February 6, 2020

The Default Mode Network: The Center of You

The Default Mode Network: The Center of You
Source: The Burgundy Zine

Take your hands off the keyboard, relax, and take a deep breath. Try your best to do absolutely nothing for a moment. Where did your mind go?

Assuming you were able to achieve a resting state, your brain’s default mode network kicked on.

There’s still much to be researched about the DMN, however, the data currently available has lead researchers to believe the DMN may be at the center of our ego.

But first, what hell is the DMN?

An Introduction to the Default Mode Network

After functional imaging studies depicted activity increases in various brain regions during resting states (increases that were also present during activities with low cognitive demand), researchers began investigating what would soon be known as the default mode network, says a 2003 study published in the Proceedings of the National Academy of Sciences.

“This is the first study, to our knowledge, to demonstrate resting-state functional connectivity between brain regions implicated in the default mode network,” the study notes.

The brain regions associated with the default mode network are the posterior cingulate cortex, ventral anterior cingulate cortex, the medial prefrontal cortex, and the left inferior parietal cortex – regions associated with:

Learning, motivation, and reinforcement; episodic memory, semantic knowledge, planning ahead, and daydreaming (PCC)
Physical and psychological pain; anxiety, fear, anger, aggression, empathy, and sadness (vACC)
Executive functions, conflict resolution, and mood regulation (MPFC)
Language and working memory (left IPC)

During the 2003 PNAS study, researchers hypothesized the DMN is involved in the recall and manipulation of episodic (personal) memories and semantic (facts and beliefs) knowledge. They also suggested aspects of the DMN could provide a neurological basis to consciousness and the connection should be further investigated.

Tag, You’re Id

In a 2010 Brain journal review, researchers investigated the neurobiological basis for Freudian concepts, particularly the id and the ego.

“It is worth noting that Freud had formal training in neuroanatomy and was influenced by people like Helmholtz, who laid many of the foundations for theoretical neurobiology,” the review explains. “Advances in empirical and theoretical neuroscience now allow us to recast some central Freudian ideas in a mechanistic and biologically informed fashion.”

The study says Freud had differentiated between two “modes of cognition.” He defined “primary process” as a mode with “free neuronal energy,” brimming with more primitive, animalistic thought processes. Non-ordinary states of consciousness such as dreaming or psychosis fell into this category.

On the other hand, “second process” sought to convert that free energy into bound energy. That’s the ego suppressing such animalistic desires and impulsions of the id.

“There is a huge amount of clinical and preclinical evidence supporting the limbic-suppressive function of the medial prefrontal cortex,” the study says. “Functional neuroimaging studies have correlated primitive thought and emotion with decreased activity in the medial prefrontal cortex and increased activity in the medial temporal lobes, while suppression of these behaviors correlated with medial prefrontal cortex activations.”

“Much of the evidence suggests that activation of the DMN suppresses activity in lower systems.”
The default-mode, ego-functions and free-energy: a neurobiological account of Freudian ideas | Brain

In conclusion, the study demonstrated how the ego suppresses stimuli through the DMN, modernizing Freudian concepts.

Id vs. Ego

Sigmund Freud proposed human personality consisted of three distinct parts: the id, ego, and superego in the early 20th century, according to a 2014 Frontiers in Psychology review.

The id is our unconscious, animalistic desires and repressed urges. It primarily seeks pleasure and reward without taking external consequences into account.

“[The id is] a cauldron full of seething excitations. We picture it as being open at its end to somatic influences, and as there taking up into itself instinctual needs which find their psychical expression in it.”
New Introductory Lectures on Psycho-Analysis | Sigmund Freud

The id is sensitive to internal stimulation with no communication to the external world, Freud said.

Conversely, the ego is the conscious part of our personality that reins in the reality hammer. It seeks to control the id through rationale but still tries to satisfy the id with more reasonable compromises.

