Less pain when you're in control?

Our responses to pain and our ability to tolerate it are known to be affected by the extent to which pain is perceived to be controllable. A study published in The Journal of Neuroscience now shows how differences in perceived pain control influence the activation of the insular cortex, secondary somatosensory cortex (SII) and anterior cingulate cortex (ACC), all of which are involved in pain processing.

Salomons et al. used painful thermal stimuli and different cues signalling controllable or uncontrollable pain to test whether subjects' perception of pain and the associated neural processing varied according to perceived controllability. Although the subjects were able to distinguish between cues signalling controllable and uncontrollable pain, there was no difference between the mean pain rating given for stimuli perceived to be controllable or uncontrollable.

The authors also used overlapping brain maps created using fMRI studies, and subtracted the activation seen in areas of interest when pain was perceived to be controllable from that seen when pain was perceived to be uncontrollable. Although parts of all three areas were activated when pain was perceived to either be controllable or uncontrollable, the degree of activation was significantly greater when pain was perceived to be uncontrollable; in particular in the dorsocaudal area of the ACC and the anterior area of the right insula. As the subjects did not give the two conditions different pain ratings, Salomons et al. conclude that the results of the overlap study cannot be explained by just the subjects' perception of pain.

The authors suggest that the results of previous pain studies might have been influenced by subjects' perceived lack of pain control, which, in imaging studies, could have led researchers to believe that pain itself caused exaggerated activation of particular areas of the brain. They also propose that further research be carried out to establish whether different subjects use different techniques, such as distraction, to help them cope with pain. Furthermore, they suggest that differences in perceived pain control might be used in studies of chronic pain and possible treatments for this condition.