Neuroscience of Mindfulness: Default Mode Network, Meditation, & Mindfulness

MRI by Nevit Dilmen / [CC-BY-SA-3.0 or GFDL]

MRI by Nevit Dilmen / [CC-BY-SA-3.0 or GFDL]

“Ipsa scientia potestas est.” ~ Sir Francis Bacon       

Translated as, “Knowledge itself is power,” this quote by Sir Francis Bacon appeared in his 1597 essay, Meditationes Sacrae (“Sacred Meditations”). Bacon has been credited as the father of the scientific method, and his work attests to the rigorous approach with which he examined natural phenomena. Bacon’s quote and historical contributions make him a fitting character to introduce our proceeding discussion.

I was humbled by the response to my last post entitled, The Neuroscience of Mindfulness and Anxiety. The outpouring of questions and comments reassured me that the science of the Self is of vital importance and is worth exploring further.

As such I want to embark on a journey into the science of mindfulness and meditation in a series of articles to follow that will lead the reader to the cutting edge of science and medicine. I would suggest beginning this journey with my previous article as I will use the information provided therein as a foundation to expand our knowledge base.

So without further digression, I offer the second installment in my Science of Mindfulness series with the conviction that Self-knowledge instills power not over but within the Self.

To begin our story we must travel back to 1924 when a German neurologist named Dr. Hans Berger invented the electroencephalograph (better know by its acronym: “EEG”). Some historians suggest that Dr. Berger went on to join the Nazi SS while others claim he was forced into retirement in 1941 because he would not comply with the SS and their medical research techniques. Regardless of which scenario represented the truth, very soon after his retirement he committed suicide at the age of 68 following a lifelong battle with major depression.

The EEG is a device that measures the electrical activity of the brain through external electrodes on the scalp. Because the brain transmits information in the form of electrical impulses, measuring electrical activity can yield information about brain function.

After a few years of working with his invention Dr. Berger made an observation in a 1929 paper that would be the first step on a long road of discovery. Until then, conventional scientific wisdom held that the brain was only electrically active when a person executed an attention-demanding physical or mental task (i.e. reading, classifying pictures, opening and closing their hands). However, Dr. Berger’s work with his EEG demonstrated that the human brain remains electrically active even at rest while attention wanders (i.e. daydreaming between activities, remembering past events, ruminating). Despite the evidence, Dr. Berger’s colleagues largely ignored his claims and continued to focus on brain function during attention-demanding behavior.

This trend of exclusively studying the brain during attention-demanding behavior continued for decades. However, all of this changed in 2001 when a neurologist by the name of Dr. Marcus Raichle at Washington University revealed a network of brain structures responsible for the inattentive wandering of our minds. Furthermore, Dr. Raichle showed that these same structures were deactivated when we engage in attention-demanding tasks. He coined the term, “default mode network,” to describe the group of structures active during our “default,” inattentive state (1).

The following decade revealed many more details about the default mode network (DMN) that further validated Dr. Berger’s almost century-old claim that the brain was still very much “on” even when we let our attention wander.

Now that we have the historical context let’s examine the importance of the DMN to mindfulness and mental health.

So what exactly do I mean when I refer to the mental state of inattention that is synonymous with the DMN?

By “inattention” I mean times when you are not attending to physical activity, engaging with the external environment, or carrying on a conversation. Inattention, in the way I am using it, describes states of daydreaming, contemplating the future, reliving the past, or general rumination. The DMN is the set of neurologic structures responsible for this ruminative mental activity.

Hold on! Right away these descriptions bring to mind the most common culprits of mental unrest, namely: anxiety (over potential pasts, presents, or futures), depression (over regretted pasts, presents, or futures), or obsessionality.

Right you are! In fact, multiple studies have demonstrated that increased connection and activity in parts of the DMN are correlated with major depression and other mental illnesses (3).

So if the DMN is a network that is so intimately related to anxiety, depression, and obsessionality why on earth would evolution have selected for it? The answer is that, like most things in life, a well-balanced DMN helps us plan tasks, review past actions to improve future behavior, and remember pertinent life details. But with the expansion of the brain’s intellectual capabilities came the unfortunate drawback that some of these functions could go too far and cause mental anguish.

Like most stories, the story of the DMN and the brain has both a protagonist and an antagonist. Perhaps it is slightly punitive to label the DMN as our antagonist, but for the purposes of our discussion the DMN must suffer this injustice.

