The Brain and the Attenuation of Pain

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We all experience pain, whether physical or emotional, pain is a normal feature of the human experience. Whilst pain is unpleasant, it is also necessary. Evolutionarily, pain acts as a social alarm for threats to help our normal life functioning. However, we all experience pain in different ways. Our perception of pain is a product of the sensory experience and the cognitive and emotional factors around it. So, how can our cognition and emotion alter our perception?

In 2019, Enrico Schulz from Ludwig-Maximilians-Universität München and colleagues from the University of Oxford found three strategies to help attenuate the perception of pain. In their latest study, the researchers wanted to investigate how brain connectivity is affected by these cognitive and emotional interventions. In other words, how the brain reacts to different mental stimulations that alter our experience of pain.

To do this, 20 healthy participants were allocated in one of four conditions whilst experiencing a painfully cold stimulus for 40 seconds. The conditions were as follows:

  1. Control: where they experience the painful stimulus with no modulation.
  2. Counting: which involved counting backwards from 1000 in steps of 7.
  3. Safe place: where they imagined being in a safe, pleasant place during the experience.
  4. Cognitive reappraisal: which consisted of reinterpreting the sensation as non-painful.

The participants were also attached to an ultra-high-field functional magnetic resonance imaging (fMRI) to investigate the whole-brain functional connections that contribute to the relief of pain from the various coping strategies. To evaluate the intensity of pain in each condition, participants were asked to rate their pain on a scale of 0 to 100.

The results seemed to indicate that all techniques resulted in lower levels of pain compared to the control condition. The counting technique was the most effective with some participants reporting up to 50% less pain. A participant even later employed this technique to ease the pain of childbirth! The data showed that a decrease in pain perception can be associated with an increase in cortical connectivity in both pain processing (such as the insula, cingulate cortex and somatosensory cortices) and task-related brain regions. However, the subjects did not report one specific area associated with all three strategies, the researchers suggested that this highly complicated process involves many different neural circuits acting in conjunction.

Internal view of the insular cortex
Wikipedia. Insular Cortex. (2020)

The counting technique showed close coordination between different parts of the insular cortex, an area associated with sensory information processing.  The counting task is suggested to need visual support for imagining the numbers and thus visual areas connect to and suppress right parietal opercular areas. These areas act in conjunction to suppress the processing of pain due to the elevated focus on the task which decreases transmission to the posterior insula during task execution.

The safe place technique showed success when there were intensive flows of information between the frontal lobes (the control centres in the brain) and somatosensory cortex (another brain area associated with the processing of pain), shown by white matter structural connectivity.  This reaction is hypothesized to signify a greater degree of control from the task making allusion to the employment of control as a distraction from the pain.

Wikipedia. Primary somatosensory cortex. (2020)

As for the reappraisal condition, the connections were more complex as there was no one connection which stood out. The connections from the inferior frontal cortex, the anterior cingulate cortex, the frontal pole and orbitofrontal cortex are all harnessed during cognitive reappraisal in order to ultimately attenuate the experience of pain.

Whilst the three conditions differed in which areas of the brain they involved; they all showed an increase in neural connectivity. All showed promise in their attenuation of pain due to their role as a distractor from the painful experience. These findings are hoped to be applied for pain relief in patients with chronic pain.

Original Source: Schulz, E., Stankewitz, A., Winkler, A., Irving, S., Witkovský, V. and Tracey, I., 2020. Ultra-high-field imaging reveals increased whole brain connectivity underpins cognitive strategies that attenuate pain. eLife, 9.

Link:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7498261/

Photo credit: The Neuroscience of Pain, The New Yorker

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