Tinnitus as the result of gain adaptation
Item
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Title
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Tinnitus as the result of gain adaptation
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Identifier
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d_2009_2013:02f79498d1a7:10706
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identifier
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10938
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Creator
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Zhou, Xiang,
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Contributor
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Lucas C. Parra
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Date
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2010
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Language
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English
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Publisher
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City University of New York.
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Subject
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Biomedical engineering | DPOAE | Tinnitus
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Abstract
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Tinnitus is the perception of a phantom sound without peripheral input signal. Usually tinnitus correlates strongly with hearing loss. However, not all subjects with hearing loss have tinnitus and not all tinnitus subjects have significant hearing loss. We hypothesized that tinnitus is the result of a gain-adaptation mechanism that when confronted with degraded peripheral input increases neuronal gains such that spontaneous neuronal activity is perceived as a phantom sound.;Following this hypothesis, the first aim of this study was to find a link between the strength of neuronal gain adaptation and cochlear compression. Compression was assessed using distortion product oto-acoustic emissions (DPOAEs). The neuronal gain adaptation was obtained with indirectly psychoacoustic measurement. The experiment results suggested that short-term dynamic adaptation leading to perceptual sensitization is the result of an active process mediated by the outer hair cells, which are thought to modulate the gain of the cochlear amplifier via efferent feedback.;Then we expected that impaired cochlear function would be predictive of the presence of tinnitus and of its spectral characteristics. To assess cochlear function, DPOAEs with high frequency resolution as well as thresholds measured using narrow-band noise. For all tinnitus subjects we obtained a "tinnitus likeness spectrum" -- a rating of the similarity of the tinnitus percept with tones of varying frequency.;Tinnitus subject had elevated thresholds, reduced DPOAE, and increased DPOAE input-output function slope. Within individual subject we found a correlation of the threshold profile with the likeness-spectrum profile and this correlation was significantly improved when taking low-level DPOAE into account. Thus we conclude that in tinnitus, cochlear function, and in particular outer hair-cell function, as measured by low input-level DPOAE, may provide additional diagnostic information over the threshold alone.;The results suggested that, not for all but for this subset of tinnitus subjects, correcting the specific peripheral deficit may restore the elevated central gains and thus reduce tinnitus. Future work will test the prediction that frequency specific compensation of compression and sensitivity has a causal effect on tinnitus loudness.
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Type
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dissertation
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Source
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2009_2013.csv
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degree
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Ph.D.
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Program
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Engineering
