Brain networks – an important puzzle piece to understand how our brain functions
Focus on the Default Mode Network: Its implication in mental health; and how meditation, breathwork, and transcranial PBM can influence its activity.
Summary
It is common knowledge that specific regions in our brains have distinct functions. It is less known that different areas show particular patterns of cooperation and communication between them, forming “brain networks”. These networks are associated with specific functions and activities. Throughout daily life, we automatically switch between those networks, depending on the tasks we are engaged in and our mental states. We mainly operate through our Default Mode Network (DMN) when we are engaged in self-referencing processes such as worrying, mind-wandering, or contemplating the past or future. Despite clearly having essential functions, overactivity of the DMN can prevent us from being aware of the present moment, reduce life quality, and even correlates with mental disorders like depression and anxiety. To a certain extent, we can learn to consciously switch between different networks by practicing meditation and breathwork. Technologies such as transcranial Photobiomodulation also have the potential to modulate network connectivity and activity. By these means, we have specific tools available that can, in some cases, have important implications for our mental health and increase our cognitive flexibility.
Brain networks
How our brains developed their incredible complexity remains one of the most fascinating mysteries of humanity. There are some incomprehensible numbers with which we can play around a bit. For example, we have approx. 170 billion brain cells within our skulls, out of which an estimated 100 billion are neurons (and much of the rest are “glia cells”; the most abundant cells that make up our brain´s immune system). These 100 billion neurons have approx. 1.000 trillion synapses, which allows each neuron to receive approx. 10.000 inputs simultaneously. Indeed a lot of input, isn´t it? We also understand that different brain functions are rooted in different brain areas and that our brains are enormously flexible in how they are wired. But still, it doesn´t give us any clue on how on earth we became capable of traveling to the moon, building computers, or doing quantum physics. What mechanisms and principles allow us to structure, select, exchange, and integrate all the information necessary for these incredible achievements? Today´s substack is about another puzzle piece of brain function that emerged over recent years – our rapidly growing understanding of brain networks.
Neuron communication creates “information highways”. “Information highways” build brain networks.
Imagine a neuron wants to communicate with another neuron somewhere else in your brain. There are many different routes to do so and many different other cells will be excited along the way, depending on the chosen route. Our brains tend to use the same routes repeatedly and thereby form neural pathways that seem like highways – there is a lot of traffic on them, while most of the area next to those highways is relatively low in traffic. In neuroscience, the process underlying the construction of these “highways” is based on a process called “long-term potentiation” – the long-lasting increase in signal transmission between neurons that regularly communicate with each other.
These communication highways – and yes, also “smaller streets” – connect specific brain regions that all have distinct functions, just like man-built streets connect cities and villages. A bunch of those highways together form what we call neural networks or brain networks. The different and mostly non-adjacent brain areas that make up these networks are characterized by extensive intercommunication and cooperation between each other. We can think of an orchestra, where all the different instruments somehow play together to create a beautiful composition.
We can use different neuroimaging methods (such as functional magnetic resonance imaging or electroencephalography) to identify the various networks. We give a person specific tasks (or let them do nothing to obtain a “resting state image” and study the below described DMN) and look for stable connectivity patterns between different brain areas while the task is performed. Simplified, the regions involved in those patterns build the hubs of the network that is currently active.
There are quite a few of those networks. How many we can identify is not exact science, but depends very much on how we choose to model them. Most models identify between six and ten major networks, but there really is no right or wrong here. What is certain is that there are attention networks, memory networks, executive networks, salience networks, and most famously, the default mode network.
Check out the “human connectome project” if you want to learn more about the current state of research in the area:
https://www.humanconnectome.org/
The Default Mode Network (DMN)
The default mode network is the network that is primarily active when we are lost in thought / mind-wandering, when we worry about the future or argue with the past, when we are day-dreaming, or in emotive reacting to the present moment – basically whenever processes of self-referencing in the absence of a specific task (which would turn on specific “task-positive networks”) take place. Anatomically, it comprises several distinct brain centers, including the midline located medial prefrontal, posterior cingulate, and precuneus cortices.
Let´s zoom out for a moment - why should all that be interesting for someone who doesn´t care so much about neuroscience?
The short answer is that we can train ourselves and / or use technology to reduce the activity of the DMN, which can shift our attention away from worrying, mind-wandering, etc., towards the present moment (which we can then enjoy more) or specific tasks (which we can then perform better).
I can most certainly say that exactly those self-referencing is what too often prevents me from being present, at ease, and in flow - despite having an overall positive perspective on life and positive expectations for the future. I guess everyone can relate to this – being lost in thought and often unnecessary worries seem to be the default mode for almost everyone I know – thus the network´s name. It simply appears to be part of our human nature. It is in line with Buddhist philosophy, which teaches us that emotive reacting related to our ego-constructs – such as attachment to personal likes and dislikes, and adverse reactions to what happens to us - are the source of unpleasantness or, in Buddhist language, suffering.
