Central mechanisms of pain perception.

Mechanisms of human nociception can be studied by the use of CO2 laser stimulation, which selectively activates nociceptive receptors, and by the use of various noninvasive techniques. In addition to the contralateral thalamus, at least several cortical areas including the contralateral SI, bilateral SII, anterior cingulated cortex, and insular cortices are involved in the pain sensation/perception. Pain perception (Fig. 8) is unique because these cortical structures seem to be activated in parallel at nearly the same latency after the stimulus presentation. SI seems to play a role in basic pain processing while SII and insula are involved in higher functions of pain perception. Emotional aspects of pain perception are mediated by anterior cingulate cortex and posterior insula/parietal operculum.