Characterization of motor nerve stimulation using sinusoidal low frequency alternating currents and cuff electrodes

Area of Science:

• Neuroscience
• Biomedical Engineering

Background:

• Direct electrical neurostimulation is evolving, with low frequency alternating currents (LFAC) emerging for neuromodulation.
• Limited data exists on peripheral nerve responses to sinusoidal LFAC, particularly below 50 Hz.

Purpose of the Study:

• To demonstrate LFAC activation of motor nerves using bipolar cuff electrodes.
• To characterize factors influencing LFAC activation thresholds, including frequency and electrode geometry.
• To compare in vivo and in silico findings for LFAC stimulation.

Main Methods:

• Acute in vivo experiments on rat sciatic nerves using bipolar/tripolar cuff electrodes.
• Quantified LFAC activation thresholds via EMG and twitch force at 1-20 Hz.
• Utilized computational models (volume conductor and nerve fiber models) to simulate LFAC effects.

Main Results:

• Sinusoidal LFAC elicited in vivo and in silico motor nerve activity with strong model-device agreement.
• Two distinct muscle activation modes (burst and unitary) were observed, phase-locked to the LFAC cycle.
• Activation threshold depended significantly on frequency and electrode contact separation.

Conclusions:

• Sinusoidal LFAC stimulation effectively activates peripheral motor nerves.
• Findings provide insights into LFAC characteristics for neuromodulation.
• Results support potential for selective nerve activation in therapeutic applications.