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Hearing and Donuts (Brain and Bagels) Seminar
October 1, 2021 @ 8:30 am - 9:30 am
Presenter: Sriram Boothalingam, Assistant Professor, Department of CSD, UW Madison
Topic: Does Turning the Cochlea Gain Down do Anything for Auditory Perception?
The medial olivocochlear reflex (MOCR), a brainstem circuit, improves the dynamic range of the auditory nerve in adverse auditory conditions by turning the cochlear gain down. This finding from animals has been extrapolated to imply that MOCR facilitates human speech perception in noisy environments. A recent meta-analysis in our lab suggests that the evidence for this hypothesis is weak at best. This result is unsurprising because speech understanding is a complex task involving many centers in the brain. As such, speech perception may not reflect the subtle changes to speech signals engendered at the periphery by the MOCR. Therefore, we approached the question of whether the MOCR plays a role in human auditory perception using simpler stimuli, clicks, and an intensity change detection task. Level increments at three temporal positions, mapped on to (1) no-, (2) part-, and (3) full-activation of the MOCR, were embedded in otherwise equal level click trains. During the behavioral task, we concurrently measured otoacoustic emissions (OAEs) and electroencephalography (EEG; N1-P2) to index the MOCR and cortical activity accompanying perceptual change detection, respectively. Preliminary group-level analyses suggest that perceptual detection of intensity change detection improves with temporal position and as MOCR activation increases. However, the position at which the best detection occurs is reached before MOCR reaches full activation. Cortical N1-P2 amplitude corresponds more closely with the perceptual intensity change detection than MOCR activation. Individual-level correlation analyses indicate no significant relationships between the MOCR activity or cortical detection of change and behavioral performance. Results of further analyses will be presented in the talk.