Reversal of age related demyelination in the auditory brain stem.

About This Grant

Project Summary One of the most common medical conditions in any aging society is presbycusis, or age-related hearing loss. Approximately one third of American adults suffer from this condition typically starting in their middle ages, and about half of adults over 70 years have a substantial hearing impairment. One of the mechanisms of presbycusis happens in the central nervous system and is termed central hearing loss. Older adults with central hearing loss may have normal or near normal audiograms yet have problems carrying on a conversation in acoustically complex environments where multiple sound sources are active at the same time, such as a busy restaurant, a public place, or any situation where background noises are active. The main reason for this difficulty is that affected individuals have trouble perceptually isolating sound sources of interest (e.g., the voice of the speaker they want to listen to) effectively from other sources, presumably because the neural mechanisms that perform this computation are less effective. Our laboratories' recent work suggests that one key age-related subcellular change in the sound localization pathway contributes to this phenomenology: A demyelination of afferent fibers to the sound localization pathway. In Mongolian gerbils, we propose to experimentally isolate this mechanism by re-creating it in young animals – effectively “making young animals old”. Furthermore, we will test an approach using a pharmaceutical agent in combination with sound stimulation to reverse this age-related change – effectively “making old animals young”. Finally, we will investigate the mechanisms driving the age-related demyelination by studying oligodendrocytes, the glia cells that produce myelin, in young and old animals. The expected results from this study will help determine the role of demyelination in central hearing loss, a common medical condition which is still poorly understood. The expected results will also suggest a potential treatment for this condition.