Our goal is to understand how outer hair cells (OHCs) produce the high sensitivity of mammalian hearing. Great progress has been made in understanding the properties of isolated OHCs, but there are fundamental unanswered questions about how OHCs work in intact cochleas. Medial olivocochlear (MOC) efferent neurons innervate OHCs and provide an important tool for understanding OHC-based mechanisms. To study the mechanical effects of OHCs in vivo, we will measure basilar-membrane (BM) motion and auditory-nerve (AN) firing patterns and the changes produced in these responses by electrical stimulation of MOC efferents. Our recent work provides strong evidence for the existence of a second traveling wave along the cochlea, a wave that may couple OHC motility to BM motion. The proposed work will characterize the properties of this second wave and its relationship to the classic transverse traveling wave. This wil be done (1) at frequencies well below the local characteristic frequency (CF), where stiffness dominates the mechanical response and the effects of the two traveling waves can be studied without the complications produced by cochlear amplification, and (2) at frequencies near CF where the cochlear amplifier has its primary effects. Our work, and that of others, has shown that the """"""""slow effect"""""""" of MOC stimulation is due to a decrease in OHC stiffness. This stiffness change will be exploited to determine how OHC stiffness affects cochlear properties such as CF, and to test the OHC piezoelectric theory, a theory that may account for how OHC somatic motility can be effective at frequencies above the OHC membrane cut-off frequency. The results of the proposed work will help to flesh out a new picture of cochlear mechanics. Mechanics is a key area of cochlear function that is disrupted by many of the pathologies that affect hearing. Understanding cochlear mechanics, and the role of OHCs in cochlear mechanics, is essential for progress in almost all aspects of hearing.

Agency
National Institute of Health (NIH)
Institute
National Institute on Deafness and Other Communication Disorders (NIDCD)
Type
Research Project (R01)
Project #
5R01DC000235-19
Application #
7000399
Study Section
Auditory System Study Section (AUD)
Program Officer
Donahue, Amy
Project Start
1984-06-01
Project End
2007-12-31
Budget Start
2006-01-01
Budget End
2006-12-31
Support Year
19
Fiscal Year
2006
Total Cost
$227,075
Indirect Cost
Name
Massachusetts Eye and Ear Infirmary
Department
Type
DUNS #
073825945
City
Boston
State
MA
Country
United States
Zip Code
02114
Guinan Jr, John J (2018) Olivocochlear efferents: Their action, effects, measurement and uses, and the impact of the new conception of cochlear mechanical responses. Hear Res 362:38-47
Berezina-Greene, Maria A; Guinan Jr, John J (2017) Electrically Evoked Medial Olivocochlear Efferent Effects on Stimulus Frequency Otoacoustic Emissions in Guinea Pigs. J Assoc Res Otolaryngol 18:153-163
Nam, Hui; Guinan Jr, John J (2017) Non-tip auditory-nerve responses that are suppressed by low-frequency bias tones originate from reticular lamina motion. Hear Res 358:1-9
Nam, Hui; Guinan Jr, John J (2016) Low-frequency bias tone suppression of auditory-nerve responses to low-level clicks and tones. Hear Res 341:66-78
Berezina-Greene, Maria A; Guinan Jr, John J (2015) Stimulus Frequency Otoacoustic Emission Delays and Generating Mechanisms in Guinea Pigs, Chinchillas, and Simulations. J Assoc Res Otolaryngol 16:679-94
Lichtenhan, J T; Hartsock, J J; Gill, R M et al. (2014) The auditory nerve overlapped waveform (ANOW) originates in the cochlear apex. J Assoc Res Otolaryngol 15:395-411
Lichtenhan, Jeffery T; Cooper, Nigel P; Guinan Jr, John J (2013) A new auditory threshold estimation technique for low frequencies: proof of concept. Ear Hear 34:42-51
Lichtenhan, Jeffery T (2012) Effects of low-frequency biasing on otoacoustic and neural measures suggest that stimulus-frequency otoacoustic emissions originate near the peak region of the traveling wave. J Assoc Res Otolaryngol 13:17-28
Guinan Jr, John J; Salt, Alec; Cheatham, Mary Ann (2012) Progress in cochlear physiology after Bekesy. Hear Res 293:12-20
Guinan Jr, John J (2012) How are inner hair cells stimulated? Evidence for multiple mechanical drives. Hear Res 292:35-50

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