How Does the “Default Mode” Network Contribute to Semantic Cognition?

Abstract

This review examines whether and how the “default mode” network (DMN) contributes to semantic processing. We review evidence implicating the DMN in the processing of individual word meanings and in sentence- and discourse-level semantics. Next, we argue that the areas that make up the DMN contribute to semantic processing by coordinating and integrating the simultaneous activity of local neuronal ensembles across multiple multimodal and unimodal cortical regions, creating a transient, global neuronal ensemble. The resulting ensemble implements an integrated simulation of phenomenological experience—that is, an embodied situation model—constructed from various modalities of experiential memory traces. We argue that these situation models are necessary not only for semantic processing but also for aspects of cognition that are not traditionally considered semantic. Although many aspects of this proposal remain provisional, we believe that it provides new insights into the relationships between semantic and nonsemantic cognition and into the functions of the DMN.