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Anatomy and Physiology > Signals of Cochlear Origin: OAEs and Gross Potentials > Flashcards

Signals of Cochlear Origin: OAEs and Gross Potentials Flashcards

1
Q

Who discovered that sound energy produced by the ear could be recorded in the ear canal?

A

David Kemp

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2
Q

Who discovered the electromotility of OHCs

A

Ed Brownell

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3
Q

Who discovered the cochlear amplifier?

A

Hallowell Davis

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4
Q

How did H. Davis describe the cochlear amplifier?

A

mechanism by which the ear responds to and resolved near-threshold stimuli

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5
Q

sounds of cochlear origin that can be recorded by a microphone fitting into the external ear cana

A

OAEs

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6
Q

what do the sounds in OAEs represent?

A

retrograde TM vibration produced in the cochlea and transmitted back through the ME

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7
Q

___________ is the source of the vibrations of OAEs

A

cochlea amplifier

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8
Q

cochlea amplifier deals with the OHC motility designed to overcome traveling wave energy loss due to __________

A

damping

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9
Q

when the cochlea amplifier provides more energy than what is needed to overcome the damping loss, then amplification ________ and energy escapes the inner ear in retrograde fashion

A

becomes possible

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10
Q

what are OAEs a result of?

A

the nonlinear nature of the cochlear amplifier

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11
Q

what are the different theories about OAE reverse propagation? (2)

A

1) compression wave theory
2) traveling wave theory

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12
Q

OAE exits cochlea dominantly through fluid

A

compression wave theory

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13
Q

OAE travels along cochlear partition
- backward direction

A

traveling wave theory

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14
Q

what theories align most with OAE reverse propagation

A

both compression and traveling wave theory

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15
Q

what are some of the limitations of OAEs (4)

A

1) sensitive to minor conductive loss (ME fluid/ear canal debris)
2) only indicative of sensory transmissive HL (damaged OHCs or cochlear amplifier dysfunction)
3) absence = doesn’t mean abnormal hearing
4) do not evaluate signal transduction by hair cells

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16
Q

what are the 5 recognizable OAEs

A

1) SOAE
2) EEOAE
3) SFOAE
4) DPOAE
5) TEOAE

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17
Q

how many sponaneous origin(s) and stimulus evoked OAEs are there

A

one spontaneous origin
4 stimulus evoked

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18
Q

SOAE is the ____________ OAE

A

spontaneous

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19
Q

EEOAE is the _________ OAE

A

electrically evoked OAE

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20
Q

SFOAE is the ______________ OAE

A

stimulus frequency OAE

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21
Q

DPOAE is the _________ OAE

A

distortion product OAE

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22
Q

TEOAE is the ____________

A

transient evoked OAE

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23
Q

what is the most accurate OAE that is used with animals and/or CIs

A

EEOAE

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24
Q

what is the OAE that is a response to pure tone stimulus

A

SFOAE

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25
Q

what is the OAE used in NBHS, providing better frequency response + harmonics of two tones together

A

TEOAE

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26
Q

what is the OAE used as a click stimulus to excite the whole cochlea

A

TEOAE

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27
Q

what OAEs are most clinically relevant (2)

A

1) DPOAE
2) TEOAE

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28
Q
  • prevent in 60-70% NH adults but overall less prevalent
  • more prevalent in females and in right ear, as well as with newborns (cochlear maturation)
  • present as one or several peaks at diff frequencies
A

Spontaneous OAE

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29
Q
  • elicited by passing a small electrical current across cochlea
    (mimics acoustic stimuli)
  • invasive placement of electrodes
    (used in research animals/possible in CI patients)
  • advantage being the response measured by electrode is relatively noise free
A

Electrically evoked OAE

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30
Q
  • response to continuous pure tones
  • more difficult to extract from other signals present in ear canal
  • have NOT found their way into clinical or research practice
A

stimulus frequency OAE

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31
Q

generated when 2 closely spaced pure tones are presented simultaneously

A

DPOAEs

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32
Q

DPOAEs: distortion products are the results of __________ of the two tones

A

intermodulations/harmonics

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33
Q

strongest DPs are created by stimulus tone ratios of…

A

f2 / f1 = 1.2

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34
Q

what is the equations for the intermodulations created by two tones

A

fdp = f1 + N(f2 - f1)
where N = any integer (positive or negative)

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35
Q

what is used as an indicator of cochlear status

A

intensity of one component in particular
(2f1-f2)

36
Q

f2 (2 f1 - f2)

A

measured across the freq spectrum relative

37
Q

a robust TEOAE response can be obtained to a click stimulus of ~_______ dB if the hearing threshold is 20 dB or better

A

84dB

38
Q

what does the waveform of the signal (in a TEOAE) represent

A

vibrations of the TM and mirrors the spectral properties of the stimulus

39
Q

what are the stimulus repetition rates commonly used in TEOAEs

A

50-100/sec

40
Q

signal average is necessary to extract TEOAE responses from _____________ noise

A

background noise

41
Q

click stimuli in TEOAEs do excite the whole cochlea, but also the response can be split into _____________ to yield a frequency-specific indication of cochlear status
- what are you seeing on the Corti

