The feasibility of a brain-computer interface functional electrical stimulation system for the restoration of overground walking after paraplegia

Abstract

BackgroundDirect brain control of overground walking in those with paraplegia due to spinal cord injury (SCI) has not been achieved. Invasive brain-computer interfaces (BCIs) may provide a permanent solution to this problem by directly linking the brain to lower extremity prostheses. To justify the pursuit of such invasive systems, the feasibility of BCI controlled overground walking should first be established in a noninvasive manner. To accomplish this goal, we developed an electroencephalogram (EEG)-based BCI to control a functional electrical stimulation (FES) system for overground walking and assessed its performance in an individual with paraplegia due to SCI.MethodsAn individual with SCI (T6 AIS B) was recruited for the study and was trained to operate an EEG-based BCI system using an attempted walking/idling control strategy. He also underwent muscle reconditioning to facilitate standing and overground walking with a commercial FES system. Subsequently, the BCI and FES systems were integrated and the participant engaged in several real-time walking tests using the BCI-FES system. This was done in both a suspended, off-the-ground condition, and an overground walking condition. BCI states, gyroscope, laser distance meter, and video recording data were used to assess the BCI performance.ResultsDuring the course of 19 weeks, the participant performed 30 real-time, BCI-FES controlled overground walking tests, and demonstrated the ability to purposefully operate the BCI-FES system by following verbal cues. Based on the comparison between the ground truth and decoded BCI states, he achieved information transfer rates >3 bit/s and correlations >0.9. No adverse events directly related to the study were observed.ConclusionThis proof-of-concept study demonstrates for the first time that restoring brain-controlled overground walking after paraplegia due to SCI is feasible. Further studies are warranted to establish the generalizability of these results in a population of individuals with paraplegia due to SCI. If this noninvasive system is successfully tested in population studies, the pursuit of permanent, invasive BCI walking prostheses may be justified. In addition, a simplified version of the current system may be explored as a noninvasive neurorehabilitative therapy in those with incomplete motor SCI.Electronic supplementary materialThe online version of this article (doi:10.1186/s12984-015-0068-7) contains supplementary material, which is available to authorized users.

Enhancing Nervous System Recovery through Neurobiologics, Neural Interface Training, and Neurorehabilitation

“…Means of extracting nervous system signals range from invasive [intracortical microelectrodes (APs, or spikes) and larger scale sub- or epidural electrodes (electrocorticography, ECoG)] to non-invasive [electroencephalography (EEG) or electromyography (EMG)]. Targeted outputs have included cursors on a screen (Wolpaw and McFarland, 1994; Kennedy and Bakay, 1998; Leuthardt et al, 2004; McFarland et al, 2010), virtual typing (Jarosiewicz et al, 2015), robotic or prosthetic arms (Collinger et al, 2013; Hotson et al, 2016), wheelchairs (Rajangam et al, 2016), exoskeletons (Donati et al, 2016), the spinal cord (Zimmermann and Jackson, 2014; Capogrosso et al, 2016), and a patient's own extremities (Ethier et al, 2012; Memberg et al, 2014; King et al, 2015; Bouton et al, 2016; Vidaurre et al, 2016). …”

“…Birbaumer et al's device was an EEG-based system designed to translate purposeful slow cortical potentials (SCPs) into a binary selection of letters or words on a screen. Since then, EEG-based systems have advanced to move cursors on a screen in up to 3 dimensions (McFarland et al, 2010), open and close a hand orthosis (Ramos-Murguialday et al, 2012), provide limited FES-control of upper and lower extremities (King et al, 2015; Vidaurre et al, 2016), and ambulate a lower extremity exoskeleton (Donati et al, 2016); however, their potential is hindered due to inherently poor reliability, latency, signal variability, and generally non-intuitive nature (reviewed in Jackson and Zimmermann, 2012). …”

Supraspinal Control Predicts Locomotor Function and Forecasts Responsiveness to Training after Spinal Cord Injury

“…The exploration of brain-machine interfaces to drive functional electrical stimulation devices for walking function in persons with paraplegia is in the early stages. 67,68 …”

Interfacing with the nervous system: a review of current bioelectric technologies

“…Additionally, BCIs have exhibited great potential in aiding paraplegics with recovery [120,162]. Nenadic et al successfully used an EEG exoskeleton coupled with an augmented reality training platform to provide superior physical rehabilitation to a paraplegic spinal cord injury patient that enabled him to regain some gait function [61,157]. Furthermore, Nenadic and colleagues have miniaturized their BCI system as well as decreased associated costs of production [78,79].…”