CU-Boulder study sheds light on brain's processing of pain

A new study led by the University of Colorado is providing insights into the ways people experience pain, and manage it, through separate pathways in the brain.

The study, published this month in PLOS Biology, shows that when people use their thoughts to dull or enhance the experience of pain, the physical pain signal in the brain conveyed by nerves in the area of a wound, for example, and encoded in multiple regions in the cerebrum does not actually change.

Rather, the act of using thoughts to modulate pain, a technique termed "cognitive self-regulation," commonly used to manage chronic pain, works by way of a separate neural pathway.

The study is credited with showing that the processing of pain in our brains goes beyond the mere physical pain signal and underscores a better understanding among neuroscientists that there is not a single pain system in the brain.

"We found that there are two different pathways in our brains that contribute to the pain experience," Choong-Wan Woo, lead author of the study and a doctoral student in CU's Department of Psychology and Neuroscience, stated in a news release.

"One way to say it is maybe it's not as important what the sensation is or the immediate pain response is, but it's important how you think about it," Tor Wager, a co-author on the study and associate professor of psychology and neuroscience at CU, said in an interview.

The first pathway mediates the effects of turning up the intensity of painful stimulation and includes regions of the brain such as the anterior cingulate cortex. The second pathway, discovered in the new study, mediates the effects of cognitive regulation and involves boosting activity in the medial prefrontal cortex and nucleus accumbens regions of the brain linked to emotion and motivation, but not typically responsive to physical pain.

This latter pathway may hold some of the keys to understanding the "emotional" aspects of pain, which can contribute substantially to long-term pain and disability.

"This pathway is really interesting in terms of what pain is and what it means," Wager said. "It doesn't change in activity if you turn up the heat and deliver pain. Its changes are more complex.

"It's really capturing the significance that you assign to pain, and to other emotional events. It turns out to be important not only for pain, but how you value things in life, how much you want or don't want, and when you generate emotional responses. It's also very important to depression, PTSD, and it's important across a range of emotion-related disorders."

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CU-Boulder study sheds light on brain's processing of pain