Figure 1.

Schematic overview of the analysis strategy. The analysis could be divided into four broad steps. First, a unique regressor was generated for every event, and event-specific evoked responses were estimated using a general linear model. The result was a map of β coefficients for each event, representing the degree to which each voxel’s activity was modulated by that event. Second, these event-specific β maps were sorted into different task conditions (cue A shown in blue, cue B show in red) and concatenated to generate a condition-specific pseudo–time series of β coefficients (i.e., a β series) at each voxel. Third, an anatomic template was used to parcellate the brain in 78 regions. The mean β series of each region was extracted, and correlations between every possible pair of regional beta series were computed to generate a {78 × 78} functional connectivity matrix for each participant and each task condition. Fourth, network connectivity and topology were analyzed using graph-based representations of network structure. Network connectivity was analyzed using the values in the correlation matrix. Edge-wise connectivity (S_E) reflected the strength of the correlation for each value in the functional connectivity matrix. For example, in the connectivity matrix shown, S_E for the connection between region of interest (ROI) 1 and ROI 2 would be .33. Region-wise connectivity (S_R) was computed as the sum of each region’s correlation values. For example, S_R for ROI 1 is computed as the sum of its correlation values with all other regions. Topologic measures were computed using graph-based representations of network structure as detailed in the main text and Section S.2 in Supplement 1. In the graph-based representation shown, each region is represented as a blue circle plotted according to the stereotactic coordinates of its centroid. Each connection, or edge, is represented as a red line and represents a suprathreshold correlation between regional beta series. The graph has been overlaid on a cortical surface rendering to provide an orientation with respect to approximate anatomical location.