The protagonist of our story is a series of structures in the brain called the Task-Positive Network (TPN).

The TPN is active during the attention-demanding tasks that we discussed in our introduction. Recall that the TPN was the network of most interest for the better part of the last century.

The TPN is responsible for directing our conscious attention towards the external environment through our five senses, towards our internal bodily states, and to the willful execution of physical and mental action. When we are engaged in conversation, feel the beat of our heart, or experience the breeze on our face we can thank our TPN for the attentional focus that brings these experiences into conscious awareness.

Whoa, whoa! Now these descriptions sound a whole lot like mindfulness practices. Indeed, the TPN is responsible for the attention required to observe one’s breath during sitting meditation, attend to our environment during walking meditation, and participate in the social world on a daily basis.

Now that we have discussed the major functions of the DMN and TPN we come to a critical point regarding their relationship: they are mutually exclusive. The activation of the DMN inhibits the TPN and vice versa.

In fact, no study has demonstrated the simultaneous activation of the two networks (4). The relationship between the DMN and the TPN is analogous to the relationship between inhalation and exhalation: despite their intimate nature, the two cannot exist simultaneously.

Now that we have the bird’s eye view of these two systems let’s examine them in more depth. Now would be a good time to go back to my previous article to refresh your knowledge of the various structures in the brain.

The DMN can simplistically be thought of as being made up of “medial” (towards the middle) parts of the brain: the medial prefrontal cortex (mPFC), the posterior cingulate cortex (PCC), the hippocampus (located in the medial temporal lobe), and the amygdala (also located in the medial temporal lobe). The inferior parietal lobule is also a component of the DMN but for the purposes of our discussion we can ignore this structure. Also note that all of these structures are “bilateral” (existing on both sides). The brain is essentially a mirror image of itself that is split down the middle into two hemispheres.

As you will hopefully recall from my previous article, the amygdala serves as the raw source of emotional content.  When we feel fearful, we can thank our amygdala. For the purposes of our current discussion we will consider the amygdala as the “Emoter.”

Not mentioned in my previous article, but equally important, the hippocampus helps generate and modulate our memories. We will refer to the hippocampus as the “Memorizer.” The hippocampus/Memorizer and amygdala/Emoter are neighbors and have highly complex interactions beyond the scope of this article.

The PCC is a structure deep in the middle of the brain that serves to integrate self-perception and emotionally relevant memory retrieval. To simplify the PCC’s role, we can refer to it as the “Emotional Integrator.”

Finally, the mPFC is located in the center of the frontal lobe and processes social and emotional information. Imagine your best friend is frowning at you. Your mPFC is the part of your brain that reacts and tries to make sense of your friend’s frown. Did I do something wrong? Am I a bad friend? Is he a bad friend?

For the aforementioned reasons we will refer to the mPFC as the “Emotional Sensor.”

Modified from original by PixGood.com through Images.Google.com “labeled for reuse with modification” URL: http://pixgood.com/brain-lobes-diagram-unlabeled.html

 

These four structures: mPFC/Emotional Sensor, PCC/Emotional Integrator, hippocampus/Memorizer, and amygdala/Emoter have a complex and interdependent relationship.

Let’s use a simplified example to understand their dynamic relationship.

Imagine that you are romantically interested in a coworker. Perhaps after a few days or weeks of gathering your courage, you decide to ask her out on a date. Your heart pounds and fear coats your upper lip with sweat as you await her response. But after an agonizing series of seconds that feel like minutes your romantic interest provides a resounding “No.”

Later that day, as you sit down for dinner, you begin to process the events of that afternoon. Your mPFC/Emotional Sensor retrieves the memory of your romantic rejection formed by your hippocampus/Memorizer. The memory is laden with fear and embarrassment courtesy of the amygdala/Emoter. The PCC/Emotional Integrator forces you to re-experience the bodily state of fear and embarrassment while the mPFC/Emotional Sensor replays the ordeal over and over again in your mind’s eye.

Now that we’ve examined the DMN in action let’s look at the TPN in more detail.

While the DMN is predominantly a medial (towards the middle) series of neurologic structures the TPN can be thought of as composing mostly “lateral” (furthest away from middle) structures.

The TPN is made up of the lateral prefrontal cortex (lPFC), the anterior cingulate cortex (ACC), the insula, and the somatosensory cortex (S1).

