Development of FES+BMI Neuroprosthesis for At-Home Use for Persons with Chronic Tetraplegia

About This Grant

The current proposal aims to develop a for at-home-use neuroprosthesis for restoring brain-controlled functional hand grasping to Veterans and others living with chronic tetraplegia due to spinal cord injury (SCI). This system leverages and advances two established technologies – functional-electrical stimulation (FES) systems for re-animating paralyzed limbs, and intracortical brain-machine interfaces (BMIs) for recording and discerning motor intent. Our previous work successfully demonstrated a Veteran with chronic tetraplegia using a simple proof-of-concept FES+BMI system, composed of temporarily implanted intramuscular wires for movement restoration and an implanted brain electrode for deciphering movement intent, to regain brain- controlled movements of basic arm and hand movements to perform limited but meaningful activities of daily living (ADLs), such as self-feeding. We have more recently demonstrated a more advanced system that uses composite flat-interface-nerve-electrode (C-FINE) cuffs to provide for more selective activation of peripheral musclesfor FES, and a multi-network BMI system for recording from multiple nodes in the cortical grasp network (primary motor, premotor, and parietal cortices) to provide for more intuitive brain control of dexterous hand function. These demonstrations have been limited in that research participants could only use them in the laboratory. The proposal, leveraging existing and to be enrolled study participants of the ReHAB (Re-connecting the Hand and Arm to the Brain) clinical trial (NCT03898804) who already have implanted C-FINE and BMI electrodes, will result in developing a C-FINE based FES system, able to be commanded by multiple modalities (voice, EMG, and a portable BMI system), that will be demonstrated for use in a home environment. A major consideration for development of at-home FES+BMI use is that factors unforeseen in the laboratory may become evident that result in variable system performance. Specifically, it is well known that the behaviors of individual neurons exhibit nonstationarities that could negative impact decoding the movement command. Additionally changes in a user's internal state (e.g. attention, stress, fatigue) has been shown to affect non-invasively recorded brain signals. As a result, neural decoders are recalibrated on a daily basis (and sometime more often) in regular laboratory use. It is unclear the time of these changes, how these changes affect neural decoding, and how to best mitigate these potentially deleterious changes during continual FES+BMI use. The present proposal aims to understand how neural variability (Aim 1), and changes in a user's internal state (measurable through correlated physiological biomarkers) (Aim 2) can be accounted for in development of an FES+BMI system for at-home use. Examples of these physiological biomarkers include: 1) heart rate variability (decreased by stress, increased by attention, decreased by fatigue), 2) blood pressure (increased by stress and attention), 3) pupil size (dilated under stress or intense attention), 4) blink rate (decreased with intense attention), and 5) saccade velocity (increased with increased attention and error state). Finally, the proposal will compare FES movement restoration through use of a portable BMI with a more standard EMG command option (Aim 3). Participants will use each during the at-home portion of the study, and will report out measures of satisfaction, perceived ease of use, and personal independence. The study will also use clinically validated tests of upper extremity function, during regular in-laboratory assessments, to compare performance of these command options for movement restoration through the FES arm and hand neuroprosthesis. The success of this proposal will result in the first FES+BMI system suitable for at-home use. The time is appropriate for this work, and the need is great, and the investigative team is the best in the world to pursue the aims of the proposal.