Less Gray Matter in Certain Brain Regions Linked with Higher Pain Sensitivity

A new study has shown that people with more gray matter in the regions that process internal thoughts and attention have lower sensitivity to pain.

The brain has both gray and white matter; with the gray being responsible for information processing and white matter connecting different brain regions. The latest study found that subtle changes in certain brain structures, especially in regions that control thoughts and attention, could impact a person's sensitivity to pain.

"We found that individual differences in the amount of grey matter in certain regions of the brain are related to how sensitive different people are to pain," said Robert Coghill, Ph.D., professor of neurobiology and anatomy at Wake Forest Baptist and senior author of the study.

For the study, researchers looked at gray matter differences in 116 people. They heated a small portion of each participant's arm to 120 degrees Fahrenheit and asked him/her to rate the pain. After this pain sensitivity test, participants were hooked on to an MRI scanner and researchers recorded images of their brains.

According to Nichole Emerson, B.S., a graduate student and first author of the study, the level of gray matter in posterior cingulate cortex, precuneus and areas of the posterior parietal cortex was strongly related with differences in pain sensitivity.

Posterior cingulate cortex and precuneus and part of a default mode network, which controls free-flowing thoughts that people have while day dreaming.

"Default mode activity may compete with brain activity that generates an experience of pain, such that individuals with high default mode activity would have reduced sensitivity to pain," Coghill said.

The brain isn't really idle while we rest. Research has shown that it uses just 5- 10 percent less blood when it isn't actively engaged in a task. Previous study has shown that this default mode network is disturbed in people with autism, schizophrenia and Alzheimer's disease.

The posterior parietal cortex is associated with attention. Researchers believe that people with good attention spans can keep pain under control.

The study is published in the journal Pain.