Life would be interesting — though not necessarily good — if we weren’t able to feel pain. But although that’s pretty much impossible, new research into how pain is processed in the brain could offer insights into how to manage it. Researchers discovered that in a person's brain, the amount of gray matter responsible for the ability to daydream was directly connected to their sensitivity to pain.

Gray matter is where information from sensory and motor neurons are processed in the brain. Gray matter structures, such as the cortex, are interconnected by white matter, which relay information between areas of gray matter and the central nervous system. While gray matter mostly consists of neural cell bodies, white matter contains myelinated axon tracts, which essentially grab the electrical signals and transfer them to other areas.

The researchers tested pain sensitivity in 166 healthy volunteers by administering heat — 120 degrees Fahrenheit — to a small area on either their arms or legs, and having them rate the intensity of their pain. They then put each of the volunteers through magnetic resonance imaging (MRI) scans in order to find correlations between their pain-intensity rating and brain structures.   

 “Subjects with higher pain intensity ratings had less gray matter in brain regions that contribute to internal thoughts and control of attention,” Nichole Emerson, a graduate student at the Coghill Lab of the Wake Forest University School of Medicine in North Carolina, said in a press release. Namely, the researchers found that gray matter concentrations were lowest in the cingulate cortex, precuneus, and some areas of the parietal cortex. The first two are part of the so-called default mode network, which are areas of the brain responsible for daydreaming and other kinds of unfocused thought.

In the same way that someone might try to not think about their pain while injured, the researchers found that someone who was more likely to daydream (more gray matter) was also less likely to feel pain. “Default mode activity may compete with brain activity that generates an experience of pain,” Dr. Robert Coghill, professor of neuroscience at Wake Forest Baptist Medical Center, said in the press release. Because the parietal cortex is responsible for attention, he said that a person who is able to stay focused may also be better at controlling their pain. “These kinds of structural differences can provide a foundation for the development of better tools for the diagnosis, classification, treatment, and even prevention of pain,” Coghill said in the release.

Some of the latest reports find that there are 76.2 million Americans who suffer from pain lasting more than 24 hours, while about 100 million have chronic pain. Treating pain becomes difficult, as it’s a subjective feeling virtually immeasurable by tests. For this reason and many more, prescription painkiller use has skyrocketed over the past few years. Since 1999, prescription painkillers have seen a 300 percent increase in sales, according to the Centers for Disease Control and Prevention.

Source: Emerson N, Zeidan F, Coghill R, et al. Pain sensitivity is inversely related to regional grey matter density in the brain. Pain. 2014.