Fascicular selectivity in transverse stimulation with a nerve cuff electrode: a theoretical approach

Area of Science:

• Biomedical Engineering
• Neuroscience
• Electrophysiology

Background:

• Selective nerve fascicle stimulation is crucial for advanced neuroprosthetics and neuromodulation therapies.
• Current stimulation techniques using cuff electrodes face challenges in achieving precise fascicle targeting.

Purpose of the Study:

• To theoretically investigate and quantify the performance of different cathode-anode configurations in cuff electrodes for selective fascicle stimulation.
• To compare the efficacy of monopolar, transverse bipolar, and transverse tripolar stimulation for recruiting specific nerve fibers.

Main Methods:

• A three-dimensional volume conductor model of a nerve trunk with four fascicles was developed.
• A myelinated nerve fiber stimulation model was employed to calculate fiber recruitment curves.
• The performance of monopole, transverse bipole, and narrow transverse tripole configurations was analyzed.

Main Results:

• Transverse bipolar stimulation demonstrated superior selectivity for recruiting 15 µm fibers within individual fascicles compared to monopolar and longitudinal tripolar configurations.
• The slope of recruitment curves was significantly reduced with transverse bipolar stimulation, enabling finer control over nerve and force recruitment.
• Additional anodes can optimize excitation area to fascicle topography, enhancing selectivity.

Conclusions:

• Transverse bipolar stimulation in a plane perpendicular to the nerve trunk axis is the most effective configuration for selective fascicle stimulation.
• This method offers improved fine-tuning of nerve recruitment and requires fewer cable connections, despite a higher stimulation current requirement.