Guest, Hannah and Munro, Kevin and Plack, Christopher John (2019) Acoustic middle-ear-muscle-reflex thresholds in humans with normal audiograms : No relations to tinnitus, speech perception in noise, or noise exposure. Neuroscience, 407. pp. 75-82. ISSN 0306-4522
MEMR_paper_181209_for_Pure.pdf - Accepted Version
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Abstract
The acoustic middle-ear-muscle reflex (MEMR) has been suggested as a sensitive non-invasive measure of cochlear synaptopathy, the loss of synapses between inner hair cells and auditory nerve fibers. In the present study, clinical MEMR thresholds were measured for 1-, 2-, and 4-kHz tonal elicitors, using a procedure shown to produce thresholds with excellent reliability. MEMR thresholds of 19 participants with tinnitus and normal audiograms were compared to those of 19 age- and sex-matched controls. MEMR thresholds did not differ significantly between the two groups at any frequency. These 38 participants were included in a larger sample of 70 participants with normal audiograms. For this larger group, MEMR thresholds were compared to a measure of spatial speech perception in noise (SPiN) and a detailed self-report estimate of lifetime noise exposure. MEMR thresholds were unrelated to either SPiN or noise exposure, despite a wide range in both measures. It is possible that thresholds measured using a clinical paradigm are less sensitive to synaptopathy than those obtained using more sophisticated measurement techniques; however, we had good sensitivity at the group level, and even trends in the hypothesized direction were not observed. To the extent that MEMR thresholds are sensitive to cochlear synaptopathy, the present results provide no evidence that tinnitus, SPiN, or noise exposure are related to synaptopathy in the population studied.