A systems-oriented evaluation of the role of joint receptors and other afferents in position and motion sense.

Position and motion sense have been considered to be primarily mediated by receptors in the joints until recently. New evidence indicates that muscle receptors and cutaneous receptors may also be critically involved. Some investigators even rule out a role for joint receptors in position and motion sense. In addition to the changing viewpoint concerning receptors, there has been a change in the view concerning the pathways of central projection of joint afferent information. Until recently, the last 10 years, the dorsal column-lemniscal system was assigned the major if not exclusive role in mediating proprioceptive information. This idea has now been revised as well. This review will cover historical and recent research results, with an emphasis on recent results. The newer findings especially the reintroduction of a sensory role for muscle spindles and a diminished role for joint receptors, are closely examined. The problem is approached from a systems analysis conceptualization. A number of quantitative results and aspects of the problem that have not been considered in the studies that have been published are included. The recent trend has been to strongly advance the case for muscle receptors, while retreating from joint receptors as mediators of kinesthetic sensation. This review focuses upon the issue of how joint receptors or other afferent information might be handled by the nervous system acting as a processor of dynamic signals. The modification imposed upon the signals as they ascend the neuraxis and the types of information that might be used by higher centers (velocity, position, acceleration, torque, force) are emphasized. The adequacy of the candidate receptors for this use is examined. The idea of position and motion sense and the way in which the sensations are defined and tested is covered.