'Daydreaming Network' Helps Us Switch to Autopilot

The default mode network is active during states of rest

daydreaming
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Can you imagine how taxing it would be to have to actually think about every little action that you engage in every day.

Fortunately, our minds wander and we daydream while doing routine tasks, such as driving to work, taking a shower, or watering the plants. Interestingly, the same portion of the brain is linked to both daydreaming and going into memory-based autopilot: the default mode network (DMN).

Moreover, new research shows that the DMN plays an integral role in autopilot mode.

The Default Mode Network

The DMN, or “daydreaming network,” is spread over diverse, interconnected regions of the cortex, including the frontal, parietal, and temporal lobes. The cortex is the outer layer of the brain.

More specifically, the DMN is divided into three principal subdivisions:

  1. the ventral media prefrontal cortex
  2. the dorsal medial prefrontal cortex
  3. the posterior cingulated cortex and adjacent precuneus plus the lateral parietal cortex (i.e., Brodmann area 39)

The entorhinal cortex has also been tied to the DMN.

Importantly, the prefrontal cortex is at the front of the brain and regulates complex thought, behavior, and emotion.

As with many things in science, discovery of the DMN was serendipitous. In 1997, using positron-emission tomography, a type of brain-imaging study, Shulman and colleagues found that compared with a resting state, blood flow over a constellation of brain areas was reduced while performing new, non-self-referential, goal-directed tasks.

Of note, decreases in blood flow in these brain areas mean decreased activity.

In 2001, Raichle and colleagues took the next crucial step in determining that these activity decreases were not a fluke … that they were not activations in the resting state caused by experimentally uncontrolled thoughts.

In a 2015 review article titled “The Brain’s Default Mode Network,” Raichle writes the following:

We used positron emission tomography (PET) measurements of regional blood flow and oxygen consumption to show, by established metabolic criteria for activation, that areas consistently exhibiting activity reductions during task performance were not activated in the resting state. Our article was titled, ‘A Default Mode of Brain Function.’ We concluded that the brain areas observed to decrease their activity during attention-demanding, goal-directed tasks were not activated in the resting state but, rather, were indicative of a heretofore-unrecognized organization within the brain’s intrinsic or ongoing activity.

By 2015, discovery of the DMN had spawned nearly 3000 papers on the topic. We’ve learned that the DMN is most active when people are left alone with their thoughts or performing automatic, reflexive, learned behaviors under specific contexts in stable environments—like watching a movie or driving a car along a familiar route. These environments are wakeful states of rest, when a person isn’t focused on the outside world. Conversely, in experimental environments that are thought intensive and cognitively taxing—like figuring out a puzzle—the DMN is less active.

The many roles of the DMN are still being elucidated. The DMN is linked to episodic memory and memory consolidation as well as social and self-related processes. The DMN is also linked to thinking about the future, reminiscing about the past, and creativity. According to Raichle, in humans, studies have shown that the DMN  “instantiates processes that support emotional processing (VMPC), self-referential mental activity (DMPC), and the recollection of prior experiences.”

In a 2009 study published in Human Brain Mapping, Uddin and co-authors write the following regarding the DMN: “Though it is possible that one comprehensive theory will arise explaining the network’s ability to support such a diverse array of functions, the greater likelihood is that the default mode network consists of functionally differentiable subdivisions or subnetworks.”

Interestingly, during meditation, DMN activity decreases. This finding makes sense because meditation is a time of decreased mind wandering and self-referential thought. During meditation, a person concentrates on the immediate experience and shifts away attention from distractions.

DMN and Autopilot

The DMN was first envisioned as information that broadly arises in a person’s external and internal environment. Because the DMN was first identified during the resting state, it’s tempting to think that the DMN is merely responsible for daydreaming, mind wandering, and spontaneous thoughts. Spontaneous cognition, often involves thoughts about the past and future, which also jells with the perceived role of the DMN. However, the DMN plays a much more fundamental role in consciousness.

In a 2017 study titled “Default mode contributions to automated information processing,” Vatansever and co-authors find that the DMN actually switches the brain over to memory-based autopilot once we understand a task. The authors hypothesize a possible framework for this process.

Vatansever and co-authors hypothesize that our brains are wired to continuously anticipate external events. We are constantly internalizing any irregularities in the environment to form the basis of our expectations. These expectations are then used to inform our decision-making and interpret, predict, and act on environmental demands.

