Noninvasive optical system for the study of the function of inner ear in living animals

The Hearing Organ has a coiled structure in which the basic geometrical arrangement of the different types of cells is repeated throughout the organ. Hearing organs of different mammalian species also utilize the same arrangement of cells. In order to understand the significance of this arrangement in processing the auditory stimuli it is essential to measure the cellular function in an intact organ of a living animal. The sensory cells in the intact inner ear of a living animal can be visualized in the basal turn of the cochlea through the round window membrane. To achieve this an imaging system is needed to detect the weak reflections from the sensory cells in the inner ear while rejecting strong reflections from structures below and above the region of interest, particularly the round window membrane itself. A confocal microscope/interferometer was developed and built to visualize the sensory cells and to measure their vibration in response to sound applied to the ear. The measuring system and some of its performance characteristics are described.