David Zeddies

Department of Biology
The University of Maryland
College Park, MD 20742

Phone: (301) 405-6903
E-mail: dzeddies@umd.edu

Curriculum Vitae

Fish, like mammals, live in highly complex acoustic environments that appear to require the animals to perform ‘auditory scene analysis’ in essentially the same manner as other vertebrates.  Moreover, because of how sound propagates in water, fish are able to extract the direction of a sound source by directly sensing the motion of the particles in the medium.  In this way, fish have information available at the auditory periphery that terrestrial animals must calculate using the first several synapses in the brainstem.  Fish may thus represent a model of hearing in which the initial processing (brainstem) is more comparable to higher-level processing in mammals. 

Otoliths are the very dense ‘stones’ in fish ears overlying sensory hair cells in fish ears that allow them to sense acceleration and sound. There is a dazzling variety of otolith shapes; possibly because shape has been optimized by adaptive processes to fulfill specific functions (form indicates function).  Currently, we do not really understand how otoliths move in response to sound (and in relation to the sensory hair bundles contacting them), and consequently do not understand the input to the fish’s ear.  The goal of my project is to be able to predict the motion of otoliths in any sound field. Our hypothesis is that otolith motion can be modeled as a simple damped oscillator, but it is possible that otolith shape, coupling to the sensory epithelium, or an active process may affect the motion. To determine whether otolith motion is simple or complex, we use a non-invasive ultrasound measurement system to determine the motion of otoliths in three dimensions.

Zeddies, D.G. and Siegel, J.H. (2004) A biophysical model of the inner hair cell. J Acoust Soc Am 116(1):426-41.

Zeddies DG and Fay RR (2005) Development of the acoustic startle response of zebrafish to tones. J Exp Biol 208(7):1363-1372.

Zeddies, D.G.; Dong, Q.; and Siegel, J.H. (in preparation) Swelling of outer hair cells in isolated, perfused, adult gerbil cochlea: Evidence for chloride channels.

Zeddies, D.G. and Siegel, J.H. (in preparation) Time-domain analysis of receptor potentials in inner hair cells of the isolated adult gerbil cochlea.

Zeddies, D.G. and Siegel, J.H. (in preparation) Frequency-domain analysis of receptor potentials in inner hair cells of the isolated adult gerbil cochlea.