title: Influence of 100Hz amplitude modulation on the human medial olivocochlear reflex.
abstract: It is well known that medial olivocochlear system (MOC) activity causes inhibition of cochlear amplification that can be measured using otoacoustic emissions (OAEs). The temporal characteristics of this MOC inhibitory effect are still not well understood. Two experiments were performed to further explore a previously reported enhancement in MOC inhibition of OAEs by a broadband noise (BBN) elicitor modulated at 100Hz (AM-BBN). In experiment I, MOC inhibition was measured for toneburst (1 and 2kHz presented at 41.67Hz) and stimulus-frequency (0.96-1.92kHz) OAEs for two elicitor conditions, BBN and AM-BBN (100% modulation depth [MD]), in 27 young normal hearing adults. In experiment II, tonebursts were presented at 50Hz instead of 41.67Hz to test if the previously reported enhancement of the MOC response to 100Hz AM-BBN is specific to a 50Hz toneburst presentation rate. All elicitors caused significant reduction of both TB- and SF-OAE amplitude. AM-BBN evoked the same OAE inhibition compared to BBN in both experiments. This pattern was consistent across OAE types, and toneburst presentation rates. Results suggest that the MOC is not especially sensitive to 100Hz AM-BBN; instead, AM dips in noise energy likely reduce its effectiveness in evoking MOC activity due to temporal energy integration.
authors.affiliation: National Centre for Audiology, Western University, London, Ontario, Canada N6G1H1. Electronic address: sboothal@uwo.ca.
authors.forename: Sriram
authors.initials: S
authors.lastname: Boothalingam
authors.affiliation: National Centre for Audiology, Western University, London, Ontario, Canada N6G1H1; School of Communication Sciences and Disorders, Western University, London, Ontario, Canada N6G1H1.
authors.forename: David
authors.initials: D
authors.lastname: Purcell
authors.affiliation: National Centre for Audiology, Western University, London, Ontario, Canada N6G1H1; School of Communication Sciences and Disorders, Western University, London, Ontario, Canada N6G1H1.
authors.forename: Susan
authors.initials: S
authors.lastname: Scollie
mesh_terms: D000161:Acoustic Stimulation; D000293:Adolescent; D000328:Adult; D001306:Auditory Pathways / Q000502:physiology; D003051:Cochlea / Q000502:physiology*; D006801:Humans; D009622:Noise; D009847:Olivary Nucleus / Q000502:physiology*; D017084:Otoacoustic Emissions, Spontaneous; D012018:Reflex; D055815:Young Adult
keywords: Amplitude modulation; Efferent inhibition; Medial olivocochlear; Otoacoustic emission