FIGURE 4.

Are atlas size effects driven by the number of regions or by the number of voxels? (a) In an atlas with 950 ROIs, we randomly selected 50, 100, 150, … , 700 ROIs to get quality estimates depending only on the number of regions but independent of the number of voxels. Neither ROI‐based tSNR nor TFC changes with the number of regions. Only the relationship between TFC and motion is slightly weaker for smaller numbers of regions. (b) To create a brain parcellation with a fixed number of regions but a varying number of voxels, we built different geometrical shapes around a central voxel of a region. (c) Within an atlas of 100 ROIs, we varied the number of voxels that formed a region. Both voxel‐based tSNR and TFC depend on the number of voxels. Moreover, while the tSNR‐DVARS relationship is stronger for the smaller number of voxels, the opposite is present for the TFC‐motion relationships