Karen Hopkin: This is Scientific American’s 60-Second Science. I’m Karen Hopkin.

It happens to us all. You might be reading a book or washing the dishes or maybe even listening to a podcast when suddenly you realize your mind was miles away. 

Well, if you’ve ever wondered why the mind wanders, you might want to pay attention to this. A new study shows that localized brain waves, resembling those present when we fall asleep, are associated with brief interruptions in our stream of consciousness.

The findings appear in the journal Nature Communications. [Thomas Andrillon et al., Predicting lapses of attention with sleep-like slow waves]

Thomas Andrillon of the Paris Brain Institute grew interested in the neural mechanisms that underlie daydreaming while on an extended road trip with his wife.

Andrillon: We traveled for a year over three continents by car, accumulating long hours on difficult roads. 

Hopkin: As time rolled slowly by, Andrillon found his attention would stray from the road ahead.

Andrillon: Indeed, somewhere deep in Patagonia, I flipped our car on the roof—just because I was thinking about something else and reacted badly when getting back to the real world.

Hopkin: No one was harmed, but the incident did make Andrillon wonder ...

Andrillon: What is going on in our brain when our mind wanders?

Hopkin: It actually happens more than you might think.

Andrillon: According to some accounts, we spend up to half our waking life mind wandering.

Hopkin: And it happens most frequently when we’re tired or fatigued. At that point ...

Andrillon: We can enter states in which part of the brain will show an activity resembling sleep, despite the rest of our brain being clearly awake.

Hopkin: It’s like part of the brain takes a power nap. But does the same thing happen when an individual is not worn out but well rested? Andrillon decided to find out.

Andrillon: To do so, we asked 26 healthy participants to perform a rather boring task ...

Hopkin: Like pressing a button each time they saw an image of a number—unless it was the number three. 

Andrillon: As you can imagine, it is easy to switch on the autopilot and perform the task mindlessly, freeing ample room for mind wandering.

Hopkin: Periodically, the researchers would interrupt to ask participants whether they were fully focused or if they were thinking of something else or even nothing at all. Based on this feedback, it seems participants were single-minded and fully “on task ...”

Andrillon:  Only half of the time.

Hopkin: To find out what was going on the rest of the time, the researchers monitored participants’ brain waves by EEG to observe their neural rhythms.

During sleep, the brain is blanketed by slow waves of synchronized neural activity. And the team saw something similar when participants indicated that they were mentally checked out.

Andrillon: These slow waves are thought to be associated with pauses in the activity of the individual neurons, which could perturb neural processes and lead to lapses of attention.

Hopkin: The only difference was that the slow waves Andrillon saw during the experiment were more localized to particular parts of the brain.

Andrillon: Importantly, the location of this slow wave within the brain could distinguish between different modes of inattention.

Hopkin: When the slow waves were concentrated in the front of the brain, volunteers found their mind was wandering, and they reacted to the images impulsively. When in the back of the brain, they said their mind was a blank, and they failed to respond at all. Andrillon says that makes sense, given what we know about what different parts of the brain do for us.

Andrillon: Frontal regions are indeed heavily involved in communicative control and the regulation of impulsivity, whereas posterior regions encode and integrate sensory information, enabling us to react to our environment.

Hopkin: The researchers are currently exploring whether these slow waves can be harnessed to promote creative thinking, which might someday lead to big rewards for sleeping on the job.

For Scientific American’s 60-Second Science, I’m Karen Hopkin. 

[The above text is a transcript of this podcast.]