Centrifugal mechanisms of sensory control

Abstract

It is often assumed that the central nervous system (C.N.S.) is organized on the basis of more or less complex reflex arcs by which the receptors control the activity of the effector organs. The fundamental notion that sensory input controls motor output must not, however, obscure the fact that there also exist output-input relations. Recent studies have shown that sensory structures at various levels of the nervous system are exposed to centrifugal control and the general thesis that the C.N.S. can control its own input has since developed into a promising field of research. Output-input relations are evidently established in various ways, in the periphery as well as within the C.N.S., and there is a growing conviction that such relations are indispensable for the operation of a great number of neural mechanisms at various levels of the neuraxis. The present review summarizes some of the data which have led up to these concepts and, even though it might seem premature, attempts are made to emphasize some functional similarities in the various neural mechanisms concerned.