two review authors each independently assessed the selected full-text articles for eligibility, extracted data and solved disagreements by consensus. Two review authors independently assessed the quality of studies using the QUADAS-2 tool. We used the hierarchical summary receiver operating characteristic (HSROC) model to fit summary ROC curves and to obtain overall measures of relative accuracy in subgroup analyses. We also used these models to obtain pooled estimates of sensitivity and specificity when sufficient data sets were available.
MAIN RESULTS
We included 33 studies, published from 1999 to 2019, with 3935 participants of whom 1341 (34%) progressed to Alzheimer's disease dementia and 2594 (66%) did not. Of the participants who did not progress to Alzheimer's disease dementia, 2561 (99%) remained stable MCI and 33 (1%) progressed to other types of dementia. The median proportion of women was 53% and the mean age of participants ranged from 63 to 87 years (median 73 years). The mean length of clinical follow-up ranged from 1 to 7.6 years (median 2 years). Most studies were of poor methodological quality due to risk of bias for participant selection or the index test, or both. Most of the included studies reported data on the volume of the total hippocampus (pooled mean sensitivity 0.73 (95% confidence interval (CI) 0.64 to 0.80); pooled mean specificity 0.71 (95% CI 0.65 to 0.77); 22 studies, 2209 participants). This evidence was of low certainty due to risk of bias and inconsistency. Seven studies reported data on the atrophy of the medial temporal lobe (mean sensitivity 0.64 (95% CI 0.53 to 0.73); mean specificity 0.65 (95% CI 0.51 to 0.76); 1077 participants) and five studies on the volume of the lateral ventricles (mean sensitivity 0.57 (95% CI 0.49 to 0.65); mean specificity 0.64 (95% CI 0.59 to 0.70); 1077 participants). This evidence was of moderate certainty due to risk of bias. Four studies with 529 participants analysed the volume of the total entorhinal cortex and four studies with 424 participants analysed the volume of the whole brain. We did not estimate pooled sensitivity and specificity for the volume of these two regions because available data were sparse and heterogeneous. We could not statistically evaluate the volumes of the lateral temporal lobe, amygdala, medial temporal gyrus, or cortical grey matter assessed in small individual studies. We found no evidence of a difference between studies in the accuracy of the total hippocampal volume with regards to duration of follow-up or age of participants, but the manual MRI technique was superior to automatic techniques in mixed (mostly indirect) comparisons. We did not assess the relative accuracy of the volumes of different brain regions measured by MRI because only indirect comparisons were available, studies were heterogeneous, and the overall accuracy of all regions was moderate.
AUTHORS' CONCLUSIONS
The volume of hippocampus or medial temporal lobe, the most studied brain regions, showed low sensitivity and specificity and did not qualify structural MRI as a stand-alone add-on test for an early diagnosis of dementia due to Alzheimer's disease in people with MCI. This is consistent with international guidelines, which recommend imaging to exclude non-degenerative or surgical causes of cognitive impairment and not to diagnose dementia due to Alzheimer's disease. In view of the low quality of most of the included studies, the findings of this review should be interpreted with caution. Future research should not focus on a single biomarker, but rather on combinations of biomarkers to improve an early diagnosis of Alzheimer's disease dementia.
Topics: Aged; Aged, 80 and over; Alzheimer Disease; Atrophy; Brain; Cognitive Dysfunction; Disease Progression; Entorhinal Cortex; Hippocampus; Humans; Lateral Ventricles; Magnetic Resonance Imaging; Middle Aged; Neuroimaging; Organ Size; Prospective Studies; Sensitivity and Specificity; Temporal Lobe
PubMed: 32119112
DOI: 10.1002/14651858.CD009628.pub2 -
HIV infection and the fronto-striatal system: a systematic review and meta-analysis of fMRI studies.AIDS (London, England) Mar 2014Functional MRI studies investigating the impact of HIV on the brain have implicated the involvement of fronto-striatal circuitry. However, to date there is no review and... (Meta-Analysis)
Meta-Analysis Review
Functional MRI studies investigating the impact of HIV on the brain have implicated the involvement of fronto-striatal circuitry. However, to date there is no review and meta-analysis of this work. We systematically reviewed the literature and performed a meta-analysis of functional magnetic resonance imaging (fMRI) studies in HIV-infected individuals using a well validated tool recently developed for use in fMRI, 'GingerALE'. Twenty-one studies (468 HIV+, 270 HIV- controls) were qualitatively reviewed, of which six (105 HIV+, 102 controls) utilized fMRI paradigms engaging the fronto-striatal-parietal network, making a quantitative analysis possible. Our meta-analysis revealed consistent functional differences in the left inferior frontal gyrus and caudate nucleus between infected participants and controls across these studies. This fronto-striatal dysfunction was qualitatively related to cognitive impairment, disease progression and treatment effects. Although further work needs to be done to further delineate the potentially confounding influence of substance abuse and HIV-related comorbidities, as well as HIV's effect on functional haemodynamic vascular coupling, these findings indicate that further investigation of the fronto-striatal sub-networks in HIV-infected patients is warranted.
