If you’ve been paying attention to recent news on psychedelics, you’ve probably heard the term default mode network (DMN). Or, perhaps you’ve read Michael Pollan’s book, How to Change Your Mind, where he details his before and after experiences with numerous psychedelic trips. In his book, he discusses how psychedelics quiet the DMN, allowing people to experience temporary deaths of the ego and form new insights and perspectives.
It turns out, when the DMN is interrupted, new channels and pathways within the brain form. New research indicates that psychedelics may be a revolutionary disruptor in the field of mental healthcare, partially because of how they affect the DMN.
What’s the Default Mode Network?
In 2001, Dr. Marcus Raichle coined the term "default mode" to describe the state when our brains are at rest. The default mode describes an activity within the brain when it’s not engaged in an active task, such as solving a math problem or learning a new job. The default mode is often associated with activities such as daydreaming, self-reflection, worrying about the past, or feeling anxiety about the future. The DMN is also where we create the picture ourselves, or our autobiographical self. The DMN is central to the story we tell ourselves about who we are and where we want to go.
The default mode network is an interconnected series of structures within our brain. There is some debate as to which parts of the brain to include. Generally, there is consensus that the prefrontal cortex, the posterior cingulate cortex, and the inferior parietal lobule are included.
fMRI scans indicate that when our brains are resting, or we’re "thinking" without a specific goal in mind, the DMN regions of the brain show higher levels of activity and blood flow. New research shows that increased activity within the DMN is linked to mental disorders such as depression, anxiety, and schizophrenia. Changes in the DMN, whether it is too much activity or too little, have also been linked to diseases such as Alzheimer’s disease, autism, PTSD, and bipolar disorder.
The DMN also allows us to perform repetitive tasks and actions without thinking much about them. For instance, many of us may have the experience of driving home, but not remembering it, yet we get back safely anyway. It turns out that rote memory is much easier than conscious thinking, and 46.9% of the time, we are turning ourselves on autopilot, which is regulated by the DMN.
While in this frame of mind, it may feel like you are doing something instinctually, and your brain no longer needs to focus. For this reason, whenever possible, the adult brain will try to switch over to save energy. The stories we tell ourselves, a multitude of actions we perform and much of our daily existence is controlled by a network in the brain on autopilot – which may or may not work in our favor.
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Psychedelics: Interrupting the Default Mode Network
It’s believed that the over-activity within the DMN, and its grip on our conscious and unconscious actions, play a central role in mental health disorders, such as depression or anxiety. Studies indicate that when activity is decreased, which is the case when psychedelics are administered, a depressed or anxious person will often feel a sense of relief, as well as an increased sense of connection; often for several months.
Scientific interest in studying psychedelics runs in parallel with the desire to treat intractable mental health disorders. In 2016, The Journal of Psychopharmacology researchers stated, "High-dose psilocybin produced large decreases in clinician- and self-rated measures of depressed mood and anxiety, along with increases in quality of life, life meaning, and optimism."
Another study found that when psilocybin was administered to patients with treatment-resistant depression, "depressive symptoms were markedly reduced 1 week and 3 months after high-dose treatment."
A new Brazilian study looked at rapid antidepressant effects of the psychedelic ayahuasca in treatment-resistant depression. The study concluded that "significant antidepressant effects of ayahuasca, when compared with placebo at all time, points… and brings new evidence supporting the safety and therapeutic value of ayahuasca, dosed within an appropriate setting, to help treat depression."
Researchers agree that the resetting of the DMN may play a significant role in reducing mental disorder symptoms. A study by the Imperial College of London tracked experiential responses within 20 participants while consuming LSD. Brain scans indicated that while under the influence, separate portions of the brain made new connections with one another while the DMN was mainly in sleep mode.
But how does this happen?
Psychedelics: Effects on the Human Brain
Psychedelics, such as psilocybin, LSD, and DMT (ayahuasca) act as serotonin receptor agonists. When you consume a psychedelic, such as magic mushrooms, the active ingredient psilocin creates the psychedelic "trip" we experience.
Seratonin receptor agonists do not harm the brain; they naturally bind with the serotonin receptors within our minds. Psilocin, for instance, is a replica of the serotonin molecule we produce. It does not harm the receptor and is a copy of serotonin, which is often called ‘the happy chemical’, as it contributes to our sense of well-being.
Once the serotonin agonist binds to our serotonin receptors, something remarkable happens. A 2012 study at the Imperial College of Medicine found that after psilocybin was administered, blood flow decreased to the DMN interrupting normal activities. When this occurs, neuroplasticity within the brain begins.
As the DMN’s capacity diminishes, normal signals within the brain are not able to run down the same neural networks. As a result, the brain automatically creates new neural pathways and alternative ways to exchange information.
Researchers from a 2014 follow on study observed when the DMN is suppressed by psychedelics, the overall communication of neurons within the brain is wildly enhanced. New connections are made across the brain, essentially creating "cross-talk," which is usually unavailable to us. The long-range effect is that separate areas of the brain connect and process information differently. fMRI scans show that brains under the influence of certain psychedelics resemble the minds of people who have active meditation practices.
When we switch off the DMN, we unlock new potential within the brain. Some liken psychedelics to a "reset button," allowing us to return to a more childlike mindset, and to see the world in a new way. It’s believed that the brain’s capacity to reset itself and create new forms of communication in lieu of the DMN, is one of the primary reasons psychedelics may be a solution for so many treatment-resistant mental health disorders.