A bit simplified, we can summarize that excessive DMN activity makes us less happy. And indeed, affective disorders like depression, anxiety, ADHD and schizophrenia, are all associated with an overactive DMN. Here is a meta-analysis on the topic:
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7355168/
Ways to modulate the activity of the DMN and other networks
Wouldn´t it be amazing to have more conscious control over the activity of the DMN and other networks? Well, that is pretty much (but not exclusively) what mindfulness techniques such as meditation and breathwork can do. It teaches us to become aware of the different network states and how to consciously switch between them. We intuitively learn to exert conscious control of our minds and gain better ability to focus our attention, regulate our emotions, enhance our body awareness, live a life with less self-referencing, and be more aware of the present moment.
However, a crucial point is that “classical” meditation requires a lot of experience and skill to deliver these effects. For me, breathwork has been a much quicker and more reliable way to enter deep meditative states. I went so far as to even start breathwork instructor training because I found it so beneficial for my well-being that I want to teach other people how it can be used in daily life. Be sure that I will write much more about that soon.
For now, I invite you to give that 28-minute interview a listen. It summarizes a recent study in which the effects of breathwork on DMN- activity were compared to the impact of psychedelic medicines on the DMN.
https://www.somabreath.com/new-study-on-effects-of-soma-breath-on-the-brain/
What I also find very intriguing is that research on transcranial Photobiomodulation also started focusing more on how the intervention influences brain network activity. Some studies suggest that tPBM can have a “balancing function”, restoring functional connectivity between different regions to “normal” levels. Naeser et al., for example found that tPBM increased functional connectivity within intrinsic neural networks in chronic stroke patients:
https://pubmed.ncbi.nlm.nih.gov/31621498/
A nice read on the how and why was published by Mitrofanis et al. in 2020. Even though the interpretations are still speculative, the authors propose an “evolutionary link”; “relating to a survival strategy for the organism against any potentially threatening or dangerous situation.”
Here is the link if you want to dive deeper into this:
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7749488/
We only begin to understand this potentially highly precise application of tPBM, but I believe that regimes consisting of diagnostic interventions such as fMRI and EEG and therapeutic interventions such as tPBM will in the future be applied as “individual precision medicine” to improve brain connectivity and thus function. And I very strongly recommend trying meditation and breathwork for yourself – it is free of cost and available to everyone from the comfort of your home.
Disclaimer
I am not a medical professional, and the above is not meant as medical advice; I am merely sharing my personal understanding of the subject.
How to obtain more information?
Simply make contact with me - best through LinkedIn or email - to obtain more information about all the above.
Resources
More about brain networks
- Seguin, C., Sporns, O. & Zalesky, A. Brain network communication: concepts, models and applications. Nat. Rev. Neurosci. 24, 557–574 (2023). https://doi.org/10.1038/s41583-023-00718-5
https://www.nature.com/articles/s41583-023-00718-5#citeas
- Human Connectome Project
https://www.humanconnectome.org/
The Default Mode Network and its role in mental health
- Raichle M. E. (2015). The brain's default mode network. Annual review of neuroscience, 38, 433–447.
https://pubmed.ncbi.nlm.nih.gov/25938726/
- Whitfield-Gabrieli, S., & Ford, J. M. (2012). Default mode network activity and connectivity in psychopathology. Annual Review of Clinical Psychology, 8, 49-76.
https://pubmed.ncbi.nlm.nih.gov/22224834/
- Metin, B., Krebs, R. M., Wiersema, J. R., Verguts, T., Gasthuys, R., van der Meere, J. J., Achten, E., Roeyers, H., Sonuga-Barke, E. (2015). Dysfunctional modulation of default mode network activity in attention-deficit/hyperactivity disorder. Journal of Abnormal Psychology, 124(1), 208-214.
https://pubmed.ncbi.nlm.nih.gov/25314265/
- Doucet, G. E., Janiri, D., Howard, R., O'Brien, M., Andrews-Hanna, J. R., & Frangou, S. (2020). Transdiagnostic and disease-specific abnormalities in the default-mode network hubs in psychiatric disorders: A meta-analysis of resting-state functional imaging studies. European psychiatry : the journal of the Association of European Psychiatrists, 63(1), e57.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7355168/
Meditation and brain networks
- Bremer, B., Wu, Q., Mora Álvarez, M. G., Hölzel, B. K., Wilhelm, M., Hell, E., Tavacioglu, E. E., Torske, A., & Koch, K. (2022). Mindfulness meditation increases default mode, salience, and central executive network connectivity. Scientific reports, 12(1), 13219.
https://pubmed.ncbi.nlm.nih.gov/35918449/
- Rahrig, H., Vago, D.R., Passarelli, M.A. et al. Meta-analytic evidence that mindfulness training alters resting state default mode network connectivity. Sci Rep 12, 12260 (2022).
https://pubmed.ncbi.nlm.nih.gov/35851275/
Transcranial Photobiomodulation and brain networks
Mitrofanis, J., & Henderson, L. A. (2020). How and why does photobiomodulation change brain activity?. Neural regeneration research, 15(12), 2243–2244.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7749488/
Naeser, M. A., Ho, M. D., Martin, P. I., Hamblin, M. R., & Koo, B. B. (2020). Increased Functional Connectivity Within Intrinsic Neural Networks in Chronic Stroke Following Treatment with Red/Near-Infrared Transcranial Photobiomodulation: Case Series with Improved Naming in Aphasia. Photobiomodulation, photomedicine, and laser surgery, 38(2), 115–131.