Topics: AIDS Dementia Complex; Frontal Lobe; HIV Infections; Humans; Magnetic Resonance Imaging; Visual Cortex
PubMed: 24300546
DOI: 10.1097/QAD.0000000000000151 -
Medicine Sep 2023This is the first meta-analysis conducted to compare the hippocampal volume measured by magnetic resonance imaging (MRI) in healthy normal subjects, mild cognitive... (Meta-Analysis)
Meta-Analysis
BACKGROUND
This is the first meta-analysis conducted to compare the hippocampal volume measured by magnetic resonance imaging (MRI) in healthy normal subjects, mild cognitive impairment (MCI) and Alzheimer disease (AD), and to analyze the relationship between hippocampal volume changes and MCI and AD.
METHODS
English literatures published from January 2004 to December 2006 were extracted from PubMed, Embase, Wanfang Medical, and China National Knowledge Infrastructure databases. Statistical analysis was carried out with Stata/SE 16.0 software.
RESULTS
The smaller the volume of the hippocampus measured by MRI, the more severe the cognitive impairment or AD. Different MRI post-measurement correction methods have different measurement results: Left hippocampal volume measured by MRI Raw volume method is negatively correlated with MCI and AD (OR [odds ratio] = 0.58, 95%CI [confidence interval]: 0.42, 0.75) right hippocampal volume measured was not associated with MCI OR AD (OR = 0.87, 95%CI: 0.56, 1.18); left hippocampal volume measured by MRI total intracranial volume (TIV) Correction was not associated with MCI and AD (OR = 0.90, 95%CI: 0.62, 1.19), measured right hippocampal volume was not associated with MCI OR AD (OR = 0.81, 95%CI: 0.49, 1.12); left hippocampal volume measured by MRI TIV Correction was not associated with MCI and AD (OR = 0.90, 95%CI: 0.62, 1.19), measured right hippocampus volume was negatively associated with MCI and AD (OR = 0.49, 95%CI: 0.35, 0.62).
CONCLUSION
The shrinkage of hippocampus volume is closely related to MCI and AD. MRI measurement of hippocampus volume is not only an auxiliary diagnostic tool for MCI and AD, but also a good prognosis assessment tool.
Topics: Humans; Alzheimer Disease; Hippocampus; Cognitive Dysfunction; Temporal Lobe; China
PubMed: 37682140
DOI: 10.1097/MD.0000000000034997 -
Wiley Interdisciplinary Reviews.... Jan 2021Prior knowledge and long-term memory can guide our attention to facilitate search for and detection of subtle targets embedded in a complex scene. A number of... (Meta-Analysis)
Meta-Analysis
Prior knowledge and long-term memory can guide our attention to facilitate search for and detection of subtle targets embedded in a complex scene. A number of neuropsychological and experimental studies have investigated this effect, yet results in the field remain mixed, as there is a lack of consensus regarding the neural correlates thought to support memory-guided attention. The purpose of this systematic review and meta-analysis was to identify a common set of brain structures involved in memory-guided attention. Statistical analyses were computed on functional magnetic resonance imaging (fMRI) studies that presented participants with a task that required them to detect a target or a change embedded in repeated and novel complex visual displays. After a systematic search, 10 fMRI studies met the selection criteria and were included in the analysis. The results yielded four significant clusters. Activity in right inferior parietal (Brodmann area [BA] 9) and right superior parietal (BA 7) lobes suggests involvement of a fronto-parietal attention network, while activity in left mid-cingulate cortex (BA 23) and right middle frontal gyrus (BA 10) suggests involvement of a fronto-parietal control network. These findings are consistent with the notion that fronto-parietal circuits are important for interfacing retrieved memories with attentional systems to guide search. This article is categorized under: Psychology > Memory Psychology > Learning Psychology > Attention.
