Acute Mechanisms of Cervical Transcutaneous Electrical Stimulation of the Spinal Cord

Study Overview
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Brief Summary
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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.

Official Title
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Investigating the Acute Effects of Transcutaneous Electrical Stimulation Parameters on Neural Circuits, Motoneuron Behavior and Motor Performance in Individuals With Cervical Spinal Cord Injury

Conditions
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Spinal Cord Injuries

Intervention / Treatment
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* Device: Cervical Transcutaneous Electrical Spinal Cord Stimulation


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: cervical level injury (C5 to C7) at least 1 year post-injury Exclusion Criteria: individuals with damage to the nervous system other than to the spinal cord pregnant women (effects of stimulation on the fetus are unknown). Transcranial magnetic stimulation-specific exclusion criteria: participants with active or inactive implants including cardiac pacemakers, implantable defibrillators, ocular implants, deep brain stimulators, vagus nerve stimulator, and implanted medication pumps participants with conductive, ferromagnetic or other magnetic-sensitive metals implanted in their head participants with a history of seizures or epilepsy participants taking any medication which may reduce seizure threshold

Ages Eligible for Study
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Minimum Age: 18 Years
Maximum Age: 75 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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Accepts Healthy Volunteers

Study Plan
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How is the study designed?
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Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Individuals with cervical spinal cord injury<br>Cohort of individuals who have experiences a chronic spinal cord injury at the cervical level (specifically C5-C7). | Device: Cervical Transcutaneous Electrical Spinal Cord Stimulation<br>* 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.<br>* Other names: tcES;|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| 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. | 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. | 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. | 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. | Assessment up to 4 hours each visit; up to 4 visits per individual (32 hours) |