Despite work by many investigators, we still do not know the functional role of medial olivocochlear (MOC) efferents. In previous attempts to correlate MOC strength with subject performance, the passive response of the MOC acoustic reflex was measured, not the MOC activation during the task. We are now able to measure MOC activation during a psychophysical task, a new paradigm that greatly increases our ability to test MOC function and descending control in the human auditory system. MOC tests based on otoacoustic emission (OAE) measurements are being used both scientifically and clinically, but the accuracy of such tests has never been ascertained. To maximize the scientific and clinical usefulness of OAE tests we will:
Aim (1A,B) Measure MOC effects using the three types of evoked OAEs and compare the resulting MOC-strength metrics in terms of signal/noise ratios and accuracy of subject ranking, using both contralateral and ipsilateral elicitors, and Aim (1C) determine, in humans, MOC reflex strength in terms of changes in cochlear sensitivity, as shown by MOC-induced changes in wave I of the auditory brainstem response. To address the functional significance of the MOC system, we will systematically measure MOC activation levels in psychophysical tasks:
(Aim 2 A-C) in which MOC activation is expected to aid performance (discrimination of transient signals in noise) vs. those in which no benefit is anticipated, and (Aim 2D-E) to determine MOC frequency selectivity in an active task. The MOC strength tests developed in this work should be useful in clinical and scientific contexts to predict susceptibility to noise damage, in the diagnosis and tracking of diseases, in evaluating the toxicity of drugs and to show the role of MOC feedback in normal hearing. The proposed work will also help to indicate the extent to which such feedback should be put in hearing aids and prosthetic devices such as cochlear implants.

Public Health Relevance

The proposed work will develop and evaluate otoacoustic emission tests for the strength of medial olivocochlear (MOC) efferent feedback to the cochlea. MOC strength tests are useful in clinical and scientific contexts to predict susceptibility to noise damage, in the diagnosis and tracking of diseases, in evaluating the toxicity of drugs and to show the role of MOC feedback in normal hearing. The proposed work will also help to indicate the extent to which such feedback should be put in hearing aids and prosthetic devices such as cochlear implants. 1

Agency
National Institute of Health (NIH)
Institute
National Institute on Deafness and Other Communication Disorders (NIDCD)
Type
Research Project (R01)
Project #
5R01DC005977-09
Application #
8279363
Study Section
Special Emphasis Panel (ZRG1-IFCN-B (02))
Program Officer
Donahue, Amy
Project Start
2003-04-01
Project End
2014-06-30
Budget Start
2012-07-01
Budget End
2013-06-30
Support Year
9
Fiscal Year
2012
Total Cost
$319,720
Indirect Cost
$116,077
Name
Massachusetts Eye and Ear Infirmary
Department
Type
DUNS #
073825945
City
Boston
State
MA
Country
United States
Zip Code
02114
Lilaonitkul, Watjana; Guinan Jr, John J (2012) Frequency tuning of medial-olivocochlear-efferent acoustic reflexes in humans as functions of probe frequency. J Neurophysiol 107:1598-611
Francis, Nikolas A; Guinan Jr, John J (2010) Acoustic stimulation of human medial olivocochlear efferents reduces stimulus-frequency and click-evoked otoacoustic emission delays: Implications for cochlear filter bandwidths. Hear Res 267:36-45
Guinan Jr, John J (2010) Cochlear efferent innervation and function. Curr Opin Otolaryngol Head Neck Surg 18:447-53
Lilaonitkul, Watjana; Guinan Jr, John J (2009) Human medial olivocochlear reflex: effects as functions of contralateral, ipsilateral, and bilateral elicitor bandwidths. J Assoc Res Otolaryngol 10:459-70
Lilaonitkul, Watjana; Guinan Jr, John J (2009) Reflex control of the human inner ear: a half-octave offset in medial efferent feedback that is consistent with an efferent role in the control of masking. J Neurophysiol 101:1394-406
Backus, Bradford C; Guinan Jr, John J (2007) Measurement of the distribution of medial olivocochlear acoustic reflex strengths across normal-hearing individuals via otoacoustic emissions. J Assoc Res Otolaryngol 8:484-96
Backus, Bradford C (2007) Bias due to noise in otoacoustic emission measurements. J Acoust Soc Am 121:1588-603
Guinan Jr, John J (2006) Olivocochlear efferents: anatomy, physiology, function, and the measurement of efferent effects in humans. Ear Hear 27:589-607
Backus, Bradford C; Guinan Jr, John J (2006) Time-course of the human medial olivocochlear reflex. J Acoust Soc Am 119:2889-904