Limb paresis (muscular weakness due to nerve damage or disease) affects millions of Americans with neurological injuries such as stroke and cerebral palsy. Functional electrical stimulation (FES) is widely used to assist weakened limb movement so that people with neurological injury can better participate in therapy. Though it has never been proven, FES is thought to promote motor skill relearning because it synchronizes a person’s intent to move with limb movement. If this is not the case, there is a risk that participants can â€slack†by reducing effort and allowing FES to passively move the weakened limb, which does not benefit motor skill relearning. This CAREER project addresses this issue by developing techniques to measure and prevent slacking during FES assisted therapy, which could have broad clinical impact as FES is widely used in rehabilitation medicine. The project's educational goal is to use video game production as a platform to develop opportunities for K-12 and college students to actively participate in rehabilitation science and engineering. Rehabilitation video game development will be integrated into ongoing science education programs for primary school, high school, and college students. A “Games for FUNction†program will train college and high school students to create video games for clinician clients and an “E-stim for Educators†lab will train primary school teachers to introduce rehabilitation engineering to their students.
The principal investigator’s long-term mission is to deploy home-based virtual environment therapies that restore lost function for people with brain injury. Towards this mission, this CAREER project will create an effort-dependent FES assistance modality and demonstrate its ability to maintain participant effort during task-based and video game-based stroke rehabilitation. Studies are designed to answer the following questions: How accurately can effort be estimated during FES? Does FES assistance cause participants to slack during task practice? Can an effort-dependent FES control algorithm maintain participant effort during hand therapy video games? The project builds on preliminary results showing that, during time-varying (dropped pulses) FES stimulation, methods can be developed to extract volitional EMG (electromyography) signals, which can be used to estimate participant effort, from EMG signals that also contain the much greater in amplitude signal evoked by the stimulation. The Research Plan is organized under three Aims. The FIRST Aim is to determine how accurately volitional EMG can be estimated during time-varying FES using existing methods. Using data obtained from adults with chronic post-stroke hemiplegia with hand opening impairment, studies are designed to reveal how well existing signal processing techniques can eliminate FES interference and estimate participant effort during volitional finger extension efforts. The SECOND Aim is to characterize the effect of FES assistance on finger extension efforts when practicing tasks with FES-assisted hand opening to determine if FES assistance causes participants to slack during finger extension efforts and to shed light on the unknown relationship between FES and effort. Computational EMG occlusion models will be used to create person-specific calibrations to prevent effort underestimation. The THIRD Aim is to design an FES assistance modality that maintains continuous effort during task practice. The design includes an effort-dependent control framework that translates the degree of non-paretic hand opening directly into the stimulation pulse width applied to the paretic hand by way of a recruitment curve. This contralaterally-controlled FES modality (CCFES) will be used to investigate whether slacking can be prevented during FES assisted finger extension when FES assistance is applied in direct proportion to volitional effort and hand opening error, with the expectation that effort dependent FES will increase participant effort compared to effort independent FES. Though this project focuses on motor function recovery following stroke, FES is widely used in rehabilitation medicine, thus the proposed effort-dependent FES modality is also expected to lead to more effective delivery therapy for people with cerebral palsy, spinal cord injury, traumatic brain injury, sports injury, and pain.
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.
