As our hypotheses focused on the DMN, we chose 20 ROIs (8 mm spheres) based on coordinates specified in a recent comprehensive analysis of functional connectivity of the DMN (Andrews-Hanna et al., 2010) (see Table 2 for all ROIs and MNI coordinates). These DMN constituents have recently been corroborated by a study examining resting state fMRI connectivity in 1000 healthy subjects (Yeo et al., 2011). Important to the current study, Andrews-Hanna et al. (2010) showed in subsequent experiments that activity in these ROIs was associated with self-relevant, future-oriented and memory-directed behaviour. Therefore, we were confident that these regions are, when active, involved in episodic memory retrieval. Further, instead of using anatomically defined regions, we calculated grey matter volume (GMV) using the same 8 mm sphere ROIs. This approach allowed holding the voxel count constant among all DMN regions and between functional connectivity and structural analyses.
