Adaptive interference reduction in nerve cuff electrode recordings

Neural signals (ENG) recorded from insulating cuffs fitted with electrodes and placed around nerve bundles may replace artificial sensors in providing feedback signals in functional electrical stimulation (FES) applications. Typical applications include correction of foot-drop, hand grasp in tetraplegic subjects and bladder voiding in certain types of incontinence. Unfortunately, the ENG signal recorded using this method is on the order of a few μV whereas interfering signals can have amplitudes of many mV. Probably the main source of such interference is the Electromyogram (EMG) which is generated by excited muscles near the cuff. A method is presented to reduce the interference pickup in nerve cuff recordings. The gains of differential amplifiers connected to true-tripole nerve cuff recording arrangement are timed adaptively to null the residual EMG. Simulation results show that extraction of the neural signal is possible using this method without the need for additional high order filtering