New research provides more detail about our 'daydream' network.
Getting through the day involves a great deal of cognitive flexibility — or the ability to adjust our behavior to an ever-changing environment.
Navigating the world is a complicated job. Flitting from conversations to complex computations, our brains do a noble job of helping us to switch seamlessly between tasks, constantly adjusting to their surroundings.
However, for many of our waking hours, it is another brain function that takes center stage: our autopilot. When driving a car, for instance, our actions are automatic, based on learned constructs of the world around us.
This ability means that we can respond quickly and efficiently to the environment without having to activate higher centers in the brain. As an example, driving involves gear changes, braking enough but not too much, signaling correctly, watching for pedestrians, stopping at stop signs, and plenty more — yet we can complete these tasks simultaneously without any bother at all.
Despite the complexities of driving home, we can often reach our destination and not remember much about the journey at all; our autopilot has taken care of the details on our behalf.
The seat of our 'autopilot'
Research has shown that the default mode network (DMN) is vital for the autopilot function. The parts of the brain involved in the DMN are activated when a person is not focused on anything in particular in the outside world.
The DMN tends to be triggered when thinking about one's self, others, the past, or the future, and it has been implicated in daydreaming and mind wandering.
When we are not taking part in an activity, the DMN is triggered by default. Conversely, when carrying out tasks that require attention, suppressing the DMN improves performance.
Abnormal activity in the DMN has been linked with a range of conditions, including Alzheimer's disease, attention deficit hyperactivity disorder, and schizophrenia. Despite having mapped much of the DMN's connections, however, there are still many questions to be answered regarding its role in "healthy" cognition.
Recently, researchers from the University of Cambridge in the United Kingdom took a fresh look at the DMN. They wanted to investigate whether and how it contributes to attention-demanding, goal-oriented tasks that involve cognitive flexibility.
Their findings are published in the Proceedings of National Academy of Sciences.
Testing the default mode network
The research, which was led by Dr. Deniz Vatansever, involved 28 participants who carried out a task while lying in an MRI scanner.
For the task, participants were shown four permanent reference cards and a fifth, alternating card. They were asked to match the fifth card with one of the original four based on three possible rules: color, number, or shape.
A brain scan showing the brain regions involved in the DMN.
Image credit: John Graner, Walter Reed National Military Medical Center
However, the volunteers were not told the rule, and they had to "work it out for themselves" using trial and error. This gave the task two distinct phases: one wherein the participant was actively attempting to figure out the rule, or the acquisition phase, and a second wherein they understood the rule and were applying it to the task, or the application phase.
A distinct difference in brain activity was observed between the two phases. In the acquisition phase, the dorsal attention network — an area of the brain known to play a role in attention-demanding information — was activated. But during the application phase, it was the DMN that was engaged.
Individual differences between participants' brain activity were also measured. Those with stronger activity between the DMN and memory centers in the brain, such as the hippocampus, performed the task faster and more accurately. This implies that the better performers were carrying out the task more successfully by accessing stored memories of the rule laid down during the acquisition phase.
"Rather than waiting passively for things to happen to us," explains Dr. Vatansever, "we are constantly trying to predict the environment around us."
He continues, saying, "Our evidence suggests it is the default mode network that enables us to do this. It is essentially like an autopilot that helps us make fast decisions when we know what the rules of the environment are."
A new side to the DMN
These findings change the way in which we think about the DMN; it is not as passive as once thought.
"The old way of interpreting what's happening in these tasks was that because we know the rules, we can daydream about what we're going to have for dinner later, and the DMN kicks in. In fact, we showed that the DMN is not a bystander in these tasks: it plays an integral role in helping us perform them."
Senior study author Dr. Emmanuel Stamatakis
The findings support a theory that two distinct systems help us to make decisions: a rational system for calculated decisions, and a faster system that makes more intuitive decisions. The current study suggests that the intuitive system may be the DMN.
Getting to grips with the DMN could have implications for understanding brain injuries wherein issues with memory and impulsivity can arise. Similarly, the DMN may play a part in addiction, depression, and obsessive-compulsive disorder.
Of course, plenty more research is needed to delve into the details, but the current study sheds some welcome light.