Effects of age and tinnitus: Limited physiological evidence and no perceptual consequence of cochlear synaptopathy

Abstract

Evidence from animal models and human temporal bones has shown that cochlear synaptopathy is associated with aging. Previous work from our lab has suggested that a weakened middle-ear-muscle-reflex (MEMR) in individuals with tinnitus and normal hearing may reflect the presence of cochlear synaptopathy. In this study, we investigated effects of age and tinnitus on the MEMR strength. We also investigated the relationship between the MEMR strength and amplitudes of auditory brainstem responses (ABRs) as well as several perceptual measures that rely on precise temporal neural coding, such as amplitude-modulation detection, the detection of envelope interaural phase difference, and spatial release from speech-on-speech masking. Younger (20–30 yrs) and older (55–69 yrs) listeners with and without tinnitus and with normal or near-normal hearing were tested. We found that aging and tinnitus were associated with significant reductions in MEMR strength and ABR-based measures. However, only the MEMR-strength reduction was significant after accounting for group differences in high-frequency hearing sensitivity. No significant group differences between the older, tinnitus and control groups were found in the perceptual measures obtained in this study. Results will be discussed in terms of sensitivity of these measures to cochlear synaptopathy in humans. [Work supported by NIH grant R01 DC015987.]