Model-based Investigations of Peripheral Nerve Stimulation Using Longitudinal Intrafascicular Electrodes

Electrical stimulation of the human peripheral nervous system can be a powerful tool to treat various medical conditions and provide insight into nervous system processes. A critical challenge for many applications is to selectively activate neurons that have the desired effect while avoiding the activation of neurons that produce side effects. To stimulate peripheral fibers, the longitudinal intrafascicular electrode (LIFE) targets small groups of fibers inside the fascicle using low-amplitude pulses and is well-suited for chronic use. This work aims to understand better the ability to use intrafascicular stimulation with LIFEs to activate small groups of neurons within a fascicle selectively.  A hybrid workflow is developed to simulate: 1) the production/propagation of the electric field induced by the stimulation pulse and 2) the effect of the electric field on fiber activation (recruitment). Results demonstrated the potential advantages of specific stimulation strategies and the sensitivity of recruitment patterns to electrode placement and tissue properties. For example, it is demonstrated that endoneurium conductivities' significant effect on threshold levels and the configuration with a LIFE as a local ground can be used to deselect its surrounding axons, how monopolar and bipolar configurations can be used to enhance spatial selectivity