The posterior cingulate cortex (PCC) is often used as a seed region for probing default-mode network (DMN) connectivity. However, there is evidence for a functional segregation between its dorsal (dPCC) and ventral (vPCC) subregions, which suggests differential involvements of d-/vPCC in regulating cognitive demands. Our paradigm included functional magnetic resonance imaging measures for baseline resting state, affective or cognitive tasks, and post-task resting states. We investigated the effect of task demands on intra-PCC coupling and d-/vPCC network assignment to major intrinsic connectivity networks (ICNs), which was estimated via edge weights of a graph network encompassing DMN, dorsal-attention network, and central-executive network (CEN). Although PCC subregions were functionally coupled during both resting-state conditions and cognitive tasks, they decoupled during affective stimulation. For dPCC, functional connectivity strength (FCS) to CEN was higher than to the other two ICNs; whereas for vPCC, FCS to DMN was the highest. We, hence, defined CEN and DMN as the canonical networks at rest for dPCC and vPCC, respectively. Switching from rest to affective stimulation, however, induced the strongest effects to relative network assignments between non-canonical networks of dPCC and vPCC. Although vPCC showed a durable functional connectivity (FC) to DMN, dPCC played a crucial role during switches of between-network FC depending on cognitive versus affective task requirements. Our results underline that it is crucial for future seed-based FC studies to consider these two subregions separately in terms of seed location and discussion of findings. Finally, our findings highlight the functional importance of connectivity changes toward regions outside the canonical networks.
Keywords: central-executive network; default-mode network; functional connectivity; graph-theory; posterior cingulate cortex; resting-state fMRI.