title: Spinal Rhythm Generation by Step-Induced Feedback and Transcutaneous Posterior Root Stimulation in Complete Spinal Cord-Injured Individuals.
abstract: BACKGROUND
  The human lumbosacral spinal circuitry can generate rhythmic motor output in response to different types of inputs after motor-complete spinal cord injury.
  
  
  OBJECTIVE
  To explore spinal rhythm generating mechanisms recruited by phasic step-related sensory feedback and tonic posterior root stimulation when provided alone or in combination.
  
  
  METHODS
  We studied stepping in 4 individuals with chronic, clinically complete spinal cord injury using a robotic-driven gait orthosis with body weight support over a treadmill. Electromyographic data were collected from thigh and lower leg muscles during stepping with 2 hip-movement conditions and 2 step frequencies, first without and then with tonic 30-Hz transcutaneous spinal cord stimulation (tSCS) over the lumbar posterior roots.
  
  
  RESULTS
  Robotic-driven stepping alone generated rhythmic activity in a small number of muscles, mostly in hamstrings, coinciding with the stretch applied to the muscle, and in tibialis anterior as stance-phase synchronized clonus. Adding tonic 30-Hz tSCS increased the number of rhythmically responding muscles, augmented thigh muscle activity, and suppressed clonus. tSCS could also produce rhythmic activity without or independent of step-specific peripheral feedback. Changing stepping parameters could change the amount of activity generated but not the multimuscle activation patterns.
  
  
  CONCLUSIONS
  The data suggest that the rhythmic motor patterns generated by the imposed stepping were responses of spinal reflex circuits to the cyclic sensory feedback. Tonic 30-Hz tSCS provided for additional excitation and engaged spinal rhythm-generating networks. The synergistic effects of these rhythm-generating mechanisms suggest that tSCS in combination with treadmill training might augment rehabilitation outcomes after severe spinal cord injury.
authors.affiliation: Medical University of Vienna, Vienna, Austria.
authors.forename: Karen
authors.initials: K
authors.lastname: Minassian
authors.affiliation: Medical University of Vienna, Vienna, Austria ursula.hofstoetter@gmail.com.
authors.forename: Ursula S
authors.initials: US
authors.lastname: Hofstoetter
authors.affiliation: Medical University of Vienna, Vienna, Austria Vienna University of Technology, Vienna, Austria.
authors.forename: Simon M
authors.initials: SM
authors.lastname: Danner
authors.affiliation: Medical University of Vienna, Vienna, Austria.
authors.forename: Winfried
authors.initials: W
authors.lastname: Mayr
authors.affiliation: Crawford Research Institute, Shepherd Center, Atlanta, GA, USA.
authors.forename: Joy A
authors.initials: JA
authors.lastname: Bruce
authors.affiliation: Crawford Research Institute, Shepherd Center, Atlanta, GA, USA.
authors.forename: W Barry
authors.initials: WB
authors.lastname: McKay
authors.affiliation: Emory University School of Medicine, Atlanta, GA, USA Atlanta Veterans Administration Medical Center, Atlanta, GA, USA.
authors.forename: Keith E
authors.initials: KE
authors.lastname: Tansey
mesh_terms: D000328:Adult; D063226:Central Pattern Generators / Q000502:physiology*; D004599:Electric Stimulation Therapy / Q000379:methods*; D004576:Electromyography; D025461:Feedback, Physiological / Q000502:physiology; D005260:Female; D006801:Humans; D007866:Leg / Q000503:physiopathology; D008161:Lumbosacral Region; D008297:Male; D008875:Middle Aged; D018482:Muscle, Skeletal / Q000503:physiopathology; D009989:Orthotic Devices; D010507:Periodicity; D012018:Reflex / Q000502:physiology; D012371:Robotics; D013119:Spinal Cord Injuries / Q000503:physiopathology* / Q000534:rehabilitation*; D013126:Spinal Nerve Roots / Q000503:physiopathology*; D016138:Walking / Q000502:physiology*
keywords: body weight supported treadmill training; driven gait orthosis; human; locomotion; spinal cord injury; spinal cord stimulation