In neuroscience the default mode network (DMN) is a network of widespread brain regions showing functional connectivity. It is active when we are not task focussed, such as when the mind is wandering. It is active when we are thinking about others, ourselves, remembering the past or planning for the future. It has been shown to be negatively correlated with other brain networks, such as attention networks (ie. they are active at different times). Disruptions to the DMN has been associated with Alzheimer’s disease, ADHD and autism spectrum disorder (Wikipedia, Brewer et al, 2011). Increased DMN activity may interfere with cognitive performance and is associated with depression, anxiety and addiction (Garrison et al, 2015).
In this blog I will review a selection of research papers investigating the effect of meditation on the default mode network, and how this may relate to some of the benefits of meditation practice.
Brewer et al (2011) investigated the brain activity of experienced and novice meditators as they engaged in meditation practices, including concentration, loving kindness and open awareness. They state that mind wandering is an activity present in 50% of our waking life and is associated with the activation of the DMN, which correlates with unhappiness and with self-referential mental processing. Given that the task of mindfulness meditation is to maintain attention on a mindfulness support and to redirect attention there each time the mind wanders, Brewer at al predicted that experienced meditators would exhibit reduced recruitment (activity) of the DMN.
The key finding was that the main nodes of the DMN were relatively deactivated in experienced meditators across all meditation types, consistent with decreased mind wandering, providing a possible neural mechanism of meditation. Their research further suggests that these effects might be present in daily life, so that experienced meditators experience a more present-centred default mode of being. This research is promising although limited by a small sample size and the use of self-report for assessing levels of mind wandering.
Garrison et al (2015) developed this research to provide further evidence that meditation leads to reduced default mode activity in using a larger group of participants. This research also compared DMN activity while meditating to DMN activity while doing an effortful task in experienced meditators versus beginners. The effortful task asked participants to make judgements about a series of adjectives. It demonstrated that for experienced meditators meditation leads to relatively reduced default mode processing beyond that observed during an effortful cognitive task.
Simon et al (2015) suggest activity levels in the DMN could be used as a biomarker for monitoring the therapeutic effects of meditation as it is currently used as a biomarker for certain drug treatments. They postulate that as increased modulation of the DMN is associated with meditative practice and that meditative practice is increasingly understood to have a beneficial effect in the treatment of mental health problems, that DMN measures might be used as a biomarker for monitoring the beneficial effects of meditation in the treatment of mental health problems.
Ramirez-Barrantes et al (2019) describe how alterations in the connectivity of the DMN have been found to participate in cognitive decline, as well as several neurodegenerative disorders. The DMN is less active when attentional networks, which are essential for executive function and memory are more active. They postulate that regulation of the DMN by the activation of attentional networks in the brain might be a strategy for neuroprotection. They state that meditation is proven to increase meta-awareness, which is a cognitive ability which involves the control of both these brain networks. In their paper they discuss the possibility of facilitating healthy ageing through meditation.
In their book ‘The Science of Meditation’ Goleman and Davidson describe the self-referential mind wandering that is associated with the activity of the DMN when the mind is at rest. They describe how this activity of the DMN frames every event in terms of how it impacts us and so knits together our sense of self, by continuously rescripting the movie of our lives. They report research from Harvard researchers asking thousands of people to report where their mind wanders to, concluding as indicated above that
a wandering mind is an unhappy mind. We ruminate over what is troubling us, problems from the past, worries about the future. When we get lost in thoughts during meditation we have fallen into the DMN.
Noticing when the mind wanders and then bringing it back into presence, a key element of meditation has a neural correlate activating regulatory circuits in the prefrontal cortex of the brain which can quiet the default mode network and associated self-focussed chatter. This increases for more experience meditators. They refer to Brewer’s research (some of which is discussed above) and describe how novice and seasoned meditators both demonstrated this regulatory control, whereas seasoned meditators in addition had less activation in the DMN per se, in particular when they practiced loving kindness meditation. The inference here is that in loving kindness meditation we focus on the wellbeing of others and so the resulting reduced DMN activation relates to reduced self-focus.
This research evidence seems quite persuasive. As always, the more practice that is done the better the results, in terms of reduced mind wandering during meditation practice (state effects) and reduced mind wandering in daily life (train effects). So time to hit the cushion!
Heather Regan-Addis
References
Brewer et al (2011) – https://www.pnas.org/content/pnas/108/50/20254.full.pdf
Garrison et al (2015) – https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4529365/
Goleman & Davidson, 2017 – https://www.goodreads.com/de/book/show/36121358-the-science-of-meditation
Ramirez-Barrantes et al (2019) – https://www.hindawi.com/journals/np/2019/7067592/
Simon et al (2015) – https://www.frontiersin.org/articles/10.3389/fpsyg.2015.00776/full
Wikipedia – https://en.wikipedia.org/wiki/Default_mode_network
