Electrical Responses to Acoustic Clicks: Influence of Electrode Location in Cats

Abstract

When wire electrodes are placed at certain locations outside the cat's bulla, the electrical responses to intense acoustic clicks differ radically from the standard round window response. The microphonic components of the response are now greatly attenuated, and it is even possible to find a neutral area in which no microphonics are detectable; the neural components are less attenuated and can now be studied without microphonic interference. Making use of the demonstrated electrical spread of neural potentials, it is possible to find electrode locations—all outside the animal's bony wall—that will accentuate various potentials originating in the brainstem and in subcortical centers. By means of differential recording, a particular neural component can be emphasized and selected for study. At the cat's auditory cortex one can observe small potentials attributable to subcortical structures. These potentials are, in latency and behavior, identical with “neurals” that are observed at more peripheral locations. Cortical potentials, similar to those recorded from the surface of the brain (dura mater), can also be picked up by electrodes situated on the animal's intact skull. The use of the technique of recording from intact animals should facilitate the study of many problems of auditory physiology.