Even more problematically, it can’t be used for people who can’t speak (the very young or the cognitively impaired) nor can it be used to compare pain levels in different people. And yet, treatment for pain usually depends on understanding the intensity of that pain. Thanks to some new fMRI studies conducted by researchers led by Tor Wager from the University of Colorado, we may now have a neurological signal for physical pain.
You know a pain study isn't going to be good news for the volunteers. Wager and his colleagues do not disappoint. 114 participants were hooked up to an fMRI machine while heat was applied to their left forearms. The heat levels were calibrated for each individual to range from warm to scorching (subjective pain level 'seven'). Each test was preceded by a warning cue, 8 seconds of anticipation, 10 seconds of applied heat, and then a 4 second evaluation period. Some people went through 75 of these trials.
There were some interesting variations. In one study, all the subjects had recently experienced a romantic rejection. These people got to look at either a picture of their ex-partner or of a close friend while being seared. In another, people were unwittingly given analgesics before the trials.
Wager, T., Atlas, L., Lindquist, M., Roy, M., Woo, C., & Kross, E. (2013). An fMRI-Based Neurologic Signature of Physical Pain New England Journal of Medicine, 368 (15), 1388-1397 DOI: 10.1056/NEJMoa1204471.