How the DMN works
The Default Mode Network (DMN) is an interconnected group of brain regions that are associated with introspective functions, internally directed thought, such as self-reflection, and self-criticism.
The functional connections that make up the DMN increase from birth to adulthood, with the DMN not being fully active until later in a child’s development, emerging around the age of five as the child develops a stable sense of narrative self or “ego.”
As we mature, we learn to respond to life’s stimuli in a patterned way, developing habitual pathways of communication between brain regions, particularly those of the DMN. Over time, communication becomes confined to specific pathways, meaning that our brain becomes more ‘constrained’ as we develop. It is these constrained pathways of communication between brain regions that quite come to constitute our ‘default mode’ of operating in the world, shaping and colouring the way we perceive reality.
An overactive DMN and mental health conditions
The DMN has evolved to provide a streamlined way of helping us live our daily lives, filtering and making sense of what could otherwise become an overload of information. But it also becomes a very efficient autopilot which prevents us from considering other options or making different choices. This can have the effect of narrowing our experience of life and can trap us in habitualised patterns of behaviour. In this way our ego can become fixed on maintaining and defending these patterns even though they may not be beneficial to us.
The DMN has been found to be particularly overactive in certain mental health conditions, such as depression, anxiety, and OCD where the DMN has formed and attached to negative patterns of thinking. Psychiatrist Dr. Matthew Brown likens DMN overactivity to experiences of “hyper-criticality”, “rigid thought patterns”, and “automatic negative thought loops” about oneself. These become hard to break down or to change because of the strength of the DMN and the pathways it has created. Interestingly it is said that the DMN is most active when we are least occupied.
How psilocybin works to reset the DMN
Psychiatric doctor and ayahuasca researcher Simon Ruffell likens the effects of psychedelics on the DMN to “defragmenting a computer.” When you take a psychedelic substance, activity of the DMN is significantly decreased whilst connectivity in the rest of the brain increases. The grip of the ego is loosened and new ways of understanding your experience and behaviour patterns can emerge.
“Brain imaging studies suggest that when psychedelics are absorbed they decrease activity in the default mode network. As a result the (constructed) sense of self appears to temporarily shut down, and thus ruminations may decrease. The brain states observed show similarities to deep meditative states, in which increased activity occurs in pathways that do not normally communicate. This process has been compared to defragmenting a computer. Following this, it appears that the default mode network becomes more cohesive (and less over active). We think this could be one of the reasons levels of anxiety and depression appear to reduce.”
Due to psychedelics’ ability to disrupt the activity of the DMN, they have a particularly strong therapeutic potential when it comes to changing negative thought patterns that have been structured by the DMN. Studies suggest that the therapeutic impact of psilocybin is linked to its ability to ‘reset’ the DMN, turning it off and reconsolidating it in a way that is less rigid and more and than before. This resulting flexibility or malleability in the brain is often described as neuroplasticity and typically results in an increased psychological flexibility.
Why we need greater psychological flexibility
Psychological flexibility allows us to deal with and manage life experiences better. With increased flexibility we have more options available to us, we are less likely to fixate on specific issues, we are more adaptable and open to change and opportunity. We are less affected by negative experiences or emotions, we can bounce back faster and feel more connected to others. Research has shown that psilocybin produces significant increases in psychological flexibility, providing an explanation for why we see decreases in depression and anxiety following a psychedelic experience. Based on what we know about the DMN and psilocybin’s effect on it, we can hypothesise that it plays an influential role in our ability to become psychologically flexible and the opposite, psychologically inflexible.
The older we are, the more likely we are to experience such psychological inflexibility, as our DMN and ego has been running the show for longer. It is hard to firstly become aware of this and then act on it to break free. This is where psychedelics such as psilocybin are such a valuable tool as they can provide an extraordinary shortcut to action and change.
Dr Matthew Brown gives an analogy for how psychedelics are able to reset the DMN, enabling an increased sense of psychological flexibility:
“If you do the same thing repeatedly, it is like you are walking down the same path all the time. Naturally, that path becomes very well worn and easy to walk down. However, you realise that maybe there is another path that might be more advantageous for you and you want to try walking down that path. Psychedelics ‘mow the lawn’ so that it doesn’t seem that the weeds are quite so high and you can walk down that new path more easily.”
These new pathways build our psychological flexibility. One can literally see them being created under brain imaging scans of people undergoing psychedelic experiences. What is becoming increasingly clear is that the expanded state of consciousness resulting from the psilocybin experience, its impact on the DMN, the resulting ’ego dissolution’ and increased “psychological flexibility”, allows for opportunities to develop new patterns of thinking and behaviour, opening up the potential for rapid personal transformation and growth.
Sources:
https://psychedelicstoday.com/2020/02/04/psychedelics-and-the-default-mode-network/
