The effect of mindfulness on the activity of the Default Mode Network supports the role of the Default Mode Network in self-referential processing

The Default Mode Network (DMN) generally refers to the pattern of brain activity during periods of non-engagement in an attentive, purposeful task. Several regions of the brain have synchronized activity when the DMN is active and for most people, a set of archetypal thought processes prevail. These include mind wandering, dwelling on the future or ruminating about the past, which are inclined towards self-referential associations and feature prominently in several mental disorders such as depression, anxiety, psychosis, ADHD and OCD.

Mindfulness as a cornerstone of many forms of meditation, features two underlying concepts which have the potential to reduce DMN activity and thus its corresponding self-referential thought modalities. In summary, these include focus of attention on the present moment experience and maintaining acceptance rather than a judgemental, reactive disposition towards all that is perceived.

Mindfulness posits a generalized categorization of three mental modes. The first being mindless emoting, second conceptualizing or doing mode and the third mindful being. The first two modes are where most people commonly reside, with alternation between the two occurring involuntarily during the resting state.

Brewer et al. (2011) showed that mindfulness meditation attenuates activity in the main nodes of the DMN, namely the Posterior Cingulate Cortex and the medial Prefrontal Cortex when meditators were compared with control subjects. This study used three forms of mindfulness meditation: Concentration, Loving-kindness and choiceless awareness. All three techniques demonstrated a reduction in the PCC and mPFC activity with increased activity in several other non DMN related brain regions such as the dorsal anterior cingulate and dorsolateral prefrontal cortex which are implicated in cognitive control and monitoring conflict. Furthermore, these distinct changes to the DMN activity pattern in meditators persisted during resting state, which supports the benefits of mindfulness upon the neural functioning of the DMN.

 

A study into the effect of novel vs practiced task execution proved that DMN activity is less active during novel than practiced tasks. Participants also reported increasing non-task focussed independent thoughts to occur during practiced tasks relative to novel tasks as their minds drifted. This effect is likely due to the cognitive demand reducing as tasks become more familiar (Mason et al 2007). Supporting the statement that Mindfulness is a cognitive task in itself, as it shifts the brain towards greater maintenance of the “novel task execution” state, where non task focussed cognition and thus self-referential thoughts are significantly suppressed.

Using fMRI analysis Buckner and Carroll (2007) verified that thinking about the future, historical recollection and theory of mind associated with DMN activation share the common theme of perceiving oneself in an alternative scenario. Such thought processes cannot arise during present moment awareness which mindfulness practice both mediates and enhances.

Numerous studies have identified a correlation between brain regions active in the DMN and specific self-referencing moieties at a more granular level. For example, the ventral mPFC gives a sense of personal self and the dorsal mPFC with our social self, with the posterior cingulate and precuneus contributing to form our space-time identity of self. Mindfulness and to a greater extent Buddhist doctrine, both emphasise the illusory nature of self. This is supported by scientific studies which show that the notion of self is generated by neural correlates which comprise the DMN and are strongly associated with a range of mental health disorders (Buckner & Carroll 2007).

Significant evidence shows that mindfulness can shift the default mode network toward a more mindful consistency which has markedly reduced mind wandering and self-referencing. This would likely correspond to a reduction in the potential for psychopathologies to develop that are linked to these maladaptive modes of thought. Mindfulness can also potentiate inhibition of the vicious cycle fuelled by such thought modes, as greater control and clarity of thought are generated through an associated increase in activity in other brain regions. Furthermore, some mindfulness methods such as loving kindness meditation suggests that the reduction in amygdala activity can also help shift psychosocial thought processing towards a healthier trajectory by suppressing fear and anxiety which is mediated by the amygdala (Brewer et al. 2011). Future studies could further investigate the differences between aging and mindfulness upon self-referential cognition, as elderly people generally display parallels to mindfulness practitioners in the diminished activity of DMN subregions that coordinate the sense of self.

 

Judson A. Brewer, Patrick D. Worhunsky, Jeremy R. Gray, Yi-Yuan Tang, Jochen Weber, Hedy Kober (2011). Meditation experience is associated with differences in default mode network activity and connectivity. Proceedings of the National Academy of Sciences Dec 2011, 108 (50) 20254-20259; DOI: 10.1073/pnas.1112029108

Mason, M. F., Norton, M. I., Van Horn, J. D., Wegner, D. M., Grafton, S. T., & Macrae, C. N. (2007). Wandering minds: the default network and stimulus-independent thought. Science, 315 (5810), 393-395

Buckner, R. L., & Carroll, D. C. (2007). Self-projection and the brain. Trends in Cognitive Sciences, 11(2), 49-57.