Earlier studies have examined the pattern of increased brain activity that follows experimentally-induced acute pain (2) and chronic pain syndromes (1,3,5). Distal pain pathways (e.g. spinothalamic tract) project to the thalamus and then discrete regions of the cortex via thalamocortical projections. Among cortical areas involved in sensation, perception, and attention in both humans and monkeys are anterior cingulate gyrus, insular cortex, primary somatosensory cortex, and secondary somatosensory cortex. PET studies with experimental human pain also demonstrate activation in brain areas related to sensory-motor integration. However, depending on the type of noxious stimulation, different areas of brain are activated (2). Components of the lateral system such as the primary somatosensory (SI) cortex do appear to be frequently activated with tonic (non-phasic experimental pain) and phasic pain (67% and 69% of studies show activations, respectively). But only 23% of studies of chronic clinical pain studies demonstrate activation of SI.