Cortical mechanism underlying the sensory and emotional components of the pain experience
PET studies mentioned in Question 25 also examined what occurs during hypnotic analgesia. When subjects were hypnotized so as to decrease the unpleasantness generated by a heat stimulus, the “activity” generated in the anterior cingulate gyrus was dramatically decreased, but without significant change in activity in the somatosensory cortex. These studies illustrate that under hypnotic analgesia, the information about the stimulus does access the cortex, but that the nature of the perception reported is altered. These results also provide strong evidence that the anterior cingulate gyrus processes information more related to the affective component of the pain experience than to the sensory discriminative component. Consistent with these findings, ablation of the anterior cingulate gyrus, in animal studies, reduces behavior indicate of the affective impact of noxious stimuli.