Network Analysis of Intrinsic Functional Brain Connectivity in Alzheimer's Disease
Figure 1
Graph metrics–degree, λ (L/Lran), γ (C/Cran), σ (γ/λ), for the AD group (Δ) and the control group (○) at three frequency intervals–0.01 to 005 Hz (green), 0.06 to 0.12 Hz (blue), and 0.13 to 0.25 Hz (red).
(A) For both groups, the mean degree–a measure of network connectivity is highest at Scale 3 for a wide range of correlation thresholds (0.01<R<0.7), (B) The mean characteristic path length (λ) is low (1<λ<1.27) and shows similar trends at all the scales (C) The clustering coefficient (γ) for both groups is highest at Scale 3. (D) Due to higher mean γ values, the small-world measure σ (γ/λ) is highest at Scale 3 for both groups. The small-world property (σ>1) showed a linear increase in small-worldness as the threshold increased (degree decreased). σ values for higher correlation thresholds are hard to interpret as at higher threshold values graphs of functional brain networks have fewer edges (smaller degree) and tend to split into isolated sub-graphs.