Article

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.
CI - (c) The Author(s) 2015.

Langue : ANGLAIS