Figure 1.
Stepwise functional connectivity analysis for identifying the brain connectome of modal cortex. A, The functional connectivity map of the posterior cingulate cortex is computed using a conventional seed-based approach, which is displayed on a cortical surface and as a network graph (star-net topology). Only one link-step connection is computed in this approach. B, On the other hand, SFC analysis takes full advantage of the whole connectivity association matrix of the individual brains to analyze the functional connectivity of seed regions using a wide range of link-step distances. C illustrates SFC analysis in detail. From any node (j; red nodes) in the brain, we compute the number of pathways (Djil) that connect to a voxel in an a priori seed node (i; blue node) with a particular number of links l (where l is the specific link-step distance). Similar to the conventional seed-based approach, in the one-link-step distance case, only direct connections to the seed are considered (small arrows in C-a). In higher-order step distances, we explore connectivity patterns beyond direct connections, subsequently expanding to the rest of the brain (C-b, C-c). Note that for schematic purposes only, one seed voxel node (blue color) is displayed in C-a, C-b, and C-c.