Posted 03.17.2020 | by AMRA

Mindfulness-based interventions can alleviate pain and suffering in some individuals, but there are important questions about its mechanism of action. Mindfulness might work “top down” by helping us to think differently about the significance of our unpleasant experiences. Alternatively, it might work “bottom up” by preventing us from experiencing the unpleasantness of negative stimuli in the first place. Moreover, it is unclear whether formal meditation practice is essential in order for mindfulness to reduce suffering, or whether learning to adopt a nonjudgmental attitude might, in and of itself, be sufficient.

Kober et al. [Social Cognitive and Affective Neuroscience] sought to clarify how an attitude of mindful acceptance affects emotional and brain responses to unpleasant and painful stimuli. Study participants acted as their own controls, at times instructed to respond to sets of negative stimuli as they naturally would, and at times instructed to respond with mindful acceptance.

The researchers recruited a sample of 17 meditation naïve adults (71% male; average age = 32). Participants were presented with a series of unpleasant and neutral images on a computer screen, and researchers also applied a series of warm or painful heat stimuli to participants’ forearms. Participants were instructed on some stimulus trials to react as they naturally would in their daily life, and instructed on other stimulus trials to adopt an attitude of “accepting experience as it is” without judgment.

Instruction in mindful acceptance was brief, and participants articulated what they were doing on practice trials to assure their understanding of the instructions provided. Participants rated their emotional negativity on an eight-point scale after each stimulus presentation.

Brain activity was recorded by functional magnetic resonance imaging (fMRI) throughout the stimulus presentations. Brain activity was analyzed for 1) prefrontal cortical activity reflecting “top down” cognitive control of emotions, 2) functional connectivity between areas of the brain associated with “acceptance” (e.g., the insula and the dorsal anterior cingulate cortex), and 3) the neurological pain signature.

The neurological pain signature is a pattern of brain activity known to vary with the intensity of experienced pain. It involves brain regions targeted by primary afferent pain fibers including the cingulate cortex, insula, thalamus, and somatosensory cortex.

The results showed that participants reported significantly more negative emotion in response to unpleasant compared to neutral images, and to hot more than warm stimuli. Adopting an attitude of acceptance significantly decreased negative affect in response to unpleasant images (d = 1.14) and painful heat stimuli (d = 1.51) compared to adopting a natural attitude.

An attitude of acceptance also decreased amygdala activity in response to unpleasant images, and reduced medial frontal gyrus, dorsal anterior cingulate cortex, sensorimotor cortex, insula, thalamus, and cerebellar activity in response to painful heat stimuli, and resulted in a 26% decline in the neurological pain signature (d = 0.65). This 26% decline is larger than the decline typically found in placebo studies.

There was no increase in prefrontal cortical activity associated with the attitude of acceptance, suggesting that acceptance is not a top-down cortical control mechanism.

This study shows that adopting an attitude of mindful acceptance as opposed to one’s natural attitude can significantly and meaningfully decrease negative emotional responses to unpleasant visual and painful physical stimuli. Unlike cognitive reappraisal strategies (e.g., challenging one’s thoughts or putting things in perspective), which are mediated by top-down prefrontal cortical activity, mindful acceptance significantly reduces the neurological pain signature. Mindful acceptance seems to have a “bottom up” effect on early stages of the pain perception process, perhaps by altering how a person initially interprets the significance of a stimulus.

Reference:

Kober, H., Buhle, J., Weber, J., Ochsner, K. N., & Wager, T. D. (2020). Let it be: Mindful-acceptance down-regulates pain and negative emotion. Social Cognitive and Affective Neuroscience.

[Link to study]