Harrison W. Lin, M.D.
Meet the Researcher
Lin received his medical degree from the University of Southern California, after which he completed surgical training as a resident at Harvard Medical School and as a neurotology and skull base surgery fellow at UC San Diego.
He then joined the faculty at UC Irvine, where he is an attending otolaryngologist, neurotologic surgeon, and an assistant professor in the department of otolaryngology – head and neck surgery.
Dr. Lin's grant was generously funded by The Barbara Epstein Foundation, Inc.
The Research
University of California, Irvine
Objective and subjective suprathreshold measures of auditory neurodegeneration
Recent research on animals convincingly demonstrates that degeneration of the auditory nerve, called auditory neurodegeneration, will result from a brief, moderate noise exposure. These animals suffered from severe, permanent deterioration of the function and microscopic appearance of the auditory nerve from a seemingly short, innocuous noise exposure. Interestingly, the animal’s ability to recognize the presence of sound fully recovered to normal threshold levels following the trauma.
However, when presented with sound levels above their ability to hear (“suprathreshold” levels), the strength of the electric signals from the auditory nerve was reduced by as much as 50 percent in some frequencies. Because standard hearing tests (audiograms) of these noise-exposed animals were indistinguishable from unexposed animals, the phenomenon of auditory neurodegeneration may result in a “hidden hearing loss,” and moreover, play a key role in the development of tinnitus, hyperacusis, and other auditory processing abnormalities.
Many military personnel who are subject to severe noise trauma and blast injuries subsequently develop chronic, oftentimes debilitating, tinnitus, and it is thought that this auditory neurodegeneration phenomenon is at least partially responsible for these symptoms. But auditory neurodegeneration in humans has not been established, and its perceptual consequences, including tinnitus, remain unknown. This project aims to establish the missing link between animal and human studies on auditory neurodegeneration and to provide quantitative and qualitative assessment of perceptual consequences of neurodegeneration.
Research areas: tinnitus, auditory neurodegeneration
Long-term goal: To determine and thoroughly evaluate the objective differences in the characteristics of a specialized but broadly available hearing test among patients with and without chronic tinnitus. This will provide clinicians and scientists with a standardized, objective method to document the extent of auditory neurodegeneration that can be correlated to tinnitus characteristics and also monitored over time to evaluate treatment options that promote the survival and health of auditory nerve cells.