Date of Award
Spring 5-2024
Degree Name
Master of Science (MS)
Degree Type
Thesis
Abstract
Spinal cord injury (SCI) is a life-changing event that causes lasting motor impairments. Transcutaneous spinal cord stimulation (tSCS), a non-invasive form of neuromodulation in which electrodes are placed on the skin and used to stimulate the spinal circuits via an electrical current, has demonstrated positive effects on motor function recovery in individuals who have had SCIs. However, the precise mechanism of how tSCS interacts with voluntary descending drive remains poorly understood. This study aims to investigate the role of voluntary descending control in influencing reflex responses triggered by tSCS.
Electromyography (EMG) recordings were performed in ten unimpaired individuals while they engaged in torque control tasks with varying amplitudes of tSCS. Muscle responses recorded during isometric dorsiflexion and plantarflexion tasks using varying levels of torque were analyzed. The peak-to-peak muscle responses at the motor threshold amplitude at rest were examined to compare the muscle responses during different levels of voluntary pre-activation.
Results demonstrate that dorsiflexion of the ankle inhibits ipsilateral extensors - the medial gastrocnemius and soleus - while ankle plantarflexion inhibits the ipsilateral medial gastrocnemius and contralateral rectus femoris and the contralateral soleus. Additionally, findings indicate smaller muscle responses during dorsiflexion compared to plantarflexion. Limitations of this study include the relatively small sample size which yielded non-significant p-values after correction for multiple comparisons. Future directions involve examining the relationship between task intensity and muscle inhibition, the impact of ankle torque direction at tSCS delivery on the extent of muscle inhibition, and the amplitude of maximum muscle responses across different task intensities.
Overall, this study provides insights into the interaction between volitional movements and tSCS, contributing to the customization of rehabilitative strategies tailored to individual needs.
Language
English (en)
Chair
Ismael Seáñez, Ph.D
Committee Members
Ismael Seáñez, Ph.D Dennis L. Barbour, MD, Ph.D Daniel W. Moran, Ph.D