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Neuronal mechanisms underlying retraining of walking after incomplete spinal cord injury Open Access


Other title
Spinal Cord Injury
Treadmill Training
Type of item
Degree grantor
University of Alberta
Author or creator
Zewdie, Ephrem Takele
Supervisor and department
Gorassin, Monica (Biomedical Engineering)
Examining committee member and department
Willman, Alan (Biomedical Engineering)
Chan, Ming (Physical Medicine & Rehabilitation)
Gorassini, Monica (Biomedical Engineering)
Yang, Jaynie (Rehabilitation Medicine)
Jones, Kelvin (Physical Education)
Calancie, Blair (Neurosurgery)
Collins, Dave (Physical Education)
Department of Biomedical Engineering

Date accepted
Graduation date
Doctor of Philosophy
Degree level
Inhibitory feedback from sensory pathways is important for controlling movement. In this thesis we characterize a long-latency inhibitory spinal pathway to ankle flexors that is activated by low-threshold, homonymous afferents. In non-injured participants, this pathway was activated by both descending and sensory inputs. A spinal origin of this inhibition was confirmed by reproducing its effect on evoked responses from direct activation of corticospinal pathways. We propose that inhibitory feedback from spinal networks activated by low-threshold homonymous afferents helps regulate the activation of flexor motoneurons by the corticospinal pathways. In the second part of the thesis we compared changes in corticospinal and spinal pathways in response to endurance and skill locomotor training in participants with incomplete, chronic spinal cord injury. Both forms of training increased the maximum evoked potential (MEPmax) elicited by transcranial magnetic stimulation over the motor cortex, but only in tibialis anterior muscles that had smaller MEPmax values before training, no matter when the specific type of training was performed. Endurance and precision training also increased the excitability of inhibitory spinal networks, as demonstrated by increases in the long-latency, homonymous spinal inhibition described above and by increases in the inhibitory component of the cutaneomuscular reflex. The increase in the descending activation of the spinal cord and the increase in excitability of inhibitory spinal networks may mediate the improved volitional control of walking and reduction of involuntary muscle spasticity, respectively, that are observed in response to intensive motor training.
Permission is hereby granted to the University of Alberta Libraries to reproduce single copies of this thesis and to lend or sell such copies for private, scholarly or scientific research purposes only. The author reserves all other publication and other rights in association with the copyright in the thesis and, except as herein before provided, neither the thesis nor any substantial portion thereof may be printed or otherwise reproduced in any material form whatsoever without the author's prior written permission.
Citation for previous publication
Zewdie ET, Roy FD, Okuma Y, Yang JF, and Gorassini MA. J Neurophysiol 111: 2544-2553, 2014.Zewdie ET, Roy FD, Yang JF, and Gorassini MA. Progress in Brain Research, 218:127-155 2015

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