title: The feasibility of a brain-computer interface functional electrical stimulation system for the restoration of overground walking after paraplegia.
abstract: BACKGROUND
  Direct 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.
  
  
  METHODS
  An 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.
  
  
  RESULTS
  During 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.
  
  
  CONCLUSIONS
  This 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.
authors.affiliation: Department of Neurology, University of California, Los Angeles, CA, USA.
authors.forename: Christine E
authors.initials: CE
authors.lastname: King
authors.affiliation: Department of Biomedical Engineering, University of California, Irvine, CA, USA.
authors.forename: Po T
authors.initials: PT
authors.lastname: Wang
authors.affiliation: Department of Biomedical Engineering, University of California, Irvine, CA, USA.
authors.forename: Colin M
authors.initials: CM
authors.lastname: McCrimmon
authors.affiliation: Department of Physical TherapyUniversity of California, University of California, Orange, CA, USA.
authors.forename: Cathy C Y
authors.initials: CC
authors.lastname: Chou
authors.affiliation: Department of NeurologyUniversity of California, University of California, Irvine, CA, USA. and@uci.edu.
authors.forename: An H
authors.initials: AH
authors.lastname: Do
authors.affiliation: Department of Biomedical Engineering, University of California, Irvine, CA, USA. znenadic@uci.edu.|Department of Electrical Engineering and Computer ScienceUniversity of California, University of California, Irvine, CA, USA. znenadic@uci.edu.
authors.forename: Zoran
authors.initials: Z
authors.lastname: Nenadic
mesh_terms: D001921:Brain / Q000503:physiopathology; D062207:Brain-Computer Interfaces; D004599:Electric Stimulation Therapy / Q000295:instrumentation* / Q000379:methods*; D004569:Electroencephalography / Q000379:methods; D005240:Feasibility Studies; D006801:Humans; D008297:Male; D010264:Paraplegia / Q000209:etiology / Q000534:rehabilitation*; D019736:Prostheses and Implants; D013119:Spinal Cord Injuries / Q000150:complications / Q000534:rehabilitation*; D016138:Walking / Q000502:physiology