Resting State Abnormalities of the Default Mode Network in Mild Cognitive Impairment: A Systematic Review and Meta-Analysis
Journal of Alzheimer's Disease June 4, 2019 L. Eyler, J. Elman, S. Hatton et al.
The default mode network (DMN) is often disrupted in Alzheimer's disease (AD), and many studies have examined DMN connectivity in people with mild cognitive impairment (MCI), a presumed AD precursor, to find a biomarker of AD risk. This systematic review and meta-analysis of 57 MCI versus healthy comparison studies found substantial inconsistency: 9 showed no group difference, 8 showed hyperconnectivity in MCI, 22 showed hypoconnectivity, and 18 showed regionally mixed directions. The meta-analysis of 31 studies revealed significant hypo- and hyperconnectivity in MCI, including hypoconnectivity in the posterior cingulate cortex/precuneus. Very few individual studies matched the meta-analytic pattern, and methodological differences did not explain the inconsistencies. No index of DMN connectivity currently qualifies as a useful biomarker of MCI or AD risk.