What’s Your Brain Doing When You’re “Doing Nothing”? Welcome to the Default Mode Network

Have you ever caught yourself staring out the window, totally zoned out—and wondered what your brain is up to in those moments? It turns out, it’s not just idling. It’s actually very busy. Neuroscience has uncovered something fascinating about our brains: we’re wired to wander.

Back in the 1950s, a researcher named Louis Sokoloff stumbled upon an unexpected discovery. While studying brain activity, he found that the brain used more oxygen during times when it wasn’t actively engaged in a task—like when someone was just daydreaming. That finding sparked decades of intensive research to try and understand what the brain is doing when it seems like we’re doing nothing.
Enter the Default Mode Network (DMN)—a system of brain regions that light up when we’re not focused on the outside world. Neuroscientist Marcus Raichle has been a key figure in uncovering how this network works. Using fMRI scans, he and others have shown that when we’re not concentrating on a goal or task, the DMN becomes highly active, especially along the midline of the brain—from front to back.

What’s even more surprising? This network burns a lot of energy—about 30% more calories (gram for gram) than almost any other part of the brain. But when we switch our attention to something external, like solving a problem or reading a book, this activity dials down.

So, what’s the DMN doing with all that energy? Raichle suggests it’s our brain’s way of “rehearsing” life—imagining future scenarios, reflecting on the past, and checking in on our sense of self. In other words, it’s the mental space where we ponder, daydream, and make sense of the world and ourselves. Supporting this, a study by Mason and colleagues in 2007 found that people often reported daydreaming when their DMN was active.

This “mind wandering” isn’t unique to humans either—other mammals have a DMN too. It’s considered a core cognitive function that forms part of our psychological baseline. It helps us maintain our identity, make decisions, and understand our place in the world. But, like anything in the brain, balance is key.

When the DMN isn’t functioning optimally, it can contribute to mental health issues. If it’s under-activated—often due to constant external stimulation and no time to reflect—it can interfere with our ability to process and integrate experiences. On the other hand, over-activation of the DMN has been linked to excessive rumination and depression. Some people, particularly those with depressive symptoms, struggle to disengage from this internal world, making it harder to shift focus or break out of negative thought patterns. In conditions like Alzheimer’s, the DMN also shows signs of disruption.

So what can be done? The goal isn’t to shut off the DMN—it’s to help people move in and out of that mode more fluidly. That’s where therapy can come in. Supporting someone to find (or re-connect with) healthy, engaging activities or social interactions can help balance this internal-external brain dance.

And here’s where mindfulness and meditation really shine. Studies show that regular meditation can reduce unnecessary mind wandering and actually reshape the brain. For example, research by Farb and colleagues (2007) found that meditation helps calm the parts of the brain involved in this self-referential thinking. Another study by MacLean et al. (2010) showed that meditators improved in tasks that require sustained attention, as seen through both brainwave activity and faster response times.

In short, when you’re sitting quietly and your thoughts drift—you’re not “wasting time.” Your brain is doing one of its most uniquely human jobs: imagining, reflecting, and keeping you grounded in who you are.

References:
Farb NA, Segal ZV, Mayberg H, Bean J, McKeon D, Fatima Z, Anderson AK. Attending to the present: mindfulness meditation reveals distinct neural modes of self-reference. Soc Cogn Affect Neurosci. 2007 Dec;2(4):313-22. doi: 10.1093/scan/nsm030. PMID: 18985137; PMCID: PMC2566754

Fox (2008) The secret life of the brain | New Scientist

MacLean KA, Ferrer E, Aichele SR, Bridwell DA, Zanesco AP, Jacobs TL, King BG, Rosenberg EL, Sahdra BK, Shaver PR, Wallace BA,

Mangun GR, Saron CD. Intensive meditation training improves perceptual discrimination and sustained attention. Psychol Sci. 2010 Jun;21(6):829-39. doi: 10.1177/0956797610371339. Epub 2010 May 11. PMID: 20483826; PMCID: PMC3132583.
Raichle ME. (2015) The brain’s default mode network. Annu Rev Neurosci. 8;38:433-47. doi: 10.1146/annurev-neuro-071013-014030. Epub 2015 May 4. PMID: 25938726.