VLSI-based system for localization of extracellular potentials

In this study, an interface between a biological nerve fiber and an arbitrary electromechanical device was implemented using an analog VLSI-based amplifier/filter circuit. A silastic cuff was fitted over a live nerve bundle, and an electrode of Teflon coated silver wire was used to sense extracellular potentials. A dedicated CMOS VLSI-based circuit then filtered and amplified those signals to an amplitude appropriate for triggering an arbitrary circuit such as the four-phase stepper motor used in this study. In circuit tests, the amplifier/filter circuit was capable of sensing signals as low as 50 microvolts in an in vitro preparation of the optic nerve of limulus polyphemus, and effect rotation of the four-phase stepper motor with detected impulses. Using a silastic cuff electrode and dedicated VLSI circuitry for compactness and reliability, this circuit has excellent long term potential as a component of a surgically implanted system. It is also a pivotal first step in the implementation of a comprehensive cybernetic interface.