Investigation of noise-induced degeneration of efferent nerve fibers in the mammalian inner ear
In my project, I will investigate whether the degeneration of efferent connections after a noise trauma causes a change in the neuronal activity of the afferents. In the inner ear of mammals, there are two types of sense cells, the inner hair cells and the outer hair cells (OHC). The OHC have piezoelectric properties (electromotility), which can amplify the mechanical signal at low sound pressure levels or attenuate the mechanical signal at high sound pressure levels. The OHCs are thus involved in the extremely sensitive hearing in mammals and contribute to the protection of the hearing function when the sound pressure is too high. The piezoelectricity of the OHCs at high sound pressure levels is reduced by means of efferents, which are connected to the basal pol of the OHC. A loss of these nerve fibers by a noise trauma could disturb this protective mechanism and have far-reaching consequences, including the development of hyperacusis. Using monaural-evoked brain stem potentials (ABRs) and otoacoustic emissions (DPOAEs, f2-f1), I will investigate the degeneration of efferent nerve fibers and their effects on neuronal processing.