The lPFC is located in the lateral aspect of the frontal lobe. The lPFC is responsible for attentional-direction, decision-making, working memory (task-specific short-term memory), and cognitive control (regulating our thoughts). For the aforementioned reasons we will refer to the lPFC as the “Director.” The lPFC dictates where we direct our attention and what we do with it.

The ACC is an exception to the lateral (away from middle) rule and sits behind and underneath the frontal lobe. The ACC enables us to direct our attentional focus towards emotional and cognitive content. We will refer to the ACC as the “Attender” because of its role in attending to mental and emotional content.

The insula is buried within the lateral sulcus, which separates the frontal and parietal lobes from the temporal lobe. The insula allows us to detect our own internal states such as the beat of our heart, the sensation of our intestines, or the feeling of a full bladder. We will refer to the insula by the very unimaginative title of the “Internal Sensor.”

And finally, S1 (1st or primary somatosensory cortex) is located in the postcentral gyrus of the parietal lobe. S1 is responsible for our bodily sensation of touch. S1 allows us to feel the sensation of grass beneath our feet, a cool breeze on our face, or the sun on our back. We will refer to S1 as the “External Sensor.”

TASK-POSITIVE NETWORK Modified from original By Mysid [Public domain], via Wikimedia Commons

As before, let’s use an example to unify these four structures: lPFC/Director, ACC/Attender, insula/Internal Sensor, and S1/External Sensor.

Imagine that you are sitting down to meditate. You rest yourself comfortably on your meditation cushion and straighten your back. Your mind is still operating on the DMN as you relive a conversation from earlier in the day or worry about a project that is due at the end of the week. But then you engage the lPFC/Director and activate the TPN, silencing the DMN (5).

The lPFC/Director directs your attention away from your ruminative thoughts to your internal and external environment. The ACC/Attender facilitates this switch in attentional focus.

Perhaps you are practicing Anapanasati, (pana meaning breath and sati meaning mindfulness) a traditional breath-following meditation technique (see Mindful Sitting). Your attentional focus, courtesy of the ACC/Attender and lPFC/Director, is then directed to the insula/Internal Sensor. The insula/Internal Sensor allows you to experience the bodily sensation of the air moving in and out of your lungs, the beat of your heart as it slows in time with your deep breaths, and the feeling of your intestines and stomach as you relax deeper into the natural ebb and flow of your body.

Maybe you feel your attention waver and hear the DMN knocking on your mental door, so you switch to Open Awareness meditation in which you nonjudgmentally attend to all components of your environment. With the focusing beam of attention from your lPFC/Director and ACC/Attender you are able to utilize your S1/External Sensor to attend to your external environment. You feel the cool sensation of air at the tip of your nose during your in-breath and the warmth of your out-breath. You feel the earth pressing up through the cushion on your bottom and legs. You feel the expansion of your rib cage and stomach as they accommodate the flow of breath.

Seated Buddha by Isidore van Kinsbergen

Seated Buddha by Isidore van Kinsbergen

Both Anapanasati and Open Awareness meditation utilize the activation of the TPN network to alleviate the mental suffering generated by the DMN.

Because of this article’s density, it is worth revisiting a few key points at this time.

An overactive DMN is highly correlated with negative mood states and certain mental illnesses.

The DMN can be simplistically conceptualized as a ruminative network. It directs our awareness to the past and future while largely ignoring the present. And while the DMN can be used responsibly to plan and organize, we must always be wary of its runaway force.

The TPN is involved in present moment awareness.

The TPN is engaged when we attend to the here and now. It is the action network. The TPN is our direct line to mindfulness and the Present Moment in which worry and sadness cannot survive.

The TPN and DMN are mutually exclusive.

By activating the TPN we deactivate the DMN. This may be the most powerful lesson of our entire discussion. The next time you feel helplessly lost in worry or self-recrimination remind yourself of the power of the TPN. Go for a walk, practice yoga, sense your breath, or engage fully in a conversation with a friend. You need not overpower your DMN to escape negative thoughts. You need only to intentionally engage your TPN and allow your natural physiology to disengage your DMN.

 

References

 1. Raichle, M. E., MacLeod, A. M., Snyder, A. Z., Powers, W. J., Gusnard, D. A., & Shulman, G. L. (2001). A default mode of brain function. Proceedings of the National Academy of Sciences, 98(2), 676-682.

