Dorsal Horn Electrophysiology

The dorsal horn is a nexus of many inputs and outputs. Afferents arrive both from the periphery and from many parts of spinal cord, brain stem and cortex. Efferents pass to the ventral horn, other spinal segments, brain stem, thalamus and cerebellum. In writing on the physiology of such a structure or in assessing an experimental paper or especially in designing an experiment, it is necessary to keep in mind that the scientists’ intellectual activities will be based on some conceptual model of the structure. One model sees the dorsal horn as a road intersection with rotary and flyover systems entered by independent units of traffic which pass through and proceed to their proper destinations except in pathological circumstances of collision, breakdown or collapse. A second analogy is that of the railway marshalling yard where units arrive and leave with theii origin and destination labelled but a central control may accelerate or slow them and may dispatch them in mixed trains. My own bias is towards a model which would add to the first two the possibilities of not only controlled collections and dispatch but also of local abstraction, integration, selection and decision. We shall review the available facts on dorsal horn physiology but before doing so it is essential to list the conceptual and technical factors which limit our knowledge.