Objective Biomarker Development for Parameter Optimization in Neuromodulation Using High-Density EMG Temporal and...

Area of Science:

• Neuroscience
• Biomedical Engineering
• Rehabilitation Science

Background:

• Transcutaneous spinal cord stimulation (tSCS) shows promise for motor recovery post-spinal cord injury (SCI).
• Current tSCS programming relies on subjective parameter selection, limiting treatment efficacy.
• Objective biomarkers are needed to personalize tSCS for individuals with SCI.

Purpose of the Study:

• To evaluate high-density surface electromyography (HD-sEMG)-derived spatial and temporal features as objective biomarkers for optimizing tSCS.
• To investigate the dose-response relationships of tSCS parameters on muscle activation.
• To establish a framework for individualized tSCS parameter selection in SCI.

Main Methods:

• Three adults with chronic cervical SCI participated.
• A 64-channel HD-sEMG array recorded stimulation-evoked responses.
• Stimulation parameters included varying levels, pulse widths, and amplitudes.
• Spatial and temporal features were extracted from activation maps.

Main Results:

• Two participants showed measurable responses, enabling paired-pulse analyses.
• Root mean square (RMS) emerged as a key discriminative feature.
• Nonlinear, muscle- and level-specific dose-response relationships were observed, with maximal suppression at intermediate amplitudes.
• Increased pulse width expanded recruitment area but not response timing.
• Polarity reversal analysis confirmed stable innervation zone localization.

Conclusions:

• A spatially resolved HD-sEMG framework can provide objective biomarkers for tSCS optimization.
• This framework supports individualized tSCS parameter selection for SCI.
• Findings highlight complex dose-response relationships crucial for effective neuromodulation.