Abstract
BackgroundTranscutaneous neuromuscular electrical stimulation is routinely used in physical rehabilitation and more recently in brain-computer interface applications for restoring movement in paralyzed limbs. Due to variable muscle responses to repeated or sustained stimulation, grasp force levels can change significantly over time. Here we develop and assess closed-loop methods to regulate individual finger forces to facilitate functional movement. We combined this approach with custom textile-based electrodes to form a light-weight, wearable device and evaluated in paralyzed study participants.MethodsA textile-based electrode sleeve was developed by the study team and Myant, Corp. (Toronto, ON, Canada) and evaluated in a study involving three able-body participants and two participants with quadriplegia. A feedforward-feedback control structure was designed and implemented to accurately maintain finger force levels in a quadriplegic study participant.ResultsIndividual finger flexion and extension movements, along with functional grasping, were evoked during neuromuscular electrical stimulation. Closed-loop control methods allowed accurate steady state performance (< 15% error) with a settling time of 0.67 s (SD = 0.42 s) for individual finger contact force in a participant with quadriplegia.ConclusionsTextile-based electrodes were identified to be a feasible alternative to conventional electrodes and facilitated individual finger movement and functional grasping. Furthermore, closed-loop methods demonstrated accurate control of individual finger flexion force. This approach may be a viable solution for enabling grasp force regulation in quadriplegia.Trial registrationNCT, NCT03385005. Registered Dec. 28, 2017
Highlights
Paralysis affects nearly 5.4 million people in the US alone with the two leading causes being stroke and spinal cord injury (Armour et al 2016)
A survey of 681 persons with spinal cord injury revealed the top priority for individuals living with quadriplegia was regaining hand function (Anderson 2004)
Textile-based electrodes were identified to be a feasible alternative to conventional electrodes and facilitated individual finger movement and functional grasping
Summary
Approval for this study was obtained from the Northwell Health Institutional Review Board (Great Neck, New York) and the study met institutional requirements for the conduct of human subject work. To allow regulated grasp force in participants with quadriplegia, a feedforward-feedback control architecture was implemented to provide closed-loop neuromuscular electrical stimulation as shown in Fig. 2 and described in Laplacian form as follows iðtÞ 1⁄4 f ð FdesiredÞ þ. For this particular test, it was observed that the middle finger was not possible in the able-body partici- controller automatically increased the current in response pants, but was in both paralyzed participants. We plan to integrate the methods and technology presented in this paper with a brain-computer interface which will decode (decipher) desired grasping forces These decoded intentions would be translated into setpoint commands that are fed into the controller to facilitate accurately regulated hand movements
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
