Loss of walking function and leg sensation are devastating consequences of spinal cord injury (SCI). These deficits have a profoundly negative impact on independence and quality of life of those affected. Moreover, wheelchair reliance after SCI increases the risk of medical complications. The healthcare costs associated with SCI are ~$50 billion/year, presenting a significant public health concern. Currently, there are no biomedical solutions capable of restoring walking and leg sensation after SCI. Clinically practical and socially acceptable solutions to these important problems are desperately needed. Employing a cyber-physical system (CPS) to bypass the damaged spinal cord may be a novel way to restore walking and leg sensation to those with leg paralysis due to SCI. The proposed multi-disciplinary effort will inspire students from traditionally underprivileged and underrepresented groups to pursue college education in STEM fields by demonstrating how engineering and science can make a difference in the well-being of those with disabilities. In addition, it will engage individuals with disabilities, their family members, friends, and caregivers, in educational opportunities in order to increase their scientific and technical literacy. The outreach to these communities will be accomplished by leveraging diverse ethnic makeup of Orange and Los Angeles Counties, geographic proximity of the three study sites, which makes outreach activities amenable to integration, and the high societal significance and visibility of the project.
Impairment or complete loss of gait function and lower extremity sensation are common after spinal cord injury (SCI). A new cyberphysical system, CPS, can be realized as a permanently implantable bi-directional (BD) brain-computer interface (BCI), which translates walking intentions from brain signals into commands for a leg prosthesis, and converts prosthesis sensor signals into electrical stimulation of the brain for artificial leg sensation. This closed-loop operation would come close to restoring able-body-like walking and leg sensation after SCI. Before such an implantable CPS is deployed in humans, its feasibility and safety must be established. The main objective of this Frontier project is to design, develop, and test a wearable analogue of a fully implantable electrocorticogram (ECoG)-based BD-BCI for walking and leg sensation. The BD-BCI CPS will be designed as an ultra-low power modular system with revolutionary techniques for interference mitigation to enable simultaneous electrical stimulation and recording. The first module will consist of a custom brain signal acquisition system that exploits ECoG signal attributes to significantly reduce power consumption. The second module will consist of a low-power processing unit, brain stimulator, and wireless communication transceiver. This module will internally execute optimized BCI algorithms and wirelessly transmit commands to a robotic gait exoskeleton for walking. Comprehensive benchtop and bedside tests will be conducted to assess proper system function. Finally, subjects with paraplegia due to SCI will be recruited to undergo a 30-day ECoG implantation to test the BD-BCI's ability to restore brain-controlled walking and leg sensation. The goals of transition to practice (TTP) are to: (1) develop a fully implantable version of the BD-BCI, (2) perform a series of industrial-standard medical device benchtop tests, and (3) test the implants safety.
