Somatosensory event-related potentials to painful and non-painful stimuli: effects of attention.

In order to determine the effects of attention and distraction on painful and non-painful stimuli, the amplitude changes of 3 components (N150, P200, P300) of the somatosensory event-related potential (SERP) elicited by painful and non-painful electrical stimuli were investigated. Painful and non-painful stimuli were determined using a visual analog scale. SERPs were recorded from 16 healthy volunteers at 5 midline and 4 left and 4 right hemispheric sites. The differences between the amplitudes of attended and ignored stimuli were quantified with a baseline-to-peak measure. ANOVA results revealed no significant attention or stimulus intensity effects for N150 but highly significant differences in P200 and P300 amplitudes between attended and ignored stimuli. In addition, P200 and P300 amplitudes were larger for strong stimuli than for weak stimuli, with no significant differences between non-painful and painful stimuli. These findings are consistent with the existence of a relative, rather than an absolute, relationship between SERP component amplitudes and subjective pain reports. Furthermore, the data give evidence that attentional manipulations represent a powerful method to decrease the perception of pain and that, when used with subjective and behavioral measures, the SERP represents a valuable asset in the multidimensional approach to pain measurement and assessment.