Examination of the Role of the Cerebral Cortex in the Perception of Pain Using Functional Magnetic Resonance Imaging.

In the following review we outline several of the unique difficulties associated with designing and interpreting functional imaging studies of pain perception. Unlike other sensory modalities, the cortical processing of pain is unique, as is the pain experience itself. Unlike other sensory systems, pain processing does not take place in one dedicated region of the cortex. Rather, nociceptive cells are sparsely distributed through the somatosensory cortex. Further, pain is singular in that it has both sensory-discriminative and affective-motivational components, which are probably subserved by different neuroanatomic substrates. Finally, abnormal pain sensation, such as neuropathic pain syndromes, may have different or additional mechanisms that require special consideration. We have illustrated these points with examples from our own work on acute pain and secondary mechanical hyperalgesia, and work from other laboratories.