From the gate to the neuromatrix

The gate control theory's most important contribution to understanding pain was its emphasis on central neural mechanisms. The theory forced the medic al and biological sciences to accept the brain as an active system that fil ters, selects and modulates inputs. The dorsal horns, too, were not merely passive transmission stations but sites at which dynamic activities (inhibi tion, excitation and modulation) occurred. The great challenge ahead of us is to understand brain function. I have therefore proposed that the brain p ossesses a neural network - the body-self neuromatrix - which integrates mu ltiple inputs to produce the output pattern that evokes pain. The body-self neuromatrix comprises a widely distributed neural network that includes pa rallel somatosensory, limbic and thalamocortical components that subserve t he sensory-discriminative, affective-motivational and evaluative-cognitive dimensions of pain experience. The synaptic architecture of the neuromatrix is determined by genetic and sensory influences. The 'neurosignature' outp ut of the neuromatrix - patterns of nerve impulses of varying temporal and spatial dimensions - is produced by neural programs genetically build into the neuromatrix and determines the particular qualities and other propertie s of the pain experience and behavior. Multiple inputs that act on the neur omatrix programs and contribute to the output neurosignature include, (1) s ensory inputs (cutaneous, visceral and other somatic receptors); (2) visual and other sensory inputs that influence the cognitive interpretation of th e situation; (3) phasic and tonic cognitive and emotional inputs from other areas of the brain; (4) intrinsic neural inhibitory modulation inherent in all brain function; (5) the activity of the body's stress-regulation syste ms, including cytokines as well as the endocrine, autonomic, immune and opi oid systems. We have traveled a long way from the psychophysical concept th at seeks a simple one-to-one relationship between injury and pain. We now h ave a theoretical framework in which a genetically determined template for the body-self is modulated by the powerful stress system and the cognitive functions of the brain, in addition to the traditional sensory inputs. (C) 1999 International Association for the Study of Pain. Published by Elsevier Science B.V.