Association between event-related potentials and pain ratings not as straightforward as often thought

The association between event-related potentials (ERP) and ratings of pain has frequently been demonstrated, usually through bivariate correlations. However, the use of bivariate correlations precludes studying or correcting for confounding factors. The current study reinvestigated the association between ERP and the subjective experience of pain, using the more extensive statistical approach of multilevel analysis. Using this technique, it was possible to investigate and correct for effects of intensity and habituation. Eighty-five healthy subjects received intracutaneous electrical pain stimuli with simultaneous EEG registration. Each subject was asked to rate the intensity of each stimulus on a numeric rating scale (NRS). The multilevel analyses revealed a within-subject association between the ERP measures (especially P1 and P3) and the NRS score. Furthermore, this association was moderated by intensity of the stimulus and habituation. These results suggest that a direct translation from the pain ERP to subjective experience is delicate and that factors such as stimulus intensity and habituation must be taken into account.