fMRI reflects neural activity indirectly, based on dynamic changes in blood oxygenation and flow resulting from changes in neural metabolic demand20. The task deployed in tfMRI (Fig 3) involves matching shapes and emotionally negative faces21 and was chosen to engage a range of neural systems, from low-level sensory and motor to perceptual (e.g., fusiform) and emotional (e.g., amygdala) areas. The 16 tfMRI IDPs quantitate the strength of brain activity changes for specific aspects of the task, in regions defined using the group-averaged activation maps shown, in three task conditions. Resting-state fMRI (Fig 4) identifies connected brain regions based on common fluctuations in activity over time in the absence of an explicit task22. Sets of voxels that co-fluctuate most strongly correspond to brain regions, referred to as network “nodes”; different nodes may have weaker co-fluctuations indicating a connection between them, a network “edge”. The group analysis of the rfMRI data generated two atlases of these functional networks - a “low-dimensional” decomposition of the brain into 21 functional sub-divisions and a higher-dimensional parcellation into 55 sub-divisions. IDPs represent a) edge connectivity strengths and b) node fluctuation amplitudes (Fig 4).
