USC researcher Karolina Charaziak, PhD, has been awarded a $3.3 million National Institutes of Health (NIH) Research Project (R01) grant to study how the cochlea, the part of the inner ear responsible for hearing, processes complex sounds encountered in everyday life.
The five-year grant will allow Charaziak and her collaborators to combine advanced cochlear imaging, electrical recordings and computational modeling to study how the cochlea processes complex sounds in heathy hearing and hearing loss. The grant is funded by the NIH's National Institute on Deafness and Other Communication Disorders (NIDCD).
The inner ear is an extraordinary biological sensor that can detect vibrations smaller than the diameter of an atom while simultaneously operating across an enormous range of sound levels. Many patients experience hearing difficulties that are not fully explained by a standard hearing test. Current clinical measures provide only a limited view of cochlear health and often cannot identify which specific structures within the inner ear are malfunctioning."
Karolina Charaziak, PhD, assistant professor, USC Caruso Department of Otolaryngology – Head and Neck Surgery, Keck School of Medicine of USC
Charaziak's research seeks to better understand how the healthy cochlea processes complex sounds and how that processing changes in hearing loss. By pairing direct measurements from lab animals with noninvasive hearing measurements, she and her team hope to identify new diagnostic markers that could eventually be used in the clinic to detect hearing problems earlier and more accurately.
"In the long term," she said, "these advances could improve diagnosis, help clinicians distinguish among different forms of sensory hearing loss and potentially guide more personalized treatment strategies. The work may also inform the design of hearing aids, cochlear implants and signal-processing algorithms by providing a more accurate understanding of how the healthy cochlea encodes speech and other complex sounds."
Sounds complicated
This project will investigate how two key properties of the cochlea shape the way people hear speech, music and other complex sounds.
"In simple terms, the first property, nonlinearity, refers to the cochlea's ability to actively amplify soft sounds while compressing louder ones," she said. "The second property, dispersion, refers to the fact that different frequencies travel through the cochlea at different speeds. We want to understand how these properties influence the way the cochlea processes sounds that change over time."
Most laboratory studies of hearing use relatively simple sounds, such as pure tones. However, natural sounds-including speech, music and environmental sounds-change continuously over time in both frequency and intensity. Charaziak's team wants to understand how the inner ear handles those complex real-world sounds.
Charaziak's preliminary work suggests that some perceptual differences may originate in the cochlea itself, before the sound information even reaches the brain.
Toward better diagnostics for hearing loss
Prior to receiving this R01 grant, Charaziak's lab had been working to develop objective, noninvasive measures of cochlear function in mice with hearing loss.
One of their most exciting findings was that tiny electrical signals, generated by the sensory cells in the inner ear, can reveal how well the cochlea amplifies and compresses sound, a function that is often disrupted by hearing loss.
By testing their method in normally hearing animals, Charaziak and her collaborators demonstrated that the measurements were reliable and reproducible. They were then able to move into testing animals with different types of hearing loss to determine whether the technique was able to distinguish among various forms of cochlear dysfunction.
Charaziak's preliminary findings were presented at the Association for Research in Otolaryngology (ARO) meeting. Their research suggests that these measurements may eventually provide clinically useful information that is currently unavailable through standard hearing tests.
Over the next decade, Charaziak's goal is to establish a leading research program focused on understanding the cochlea and translating that knowledge into improved diagnostic tools for hearing disorders.
The R01 grant provides an opportunity to pursue fundamental questions about how the inner ear processes complex sounds while also building the foundation for future translational work.
"I hope that by the end of this project, we will have significantly advanced our understanding of dynamic sound processing in the cochlea and identified new noninvasive measures that can be used to assess cochlear function," she said. "Beyond the science itself, I am excited about training the next generation of scientists and engineers who will continue pushing the field forward. It is an exciting time to be in the field, and I am grateful for the opportunity to contribute to that progress."
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