PROJECT SUMMARY/ABSTRACT The overall goal of the proposed research is to develop new control systems to restore seated function and enhance the postural stability of the trunk for individuals paralyzed by spinal cord injury (SCI). Systems that provide persons with the ability to sit erect, alter their seated posture, and maintain balance by automatically adjusting stimulation to the paralyzed muscles will be designed, optimized in simulation, and evaluated experimentally in nine volunteers with SCI. The project will result in a unique, comprehensive trunk balance control system that extends the capabilities and improves the safety of all currently available trunk neuroprostheses. The first aim of the study is to design, deploy and test an advanced neuroprosthesis to stabilize the trunks of individuals with SCI and maintain upright sitting. A disturbance-rejection controller using information from body-mounted sensors will be optimized to maintain erect posture for disturbances in all directions around the seated user. In that way restrictive chest straps or custom seating adaptations are completely eliminated and the likelihood of falling from the wheelchair reduced to a minimum. The objective of the second aim is to tune, characterize and asses the performance of a system that will allow individuals with paraplegia to safely deploy their trunks and maintain the stability of non-erect postures, thus expanding their reachable workspace. Performance of this posture-changing controller will be determined in a series of experiments that deploy the trunk to different positions away from the backrest and testing the ability to remain steady at the desired postures. In the third aim, we will characterize the consistency, accuracy and fidelity of the implanted sensors in the new networked neuroprosthesis (NNPS). This will be done by collecting data in a series of experiments and developing an algorithm that will fuse the signals from the various sensors to produce a robust feedback signal suitable for control studies. Thereafter we will implement the disturbance-rejection and posture-changing control systems without external components with this new technology. This application addresses the main mission of the National Institutes of Health (NIH) to help lead the way toward important medical discoveries that improve people's health and save lives. In particular it coincides with the missions of NINDS to reduce the burden of neurological disease, NIBIB to improve health by leading the development and accelerating the application of biomedical technologies, and NCMRR to foster development of scientific knowledge needed to enhance the health, productivity, independence, and quality-of-life of people with disabilities.