Figure 1.
Whole-brain functional networks in CN, MCI, and AD.
The first row displays the correlation matrices obtained from partial correlation coefficients (indicated by color bar, range from −1.0 to 1.0) between 90 regions of interests controlling for age, education and gender. The second row displays binary matrices thresholded at a fixed density 15%. The third row illustrates the corresponding brain connectivity graph from the binary matrices. Brain connectivity graphs were visualized using the BrainNet viewer (NKLCNL, Beijing Normal University). Abbreviations for the regions are expanded in Table 1. CN = cognitively normal; MCI = mild cognitive impairment; AD = Alzheimer’s disease.
Table 1.
Anatomical parcellation defined by automated anatomical labeling atlas and abbreviations for the regions.
Table 2.
Demographic and clinical characteristics.
Figure 2.
Small-world index of functional brain networks in CN, MCI, and AD.
σ = Small-world index; CN = cognitively normal; MCI = mild cognitive impairment; AD = Alzheimer’s disease. *p<0.05 for CN vs. MCI (significant at density of 14%∼15%); †p<0.05 for AD vs. MCI (significant at 15% and 18%).
Figure 3.
AD- and MCI- related alterations in small-world parameters. A.
The clustering coefficients (Cp) from cognitively normal (CN, black dotted line), mild cognitive impairment (MCI, blue line) and Alzheimer’s disease (AD, red line). *p<0.05 for CN vs. MCI (significant at density of 19%∼40%).; †p<0.05 for CN vs. AD (significant at 19%∼26%, and 32%∼40%); ‡p<0.05 for MCI vs. AD (significant at 11%∼12%, 17%∼19% and 22%∼23%). B. The Lp from CN, MCI and AD. *p<0.05 for MCI vs. AD (significant at 13%, 23%, and 25%∼26%). C. The Cp from AD with clinical dementia rating (CDR) 0.5 (AD_very mild, orange line), and AD with CDR 1.0 (AD_mild, purple line). *p<0.05 for AD_very mild vs. AD_mild (significant at 18%∼38%). D. The Lp from AD_very mild and AD_mild. *p<0.05 for AD_very mild vs. AD_mild (significant at 11%∼39%).
Figure 4.
AD- and MCI -related alterations in hub regions.
Hubs were visualized using the BrainNet viewer (NKLCNL, Beijing Normal University). Purple circle indicates the regions where both Alzheimer’s disease (AD) and mild cognitive impairment (MCI) networks showed decreased betweenness centrality compared with cognitively normal (CN). Red circle indicates the regions where AD network additionally showed decreased betweenness centrality compared with CN. Blue circle indicates the regions where MCI network additionally showed decreased betweenness centraility compared with CN. Abbreviations for the regions are expanded in Table 1. L = left; R = right.
Figure 5.
Connectivity associated with left IFGtriang seed and connectivity reductions in CN, MCI, and AD. A.
Correlation coefficients map (R-map) showing connectivity associated with left IFGtriang seed in CN. B. R-map showing connectivity associated with left IFGtriang seed in MCI. C. R-map showing connectivity associated with left IFGtriang seed in AD. D. Z-statistics map showing reduced connectivity with left IFGtriang seed in MCI compared to CN. E. Z-statistics map showing reduced connectivity left IFGtriang seed in AD compared to CN (p<0.05, FDR-corrected). IFGtriang = triangular part of inferior frontal gyrus; CN = cognitively normal; MCI = mild cognitive impairment; AD = Alzheimer’s disease; L = left; R = right.
Figure 6.
Connectivity associated with left PCUN seed and connectivity reductions in CN, MCI, and AD. A.
Correlation coefficients map (R-map) showing connectivity associated with left PCUN seed in CN. B. R-map showing connectivity associated with left PCUN seed in MCI. C. R-map showing connectivity associated with left PCUN seed in AD. D. Z-statistics map showing reduced connectivity with left PCUN seed in MCI compared to CN. E. Z-statistics map showing reduced connectivity left PCUN seed in AD compared to CN (p<0.05, FDR-corrected). PCUN = precuneus; CN = cognitively normal; MCI = mild cognitive impairment; AD = Alzheimer’s disease; L = left; R = right.