Electroneurography

Abstract

AbstractAn essential part in the success of recording peripheral nerve signals is the neural interface. This article gives the theoretical basis of how the action potential in a nerve is generated, and how this, in turn, results in a change in the electric field in the extracellular space. These potentials can be detected using neural interfaces (electrodes) in mono‐ to multipolar recording configurations to maximize the neural signal detected and minimize the noise pickup. These configurations are discussed along with a characterization of the recorded electroneurogram (ENG). Whether the ENG signals are recorded from extrafascicular or intrafascicular neural interfaces, it can be seen that ENGs are low amplitude signals and require amplification of between 1000X and 100,000X to bring the amplitude into the ∼ 1 V range. Electrode impedance models are derived to illustrate how the common mode rejection ratio (CMRR) of an ENG amplifier is influenced by frequency depended impedances.Peripheral neural electrodes can be grouped according to the way that they interface with the peripheral neural tissue. The three main groups are regenerating, intraneural, and extraneural electrodes. Common for all electrode interfaces presented here are that they record the extracellular potential from one or many peripheral nerve axons simultaneously.This article concludes with a section on recent studies performed with chronically implanted nerve cuffs in animal models and disabled human subjects. Exmples are presented of the potential value of peripheral nerve recordings to furnish sensory information for feedback control in fully implantable neuroprostehsis systems.