Effects of response conflict on pain-evoked medial prefrontal cortex activity

Experimental studies of pain may introduce a response conflict, where the subject must inhibit an escape response and make a pain-rating response. Several lines of evidence have shown that the medial prefrontal cortex is activated by painful stimuli and by response conflict. It is not clear, however, to what extent pain-evoked medial prefrontal cortex activation reflects response conflict. We examined this question using the Simon task. The participants identified pain threshold and moderately painful target stimuli presented to the left or right sural nerves using their left or right hands. Response conflict occurred when the response was made with the hand contralateral to the target stimulus. The results suggest that pain-evoked medial prefrontal cortex activity occurring 70 to 190 ms poststimulus, as estimated from the sural nerve somatosensory evoked potential, is not involved in response conflict.