The functional convergence and heterogeneity of social, episodic, and self-referential thought in the default mode network

Abstract

The default mode network (DMN) is engaged in a variety of cognitive settings, including social, semantic, temporal, spatial, and self-related tasks. Andrews-Hanna et al. (2010, 2012) proposed that the DMN consists of three distinct functional-anatomical subsystems - a dorsal medial prefrontal cortex (dMPFC) subsystem that supports social processing and introspection about mental states; a medial temporal lobe (MTL) subsystem that contributes to memory retrieval and construction of mental scenes; and a set of midline core hubs that are involved in processing self-referential information. We examined activity in the DMN subsystems during six different tasks: (1) theory of mind and (2) moral dilemmas (for social cognition), (3) autobiographical memory and (4) spatial navigation (for memory-based construction/simulation), (5) self/other adjective judgement (for self-related cognition), and finally, (6) a rest condition compared to a working memory task. At a broad level, we observed similar whole-brain activity maps for the six contrasts, and some response to every contrast in each of the three subsystems. In more detail, both univariate analysis and multivariate activity patterns showed partial functional separation, much of it in close accord with the proposals of separate dMPFC and MTL subsystems, though with less support for common activity across anterior and posterior regions of a midline core. Integrating social, spatial, self-related, and other aspects of a cognitive situation or episode, multiple components of the DMN may work closely together to provide the broad context for current mental activity.\n\nSignificance StatementActivity in the default mode network (DMN) can been found across a wide range of high-level tasks that involve social, semantic, episodic, or self-referential cognition. Given this diversity, an important proposal is that the DMN can be parcellated into subsystems with different cognitive functions. The current experiment employed a wide range of experimental tasks to directly test for functional convergence and heterogeneity between DMN regions. The results support both partial differentiation and integration; working together, distributed DMN regions may assemble the multiple contextual components of a cognitive situation or episode.