2. Raichle, M. E. (2010). The brain’s dark energy. Scientific American, 302(3), 44-49.

3. Guo, W., Liu, F., Zhang, J., Zhang, Z., Yu, L., Liu, J., … & Xiao, C. (2014). Abnormal Default-Mode Network Homogeneity in First-Episode, Drug-Naive Major Depressive Disorder. PloS one, 9(3), e91102.

4. Buckner, R. L., Andrews‐Hanna, J. R., & Schacter, D. L. (2008). The brain’s default network. Annals of the New York Academy of Sciences, 1124(1), 1-38.

5. Farb, N. A., Anderson, A. K., & Segal, Z. V. (2012). The mindful brain and emotion regulation in mood disorders. Canadian journal of psychiatry. Revue canadienne de psychiatrie, 57(2), 70.

6. Farb, N. A., Segal, Z. V., & Anderson, A. K. (2012). Mindfulness meditation training alters cortical representations of interoceptive attention. Social cognitive and affective neuroscience, nss066.

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22 Responses

  1. Lane says:

    Thank you for this. As I’m taking the U. of Mass. Medical School Stress Clinic MBSR Course, your explanation is so very helpful. Again, I’m sharing it with my friends.

    • I’m so glad to hear this Lane! And what a wonderful course to be taking. The original mindfulness project that inspired this blog was based off of Dr. Kabat-Zinn’s MBSR course. Dr. Kabat-Zinn and his colleagues have a great way of simplifying what can feel like a complex topic into practical steps that lead to real change. Thanks again for your comment and I’m so glad you enjoyed the post.
      ~ Matthew

  2. saijanai says:

    Extremely high activation of the DMN is also associated with “pure consciousness” during Transcendental Meditation.

    • Very interesting! As you mentioned in our email conversation:
      “TM (Transcendental meditation) is described as allowing the mind to wander, so the fact that the EEG signature of TM is very similar to “mind wandering” and that the brain activity is as well, shouldn’t be either.”
      The article you provided, http://www.ncbi.nlm.nih.gov/pubmed/19862565, was also very interesting. Thank you for your enthusiasm and for sharing your knowledge about meditation.
      ~ Matthew

  3. How does this square with Dr Jill Bolte Taylor’s experience of left and right brain?
    See her TED talk

    • Michael,
      Thank you for your interest. I am familiar with Dr. Bolte Taylor’s book but not familiar enough to comment at this time. How do you feel like this squares the her experience? I will follow up when I have time to examine her work in more detail.

  4. Another nice post on this topic. The connections between the Default Mode Network and the Task Positive Network are very interesting and this confirms experiential observations I’ve made over the years.

  5. troybryden says:

    Hi Matthew! literally one of the best articles I have ever read (pull together and explained many concepts much better then my university lecturers did)

    Im confused on one aspect however. Recently I read a journal article, basically suggesting that periods of mindfulness meditation provided a space for diminished blood glucose levels to replenish (as previously depleted from an activity). So I was under the impression (as confirmed by experience) that living a mindful lifestyle is a lifestyle which allows for glucose to replenish and for your energy levels to be generally higher (as when you get caught in DMN spirals, it really is draining). However, I have always thought that the TPN which is responsible for active tasks would consume more energy.

    I guess I was under the impression that both the TPN uses a lot of energy and I thought that projecting into the future, reflecting on the past and general rumination, would be part of this energy burning networking, where as mindfulness is more of a ‘resting’ non attending and simply ‘being state’. (clearly this isn’t the case as this article describes) But I’m just having a little bit of trouble reconciling in my mind, how a mindful state replenishes energy when it is TPN that is active. Or am I thinking about this wrong, such as , certain aspects of the task-positive network are draining, but other aspects are not? Because when you are tactically planning on a physical schedule the next day or reading through dense material I feel although the TPN would be active, although these two activities can be very mentally exhausting.

    Looking forward to hearing your insight,
    Troy

    • Thank you for your comments and I’m so glad you enjoyed the article.

      The brain consumes glucose as its primary energy source almost exclusively in most situations (there are exceptions that involve ketones, but we won’t consider this). In a relatively physically sedentary state the brain consumes about 60% of the body’s glucose intake. To your question, there is actually very little (if any) difference in glucose consumption in the brain during willful mental activity and so-called resting state.

