revised estimates of human cochlear tuning from otoacoustic and behavioral measurements
DESCRIPTION
Revised estimates of human cochlear tuning from otoacoustic and behavioral measurements. Christopher A. Shera, John J. Guinan, Jr., and Andrew J. Oxenham. Background. Key characteristic of hearing: frequency tuning of cochlear filters Sensory cells respond to a preferred range of energy - PowerPoint PPT PresentationTRANSCRIPT
![Page 1: Revised estimates of human cochlear tuning from otoacoustic and behavioral measurements](https://reader036.vdocument.in/reader036/viewer/2022070419/56815ad9550346895dc8a5e1/html5/thumbnails/1.jpg)
Revised estimates of human cochlear tuning from
otoacoustic and behavioral measurements
Christopher A. Shera, John J. Guinan, Jr., and Andrew J.
Oxenham
![Page 2: Revised estimates of human cochlear tuning from otoacoustic and behavioral measurements](https://reader036.vdocument.in/reader036/viewer/2022070419/56815ad9550346895dc8a5e1/html5/thumbnails/2.jpg)
Background
• Key characteristic of hearing: frequency tuning of cochlear filters– Sensory cells respond to a preferred range of
energy– Filter bandwidth 1/ sharpness of tuning
![Page 3: Revised estimates of human cochlear tuning from otoacoustic and behavioral measurements](https://reader036.vdocument.in/reader036/viewer/2022070419/56815ad9550346895dc8a5e1/html5/thumbnails/3.jpg)
Background
Assessments of cochlear tuning
• Non-human mammals– ANF recordings in live anesthetized animals
• Humans– Psychophysical measures
• Masking procedures
• Pure tone detection in background noise
![Page 4: Revised estimates of human cochlear tuning from otoacoustic and behavioral measurements](https://reader036.vdocument.in/reader036/viewer/2022070419/56815ad9550346895dc8a5e1/html5/thumbnails/4.jpg)
Downfalls
• Assumptions underlying pure tone detection method are uncertain
• Physcophysical detection tasks depend on filter characteristics as well as neural processing
• No way to validate behavioral measures in humans
•Humans
–Psychophysical measures
•Masking procedures
•Pure tone detection in background noise
Authors believe that human cochlear tuning has been underestimated
![Page 5: Revised estimates of human cochlear tuning from otoacoustic and behavioral measurements](https://reader036.vdocument.in/reader036/viewer/2022070419/56815ad9550346895dc8a5e1/html5/thumbnails/5.jpg)
Aims
• Compare current measures of human cochlear tuning with animal measures
• Develop a noninvasive measure of cochlear tuning based on otoacoustic emissions
• Test correspondence between physiological and behavioral measures of frequency selectivity
![Page 6: Revised estimates of human cochlear tuning from otoacoustic and behavioral measurements](https://reader036.vdocument.in/reader036/viewer/2022070419/56815ad9550346895dc8a5e1/html5/thumbnails/6.jpg)
Aims
• Compare current measures of human cochlear tuning with animal measures
• Develop a noninvasive measure of cochlear tuning based on otoacoustic emissions
• Test correspondence between physiological and behavioral measures of frequency selectivity
![Page 7: Revised estimates of human cochlear tuning from otoacoustic and behavioral measurements](https://reader036.vdocument.in/reader036/viewer/2022070419/56815ad9550346895dc8a5e1/html5/thumbnails/7.jpg)
Determination of bandwidth
QERB
• Measure of “sharpness” of tuning based on critical bandwidth
• QERB(CF) = CF/ERB(CF)
Smaller bandwidth = higher QERB
Frequency
Le
vel (
dB
SP
L)
SignalMasker
Auditory filter
2 kHz
![Page 8: Revised estimates of human cochlear tuning from otoacoustic and behavioral measurements](https://reader036.vdocument.in/reader036/viewer/2022070419/56815ad9550346895dc8a5e1/html5/thumbnails/8.jpg)
Results
Genuine species differences or erroneous human data?
