IMPROVED NERVE CUFF ELECTRODE RECORDINGS WITH SUBTHRESHOLD ANODIC CURRENTS

A method has been developed for improving the signal amplitudes of the recordings obtained with nerve cuff electrodes, The amplitude of the electroneurogram (ENG) has been shown to increase with increasing dist ance between the contacts when cuff electrodes are used to record peri pheral nerve activity [9]. The effect is directly related to the propa gation speed of the action potentials. Computer simulations have shown that the propagation velocity of action potentials in a length of a n erve axon can be decreased by subthreshold extracellular anodic curren ts. Slowing the action potentials is analogous to increasing the cuff length in that both result in longer intercontact delays, thus, larger signal outputs. This phenomenon is used to increase the amplitudes of whole nerve recordings obtained with a short cuff electrode. Computer simulations predicting the slowing effect of anodic currents as well as the experimental verification of this effect are presented. The inc rease in the amplitude of compound action potentials (CAP's) is demons trated experimentally in an in vitro preparation. This method can be u sed to improve the signal-to-noise ratios when recording from short ne rve segments where the cuff length is limited.