Non-Invasive Assays of Cochlear Synaptopathy -- Candidates and Considerations

Publication date: Available online 8 March 2019Source: NeuroscienceAuthor(s): Hari M. Bharadwaj, Alexandra R. Mai, Jennifer M. Simpson, Inyong Choi, Michael G. Heinz, Barbara G. Shinn-CunninghamAbstractStudies in multiple species, including in post-mortem human tissue, have shown that normal aging and/or acoustic overexposure can lead to a significant loss of afferent synapses innervating the cochlea. Hypothetically, this cochlear synaptopathy can lead to perceptual deficits in challenging environments and can contribute to central neural effects such as tinnitus. However, because cochlear synaptopathy can occur without any measurable changes in audiometric thresholds, synaptopathy can remain hidden from standard clinical diagnostics. To understand the perceptual sequelae of synaptopathy and to evaluate the efficacy of emerging therapies, sensitive and specific non-invasive measures at the individual patient level need to be established. Pioneering experiments in specific mice strains have helped identify many candidate assays. These include auditory brainstem responses, the middle-ear muscle reflex, envelope-following responses, and extended high-frequency audiograms. Unfortunately, because these non-invasive measures can be also affected by extraneous factors other than synaptopathy, their application and interpretation in humans is not straightforward. Here, we systematically examine six extraneous factors through a series of interrelated human experiments aimed at underst...

Source: Neuroscience - March 8, 2019 Category: Neuroscience Source Type: research