1. Peripheral Auditory System
MEDS 371
Peripheral Auditory System
Dr. Duck O. Kim

2. SPL: sound pressure level dB SPL = 20 log10 (pressure/ref)
dB: decibel
SPL: sound pressure level
dB SPL = 20 log10 (pressure/ref)
ref = 20 mPa

3. dB SPL re 20 mPa frequency (Hz) Davis & Silverman, 1970
threshold of hearing
frequency (Hz)
audible freq. range for humans: approx. 20 ~ 20,000 Hz

4. Purves
Fig 13.4

5. Purves
Fig 13.3

6. tensor tympani - malleus
the middle ear
middle-ear muscles:
tensor tympani - malleus
stapedius - stapes
Pickles, 1988
Impedance
transformation
Pickles, 1988

7. Bekesy, 1960
external ear
middle ear
inner ear

8. data from human cadavers origin of tonotopic organization
bas. mem. disp. amplitude
origin of
tonotopic
organization
Bekesy, 1960
distance from stapes (mm)

9. cochlea
temporal bone SV ST
Pickles, 1988

10. inner ear

12. Purves

13. fluid in ST & SV: perilymph (like CSF)
fluid in SM: endolymph (high K+)

14. cochlear partition SV RM SM TM
Smith,
1975 BM ST

15. inner hair cell
outer hair cell
afferent
afferent * *
Smith, 1975

16. tip-link model of hair-cell excitation
Pickles, 1984

17. Purves, Fig 12-8;
adapted from
Lewis & Hudspeth,
1983

19. Purves
Fig 13-6

20. frequency tuning curves
threshold (dB SPL)
frequency (kHz)
basilar
membrane
cochlear
neuron
Sellick et al, 1982
Neely & Kim, 1983

21. frequency tuning curves of cochlear neurons
OHC damage
frequency (kHz)
threshold (dB SPL)
normal
Robertson &
Johnstone,
1979

22. mammalian cochlear OHC
HB motility
OHC motilities
underlie
the cochlear
amplifier.
somatic
motility
Kim, 1986

23. Innervation of IHCs and OHCs by cochlear neurons
adapted from Spoendlin, 1972

24. Phase-locked discharges of a cochlear nerve fiber
Stimulus: 300 Hz pure tone
Evans, 1975

25. two codes
of frequency
in auditory
nerve fibers
val

26. coding of sound intensity
increase of sound intensity ->
(1) increase of discharge rates of
cochlear nerve fibers (with low
spontaneous rates);
(2) increase of number of excited
cochlear nerve fibers
discharge rate (spikes/s)
Kim et al., 1991
distance along cochlea

27. hearing loss examples_____
conductive hearing loss otosclerosis
otitis media
impaction of ear canal
sensorineural hearing loss acoustic trauma
ototoxic drugs
Meniere’s disease
mixed hearing loss presbycusis

28. Purves Box 13-C