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Hearing and Deafness - Anatomy and physiology PowerPoint Presentation

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Published on : Jul 10, 2021 | Views : 2816 | Downloads : 3

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Slide 1-

Hearing and Deafness 1. Anatomy & physiology Chris Darwin Web site for lectures, lecture notes and filtering lab: http://www.lifesci.susx.ac.uk/home/Chris_Darwin/ safari
Slide 2-

Protection Impedance match Capture; Amplify mid-freqs Vertical direction coding Frequency analysis Transduction Outer, middle & inner ear
Slide 3-

Middle ear structure
Slide 4-

Conductive hearing loss Sounds don’t get into cochlea Middle ear problems Helped by surgery and by amplification
Slide 5-

Protection Impedance match Capture; Amplify mid-freqs Vertical direction coding Frequency analysis Transduction Outer, middle & inner ear
Slide 6-

Cochlea
Slide 7-

Cochlea cross-section
Slide 8-

Travelling wave on basilar membrane sorts sounds by frequency
Slide 9-

Reponse of basilar membrane to sine waves Each point on the membrane responds best to a different frequency: high freq at base, low at apex. amadeus praat
Slide 10-

Organ of Corti
Slide 11-

Inner hair cell
Slide 12-

Hair Cell Stereocilia
Slide 13-

Auditory nerve innervation OHC (2) spiral afferent (green) medial efferent (red) IHC (1) radial afferent (blue) lateral efferent (pink)
Slide 14-

Auditory nerve rate-intensity functions
Slide 15-

Phase Locking of Inner Hair Cells Auditory nerve connected to inner hair cell tends to fire at the same phase of the stimulating waveform.
Slide 16-

Phase-locking
Slide 17-

Inner vs Outer Hair Cells
Slide 18-

Inner vs Outer Hair Cells
Slide 19-

OHC movement Passive No OHC movement Active With OHC movement
Slide 20-

OHC activity Increases sensitivity (lowers thresholds) Increases selectivity (reduces bandwidth of auditory filter) Gives ear a logarithmic (non-linear) amplitude response Produce Oto-acoustic emissions OHCs are relatively more active for quiet sounds than for loud sounds. They only amplify sounds that have the characteristic frequency of their place.
Slide 21-

Auditory nerve frequency-threshold curves
Slide 22-

Auditory tuning curves Healthy ear Inner hair-cell damage
Slide 23-

Outer-hair cell damage
Slide 24-

BM becomes linear without OHCs (furosemide injection)
Slide 25-

Amplification greater and tuning more selective at low levels Robles, L. and Ruggero, M. A. (2001). "Mechanics of the mammalian cochlea," Physiological Review 81, 1305-1352.
Slide 26-

Conductive vs Sensori-neural deafness Becomes linear, so No combination tones Or two-tone suppression Mostly a combination of OHC and IHC damage
Slide 27-

Normal vs Impaired Dynamic Range
Slide 28-

Normal auditory non-linearities Normal loudness growth (follows Weber’s Law) Combination tones Two-tone suppression Oto-acoustic emissions