Dissociation Between Individual Differences In Self-Reported Pain Intensity And Underlying Brain Activation

Pain is a uniquely individual experience. Previous studies have highlighted changes in brain activation and morphology associated with inter- and intra-individual pain perception. In this study we sought to characterize brain mechanisms associated with individual differences in pain in a large sample of healthy participants (N = 101). Pain ratings varied widely across individuals. Moreover, individuals reported changes in pain evoked by small differences in stimulus intensity in a manner congruent with their pain sensitivity, further supporting the utility of subjective reporting as a measure of the true individual experience. However, brain activation related to inter-individual differences in pain was not detected, despite clear sensitivity of the BOLD signal to small differences in noxious stimulus intensities within individuals. These findings raise questions about the utility of fMRI as an objective measure to infer reported pain intensity.