Pain-evoked anterior cingulate activity generating the negative difference potential may reflect response selection processes

The effects of a heterotopic cold pain stimulus applied to the hand on the scalp-recorded negative difference potential (NDP) and subjective pain ratings elicited by electrical stimulation of the sural nerve were examined in 24 participants. Our previous work strongly suggests that the NDP is generated in part by the cognitive division of the anterior cingulate cortex (ACCcd). The latency and magnitude of the ACCcd activity were estimated from the NDP and from the dipole source localization analysis of the NDP. As expected, the sural nerve pain ratings were smaller in the cold pain condition than in the control condition. The ACCcd activity underlying the 125-ms peak of the NDP did not change across conditions, whereas the ACCcd activity underlying the 210-ms NDP peak was largest in the cold pain condition. The dissociation between pain-evoked ACCcd activity and pain ratings observed here and elsewhere suggest that not all of the nociresponsive neurons in the ACCcd are involved in pain sensation. Rather, differences in the cognitive demands of the control and cold pain conditions suggest that the pain-evoked 210-ms ACCcd activity reflects response selection processes, perhaps response competition monitoring.