      This question addresses a key component of the DMN-TPN puzzle. Both systems are necessary for our daily lives. The calming effects of the TPN engagement that can be achieved through meditation have more to do with the parasympathetic nervous system than with glucose consumption. Also, it’s important to remember that neither is the TPN “good,” nor the DMN “bad.” The balance between the two is a dynamic relationship.

      I hope this began to answer the question. Thank you again for reading and I am so glad that you enjoyed the article!

      • Troy says:

        Thanks a lot for your andwer!

        I will definately continue to read up on the latest literature.

        For months I have not even bothered to try convincing my friends to meditate, however after sharing this article with them they are easily able to see the real benefits and are able to see the scientific benefit to meditation and detach from an image of it as an almost purely spiritual practise.

        Keep up the good work!

        Troy

  6. Andrew Lowry says:

    Howdy Matthew–

    This article was discussed in a Zen talk given at the Rochester Zen Center, which I listened to as a podcast. The speaker was Wayman Kubicka and it’s dated 09/12/2015. I was intrigued enough to track down your site and am enjoying reading through it, and would like to thank you for taking the time to write and post your various observations and explanations.

    Here’s the URL for the podcast:
    https://s3-us-west-1.amazonaws.com/rzc/podcasts/2015-9_1-WK.mp3

    • Andrew,

      Thank you for sharing this with me! How humbled I feel to have been included in a Zen talk! It was great to listen to and wonderful to know that this article has helped clarify how the proposed physiology behind mindfulness lends itself to the reality of the practice. Again, I can’t tell you how much this means to me that you took the time to track my site down and share this piece of information!

  7. Hello . Thank you SO much for this. I’m working on a presentation for work on the benefits of meditation and I think this is going to be very helpful!!!

    I know you say that these two systems are mutually exclusive, but I wonder… In the case of long term meditators if they start to integrate at all. I say this bc I think I operate from TPN most of the time and I have found when I engage in certain activities (like memory recall) that are needed for something like writing that the information is just there and I don’t have to “think” about it…. Or maybe the TPN can activate regions of the brain typically associated with the DMN? Have you read Heen & Stone’s “Thanks for the Feedback”? They talk about developing a type of emotional awareness such that you’re noticing your own emotional reactions during a conflict… That sounds like the TPN, but it is info associated with DMN regions that makes this info relevant… So was curious how these regions might work together in such a case?

    • Thanks for reading and great questions! I’m not sure I’ll be able to answer them completely, but I will do my best. The article may make it seem like the DMN and TPN are antagonistic, but for all intents and purposes they are unaware of each other’s (or their own) existence. I make an argument that the modern mind tends to be more heavily weighted on the DMN side of things, but this is not to say that the DMN is bad while the TPN is good. Both serve their own purpose and are necessary for survival. I would hypothesize that rather than integration between networks advanced meditators become more dextrous in their ability to switch between networks. After all, the DMN is fine until we use it to ruminate, self-blame, or worry. I haven’t ready “Thanks for the Feedback” but I’m going to put it on my list. Thanks again for reading!

  8. Steve says:

    I’ve been to a few guided meditation sessions in the past year. I didn’t really understand the purpose of a lot of the stuff they said, like concentrating on the present and different areas of the body while letting go of feelings and thoughts about the past. I recently met someone who has a degree or two in the neurosciences who also practices meditation; this person explained some things about DMN/TPN and what is actually happening to the brain, but I still had some questions. This article helped fill in some of the blanks. Thank you!

    Skiing and mountain biking aggressively seem to help me in similar ways to guided meditation. I guess careening over moguls and through trees at high speeds is pretty effective at cranking up the TPN out of necessity to preserve life and limb.

  1. July 19, 2014

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  2. January 3, 2015

    […] If you are glass half empty person you are not alone. I recently learnt about the Default Mode Network (DMN) which I found very insightful. The DMN is a set of brain structures that represent our mental state of inattention; times when we are not exercising, interacting with the external environment, or having a conversation. An example would be when we first wake up in the morning. The most common culprits of this state of mental unrest are anxiety and depression (over past, present, or future events) or obsessionality (Neuroscience of Mindfulness). […]

  3. February 4, 2016

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  4. February 15, 2016

    […] Scientists have discovered that when our minds are not occupied with a task, they default to a kind of daydreaming, mind-wandering state called the Default Mode Network. […]

  5. February 20, 2016

    […] [1] See information from the NIH and a particularly good post about this here. […]

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