Auditory Physiology Laboratory
David Dolan, Ph.D., Laboratory Director
Introduction
The primary objective of this laboratory is the study cochlear function in normal and abnormal ears. We are particularly interested in the role of the efferent system in normal transduction processes. We use a variety of techniques to activate the efferent system and its effects on various cochlear potentials. Since the medial efferent system provides rich innervation of the outer hair cell, the likely source of the cochlear amplifier, activation of the efferents can help determine the effects of ototoxic insults.
We have developed a new method to activate the efferents. Localized current within the inferior colliculus causes frequency specific efferent effects with the cochlea. This method of efferent activation likely mimics the normal feedback in the awake animal.
Photomicrograph of a slice through the inferior colliculus. Two lesions confirm the physiological findings that the electrode was placed in the central (ICC) and external (EIC) nuclei of the colliculus. Cellular responses in the EIC showed broad tuning while cells in the ICC were narrowly tuned. Electrical stimulation within the EIC produced broad reductions of the cochlear whole-nerve action potential (CAP) while stimulation of the ICC produced frequency specific reductions of the CAP.
