From the resulting time series dataset, seed masks representing regions identified as important for working memory and cognitive control (Paskavitz et al., 2010; Tapert et al., 2001; 2004) were created by depositing 12-mm diameter spheres in each participant’s left and right PPC and DLPFC (see Figure 1). 12-mm spheres were used based on the degree of spatial filtering applied and because ROIs of this size have been shown maintain anatomical specificity and signal sensitivity (Marrelec & Fransson, 2011). A BOLD response time series from the supra-span (6-dot) VWM task, averaged across the region for each repetition, was extracted from each of the 4 seed ROIs. Zero-order correlation analyses were then conducted between the time series extracted from the seed ROIs (i.e., correlation between right PPC and right DLPFC; left PPC and left DLPFC; right PPC and left DLPFC; and left PPC and right DLPFC) and then exploratory analyses examined correlations between the seed regions and all other brain voxels (from the whole brain time series dataset) for each subject (AFNI 3dDeconvolve). Resulting correlation coefficients were normalized using a Fisher z-transform.
