Examining Within-Module and Between-Module Connectivity of the LIFG (Triangularis)

Given that the graph-theoretic measure PC only quantifies a node’s connectivity diversity across modules with a single value (Eq. 1), it is also of interest to examine the specific connectivity patterns that give rise to any overall pre-post treatment PC changes. To do so, we examined the within- and between-module connectivity for the target ROI LIFG-tri: The former refers to the connections between the LIFG-tri and the nodes that were in the same module, and the latter refers to the connections between the LIFG-tri and nodes in other modules (see Figure 2 and section “The Reference Modular Organization,” for the modular organization used in the analyses).

To quantify the within- and between-module connectivity, we simply counted the number of connections of the LIFG-tri within or outside its own module. Specifically, to be consistent with the PC calculation (section “Network Measure Calculation”), we counted the connections at each proportional threshold value that was used to construct the binary graphs, and then used the averaged values across the thresholds in subsequent analyses. Pre- to post-treatment connectivity changes were compared with paired t-tests and values of each time-point were compared to the HC group with independent t-tests. Furthermore, to evaluate whether any effects were restricted to a specific module/s, we evaluated separately the between-module connectivity of the LIFG-tri with every other module. The same statistical comparisons described above were carried out for each set of between-module connections and the results were corrected using the FDR procedure (Yekutieli and Benjamini, 1999).

Finally, we examined within- and between-module connectivity for each hemisphere separately following the same procedures, i.e., counting the number of connections between the LIFG-tri and other nodes in the left or right hemisphere, respectively (see section “The Reference Modular Organization” and Figure 2).