Topics: Attention; Brain; Frontal Lobe; Humans; Magnetic Resonance Imaging; Memory; Nerve Net; Parietal Lobe
PubMed: 33099860
DOI: 10.1002/wcs.1546 -
The European Journal of Neuroscience Mar 2009The age of an experimental animal can be a critical variable, yet age matters are often overlooked within neuroscience. Many studies make use of young animals, without... (Review)
Review
The age of an experimental animal can be a critical variable, yet age matters are often overlooked within neuroscience. Many studies make use of young animals, without considering possible differences between immature and mature subjects. This is especially problematic when attempting to model traits or diseases that do not emerge until adulthood. In this commentary we discuss the reasons for this apparent bias in age of experimental animals, and illustrate the problem with a systematic review of published articles on long-term potentiation. Additionally, we review the developmental stages of a rat and discuss the difficulty of using the weight of an animal as a predictor of its age. Finally, we provide original data from our laboratory and review published data to emphasize that development is an ongoing process that does not end with puberty. Developmental changes can be quantitative in nature, involving gradual changes, rapid switches, or inverted U-shaped curves. Changes can also be qualitative. Thus, phenomena that appear to be unitary may be governed by different mechanisms at different ages. We conclude that selection of the age of the animals may be critically important in the design and interpretation of neurobiological studies.
Topics: Age Factors; Aging; Animals; Behavior; Hippocampus; Humans; Long-Term Potentiation; Neurons; Neurosciences; Research Design
PubMed: 19291226
DOI: 10.1111/j.1460-9568.2009.06648.x -
Reviews in the Neurosciences Apr 2023The last decades have seen a rise in the use of transcranial direct current stimulation (tDCS) approaches to modulate brain activity and associated behavior.... (Review)
Review
The last decades have seen a rise in the use of transcranial direct current stimulation (tDCS) approaches to modulate brain activity and associated behavior. Concurrently, eye tracking (ET) technology has improved to allow more precise quantitative measurement of gaze behavior, offering a window into the mechanisms of vision and cognition. When combined, tDCS and ET provide a powerful system to probe brain function and measure the impact on visual function, leading to an increasing number of studies that utilize these techniques together. The current pre-registered, systematic review seeks to describe the literature that integrates these approaches with the goal of changing brain activity with tDCS and measuring associated changes in eye movements with ET. The literature search identified 26 articles that combined ET and tDCS in a probe-and-measure model and are systematically reviewed here. All studies implemented controlled interventional designs to address topics related to oculomotor control, cognitive processing, emotion regulation, or cravings in healthy volunteers and patient populations. Across these studies, active stimulation typically led to changes in the number, duration, and timing of fixations compared to control stimulation. Notably, half the studies addressed emotion regulation, each showing hypothesized effects of tDCS on ET metrics, while tDCS targeting the frontal cortex was widely used and also generally produced expected modulation of ET. This review reveals promising evidence of the impact of tDCS on eye movements and associated psychological function, offering a framework for effective designs with recommendations for future studies.
Topics: Humans; Transcranial Direct Current Stimulation; Eye Movements; Prefrontal Cortex; Cognition; Nervous System Physiological Phenomena
PubMed: 36310385
DOI: 10.1515/revneuro-2022-0082 -
Journal of Magnetic Resonance Imaging :... Aug 2022Automated magnetic resonance imaging (MRI) volumetry is a promising tool to evaluate regional brain volumes in dementia and especially Alzheimer's disease (AD). (Meta-Analysis)
Meta-Analysis
BACKGROUND
Automated magnetic resonance imaging (MRI) volumetry is a promising tool to evaluate regional brain volumes in dementia and especially Alzheimer's disease (AD).
PURPOSE
To compare automated methods and the gold standard manual segmentation in measuring regional brain volumes on MRI across healthy controls, patients with mild cognitive impairment, and patients with dementia due to AD.
STUDY TYPE
Systematic review and meta-analysis.
DATA SOURCES
MEDLINE, Embase, and PsycINFO were searched through October 2021.
FIELD STRENGTH
1.0 T, 1.5 T, or 3.0 T.
ASSESSMENT
Two review authors independently identified studies for inclusion and extracted data. Methodological quality was assessed using the Quality Assessment of Diagnostic Accuracy Studies 2 (QUADAS-2).
STATISTICAL TESTS
Standardized mean differences (SMD; Hedges' g) were pooled using random-effects meta-analysis with robust variance estimation. Subgroup analyses were undertaken to explore potential sources of heterogeneity. Sensitivity analyses were conducted to examine the impact of the within-study correlation between effect estimates on the meta-analysis results.
RESULTS
Seventeen studies provided sufficient data to evaluate the hippocampus, lateral ventricles, and parahippocampal gyrus. The pooled SMD for the hippocampus, lateral ventricles, and parahippocampal gyrus were 0.22 (95% CI -0.50 to 0.93), 0.12 (95% CI -0.13 to 0.37), and -0.48 (95% CI -1.37 to 0.41), respectively. For the hippocampal data, subgroup analyses suggested that the pooled SMD was invariant across clinical diagnosis and field strength. Subgroup analyses could not be conducted on the lateral ventricles data and the parahippocampal gyrus data due to insufficient data. The results were robust to the selected within-study correlation value.
