The best way doctors have to find out how much pain a patient's in is to ask---but that approach can fall short when someone's unable to speak, exaggerating or downplaying their condition, or just plain unsure how to rate their pain on a 10-point scale. Because of these problems with self-reporting, scientists have long been looking for an objective, physiological measure to quantify pain. A recent brain scanning study, in which the researchers could pick out painful experiences based on neural activity, brings that goal closer. How the Heck:
What's the News:
The researchers gave each of 24 participants an fMRI scan, which measures blood flow in the brain. They tracked the participants' brain activity as a small portion of their forearm was exposed to heat, which was either painful (quite hot) or not painful (pleasantly warm). A computer algorithm then analyzed the data for patterns, looking for types of brain activity that occurred in response to painful or not painful heat.
The team next had 16 other people do the same thing, getting their brains scanned while their arms were exposed to various levels of heat. This time, the researchers used the computer algorithm---now that it was trained on data from the earlier subjects---to analyze the scans, classifying each heat exposure as painful or not based on brain activity. The computer model could correctly identify which experiences were painful 81% of the time.
Not So Fast:
The study was small, and only looked at a yes-no division (does it hurt or not?) rather than trying to tell more or less painful experiences apart.
It also used just one type of pain, heat. Larger studies aimed at discriminating different levels of pain will be required to show whether this technique could be useful in the clinic.
The Future Holds: In addition to looking at varying levels of pain, the team wants to see whether this technique can be used for different sorts of pain---for instance, pain from a wound or a pinched nerve rather than heat. They're also investigating whether brain scans can measure not just single episodes of pain, but chronic pain, as well. Reference: Justin E. Brown, Neil Chatterjee, Jarred Younger & Sean Mackey. "Towards a Physiology-Based Measure of Pain: Patterns of Human Brain Activity Distinguish Painful from Non-Painful Thermal Stimulation." PLoS ONE, September 13, 2011. DOI: 10.1371/journal.pone.0024124