Comparison between monopolar and tripolar configurations in chronically implanted nerve cuff electrodes

Nerve cuff electrodes have been shown to be safe and able to activate selectively specific fascicles in a nerve trunk. Selectivity has been shown using a cuff with four radially placed tripoles thus requiring twelve contacts and twelve lead wires. This study evaluates a simplified cuff electrode, consisting of four radially placed monopole electrodes, requiring only four lead wires, and compares the results to the tripolar electrode configuration. Experiments were performed on two cats, each with an electrode that was implanted for over six months. Results from a correlation analysis and a torque vector likeness measure indicated that the recruitment characteristics of the two configurations were similar in 6 of 8 cases.