Default mode network synchrony reflects shared understanding

The default mode network (DMN) has been linked to self-reflection and theory of mind, suggesting that it facilitates understanding others by reflecting on ourselves. This raises the question of whether shared (synchronized) DMN responses are associated with mutual understanding. The current paper reviews studies on DMN synchronization during shared understanding of external events, regarding experimentally manipulated states (with presentation of external contexts), inherent traits (e.g. paranoia), interpersonal closeness (e.g. friends), and group identity (e.g. political affiliation). It also reviews DMN synchronization in shared understanding of interpersonal events, as in communication (e.g. teachers and students). We propose four research directions: investigating the role of DMN synchronization in simulating others’ mental states, testing if DMN synchronization is a trait, exploring its causal role in shared understanding, and testing coupling beyond synchronization. Advancing knowledge on DMN synchronization could answer fundamental questions about shared understanding and foster positive interactions among individuals and groups. • DMN synchronization is associated with similar narrative interpretation. • Synchronized DMN responses among individuals who share traits and preferences. • Social group affiliations impact DMN neural synchronization. • DMN synchronization underpins mutual understanding. • Future directions include simulation, synchronization as a trait, and causality.