DATA CONCLUSION
While automated methods are generally comparable to manual segmentation for measuring hippocampal, lateral ventricle, and parahippocampal gyrus volumes, wide 95% CIs and large heterogeneity suggest that there is substantial uncontrolled variance. Thus, automated methods may be used to measure these regions in patients with AD but should be used with caution.
EVIDENCE LEVEL
3 TECHNICAL EFFICACY: Stage 3.
Topics: Alzheimer Disease; Cognitive Dysfunction; Hippocampus; Humans; Lateral Ventricles; Magnetic Resonance Imaging
PubMed: 34964531
DOI: 10.1002/jmri.28037 -
Revista de Psiquiatria Y Salud Mental 2022The neural correlates of the cognitive dysfunction in first-episode psychosis (FEP) are still unclear. The present review and meta-analysis provide an update of the... (Meta-Analysis)
Meta-Analysis Review
INTRODUCTION
The neural correlates of the cognitive dysfunction in first-episode psychosis (FEP) are still unclear. The present review and meta-analysis provide an update of the location of the abnormalities in the fMRI-measured brain response to cognitive processes in individuals with FEP.
METHODS
Systematic review and voxel-based meta-analysis of cross-sectional fMRI studies comparing neural responses to cognitive tasks between individuals with FEP and healthy controls (HC) according to PRISMA guidelines.
RESULTS
Twenty-six studies were included, comprising 598 individuals with FEP and 567 HC. Individual studies reported statistically significant hypoactivation in the dorsolateral prefrontal cortex (6 studies), frontal lobe (8 studies), cingulate (6 studies) and insula (5 studies). The meta-analysis showed statistically significant hypoactivation in the left anterior insula, precuneus and bilateral striatum.
CONCLUSIONS
While the studies tend to highlight frontal hypoactivation during cognitive tasks in FEP, our meta-analytic results show that the left precuneus and insula primarily display aberrant activation in FEP that may be associated with salience attribution to external stimuli and related to deficits in perception and regulation.
Topics: Cognition; Cross-Sectional Studies; Humans; Magnetic Resonance Imaging; Parietal Lobe; Psychotic Disorders
PubMed: 35840277
DOI: 10.1016/j.rpsmen.2022.06.004 -
Molecular Psychiatry Mar 2022There is growing evidence that placebo effects can meaningfully modulate the brain. However, there has been little consideration of whether these changes may overlap... (Meta-Analysis)
Meta-Analysis
There is growing evidence that placebo effects can meaningfully modulate the brain. However, there has been little consideration of whether these changes may overlap with regions/circuits targeted by depression treatments and what the implications of this overlap would be on measuring efficacy in placebo-controlled clinical trials. In this systematic review and meta-analysis, we searched PubMed/Medline and Google Scholar for functional MRI and PET neuroimaging studies of placebo effects. Studies recruiting both healthy subjects and patient populations were included. Neuroimaging coordinates were extracted and included for Activation Likelihood Estimation (ALE) meta-analysis. We then searched for interventional studies of transcranial magnetic stimulation (TMS) and deep brain stimulation (DBS) for depression and extracted target coordinates for comparative spatial analysis with the placebo effects maps. Of 1169 articles identified, 34 neuroimaging studies of placebo effects were included. There were three significant clusters of activation: left dorsolateral prefrontal cortex (DLPFC) (x = -41, y = 16, z = 34), left sub-genual anterior cingulate cortex (sgACC)/ventral striatum (x = -8, y = 18, z = -15) and the right rostral anterior cingulate cortex (rACC) (x = 4, y = 42, z = 10). There were two significant deactivation clusters: right basal ganglia (x = 20, y = 2, z = 7) and right dorsal anterior cingulate cortex (dACC) (x = 1, y = -5, z = 45). TMS and DBS targets for depression treatment overlapped with the left DLPFC cluster and sgACC cluster, respectively. Our findings identify a common set of brain regions implicated in placebo effects across healthy individuals and patient populations, and provide evidence that these regions overlap with depression treatment targets. We model the statistical impacts of this overlap and demonstrate critical implications on measurements of clinical trial efficacy for this field.
Topics: Depression; Gyrus Cinguli; Humans; Magnetic Resonance Imaging; Neuroimaging; Placebo Effect; Prefrontal Cortex; Transcranial Magnetic Stimulation
PubMed: 34903861
DOI: 10.1038/s41380-021-01397-3