Cutaneous and proprioceptive reflex effects on intact muscle efferents and afferents

Abstract

Some groups of afferent and efferent fibres of a muscle nerve appear to function as part of a servoregulatory loop controlling muscle contractions (Matthews, 1972). The knowledge of the internal functioning of such loops comes from the single unit analysis of the activity, generally recorded at the level of spinal roots or of peripheral nerve, of neurons forming a part of these loops. Action potentials are recorded from nerve axons with microelectrodes or conventional hook electrodes. Using the latter type of recording, it is necessary to split spinal rootlets or to tease a nerve in order to prepare filaments fine enough so that the discharge of a single element functionally identified is prominent in the record and can be distinguished from all other activity on the basis of amplitude and shape (Hunt, 1951). Such a method leads entirely or partially to an impairment of the functioning of the peripheral control loop. In addition, experiments are often performed on curarised animals or after extensive denervation of limbs.