The Secondary Spiral Lamina in intracochlear mechanics: A natural hearing protection against high-frequency hearing loss?

The Secondary Spiral Lamina (SSL) is a bony structure of the inner ear that is often overlooked in hearing research. The function of the SSL has never been extensively researched before and is, to date only estimated from evolutionary biology, wherein it plays a major role in high-frequency hearing. Yet the presence of the SSL is highly variable and sometimes not even present at all in highfrequency hearing mammals. Hence, it may have additional functionality and is suspected to be involved in the dissipation of waves from high-intensity sounds, providing natural hearing protection. As such, it may play a vital role in (high-frequency) age related hearing loss. The TESSLA project aims to identify the exact anatomy and dimensions of the SSL by using radiographic and infrared imaging. These will be aided by developing vibrometry OCT, to investigate the function of the SSL by examining the wave propagation and dissipation on ex vivo human temporal bones and in vivo in gerbils. The obtained experimental data will be used to expand a lumped element model, enabling an estimation of the impact of alterations to the SSL on the cochlear hydro-mechanical frequency response. This project will contribute to the fundamental understanding of the ongoing debate about the role of the secondary spiral lamina in human high-frequency hearing and natural hearing protection