In contrast to the seed map approach, which finds voxels related to only a single seed, a region or seed matrix approach can be used to study the relationships between a defined set of regions. While on the surface, this approach may be thought of as “seed based” in that it utilizes seed regions, it is very different from the seed maps described above. Instead of starting with a single functionally- or anatomically-defined region of interest and correlating its timecourse with every other voxel, one starts with a group of regions either functionally or anatomically defined. The average timecourse of each region is then correlated with that of each other region to make a matrix of correlation values (see Fig. 2). Since the rs-fcMRI correlations used to define edges are a measure of similarity between two regions, each cell of the matrix will have a value. In an attempt to study biologically significant functional relationships, correlations above a given value may be labeled as connections or edges (see Dosenbach et al. 2007 and Fair et al. 2007 for examples). However,
