Date on Master's Thesis/Doctoral Dissertation


Document Type

Doctoral Dissertation

Degree Name

Ph. D.


Anatomical Sciences and Neurobiology

Degree Program

Anatomical Sciences and Neurobiology, PhD

Committee Chair

Harkema, Susan

Committee Co-Chair (if applicable)

Behrman, Andrea

Committee Member

Behrman, Andrea

Committee Member

Howland, Dena

Committee Member

Hubscher, Charles

Committee Member

Magnuson, David

Committee Member

Petruska, Jeffrey

Author's Keywords

propriospional; spinal cord injury; assessment; neurophysiology; electrophysiology


Spinal Cord Injury (SCI) in humans is a heterogeneous diagnosis, resulting in variable paralysis and paresthesia based on the mechanism, rostro-caudal location, and severity of injury. Both neurophysiological and anatomical studies have suggested that subclinical residual supraspinal-spinal connectivity exists in a subset of individuals deemed to have motor and sensory complete injuries. Recent reports of volitional movement in chronic, motor complete individuals during epidural spinal stimulation have provided compelling evidence that these residual projections may be capable of mediating volitional movement when the functional state of spinal circuitry is electrically modulated. It was the goal of this project to identify subclinical and pathway-specific subliminal influences on spinal excitability after human SCI, and further to determine their relationship to volitional muscle activation after injury. Results demonstrated that volitional muscle activation can be identified and quantified in an objective manner via neurophysiological assessment, with greater resolution than current clinical measures. Electrophysiological studies probing the nervous system in subjects with chronic SCI, evidence was obtained of residual descending influence even in subjects classified as having motor and sensory complete injuries. Comparisons between volitional muscle activation and detection of descending modulation of multisegmental muscle responses in incomplete SCI participants revealed that interlimb modulation of a given motor pool was a strong predictor of predicted volitional movement, but was also observed in muscles without volitional activation, suggesting the pathways mediating the observed modulation may be necessary but not sufficient for volitional muscle activation after SCI.