The Default Mode Network in Healthy Individuals: A Systematic Review and Meta-Analysis.
Level 3 - non-randomized controlled study
Systematic review and meta-analysis of observational neuroimaging studies
PubMed 27917679 · doi:10.1089/brain.2016.0438
What was done
The authors systematically searched literature up to August 2016 for studies evaluating resting-state default mode network (DMN) functional connectivity in healthy individuals across age, sex, cognitive function, and analysis type. Two independent reviewers selected eligible studies based on predetermined criteria. Studies providing sufficient spatial statistical data were included in a voxel-wise meta-analysis to evaluate age-related connectivity differences.
What was found
The abstract reports qualitative directions without effect sizes, test statistics, or confidence intervals. DMN functional connectivity strength followed an inverse U-shape across age, peaking in adulthood and remaining lowest in children and older adults. Cognitive performance correlated positively with DMN connectivity, and females demonstrated stronger intranetwork connectivity than males. The voxel-wise meta-analysis confirmed an immature network in children relative to adults and diminished connectivity in older adults relative to younger adults. The effect of specific fMRI analysis techniques was inconclusive.
Why it matters
Characterizing normal variation in DMN connectivity across demographics provides a normative baseline required to distinguish healthy developmental trajectories from neurodegenerative or psychiatric network disruptions.
Limits
The abstract reports no numerical values, effect sizes, sample sizes, or total count of included studies. Quantitative voxel-wise meta-analysis could only be performed for the age comparison due to data limitations across other variables. Inherent heterogeneity across imaging parameters and fMRI analysis pipelines limited definitive methodological conclusions.
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