Performance of alternative amplifier configurations for tripolar nerve cuff recorded ENG

Recording cuffs used to register the activity of sensory afferents in peripheral nerves hold promise to provide feedback signals for closed-loop FES systems. This paper compares two modes in which the electrodes of a tripolar nerve cuff may be connected to amplifier components. The authors recorded evoked sensory activity from the sciatic nerve in an anesthetized rabbit while mechanical stimulation was applied to the central toe pad. A commercial transformer coupled amplifier and a custom amplifier that uses AMPO1 integrated circuit components were compared when each amplifier was configured in a 'quasi-tripolar' verses true tripolar configuration. Results showed that the true tripolar configuration had superior signal to noise ratio in both amplifiers. Furthermore, an excellent performance was demonstrated for the AMPO1 based amplifier without transformer coupling, suggesting that amplifiers designed for implantation (which precludes using bulky transformers) need not compromise the quality of the neural recordings.