<strong>Cochlear physiology and ultrastucture</strong>
A prominent area of Dr. Siegel's research concerns the physiology of the sensory receptor cells (the hair cells) of the mammalian hearing organ (the cochlea) and how they communicate with the sensory neurons of the spiral ganglion at specialized synapses. To overcome the practical difficulties in gaining access to this system, Dr. Siegel and his students have developed a procedure to isolate the inner ear from the skull and maintain it in short-term culture. The use of the intact hearing organ is necessary to preserve the synaptic connections.
Experiments using fluorescent indicators of intracellular sodium and calcium have recently shown how hair cell homeostasis can be maintained in vitro. Biophysical modeling has been used to understand how experimental artifacts and culture conditions affect hair cell function, including their responses to stimuli. A second area of Dr. Siegel's research is the phenomenon of otoacoustic emissions: sounds emitted by healthy ears that may be monitored with a sensitive microphone placed in the ear canal. These emissions are by-products of a vibration-amplification function of hair cells. Dr. Siegel and his students have developed procedures for evoking emissions with stimulus frequencies up to the limit of human hearing (20 kHz).