Tapping into spinal circuits to restore motor function

Motivated by the challenge of improving neuroprosthetic devices, the author s review current knowledge relating to harnessing the potential of spinal n eural circuits, such as reflexes and pattern generators. If such spinal int erneuronal circuits could be activated, they could provide the coordinated control of many muscles that is so complex to implement with a device that aims to address each participating muscle individually. The authors' goal i s to identify candidate spinal circuits and areas of research that might op en opportunities to effect control of human limbs through electrical activa tion of such circuits. David McCrea's discussion of the ways in which hindl imb reflexes in the cat modify motor activity may help in developing optima l strategies for functional neuromuscular stimulation (FNS), by using knowl edge of how reflex actions can adapt to different conditions. Michael O'Don ovan's discussion of the development of rhythmogenic networks in the chick embryo may provide clues to methods of generating rhythmic activity in the adult spinal cord. Serge Rossignol examines the spinal pattern generator fb r locomotion in cats, its trigger mechanisms, modulation and adaptation, an d suggests how this knowledge can help guide therapeutic approaches in huma ns. Hugues Barbeau applies the work of Rossignol and others to locomotor tr aining in human subjects who have suffered spinal cord injury (SCI) with in complete motor function loss (IMFL). Michel Lemay and Warren Grill discuss some of the technical challenges that must be addressed by engineers to imp lement a neuroprosthesis using electrical stimulation of the spinal cord, p articularly the control issues that would have to be resolved. (C) 1999 Els evier Science B.V. All rights reserved.