Default Mode Network

What Is the Default Mode Network

The default mode network (DMN) is a network of brain regions including the medial prefrontal cortex, posterior cingulate cortex, and angular gyrus that activates when attention is not directed at external tasks. In 2001, Marcus Raichle and colleagues proposed the notion of a "default mode" on the basis of quantitative PET measurements of oxygen use and blood flow. Because the same regions consistently turned their activity down whenever an external task began, they reasoned that the brain maintains a baseline state unrelated to any task. The brain uses roughly 20% of the body's entire energy budget, much of it going to neuronal signaling itself - the resting brain is far from idle.

DMN Functions and Rumination

The functions served by the DMN are wide-ranging: recollection of past events, planning and simulation of the future, inferring others' perspectives (theory of mind), and self-reflection. All of these are thoughts directed toward the inner world rather than the external environment of the "here and now." The reason creative insights and problem-solving breakthroughs tend to arrive not at the desk but in the shower or on a walk is often explained in terms of DMN activity. But it is not as simple as the DMN switching on and creativity following. Studies of creative idea production report that the DMN works in concert with the executive control network, which handles attention and evaluation, and that being able to move between the two is what marks out highly creative thinking. The fragments that surface while the mind wanders still have to be picked out and shaped into something usable. However, excessive DMN activation is associated with rumination. Replaying past failures on repeat, endlessly simulating future anxieties. Reports that DMN activity and the connectivity between its regions are heightened in people with depression are taken as support for this connection.

DMN and Mindfulness

In individuals trained in mindfulness meditation, changes in DMN activity patterns have been reported. Specifically, even when the DMN activates, the ability to notice it and redirect attention to the present improves. In other words, mindfulness does not shut down the DMN - it enables observing DMN activity without getting swept up in it. Spacing out itself is not a problem. The problem is when spacing out turns into rumination and you cannot find your way back. If rumination persists and begins to interfere with daily life or brings intense distress, it is worth consulting a mental health professional such as a psychiatrist.