![Page 9: Revised estimates of human cochlear tuning from otoacoustic and behavioral measurements](https://reader036.vdocument.in/reader036/viewer/2022070419/56815ad9550346895dc8a5e1/html5/thumbnails/9.jpg)
Aims
• Compare current measures of human cochlear tuning with animal measures
• Develop a noninvasive measure of cochlear tuning based on otoacoustic emissions
• Test correspondence between physiological and behavioral measures of frequency selectivity
![Page 10: Revised estimates of human cochlear tuning from otoacoustic and behavioral measurements](https://reader036.vdocument.in/reader036/viewer/2022070419/56815ad9550346895dc8a5e1/html5/thumbnails/10.jpg)
Experiment II• Subjects
– Guinea pigs (n=9)– Cats (n=7)– Humans (n=9)
• Measure stimulus-frequency otoacoustic emissions (SFOAEs)
– Cochlear traveling waves scattered by the mechanical properties of the cochlea– Recordable sounds emitted from the ear– Evoked by a pure tone
• Calculate SFOAE group delays (NSFOAE)– Negative of slope of emission-phase vs frequency
![Page 11: Revised estimates of human cochlear tuning from otoacoustic and behavioral measurements](https://reader036.vdocument.in/reader036/viewer/2022070419/56815ad9550346895dc8a5e1/html5/thumbnails/11.jpg)
Theory
• NSFOAE = 2(NBM)Normalized emitted wave delay is double the normalized BM
transfer function delay
• NBM= delay of BM transfer function• NSFOAE = emission group delay
Can use measurable NSFOAE group delays to estimate NBM
![Page 12: Revised estimates of human cochlear tuning from otoacoustic and behavioral measurements](https://reader036.vdocument.in/reader036/viewer/2022070419/56815ad9550346895dc8a5e1/html5/thumbnails/12.jpg)
Traveling wave delays
![Page 13: Revised estimates of human cochlear tuning from otoacoustic and behavioral measurements](https://reader036.vdocument.in/reader036/viewer/2022070419/56815ad9550346895dc8a5e1/html5/thumbnails/13.jpg)
Theory II
• At low levels, smaller bandwidths (larger QERB) correspond to steeper phase slopes (longer delays)
• BM tuning at low levels nearly identical to ANF tuning so:
QERB NBM ==> QERB = kNBM
Where k is a measure of filter shape
![Page 14: Revised estimates of human cochlear tuning from otoacoustic and behavioral measurements](https://reader036.vdocument.in/reader036/viewer/2022070419/56815ad9550346895dc8a5e1/html5/thumbnails/14.jpg)
Application
• Use measurable SFOAE emissions to estimate NBM
• Use NBM to estimate QERB using known k values from other species
![Page 15: Revised estimates of human cochlear tuning from otoacoustic and behavioral measurements](https://reader036.vdocument.in/reader036/viewer/2022070419/56815ad9550346895dc8a5e1/html5/thumbnails/15.jpg)
Results
![Page 16: Revised estimates of human cochlear tuning from otoacoustic and behavioral measurements](https://reader036.vdocument.in/reader036/viewer/2022070419/56815ad9550346895dc8a5e1/html5/thumbnails/16.jpg)
![Page 17: Revised estimates of human cochlear tuning from otoacoustic and behavioral measurements](https://reader036.vdocument.in/reader036/viewer/2022070419/56815ad9550346895dc8a5e1/html5/thumbnails/17.jpg)
If this is right, it suggests: 1) Human k is a factor of
3 larger than in animals
2) Human QERB is very different from cats and guinea pigs
![Page 18: Revised estimates of human cochlear tuning from otoacoustic and behavioral measurements](https://reader036.vdocument.in/reader036/viewer/2022070419/56815ad9550346895dc8a5e1/html5/thumbnails/18.jpg)
If this is right, it suggests: 1) Previous measures
underestimate human filter “sharpness”
2) Such sharp tuning may facilitate speech communication
![Page 19: Revised estimates of human cochlear tuning from otoacoustic and behavioral measurements](https://reader036.vdocument.in/reader036/viewer/2022070419/56815ad9550346895dc8a5e1/html5/thumbnails/19.jpg)
Aims
• Compare current measures of human cochlear tuning with animal measures
• Develop a noninvasive measure of cochlear tuning based on otoacoustic emissions
• Test correspondence between physiological and behavioral measures of frequency selectivity
![Page 20: Revised estimates of human cochlear tuning from otoacoustic and behavioral measurements](https://reader036.vdocument.in/reader036/viewer/2022070419/56815ad9550346895dc8a5e1/html5/thumbnails/20.jpg)
Experiment III• 8 Normal-hearing humans
• Detection of a sinusoidal signal– 10dB above threshold in quiet– Frequencies: 1,2,4,6,8 kHz– 5ms after offset of burst of masker
• Frequencies: 2 .25f wide spectral bands of Gaussian noise placed 0, 0.1, 0.2, 0.3, 0.4 f below signal frequency
– gated by 5ms raised-cosine ramps
• Measured thresholds using 3-alternative forced-choice procedure
• Use mean data to derive cochlear filter magnitude responses
![Page 21: Revised estimates of human cochlear tuning from otoacoustic and behavioral measurements](https://reader036.vdocument.in/reader036/viewer/2022070419/56815ad9550346895dc8a5e1/html5/thumbnails/21.jpg)
Reasoning behind methodology
• Use low, near threshold tuning curves – Avoid compression & non-linear affects
• Noise masker extends spectrally above and below signal frequency– avoid off-frequency listening – avoid confusion between masker & signal
• Non-simultaneous masking– Minimize suppressive interactions between masker and
signal
• Constant signal level (instead of masker level)– paradigm used in neural threshold measurements
![Page 22: Revised estimates of human cochlear tuning from otoacoustic and behavioral measurements](https://reader036.vdocument.in/reader036/viewer/2022070419/56815ad9550346895dc8a5e1/html5/thumbnails/22.jpg)
Results
![Page 23: Revised estimates of human cochlear tuning from otoacoustic and behavioral measurements](https://reader036.vdocument.in/reader036/viewer/2022070419/56815ad9550346895dc8a5e1/html5/thumbnails/23.jpg)
Conclusions• Human cochlear filters are substantially sharper than
commonly believed• Contrary to prior beliefs
– Human Q filters are not constant above 500Hz– Human tuning may be sharper than cat – Human and cat tuning may vary similarly with CF
• Supports the assumption that k is invariant across species
• Suggests revised understanding of the cochlear frequency-position map