For example, a conversation between the id and ego may look like:

Id: “I’M BORED. I WANT TO WATCH YOUTUBE VIDEOS.” Ego: “But you have to homework due tomorrow! Finish your studies, then indulge.”
Id: “I WANT ICE CREAM.” Ego: “But dinner’s almost ready! Eat your veggies, then indulge.”
Id: “I HAVE TO PEE.” Ego: “But the professor is going over information for next week’s test! Wait for him to move on, then use the restroom.”
Id: “I WANT TO SLEEP.” Ego: “But you’re at work! You can nap once you get home, after your shift.”

In essence, the ego is the little, doting mother that lives in all of our heads – but, just like a mother, the ego can get a little overprotective.

See, the ego is also concerned with self-preservation and anticipating danger. Thus, if the id wants to go on the ferris wheel, the ego might start rambling on about how the ferris wheel will derail and fly off into space as it does in the 2001 movie “Jimmy Neutron: Boy Genius.”

Jimmy Neutron and friends blast off into space on amusement park rides
Source: Jimmy Neutron: Boy Genius (5/10) Movie CLIP – Blast Off (2001) HD | Movieclips

Consequently, there’s a whole lot that can happen if things start to go awry with the DMN.

The Default Mode Network in Dysfunction

More recently, researchers have devoted their focus to the role of the DMN in various neurological and neuropsychiatric disorders.

In particular, a 2016 Yale Journal of Biology and Medicine review analyzed the DMN in cases of Alzheimer’s disease, Parkinson’s disease, temporal lobe epilepsy, attention-deficit hyperactivity disorder, and mood disorders.

“Decreased functional connectivity in the DMN of patients with Alzheimer’s disease has been consistently demonstrated, especially between posterior (precuneus and posterior cingulate cortex) and anterior (anterior cingulate cortex and medial prefrontal cortex) regions,” the review says. “Changes in functional connectivity of regions within the DMN have also been found in individuals at high risk of developing Alzheimer’s disease, suggesting that these changes may provide potential biomarkers for Alzheimer’s disease.”

The study also found dysfunctional DMN connectivity (both increases and decreases in connectivity) in patients with Parkinson’s disease.

“Interestingly, several studies have demonstrated that increased connectivity within the DMN of Parkinson’s disease is related to visual hallucinations,” the study notes.

In patients with temporal lobe epilepsy, the study said disrupted connectivity within the DMN could contribute to impairments associated with the condition.

In cases of ADHD, the review observed stronger connections within the DMN than other nodes of the inhibition network, thus contributing to decreases in task performance.

This basically puts the DMN and cognitive control network in a game of tug-o-war for directing the patient’s attention.

In mood disorders, the review pointed to abnormal DMN function as the potential cause of symptoms such as an inability to focus, executive function disturbances, and rumination.

Attention deficits and altered DMN connectivity seem to be a reoccurring theme, as a 2018 Frontiers in Psychology study had similar findings when observing the DMN’s role in attention deficits associated with schizophrenia and obsessive-compulsive disorder.

DMN disruptions are also present in cases of post-traumatic stress disorder, says a 2018 Biological Psychiatry: Cognitive Neuroscience and Neuroimaging study.

Abnormal DMN connectivity is apparent in cases of substance use disorder as well, says a 2019 Neuroimage study.

“The DMN is prominently engaged during the withdrawal and preoccupation phases of the addiction cycle.”
Brain Default-Mode Network Dysfunction in Addiction | Neuroimage

A 2017 Yonsei Medical Journal study found decreases in DMN connectivity in low-empathy subjects, indicating an impairment in self-referential stimulation (in other words, the subjects have a hard time relating information to themselves).

The Future of Default Mode Network Research

Currently, the US National Library of Medicine lists 31 active and recruiting studies related to the DMN.

There are studies underway on how the DMN relates to adolescent depression, type one diabetes, social phobia and body dysmorphic disorder, psilocybin treatment for cocaine use, among others.

In Conclusion

There’s still a lot to be learned about the DMN, but studies so far have made profound discoveries.

The DMN provides basis for the ego, a point of reference for the center of you.

While neuroscientists are still seeking answers as to where consciousness stems from, we at least know the DMN is involved in learning, memory, motivation, pain, empathy, and mood regulation, making it a focal point when studying various neurological and neuropsychiatric disorders.

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