2.3.4. Functional connectivity density

A FCD analysis was also conducted on all datasets. Both lFCD and gFCD were computed using 3dLFCD and 3dDegreeCentrality in AFNI, respectively. The number of voxels connected to a specific voxel was determined using Pearson correlation and a correlation threshold of r ≥ 0.6. Briefly, lFCD for a given voxel was defined as the size of the continuous cluster of spatially connected voxels that were all correlated with that voxel at r ≥ 0.6 (Cohen et al., 2018; Tomasi and Volkow, 2010, 2011). This procedure was repeated for every voxel in the brain (Kundu et al., 2012; Tomasi and Volkow, 2010, 2011). gFCD was computed by counting the number of voxels functionally connected to each voxel throughout the whole brain with r ≥ 0.6 (Tomasi and Volkow, 2011).