The purpose of this study is to examine how delivery of subthreshold electrical stimulation of the spinal cord alters the excitability of neural pathways and consequently movement performance in healthy and spinal cord injured individuals. Specifically, we assess how stimulation parameters such as electrode configurations and stimulation frequency affect spinal excitability, corticospinal excitability, intracortical excitability, motor unit properties and force production. This study is not an intervention study, but a mechanistic study trying to shed light on how this novel neuromodulatory technique acutely affects the central nervous system.
Study Type
OBSERVATIONAL
Surface electrodes are placed over the cervical spinal cord. Constant current is delivery through these electrodes. Stimulation frequency and electrode configuration are manipulated, and outcome measures are recorded.
University of Louisville, Kentucky Spinal Cord Injury Research Centre
Louisville, Kentucky, United States
Motor evoked potentials recruitment curves
Motor evoked potentials are obtained to assess changes in the input/output properties of the corticospinal tract during delivery of tcES. Comparisons are made between no stimulation and stimulation at different frequencies, or with different electrode configurations. This assessment is repeated for different muscles on different days.
Time frame: Assessment up to 4 hours each visit; up to 4 visits per individual (32 hours)
Intracortical excitability
Paired stimulation of the motor cortex is used to assess short interval intracortical inhibition intracortical facilitation during delivery of tcES. Comparisons are made between no stimulation and stimulation at different frequencies, or with different electrode configurations. This assessment is repeated for different muscles on different days.
Time frame: Assessment up to 4 hours each visit; up to 4 visits per individual (32 hours)
Intramuscular coherence
High-density surface electromyography is used to decompose motor units and assess changes in intramuscular coherence during performance of a motor task in the presence of tcES. Comparisons are made between no stimulation and stimulation at different frequencies, or with different electrode configurations. This assessment is repeated for different muscles on different days.
Time frame: Assessment up to 4 hours each visit; up to 4 visits per individual (32 hours)
Force control
Force control during a variety of motor tasks is assessed during delivery of tcES. Comparisons are made between no stimulation and stimulation at different frequencies, or with different electrode configurations within each session. This assessment is repeated for different muscles on different days.
Time frame: Assessment up to 4 hours each visit; up to 4 visits per individual (32 hours)
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