Electrophysiological indices of orienting attention toward pain.

This study examined the effects of orienting on two pain-related components of the sural nerve-evoked somatosensory evoked potential: the NDP (80-230 ms), which is generated in part by the anterior cingulate cortex (ACCc), and SP6 (280-340 ms). NDP and SP6 amplitudes were larger when subjects oriented their attention away from an invalidly cued location and toward the sural nerve pain than when their attention remained focused on the pain. These results and our earlier studies suggest that the ACCc activity generating the NDP is involved in detecting transient painful stimuli. This activity is enhanced when the pain occurs outside the focus of attention, and it may signal other brain areas that attention should be oriented away from its current focus and toward the pain. SP6 appears to be a pain-evoked P3a event-related potential, with an anterior component involved in orienting attention away from some other task and toward the pain, and an posterior component involved in evaluating the pain.