Decoding the DMN: The brain’s mysterious “resting-state” network

The brain is constantly processing stimuli from our surroundings — sights, smells, sounds, and more — through organized structures designed particularly for their specific function. But what happens when the brain is at rest? When focus is not directed at a specific task or stimuli, the brain does not just shut down. Instead, it diverts activity inward, to functions such as introspection, day-dreaming, reflection, and self-awareness. The default mode network (DMN) is the brain’s “resting-state network,” which turns on when everything else turns off.

The DMN is responsible for a range of internally-focused processes, including memory consolidation, understanding of self, and mind-wandering, particularly to events from an individual’s past or future. The network also plays a role in learning, because the brain uses its time at rest to organize knowledge and memories. The DMN has only recently become an area of focus for neuroscientists, as its lack of engagement with the outside environment makes it more of a mystery. Only with more recent imaging advances such as fMRI have scientists begun to break down the intricacies of the network, and they are still only scratching the surface.

“The default mode network (DMN) is the brain’s ‘resting-state network,’ which turns on when everything else turns off.”

The discovery of the default mode network was documented in a 2001 study by Marcus Raichle and his team, who used fMRI to describe a pattern of brain activity during resting states that was different from the patterns observed in task-related active states. As investigators began to observe that these patterns were consistent and reproducible, the field of default mode network research gained traction. Now, as neuroscientists continue to examine the functions of the DMN, research is focused on understanding the connection between internal thought processes and external experiences, as well as the implications of the network in mental health disorders, as many psychiatric disorders are related to disrupted inner thought and memory impairment.

The structure of the DMN is still not entirely defined, but it is primarily composed of the medial prefrontal cortex, posterior cingulate cortex, precuneus, and angular gyrus. The network has high connectivity throughout the brain, and it interacts with other brain regions to promote learning, self-thought, imagination, and consolidation. Thinking about others and empathizing, self-reference and emotional reflection, learning and memory consolidation, and inspiration and creativity are all understood to be functions of the DMN, but much of the network remains largely elusive. The DMN’s exact brain regions, specific mechanisms, and range of interactions and connections in the brain are not yet fully understood.

With connections to consciousness, sense of self, mental health, and processing of personal experiences, the default mode network plays a critical role in existence and personhood. With rapidly advancing imaging technology and growing interest in DMN research, the potential discoveries are endless. As the default mode network is explored, some of neuroscience’s largest questions — those of personality, consciousness, memory, and mind-body connection — are beginning to be unraveled.