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MONDAY, June 23, 2003 (HealthDayNews) -- Pain may be subjective, but how do you know if someone's refusals to grimace are real or mere bravado?
A new study shows men and women who report feeling pain differently show marked differences in brain activity during the experience. The study lends support to standard psychological tools for discomfort -- in other words, asking. And, experts say, the work could help doctors better administer pain relief.
"People are very capable of looking into themselves and giving you a very accurate measure of what they're feeling," says study leader Robert Coghill, a neurophysiologist at Wake Forest University School of Medicine in Winston-Salem, N.C. "These individual differences are real, and that enables us to use them to better treat patients."
A recent study, for example, found surgery patients who were more sensitive to heat before their operation complained of more pain after the procedure. "If you can identify more sensitive individuals, you can give them [higher does of painkillers] as they're coming out of surgery," Coghill says. "With others, you could back off the standard dose and spare them some side effects."
A report on the findings appears this week in the Proceedings of the National Academy of Sciences.
Coghill and his colleagues studied the pain responses of nine men and eight women, aged 21 to 40. All the volunteers had a form of magnetic resonance imaging (MRI) of their brain while being exposed to the laboratory equivalent of a hot poker on their legs. They were also asked to rate the sensations on a standard test.
The rankings varied widely. One person called the heat -- which reached 120 degrees Fahrenheit -- almost a nine out of 10, while another said it was barely a one on the scale.
Those who reported less discomfort during the pain tests also had significantly different results on their brain scans, the researchers say. Areas of the brain known to process pain, including the anterior cingulate cortex, the prefrontal cortex and the primary somatosensory cortex, "lit up" more strongly in the subjects whose reaction to the heat was strongest.
Another brain region, the thalamus, acts as a relay station for pain sensations that travel up the spinal cord, communicating them to other areas of the brain. Interestingly, Coghill says, the least sensitive volunteers had no less, and possibly a little more, activity in their thalamus than the more sensitive subjects.
That finding suggests differences in the perception of pain are cognitive, Coghill says. In other words, they involve things such as how a person has experienced pain in the past, what they associate with pain, and what pain means for them emotionally.
Donald Price, a neuroscientist and pain expert at the University of Florida in Gainesville, calls the latest study "a breakthrough" that's "critically important" for the field of pain research. "It really validates the ability to measure pain in human beings," Price says.
Although the study looked only at immediate, or acute pain, Price says in theory it should apply to chronic pain, too. As many as 15 million Americans suffer chronic pain so severe it's debilitating, according to the National Foundation for the Treatment of Pain.