Sensitivity to pain linked to differences in brain structure

Date: Jan-15-2014Researchers in the US have discovered a new clue to why everybody feels pain

differently - it could be because of individual differences in brain structure.

Writing about their findings in a recent online issue of the journal Pain,

scientists at Wake Forest Baptist Medical Center in Winston-Salem, NC, describe how they

compared people's perceived pain intensity with differences in brain structure seen in MRI

scans.

Robert Coghill, senior study author and professor of neurobiology and anatomy at Wake Forest

Baptist, says:

"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."

The brain contains grey matter, which processes information, and white matter, which

coordinates communication among the various brain regions.

For their study, the researchers recruited 116 healthy volunteers and tested their pain

sensitivity by asking them to rate pain intensity as a small area of skin on their arm or leg

was heated to 120 degrees F (49 degrees C).

After the pain sensitivity test, the participants underwent MRI scans to record images of

their brain structure.

Higher pain intensity linked to less grey matter in brain regions

The results showed that participants with the highest pain intensity ratings had less grey

matter in brain regions known to be involved in internal thoughts and attention control.

These brain regions include the posterior cingulate cortex and two regions that are part of

the default mode network: the precuneus and areas of the posterior parietal cortex.

The default mode network is a group of interlinked brain regions that are associated with

the free-flowing thoughts people experience as "day-dreaming."

Prof. Coghill says:

"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."

People better at attention control may be better at controlling pain

Some parts of the posterior parietal cortex are important for attention control, and Coghill

suggests people who can keep their attention focused may also be better at keeping their pain

under control.

He suggests findings like theirs may help develop better ways of diagnosing, classifying,

treating and perhaps even preventing pain.

Meanwhile in another study, researchers found that by attaching a signal to a small molecule

called saxitoxin and injecting it into rats, they could "see pain" on PET scans.

Written by Catharine Paddock PhD

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