Using stimulus frequency otoacoustic emissions to study basic properties of the human medial olivocochlear reflex

The medial olivocochlear reflex (MOCR) is a brainstem-based neural feedback circuit by which mammals adaptively adjust the gain of their ears in response to changing environmental conditions. Activating the reflex with sound reduces cochlear gain, but the mechanisms by which the reflex produces its cochlear effects, the role(s) the reflex plays in hearing and many basic reflex properties are not well-understood. This thesis quantifies four basic properties of the reflex in humans using stimulus-frequency-otoacoustic-emissions (SFOAEs) that address the following issues: (1) The relative strengths of ipsilateral and contralateral reflex pathways (2) The reflex time-course (3) The response of the reflex to amplitude modulated (AM) noise (4;) The distribution of reflex strengths across a normal-hearing population Activating the reflex with ipsilateral or contralateral noise produced, on average, the same effect in cochlea at the 1 kHz place, contrary to expectations based upon animal studies. Simultaneous bilateral activation produced an effect that was equivalent to the sum of ipsilateral and contralateral activations, on average. Thus, no prevailing binaural interaction took place for our stimulus. Activating the reflex caused detectable changes in the cochlea within 25 ms; the changes continued to develop for 100's of milliseconds.

Department dc:contributor.department

Harvard University--MIT Division of Health Sciences and Technology.

Grantor dc:publisher

Massachusetts Institute of Technology

Year dc:date.issued

2005

Author dc:creator

• Backus, Bradford Clark

Advisor dc:contributor.advisor

• John J. Guinan.

• Harvard University--MIT Division of Health Sciences and Technology.

Statement dc:rights

• M.I.T. theses are protected by copyright. They may be viewed from this source for any purpose, but reproduction or distribution in any format is prohibited without written permission. See provided URL for inquiries about permission.

Licence dc:rights.uri

• http://dspace.mit.edu/handle/1721.1/33840
• http://dspace.mit.edu/handle/1721.1/7582

Language dc:language.iso

eng

Identifier URI

http://dspace.mit.edu/handle/1721.1/33840

OAI identifier oai:identifier

oai:dspace.mit.edu:1721.1/33840