Brain study reveals sender and receiver roles in default mode network

The default mode network (DMN) is a distributed set of interconnected brain regions that has long been associated with internally oriented cognition such as remembering the past, thinking about the future, or thinking about oneself. Accumulating evidence also indicates that the DMN is engaged during tasks involving external perceptual input, such as language comprehension and social perception. However, the mechanism by which the same network supports both internally and externally oriented cognition has remained unknown.

Now, a research team led by ZHANG Meichao from the Institute of Psychology of the Chinese Academy of Sciences (CAS) has identified an organizational principle within the DMN that helps explain how the network supports both internal and external cognition.

The study, published in PNAS on April 7, reveals that distinct subregions within the DMN act as "senders" and "receivers" of information, enabling flexible shifts between perception and memory-driven thought.

To understand how the DMN works, the researchers combined analyses of directional functional connectivity, intrinsic network organization, and task-evoked brain activity across multiple independent datasets. Their findings reveal that the DMN is not functionally uniform, but is instead composed of subregions with distinct connectivity biases.

Specifically, receiver-like DMN subregions, which are biased toward afferent (incoming) input, show stronger connectivity with heteromodal association networks-a profile that may support information integration during perception. Conversely, sender-like subregions, which are biased toward efferent (outgoing) projections, exhibit stronger coupling with distributed sensorimotor systems, a profile that may guide memory-based behavior.

Consistent with this interpretation, these subdivisions systematically correspond to different cognitive modes. Receiver-like subregions are preferentially engaged during perceptually grounded face decisions-i.e., decisions based on visual information from faces-and sender-like subregions are preferentially engaged during memory-guided decisions.

"These findings suggest that the engagement of the DMN in both external and internal cognition is rooted in its microarchitectural differentiation into complementary receiver- and sender-like zones," said Dr. ZHANG, corresponding author of the study.

This study provides a novel organizational framework for understanding how the association cortex supports both external perception and internal thought. It offers a multilevel account of how the brain facilitates transitions between perceptual and memory-based cognition.

This work was supported by the National Natural Science Foundation of China, CAS, and the European Research Council.