PERSPECTIVES ON THE ROLE OF AFFERENT SIGNALS IN CONTROL OF MOTOR NEUROPROSTHESES

K. O. Johnson reviews the architecture and low level neural mechanisms by which the external environment is transduced and encoded into the neural system, summarizing work that correlates neurophysiological and psychophysical testing with isolation of sensory components. The slow ly adapting Type I afferent system is responsible for form and texture perception; the rapidly adapting afferent system is responsible for m otion perception; and the Pacinian cor corpuscle system is responsible for vibratory sensation. RR Rise reviews the current level of underst anding of the major factors to be considered in the design of a functi onal neuromuscular stimulation (FNS) grasp controller that uses cutane ous sensory feedback to detect slip. The elegant natural control schem e that matches the ratio of grip and lift forces to frictional conditi ons provides a model for implementing a slip-based control algorithm. D. Popovic discusses the possible use of recordings from more proximal peripheral nerves to determine needed information for synthesis of lo comotion. The discussion is illustrated with an animal model where rul e-based, closed-loop control is used for the ankle joint during treadm ill locomotion. Neural signals from the tibial and superficial peronea l nerves were employed to substitute for missing afferent input from c utaneous and proprioceptive sensors. The feasibility of more invasive intraneural electrodes for distinguishing sensory from motor informati on in mixed nerves is considered. M. Koris raises surgical and functio nal issues relevant to developing clinical FNS systems. C. Van Doren s uggests alternative neurophgsiological and engineering approaches.