Neuroimaging Research has grappled with the concept of a “resting brain”. Researchers interested in Consciousness have grappled with localizing subjective states of awareness and the elusive “self”. It seems that contemplative science is bringing both concepts to the table given the profound interest in tracing neurophenomenological states associated with “the self” and intentional, meditative practices.
All functional neuroimaging research has focused on Blood-oxygenation-level-dependent (BOLD) changes in the whole brain associated with a particular active, goal-directed, cognitive or emotional function and which has shown to be statistically different from BOLD activity across the whole brain during a “passive” baseline state. The baseline state that most researchers use is typically a 5-6 min long period of passive “rest”. The instructions are typically, “Let your mind freely wander” and “try not to think of anything in particular”. These instructions sound benign and appear to be the perfect baseline state, but as it turns out, [surprise…surprise] a wandering mind is quite active. The mind in this baseline state has shown to have a tendency to wander towards self-reflection (in the past and into the future). Some researchers have called this type of wandering, “mental time travel”.
Recently, a growing body of research has investigated the nature of this resting, or “default” state, and has found that brain activation previously considered to be spontaneous noise actually reflects the operation of active and functionally connected neural networks. These patterns of activation has been termed the default mode network (DMN), have been shown to increase during passive states of rest, to diminish during tasks involving attention or goal-directed behavior, and tend to implicate brain areas associated with self-reflection, internal mentation, and narrative self-focus. In many forms of psychopathology, the DMN has been found to be more active during resting states and less likely to decrease in activation during active goal-directed tasks, suggesting a relationship between psychopathology, excessive self-reflection or rumination [about past events], and increased self-projection [into the future].
In a recent study[Link] by friend and colleague, Judson Brewer at Yale University, adept meditators trained in meditation techniques rooted mostly in Theravada (vipassana/insight) traditions actively meditated using multiple types of meditation practices (Concentration, Loving-Kindness, Choiceless Awareness) while being imaged in the MRI. A “mind-wander” rest state was the baseline state in this case, and comparisons were made also between the adepts and a group of novices who had brief instructions how to perform each meditative practice.
As seen below, Experienced meditators demonstrate decreased DMN activation during meditation. Brain activation in meditators > controls is shown, collapsed across all meditations (relative to baseline). (A and B) BOLD activations were found to be greater in the left mPFC and PCC for adepts. Although, one should take note that the % change was very minimal (about .25 % at most). The mPFC and PCC are critical nodes of activation during typical mind wandering, self-reflection, and the core areas for the DMN.
Choiceless Awareness (green bars), Loving-Kindness (red), and Concentration (blue) meditations. Note that decreased activation in PCC in meditators is common across different meditation types. n = 12 per group.
What does this mean?
You may ask what this means and how it relates to mindfulness and mind-wandering. It suggests that adept meditators spend less time using the self-reflective network or “DMN” while meditating. This makes sense given the heavy reliance on concentration in these practices. But how about when adepts are simply “wandering” during passive rest? Are they like everyone else? Do they also reflect upon themselves in the past or into the future? This study did not quite capture the phenomenological differences between the groups, but it did find that the DMN had different functional connectivity patterns.
Using mPFC as a seed region for connectivity, they found increased connectivity with the fusiform gyrus, inferior temporal and parahippocampal gyri, and left posterior insula (among other regions) in meditators relative to controls during meditation. Using the PCC as a seed region, increased connectivity (compared with controls) was found with the dorsal ACC and DLPFC during all meditative states and baseline wandering, suggesting increased cognitive monitoring and working memory across both meditative and passive resting states. It would be helpful to know if there was a qualitative aspect of “wandering” that was about equal for meditators and controls.
Similarly, David Creswell and Lisa Kilpatrick demonstrated that 8-weeks of MBSR training showed increased functional connectivity of dmPFC (an anterior DMN region) with an auditory/salience neural network (especially with BA 22/39 (associated with auditory processing) and the dorsal ACC (involved in salience) . They suggest these results indicate greater positive coherence between self-referential, attention, and auditory sensory processing and may underlie greater attention and reflective awareness of auditory experience in MBSR trained subjects.
Again, the DMN is used here as a proxy for a “wandering mind”. Decreased activity in the cortical midline structures that make up this network reflects less self-reflection or narrative self-processing, and suggests more present-centered awareness, monitoring, and attention of interoceptive and exteroceptive stimuli in the environment and associated with the body. The reason I bring attention to this area of research is that contemplative neuroscientists will likely have to take these differences in the DMN between novices and adepts into consideration when scanning meditative states. In other words, a passive mind wandering state may be different between adepts and novices or naives. Thus, between groups comparisons should likely account for these differences and at the very least, quantify the qualitative aspects of mind wandering between groups.
ON THE OTHER HAND….
There is some evidence that mind wandering is adaptive. One study (for example) by Jonathan Schooler and colleagues demonstrates that increased mind wandering during a boring task increased creativity. Schooler has previously demonstrated a correlation between daydreaming and creativity—those who are more prone to mind-wandering tend to be better at generating new ideas.
See New Yorker write up [Link]
Here are some links to press related to these studies:
psychology today [Link]
- Meditation May Help Brains Rewire, Protect Against Mental Illness – KABC (kabc.com)
- Mind-wandering and mindfulness (psychologytoday.com)
- Our Wandering Minds…. (joannewellington.wordpress.com)
- MIND AND HEALTH Relax your mind and focus (tech.mit.edu)
- Meditation leads to less mind wandering, more doing (mentalflowers.wordpress.com)
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