Fig. 1. Overview of the intrinsic connectivity distribution analysis method.

Intrinsic Functional Connectivity of each voxel, as measured by the Intrinsic Connectivity Distribution (ICD), is calculated by correlating the time series for a grey matter voxel with every other voxel’s time course. This procedure is repeated for every voxel, resulting in a voxel-by-voxel correlation matrix. From this matrix, a single row is extracted, which represents all correlations to a voxel, and converted to a histogram to estimate the distribution of connectivity for that voxel. From this distribution, a survival function is constructed and fitted with a stretch exponential with unknown parameters α and β. For our purposes, α controls the rate of decay of the survival function with a larger α indicating a slower decay and larger global connectivity. The α ICD maps can then be thresholded resulting in a whole-brain parametric image that reveals putative hubs of the individual connectome.