A

frequency bands

42
Q

what are the clinical uses of OAEs

A

1) NBHS and school screenings
2) Otitis media
3) diabetes mellitus
4) ICU
5) surgical monitoring
6) meniere’s disease

43
Q

DPOAEs amplitudes are _________ with otitis media

A

decreased

44
Q

Type I diabetes can exhibit __________ OAE amplitudes

A

reduced

45
Q

OAEs can be used to monitor ____________ in ICU

A

ototoxicity

46
Q

what is the clinical use of OAEs in surgical monitoring

A

to watch for compromised blood flow to cochlea

47
Q

how can OAEs be used for Meniere’s disease?
OAEs will show amplitudes _______

A

may be used to follow progression however not a good diagnostic tool
- amplitudes will be reduced

48
Q

what are the three different sound-evoked (stimulus evoked) electrical potentials that can be recorded from the cochlea:

A

1) cochlear microphone (CM)
2) summating potential (SP)
3) action potential (AP)

49
Q

a cochlear potential, the endocochlear potential (EP) is a ______ potential

A

steady potential
- not evoked by sound

50
Q

recordings of the sound evoked potentials

A

electrocochleogram

51
Q

how can electrocochleograms be used?

A

as a diagnostic tool in assessing pathologies of the ear

52
Q

where is the electrode of electrocochleogram commonly place?

A

on the cochlear capsule in ME space or in ear canal near TM

53
Q

what will determine which response (potential) dominates the recording

A

the type of stimulus

54
Q

the response to a transient stimulus (like a click) will be dominated by the _____

A

action potential (AP)

55
Q

the response to a tone of a low freq will be dominated by the ________

A

cochlear microphonic (CM)

56
Q

the response to a tone of a high freq will be dominated by the ________

A

summating potential (SP)

57
Q

the ______ and ______ are generated by hair cells while the _______ is generated by the auditory nerve and cochlear nucleus

A

CM and SP; AP

58
Q

what was termed the discovery of when a person spoke into the animal’s ear you could hear the speech sounds as if the ear were functioning like a microphone

A

cochlear microphonic

59
Q

where was the electrode placed during the discovery of the cochlear microphonic

A

round window membrame

60
Q

this observation of the CM generated more _______- than any other single phenomenon of hearing

A

research

61
Q

what is the signal generated by in the CM

A

large population of OHCs

62
Q

what does the signal of the CM mimic

A

the waveform of the stimulus

63
Q

the amplitude of the CM _________ linearly with stimulus amplitude to a certain plateau, then _________ with increasing stimulus amplitude

A

increases ; diminishes

64
Q

what is actually the summating potential ?

A

summation of sound evoked potentials

65
Q

what is the SP generated by

A

cochlear hair cells (both inner and outer hair cells)

66
Q

what contributes to the SP and can be altered if it is damaged

A

OCB

67
Q

the form of the SP follows the __________ of the stimulus

A

envelope

68
Q

what is sensitive to pressure within the cochlea and can be used to help disorders associated with distension of Reissner’s Membrane (like Meniere’s)

A

summating potential

69
Q

summating potential is the result of the BM not being _________ the same in both directions
- causes asymmetry of BM motion

A

deflected

70
Q

what are the two components of the electrical response of hair cells to acoustic stimuli

A

1) continuous component (SP)
2) alternating component

71
Q

what duplicates the acoustic stimulus envelope

A

continuous component (SP)

72
Q

what corresponds to the pure sound frequency

A

alternating component (CM)

73
Q

what do the continuous and alternating components depend on

A

the frequency of sound stimulation

74
Q

amplitude of the SP grows with _________and dis more dominant in the __________ hair cells

A

frequencies; inner

75
Q

the CM is more important for _______ frequencies and ____________ hair cells

A

low; outer

76
Q

the AP has two distinct components called _____ and ______, which are negative peaks

A

N1 and N2

77
Q

______ is generated by distal portion of the auditory nerve (compound action potential - CAP)

A

N1

78
Q

what is the compound action potential (CAP)

A

the synchronous firing of the auditory nerve at the 1st node of Ranvier (high frequencies bc of basal portion has greater synchronicity)

79
Q

______ is generated by the cochlea nucleus and is typically negligible due to long distance between cochlea and cochlea nucleus

A

N2

80
Q

AP is the most important aspect for electrocochleogram for determining ___________

A

cochlear pathologies

81
Q

CM and SP have no appreciable _________ relative to stimulus onset

A

latency

82
Q

N1 peak exhibits a ________ msec latency

A

1.5 msec

83
Q

the AP latency _________ and amplitudes _________ with increasing stimulus amplitude

A

decreases; increases

84
Q

latency is ________ to high freq sounds than to low freq sounds of same intensity

A

shorter

85
Q

what are the clinical uses of electrocochleography (ecog)

A
  • estimate auditory thresholds in children difficult to test
  • diagnose present of endolymphatic hydrops
  • monitor cochlear function during surgery and cochlear implant insertion
  • record residual hearing using electrode on CI array as the non-inverting (active) electrode

Anatomy and Physiology (17 decks)

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