Motor unit sampling from intramuscular micro-electrode array recordings

Area of Science:

• Biomedical Engineering
• Neuroscience
• Motor Control

Background:

• Muscle electrical activity reflects spinal motor neuron output.
• High-density surface EMG (HD-sEMG) and intramuscular EMG (HD-iEMG) decode motor unit activity.
• HD-iEMG yields more motor units than HD-sEMG, but electrode parameter effects are unknown.

Purpose of the Study:

• Investigate how electrode number, spacing, and muscle insertions impact motor unit yield using HD-iEMG.
• Determine optimal HD-iEMG configurations for accurate motor unit sampling.
• Compare HD-iEMG and HD-sEMG performance in motor unit decomposition.

Main Methods:

• Recorded HD-sEMG and HD-iEMG from the Tibialis Anterior muscle in two subjects.
• Utilized novel HD-iEMG electrodes with over 140 sites per muscle insertion.
• Tested various electrode configurations and contraction intensities (10%, 30%, 70% MVC).

Main Results:

• Electrode density within HD-iEMG arrays is the primary factor for maximizing motor unit identification and accuracy.
• HD-iEMG consistently captured more motor units than HD-sEMG across subjects and contraction levels.
• Multiple muscle insertions with HD-iEMG electrodes enabled recordings from hundreds of sites.

Conclusions:

• HD-iEMG, particularly with high electrode density, is a powerful tool for precise motor unit decomposition.
• This technology holds significant potential for clinical diagnostics and neuroscience research.
• Optimized HD-iEMG setups can enhance our understanding of neural control of movement.