Indeed, the intrinsic activity of the brain, specifically that of the DMN, which uses a considerable portion of our brain energy supplies, is suggested to reflect such internal models of the world that could aid in the interpretation of our surroundings. Although such predictive processing may constitute the common mechanism by which the brain processes information as a whole, what may distinguish the DMN is its ability to provide a common workspace for convergence of information with its extensive functional and structural connections to the rest of the brain and specifically its access to memory-based information. This integrative capacity of the DMN is thought to be a hallmark of consciousness, the levels of which have been previously associated with DMN integrity.

In the study, the University of Cambridge researchers recruited 28 participants to engage in a task while lying in a functional MRI scanner. The participants were shown four cards and asked to match a target card to these four cards. The target card could match by either color, shape, or number, and participants needed to figure out the rule for matching. The functional MRI scanner measured oxygen levels in the brain, which served as a proxy for brain activity.

There were two stages in this task. The first stage was acquisition in which the volunteers learned to matching rule through trial and error. The second stage was application in which the volunteers had already figured out the rule and were now applying it.

The researchers found that during the acquisition stage, the dorsal attention network was most active. The dorsal attention network is linked to the processing of attention-demanding information. During the application stage, when the participants already knew the rule and were merely applying it, the DMN was more active.

The researchers also observed that during the application stage, the stronger the relationship between activity in the DMN and areas of the brain involved in memory such as the hippocampus, the faster the participants were able to respond to the task. This finding suggests that during the application stage, the brain was dipping into memory, and responded to the task using a rule from memory.

It appears that the DMN with its diverse connections throughout the brain helps establish a proactive framework in the brain. In established contexts and times of wakeful states of rest or routine, the DMN makes memory-based predictions and thus allows us to function in autopilot. However, when the DMN isn’t able to predict the future in a reliable way, autopilot switches to “manual” mode and parts of our brain that process attention-demanding information take over.

According to the researchers, this framework established by the DMN could provide “an all-important scaffold to explain not only the DMN’s ongoing activity in stable ‘rest’ conditions, but also its contribution to social interactions (e.g., theory of mind, intuition, and stereotyping), a conscious sense-of-self, creativity, and a variety of other cognitive domains that all require the stable use of learned information for predicting the world around us.”

Implications

Like the role of the DMN itself, the implications of DMN research done by Vatansever are broad and could help us better understand conditions like traumatic brain injury. In traumatic brain injury, problems with memory and impulsivity make social reintegration difficult. Furthermore, these findings may help us better understand other types of mental illness including addiction, depression, and obsessive-compulsive disorder. Finally, this research could help elucidate the mechanisms of anesthetic drugs on the brain.

Bottom Line

Ever since its discovery nearly 20 years ago, the DMN has been a boon to scientific researchers and has helped reshape the way that we think about brain function. With each passing year, we learn more about this multifaceted network that plays an integral role in consciousness. Research explaining its role in memory-based autopilot takes our understanding of the DMN one step further by reinforcing that the DMN is not merely background noise and is an important conduit for information.

On a final note, a better understanding of the DMN has helped shed light on the inner experience of being human. Consider this description by Callard and Margulies from an article titled “What we talk about when we talk about the default mode network”:

The DMN has been remarkably productive in bringing hitherto marginalized fields and methods inside the perimeters of cognitive neuroscience—and, through such incursions, sparked new lines of conceptual and methodological inquiry. Topics such as mind-wandering, previously considered largely beyond the purview of cognitive psychology, have emerged as heated areas of research. Neuropsychoanalytic researchers have found the DMN to be a rich concept through which to advance formulations about psychic energy, psychodynamic concepts of self in relation to objects and fantasy.

Sources:

Callard F, Margulies DS. What we talk about when we talk about the default mode network. Front Hum Neurosci. 2014;8:619.

Raichle ML. The Brain’s Default Mode Network. Annu. Rev. Neurosci. 2015. 38:433–47.

Uddin LQ, et al. Functional connectivity of default mode network components: correlation, anticorrelation, and causality. Hum Brain Mapp. 2009 Feb;30(2):625-37.

Vatansever D, Menon DK, Stamatakis EA. Default mode contributions to automated information processing. Proc Natl Acad Sci U S A. 2017; pii: 201710521.

 

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