CAREER: Neuroprostheses for Functional Reaching by Users with High Tetraplegia

Cleveland State University, Cleveland OH

Investigators

Abstract

Functional-electrical-stimulation (FES) neuroprostheses are devices capable of restoring hand and arm function to individuals experiencing paralysis resulting from spinal cord injury. However, individuals with whole-arm paralysis typically do not receive much benefit from these types of neuroprotheses because the devices are not yet capable of replicating the complexity and range of motion of human arm movements. Additionally, the devices must be regularly "tuned" by experts to meet the wearer's changing needs. Thus, there is a significant need to develop FES neuroprostheses capabilities for use by people with whole-arm paralysis. This study will create ways to coordinate electrical stimulation of the wearer's shoulder and arm muscles with control of reaching movements. It will also create a way for a non-expert to update control to respond to changes in the user's muscles and desired movements. The study will test the hypothesis that models of muscle response to electrical stimulation, specific to each wearer, can be learned by the neuroprosthesis and used to coordinate muscles to perform reaching movements. A secondary hypothesis that will be tested is that a caregiver can apply physical cues at the patient's forearm, "teaching" the neuroprothesis to refine and expand reaching movements. Research and education are integrated in the project through the creation of an empathy training program for aspiring rehabilitation engineers. Engineering students, alongside medical, therapy, social work, and nursing students, will visit the homes of people with disabilities. Through these home visits and classroom instruction, engineers will develop empathetic skills like affective sharing, self- and other-awareness, perspective taking, and emotional regulation. The PI's long-term career goal is to create easily usable and widely available neuroprostheses to restore arm function to people with high tetraplegia. Toward this goal, the research objectives for this project are to: (1) create an architecture to control whole-arm reaching motions with FES that retains the arm's natural kinematic and force-producing flexibility and (2) empower a non-expert to easily improve and expand the capabilities of an FES neuroprosthesis. Experiments will address the question of how to control a multi-joint system where the direction of muscle action is state dependent. The PI will gather force and motion data during stimulation of muscles and apply the data to plan achievable hand motions, predict shoulder and elbow torques required to move the arm, and choose muscle stimulation commands to produce those torques. Additionally, the PI will investigate approaches to train the FES controller based on intuitive human intervention. Caregivers will apply manual corrections to the patient's forearm to adjust the system's control policy and refine inaccurate movements. The outcome of the study will be a flexible, subject-specific FES planning and control strategy to coordinate muscles across multiple joints that non-experts can easily modulate, which is a significant step toward neuroprostheses that achieve functional tasks like grooming and feeding oneself. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.