Fractionating the Default Mode Network: Distinct Contributions of the Ventral and Dorsal Posterior Cingulate Cortex to Cognitive Control

The posterior cingulate cortex (PCC), a core region of the default mode network (DMN), shows distinct roles in attention depending on its dorsal and ventral parts. Using fMRI during a working-memory task, standard subtraction analysis showed overall deactivation with increasing difficulty. However, dual-regression functional connectivity revealed a dissociation: the ventral PCC reduced integration with the DMN and anticorrelation with the cognitive control network (CCN) as task demands rose, while the dorsal PCC increased DMN integration and anticorrelation with the CCN. At rest, the dorsal PCC connected with both DMN and attentional networks. These results indicate the PCC supports internally directed thought at low demands and that the dorsal PCC modulates dynamic interactions between networks for attention allocation.

Study at a glance

Abstract

The posterior cingulate cortex (PCC) is a central part of the default mode network (DMN) and part of the structural core of the brain. Although the PCC often shows consistent deactivation when attention is focused on external events, anatomical studies show that the region is not homogeneous, and electrophysiological recordings in nonhuman primates suggest that it is directly involved in some forms of attention. We report a functional magnetic resonance imaging study of an attentionally demanding task (either a zero- or two-back working memory task). Standard subtraction analysis within the PCC shows a relative deactivation as task difficulty increases. In contrast, a dual-regression functional connectivity analysis reveals a clear dissociation between ventral and dorsal parts of the PCC. As task difficulty increases, the ventral PCC shows reduced integration within the DMN and less anticorrelation with the cognitive control network (CCN) activated by the task. The dorsal PCC shows an opposite pattern, with increased DMN integration and more anticorrelation. At rest, the dorsal PCC also shows functional connectivity with both the DMN and attentional networks. As expected, these results provide evidence that the PCC is involved in supporting internally directed thought, as the region is more highly integrated with the DMN at low task demands. In contrast, the task-dependent increases in connectivity between the dorsal PCC and the CCN are consistent with a role for this region in modulating the dynamic interaction between these two networks controlling the efficient allocation of attention.