Brain’s autopilot is daydream believer

Pull on your pants, button your shirt, tie your shoelaces. Unless you’re a toddler, you can probably do these things without much thought.

Now, a study from the University of Cambridge in the UK has revealed which parts of your brain are active when this ‘autopilot’ mode kicks in. 

Neuroscientists have long known that brains are constantly humming with activity, even when we are seemingly doing very little. The regions that spark up between tasks have become known as the default mode network (DMN). 

Everything from daydreaming and mind-wandering to thinking about ourselves and planning for the future have been associated with activity in this network. Breakdown in the DMN has been linked to disorders such as Alzheimer’s disease and autism, and hyperactivity to depression and chronic pain. 

But this new research shows the DMN to be more than a passive circuit that kicks in when we have nothing better to do than listlessly navel-gaze. It is crucial for enabling us to effortlessly perform tasks with which we are familiar. 

In the study, the team, led by Deniz Vatansever, had 28 volunteers complete a card-sorting task while having their brains scanned for oxygen concentration – a proxy for neural activity – using a functional magnetic resonance imager (fMRI). 

Participants were presented with a spread of four cards with simple diagrams – three green triangles, two red circles, four blue crosses, say. A fifth ‘target’ card was shown, which the participants had to match to one of the reference cards. 

But there was a catch. Participants weren’t told whether to match the card on the basis of shape, colour or number. They had to deduce this rule – which held for a series of 10 target cards – through trial and error. Once participants had cottoned on to the rule, their responses became more rapid and accurate. 

The researchers compared brain activity during the first five target cards (the learning phase), to the last 5 target cards (where participants were applying the rule). 

During the learning phase, a matrix known as the dorsal attention network was active. This lights up when a demanding task requires us to process external information. 

But once the brain starts relying on memory to apply a rule, the DMN kicks in, enabling rapid, efficient responses. 

“It is essentially like an autopilot that helps us make fast decisions when we know what the rules of the environment are,” says Vatansever. 

Greater connectivity between the default mode network and regions associated with memory retrieval, such as the hippocampus, boosted reaction speeds and accuracy. 

“The DMN is not a bystander in these tasks: it plays an integral role in helping us perform them,” says senior author Dr Emmanuel Stamatakis.

It’s possible that what the researchers have witnessed is the hallmark of the ‘fast’ thinking described by Daniel Kahneman, who won the Nobel Prize in Economics in 2002, in his book Thinking, Fast and Slow. 

The work was published in the journal Proceedings of the National Academies of Sciences.