The gate control theory’s most important contribution to pain research and therapy is its emphasis on the central rather than the peripheral nervous system (Melzack, 1998, 1999; Melzack & Wall, 1996). Knowledge of spinal mechanisms has advanced enorously, and the great challenge at present is to understand brain mechanisms. When the gate control theory was published, it generated vigorous debate as well as a great deal of research to disprove or support the theory. By the mid- 1970s, the theory was presented in almost every major textbook in the biological and medical sciences. At the same time, there was an explosion in research on the physiology and pharmacology of the dorsal horns and the descending control systems.
Melzack and Casey made a start by proposing that specialized systems are involved in the sensory- discriminative, motivationalaffective, and cognitive evaluative dimensions of pain. So too, the McGill Pain Questionnaire, which taps into subjective experience generated by the brain, was developed and is widely used to measure pain.