title: Effect of Contralateral Medial Olivocochlear Feedback on Perceptual Estimates of Cochlear Gain and Compression.
abstract: The active cochlear mechanism amplifies responses to low-intensity sounds, compresses the range of input sound intensities to a smaller output range, and increases cochlear frequency selectivity. The gain of the active mechanism can be modulated by the medial olivocochlear (MOC) efferent system, creating the possibility of top-down control at the earliest level of auditory processing. In humans, MOC function has mostly been measured by the suppression of otoacoustic emissions (OAEs), typically as a result of MOC activation by a contralateral elicitor sound. The exact relationship between OAE suppression and cochlear gain reduction, however, remains unclear. Here, we measured the effect of a contralateral MOC elicitor on perceptual estimates of cochlear gain and compression, obtained using the established temporal masking curve (TMC) method. The measurements were taken at a signal frequency of 2 kHz and compared with measurements of click-evoked OAE suppression. The elicitor was a broadband noise, set to a sound pressure level of 54 dB to avoid triggering the middle ear muscle reflex. Despite its low level, the elicitor had a significant effect on the TMCs, consistent with a reduction in cochlear gain. The amount of gain reduction was estimated as 4.4 dB on average, corresponding to around 18 % of the without-elicitor gain. As a result, the compression exponent increased from 0.18 to 0.27.
authors.affiliation: Medical Research Council Institute of Hearing Research, The University of Nottingham, University Park, Nottingham, NG7 2RD, UK.|School of Psychology, University of Nottingham, University Park, Nottingham, NG7 2RD, UK.|Institute of Sound and Vibration Research, University of Southampton, Highfield Campus, Southampton, SO17 1BJ, UK.
authors.forename: Mark D
authors.initials: MD
authors.lastname: Fletcher
authors.affiliation: Medical Research Council Institute of Hearing Research, The University of Nottingham, University Park, Nottingham, NG7 2RD, UK. katrin@ihr.mrc.ac.uk.
authors.forename: Katrin
authors.identifier: http://orcid.org/0000-0001-8297-2628
authors.initials: K
authors.lastname: Krumbholz
authors.affiliation: Medical Research Council Institute of Hearing Research, The University of Nottingham, University Park, Nottingham, NG7 2RD, UK.
authors.forename: Jessica
authors.initials: J
authors.lastname: de Boer
mesh_terms: D000328:Adult; D003051:Cochlea / Q000502:physiology*; D003939:Diagnostic Techniques, Otological; D005260:Female; D006801:Humans; D008297:Male; D012022:Reflex, Acoustic; D000159:Vestibulocochlear Nerve / Q000502:physiology*; D055815:Young Adult
keywords: click-evoked otoacoustic emissions (CEOAEs); cochlear amplification; contralateral acoustic stimulation; medial olivocochlear reflex (MOCR); temporal masking curve (TMC)