S ummary The default mode network (DMN), a set of brain regions in parietal, temporal and frontal cortex, is implicated in many aspects of complex thought and behavior. However, understanding the role of the DMN is complicated because is implicated in functional states that bridge traditional psychological categories and that may have antagonistic features, notably perceptually-decoupled mind-wandering vs perceptually-driven decision making. Here, we leverage post mortem histology and high field in vivo neuroimaging to show how the anatomy of the DMN helps to explain its broad functional associations. The DMN contains cytoarchitecture associated with unimodal, heteromodal, and memory-related processing, an architecture that can enable complex behaviours dependent on integration of perception and memory. Anatomically, the DMN contains regions receptive to input from sensory cortex and a core that is relatively insulated from environmental input, a division that may explain the network’s role in internally- and externally-focussed states. Finally, the DMN is unique amongst cortical networks in balancing its output across the levels of sensory processing hierarchies, a pattern that may help coordinate and homogenise distributed neural function. Together, our study establishes an anatomical foundation for mechanistic accounts of how the DMN contributes to human thought and behaviour by integrating experiences of the inner and outer worlds.

The unique cytoarchitecture and wiring of the human default mode network