Pain: past, present and future.

Descartes' concept that pain is produced by a direct, straight-through transmission system from injured tissues in the body to a pain centre in the brain has dominated pain research and therapy until recently. The gate control theory of pain, published in 1965, proposes that a mechanism in the dorsal horns of the spinal cord acts like a gate which inhibits or facilitates transmission from the body to the brain on the basis of the diameters of the active peripheral fibers as well as the dynamic action of brain processes. As a result, psychological variables such as past experience, attention and other cognitive activities have been integrated into current research and therapy on pain processes. The gate control theory, however, is not able to explain several chronic pain problems, such as phantom limb pain, which require a greater understanding of brain mechanisms. A new theory of brain function, together with recent research that has derived from it, are described. They throw light on complex pain problems and have important implications for basic assumptions in psychology.