The default mode network (DMN) integrates memory, language, and semantic representations to create a coherent internal narrative that reflects individual experiences. This narrative is central to constructing a sense of self, shapes self-perception and social interaction, may originate in childhood self-directed speech, and forms a vital component of human consciousness. The review traces the DMN's discovery, its roles in self-reference, social cognition, episodic and autobiographical memory, language, semantic memory, and mind wandering, and proposes new perspectives on its function in human cognition.
The default-mode network (DMN) undergoes significant developmental changes in functional and structural connectivity from childhood to adulthood, but these changes are not uniform across all DMN nodes. The connection between the posterior cingulate cortex (PCC) and medial prefrontal cortex (mPFC) along the cingulum bundle is the most immature link in children. Structural connectivity between PCC and left medial temporal lobe is weak or non-existent in children, yet functional connectivity does not differ from adults. Gray matter volume differences and macrostructural and microstructural differences in the dorsal cingulum bundle also appear. Maturation of PCC-mPFC structural connectivity likely supports self-related and social-cognitive functions emerging during adolescence.