Functional Magnetic Resonance Imaging of Pain Consciousness: Cortical Networks of Pain Critically Depend on What is Implied by "Pain"

Brain imaging studies, using primarily functional magnetic resonance imaging (fMRI), are reviewed. These studies are aimed at developing imaging approaches that can be used in the clinical setting to investigate clinically relevant pain states. To this end, our recent studies indicate that by taking advantage of the temporal variations in pain perception, we are able to identify cortical regions that may be uniquely involved in pain consciousness. This procedure in turn becomes a general approach with which clinical pain states can be studied. Preliminary results are shown in patients suffering from chronic reflex sympathetic dystrophy (RSD) and chronic back pain. The review emphasizes that different experimental pain states, and chronic and acute clinical pain states, seem to involve dramatically different networks, the details of which remain to be worked out. It is concluded that these procedures need to be applied in the larger clinical setting in which multicentered studies may be conducted to begin building the brain pain network atlas.