Structural and functional image processing used Analysis of Functional NeuroImages software (AFNI; http://afni.nimh.nih.gov; Cox, 1996), FreeSurfer (Fischl et al., 2002), and FMRIB Software Library (FSL; http://www.fmrib.ox.ac.uk/fsl/index.html; Smith et al., 2004). Functional connectivity MRI (fcMRI) assessed the temporal correlations between the BOLD time series data of the VWM task in PPC and DLPFC seed regions. FcMRI preprocessing steps were conducted to reduce the influence any non-task effects. Abnormal values were removed (AFNI 3ddespike), and time series data were temporally aligned and coregistered to a stable base volume (AFNI 3dvolreg). Each participant’s anatomical image was segmented with FreeSurfer, to which time series data were aligned. White matter and ventricle masks were defined and eroded by one voxel along each axis, and time series signal from these white matter and ventricle sources was obtained using AFNI’s ANATICOR pipeline (Jo et al., 2010) and regressed out of the VWM task time series along with motion adjustments made in coregistration (AFNI 3dDeconvolve). Temporal band-pass filtering (0.009 Hz<f<0.08 Hz), spatial smoothing at 6 mm full-width at half-maximum, and neuroanatomical standardization were applied using AFNI.
