Phase anomalies and plateaus in auditory nerve fiber responses to high-frequency tones

Phase reversals and phase plateaus have been found in studies that measure motion of the basilar membrane (BM) at the base of the cochlea in response to high-level sounds above the characteristic frequency (CF). In contrast, such patterns have not been found in responses of auditory-nerve fibers (ANF) from the base of the cochlea, primarily because these ANFs do not have synchronized responses to high-frequency tones. We sought counterparts to the BM responses in auditory nerve fibers (ANF) by using a new method that extracts phase information from beat-producing multi-tone stimuli. The method can determine the relative phases of ANF responses to high-frequency tones by measuring the phases of low-frequency beats and from these beats, reconstructing the relative phases of the original tone response. We also used amplitude modulated (AM) tones at high sound levels. The data collected suggest that the new beat-producing phase-analysis method is effective at tip and tail regions of the ANF tuning curves. However, this method has low success in measurements at frequencies above CF due to low signal-to-noise ratios and large distortion products in the ANF responses. AM tones, however, were more successful and showed significant evidence of a phase plateau at high levels and at frequencies well above the fiber's CF.

Department dc:contributor.department

Massachusetts Institute of Technology. Dept. of Electrical Engineering and Computer Science.

Grantor dc:publisher

Massachusetts Institute of Technology

Year dc:date.issued

2005

Author dc:creator

• Cheng, Holden

Advisor dc:contributor.advisor

• John J. Guinan, Jr.

• Electrical Engineering and Computer Science.

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/1721.1/7582

Language dc:language.iso

eng

Handle dc:identifier.uri

http://hdl.handle.net/1721.1/34114

OAI identifier oai:identifier

oai:dspace.mit.edu:1721.1/34114