Comparision of methods for interference neutralisation in tripolar nerve recording cuffs

The aim of this paper is to compare three recording methods for interference rejection from tripolar nerve cuffs by testing in a saline-filled tank. The three methods were: the quasi-tripole (QT), the modified-quasi-tripole (mQT) and adjusted true tripole (aTT). When the interfering electric field that surrounds the cuff is solonoidal and coaxial with the cuff, the mQT allows the interference that happens to be present due to asymmetry to be neutralized at one frequency, and reduced across the ENG band. The aTT is better in this situation, allowing almost complete neutralization at all frequencies. However, when the electric field is altered after adjustment, the interference was greater for the aTT than the mQT. In an implant, the interference is likely to come from nearby muscles and the fields will be continuously changing as the action potentials propagate. Therefore, it is likely that mQT will be better than the aTT.