The objective of this research is to explore the safety and effectiveness of microstimulation of the spinal cord. If successful, such a technique could be part of a prosthesis to restore genito- urinary, bowel, and other motor functions to victims of spinal cord injury. Information from spinal cord microstimulation studies is especially needed by designers of neural prostheses for paraplegic individuals who have sustained injuries to their spinal cords above the lumbosacral region. In particular, evidence from current studies indicate that is possible to selectively excite neurons innervating the bladder detrusor muscle while simultaneously stimulating interneurons which have inhibitory synaptic connections with neurons innervating the external urethral sphincter. Likewise, discrete control of penile erection, ejaculation, bowel evacuation, and control of the somatic musculature of the limbs may be possible by selective spinal cord microstimulation below the level of spinal cord injury. Current contract research has provided information about the locations of afferent and efferent neurons as well as interneurons controlling urinary function in the cat spinal cord using both normal and spinalized animals. Limited mapping has also been performed on the neurons that control erection in the male cat. The current contract research is also studying the possibility of controlling, by spinal cord microstimulation, the somatic musculature of individuals paralyzed as the result of spinal cord injuries. As an initial feasibility study, the locations of the neurons controlling the flexors and extensors of the knee are being mapped. Microstimulation of these mapped areas has demonstrated activation of both knee flexors and extensors. The present research will provide more detailed maps, and will determine quantitatively, the degree of motor control of paralyzed muscles that can be produced by microstimulation of the lumbosacral spinal cord.
