Introduction

Abstract

Prior to 1967, the discharge properties of peripheral receptors, both vertebrate and invertebrate, had been examined and described in great detail. But one great weakness of all of this work was that the data had been obtained in immobile, usually anaesthetised animals. While this was not seen as a serious impediment to the understanding of the role of “passive” receptors, such as those in mammalian skin, it was clearly unsatisfactory for receptors whose sensitivities were under the control of efferents from the CNS (e.g.muscle spindles).Theories of motor control had tended to be built partly on what was known of segmental reflex organisation, and partly on the presumed behaviour of proprioceptors under natural conditions (e.g. Lundberg, 1969).Indeed to some extent the theories stood or fell, depending on the accuracy of these guesses regarding normal afferent activity.