Figure 2. Degree is influenced by community size in RSFC graphs.
A) The RSFC correlation matrix of a 264-node graph in 120 young adults. Communities over a range of thresholds are shown as colors in the second panel. The number of nodes in the communities and node strengths at every threshold are shown in the third and fourth panels. A linear fit of node strength to community size is plotted for the 2, 4, 6, and 8% edge density analyses. Small dots indicate individual datapoints, large dots indicate average values in a community. Fits excluded communities with fewer than 5 nodes. The threshold range used corresponds to that used in (Power et al., 2011) and spans thresholds where many communities are present (higher edge densities such as 20% or 15% yield coarse structure with 2 or 4 communities) down to thresholds where the graph begins to fragment due to edge removal. B) Communities were identified in a voxelwise graph formed in the same subjects. For the 5% edge density analysis, for every voxel, the size of its community and its strength is shown on a brain surface. The default mode system is the largest community and contains the voxels with highest degree. Linear fits of node strength to community size at several thresholds are shown. Fits excluded communities with less than 250 nodes. These thresholds correspond to those used in (Power et al., 2011). C) R2 of linear fits of node strength to community size at several thresholds in each network (thresholds are reported in terms of edge density and the threshold used on the correlation matrix to produce the desired edge density).