October 25, 2017

Where Your Mind Goes When You Space Out

This brain network kicks in when we don't need to pay close attention, allowing our minds to wander.

Anyone who has driven long distances has experienced the sensation of zoning out — suddenly realizing you’ve driven many miles without even really being aware of it. The same may apply to getting lost in thought and eating way more cake or chips than you meant to as you watch television.

When we’re on “autopilot,” the part of the brain that’s also active when our minds are wandering seems to take over, a new study finds.

The ability to go on autopilot certainly makes our lives easier and probably saves a lot of energy.

The aptly-named default mode network (DMN) is a collection of regions that are active when we’re not doing anything in particular — that is, when we’re just sitting around, letting our minds wander. It’s also affected in people who have Alzheimer's disease, schizophrenia, ADHD and disorders of consciousness, the University of Cambridge researchers believe.

They had people sit inside a functional MRI (fMRI) scanner so their brain activity could be monitored in real time as they did a simple cognitive task. The task involved being presented with four cards, which showed different images, varying in shape, color and number. They were also presented with a single target image, which the participant had to match to the correct background image. The researchers didn’t tell the participants how they were to match it — by shape, color or number. Rather, the participants had to figure that out by trial and error.

The team recorded which brain regions were active when the participants were solving the challenge, usually over several attempts, and the regions that were active after they had learned it and were simply carrying out the rest of the matching task.

It turned out that when the participants were learning the task, areas related to attention and information-processing were active. But when the participants were executing the learned task, the DMN was active. Additionally, when a participant’s DMN was more connected with the hippocampus, the brain region that governs learning and memory, the better the participants performed on the task.

“[The DMN] is essentially like an autopilot that helps us make fast decisions when we know what the rules of the environment are. So for example, when you're driving to work in the morning along a familiar route, the default mode network will be active, enabling us to perform our task without having to invest lots of time and energy into every decision,” explained study author, Deniz Vatansever, in a statement. The ability to go on autopilot certainly makes our lives easier and probably saves a lot of energy.

Interestingly, the DMN is also a central region that’s “on” when we’re having self-centric, worry-based thoughts and it quiets down when people meditate. More work will be needed to fully understand when it’s active and when it’s not — and when zoning out is beneficial to our functioning and when it's a handicap.

In any case, the study underlines how complex the brain is and how efficiently it seems to operate. The next time you miss an exit, blame it on your default mode network.

The study is published in Proceedings of the National Academy of Sciences.

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