Posted 08.28.2018 | by AMRA

Mindfulness-based interventions can enhance emotional regulation and improve mood, but we are only just beginning to understand the brain mechanisms responsible for these benefits. Kral et al. [Neuroimage] compared the brain activity of long-term meditators, short-term meditators, and non-meditators in response to emotionally positive, negative, and neutral images. The researchers sought to discover whether or not the amount of an individual’s meditation practice correlated with their response to emotional stimuli.

The researchers recruited a sample of 31 long-term Vipassana mediators (average age = 50 years, 55% female, average meditation practice = 9,000 hours) and compared them to a sample of 127 meditation-naive recruits. Following initial data collection, 86 of the meditation-naïve recruits (average age = 48, 63% female) were randomly assigned to a standard 8-week Mindfulness-Based Stress Reduction (MBSR) program or a Health Enhancement program (HEP) which served as a time-and-attention control.

The long-term mediators and the meditation-naive participants spent a day in the laboratory prior to the meditation-naive group’s random assignment to intervention. Following intervention, the meditation-naive group returned to the laboratory for re-assessment.

In the laboratory, participants were shown emotionally positive, negative, and neutral images while undergoing functional magnetic resonance imaging (fMRI), a procedure that measures metabolic activity in different regions of the brain. The researchers measured fMRI activity in two specific brain regions: the amygdala, which plays a role in generating emotion, and the ventromedial prefrontal cortex (VMPFC), which plays a role in regulating emotion. Participants also completed a self-report measure of mindfulness, the Five Facet Mindfulness Questionnaire (FFMQ).

Results from the pre-intervention data showed that meditation-naive participants had significantly greater right amygdala activity in response to positive images than long-term meditators. While there were no overall group differences in response to negative images, long-term mediators with the most lifetime Vipassana retreat hours had the smallest right amygdala response to negative images (r = -.47).

For all participants, higher scores on the FFMQ Non-reactivity scale (“When I have distressing thoughts or images I just notice them and let them go”) were associated with less right amygdala reactivity to positive images (r = .24). Long-term meditators had significantly higher FFMQ Non-reactivity scores than meditation-naïve participants. HEP control group participants showed significantly greater right amygdala activity in response to positive images than the MBSR participants immediately after the interventions.

The researchers also looked at the degree of functional connectivity (the degree to which activity varied in tandem) between the amygdala and the VMPFC. Long-term meditators showed significantly greater amygdala-VMPFC connectivity in response to negative images than to neutral images. Meditation-naive participants failed to show the same pattern, but the between-group difference was not significant. MBSR participants showed significantly greater amygdala-VMPFC connectivity during positive and negative as opposed to neutral images than HEP controls.

The study shows that short-term meditation practice reduces emotional reactivity by VMPFC dampening of amygdala activity. Long-term meditators, however, regulate their amygdala activity without VMPFC dampening and report superior levels of emotional non-reactivity.

The authors suggest that amygdala activity reflects the tendency to hold on to or avoid stimuli rather than the tendency to experience them as pleasant or unpleasant. Long-term meditators may have developed the capacity to attend to stimuli without grasping at them or pushing them away. This differs from the short-term meditators suppression of emotional reactivity after the fact of its occurrence. The results also suggest that meditation retreats are more effective than non-retreat daily practice in developing this non-reactive capacity.

Reference:

Kral, T. R., Schuyler, B. S., Mumford, J. A., Rosenkranz, M. A., Lutz, A., & Davidson, R. J. (2018). Impact of short-and long-term mindfulness meditation training on amygdala reactivity to emotional stimuli. NeuroImage.

[Link to abstract]