A state-space perspective on the role of the default mode network in semantic cognition

Semantic cognition allows us to understand language, interpret perceptual inputs, retrieve knowledge, and generate meaningful thought. The default mode network (DMN) is often engaged during semantic tasks, yet its precise contribution remains debated, given its involvement in a broad range of cognitive states and domains, including spontaneous thought, autobiographical memory, and social cognition. This review argues that while the DMN's role is difficult to define in traditional psychological terms, it supports several core processes essential for semantic cognition. These include integrating multisensory features, drawing on long-term knowledge to guide thought and perception, and enabling context-appropriate retrieval. The DMN's position in the cortical hierarchy — at a maximal distance from sensory and motor regions — allows it to link diverse sources of information, represent abstract knowledge, and connect flexibly with other large-scale networks. We propose a state space framework to capture how the DMN interacts dynamically with other systems over time, based on intrinsic connectivity patterns. Semantic retrieval occurs in different network states — either when the DMN and executive control networks are co-activated to support effortful search, or when they decouple, with control systems guiding goal-directed retrieval and the DMN supporting more automatic access to knowledge. DMN regions can also couple with and separate from perceptual regions. This framework highlights how dynamic whole-brain states shape the DMN's contributions to semantic cognition across contexts.