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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
what is the OAE used in NBHS, providing better frequency response + harmonics of two tones together
TEOAE
26
what is the OAE used as a click stimulus to excite the whole cochlea
TEOAE
27
what OAEs are most clinically relevant (2)
1) DPOAE 2) TEOAE
28
- 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
Spontaneous OAE
29
- 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
Electrically evoked OAE
30
- 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
stimulus frequency OAE
31
generated when 2 closely spaced pure tones are presented simultaneously
DPOAEs
32
DPOAEs: distortion products are the results of __________ of the two tones
intermodulations/harmonics
33
strongest DPs are created by stimulus tone ratios of...
f2 / f1 = 1.2
34
what is the equations for the intermodulations created by two tones
fdp = f1 + N(f2 - f1) where N = any integer (positive or negative)
35
what is used as an indicator of cochlear status
intensity of one component in particular (2f1-f2)
36
f2 (2 f1 - f2)
measured across the freq spectrum relative
37
a robust TEOAE response can be obtained to a click stimulus of ~_______ dB if the hearing threshold is 20 dB or better
84dB
38
what does the waveform of the signal (in a TEOAE) represent
vibrations of the TM and mirrors the spectral properties of the stimulus
39
what are the stimulus repetition rates commonly used in TEOAEs
50-100/sec
40
signal average is necessary to extract TEOAE responses from _____________ noise
background noise
41
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
frequency bands
42
what are the clinical uses of OAEs
1) NBHS and school screenings 2) Otitis media 3) diabetes mellitus 4) ICU 5) surgical monitoring 6) meniere's disease
43
DPOAEs amplitudes are _________ with otitis media
decreased
44
Type I diabetes can exhibit __________ OAE amplitudes
reduced
45
OAEs can be used to monitor ____________ in ICU
ototoxicity
46
what is the clinical use of OAEs in surgical monitoring
to watch for compromised blood flow to cochlea
47
how can OAEs be used for Meniere's disease? OAEs will show amplitudes _______
may be used to follow progression however not a good diagnostic tool - amplitudes will be reduced
48
what are the three different sound-evoked (stimulus evoked) electrical potentials that can be recorded from the cochlea:
1) cochlear microphone (CM) 2) summating potential (SP) 3) action potential (AP)
49
a cochlear potential, the endocochlear potential (EP) is a ______ potential
steady potential - not evoked by sound
50
recordings of the sound evoked potentials
electrocochleogram
51
how can electrocochleograms be used?
as a diagnostic tool in assessing pathologies of the ear
52
where is the electrode of electrocochleogram commonly place?
on the cochlear capsule in ME space or in ear canal near TM
53
what will determine which response (potential) dominates the recording
the type of stimulus
54
the response to a transient stimulus (like a click) will be dominated by the _____
action potential (AP)
55
the response to a tone of a low freq will be dominated by the ________
cochlear microphonic (CM)
56
the response to a tone of a high freq will be dominated by the ________
summating potential (SP)
57
the ______ and ______ are generated by hair cells while the _______ is generated by the auditory nerve and cochlear nucleus
CM and SP; AP
58
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
cochlear microphonic
59
where was the electrode placed during the discovery of the cochlear microphonic
round window membrame
60
this observation of the CM generated more _______- than any other single phenomenon of hearing
research
61
what is the signal generated by in the CM
large population of OHCs
62
what does the signal of the CM mimic
the waveform of the stimulus
63
the amplitude of the CM _________ linearly with stimulus amplitude to a certain plateau, then _________ with increasing stimulus amplitude
increases ; diminishes
64
what is actually the summating potential ?
summation of sound evoked potentials
65
what is the SP generated by
cochlear hair cells (both inner and outer hair cells)
66
what contributes to the SP and can be altered if it is damaged
OCB
67
the form of the SP follows the __________ of the stimulus
envelope
68
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)
summating potential
69
summating potential is the result of the BM not being _________ the same in both directions - causes asymmetry of BM motion
deflected
70
what are the two components of the electrical response of hair cells to acoustic stimuli
1) continuous component (SP) 2) alternating component
71
what duplicates the acoustic stimulus envelope
continuous component (SP)
72
what corresponds to the pure sound frequency
alternating component (CM)
73
what do the continuous and alternating components depend on
the frequency of sound stimulation
74
amplitude of the SP grows with _________and dis more dominant in the __________ hair cells
frequencies; inner
75
the CM is more important for _______ frequencies and ____________ hair cells
low; outer
76
the AP has two distinct components called _____ and ______, which are negative peaks
N1 and N2
77
______ is generated by distal portion of the auditory nerve (compound action potential - CAP)
N1
78
what is the compound action potential (CAP)
the synchronous firing of the auditory nerve at the 1st node of Ranvier (high frequencies bc of basal portion has greater synchronicity)
79
______ is generated by the cochlea nucleus and is typically negligible due to long distance between cochlea and cochlea nucleus
N2
80
AP is the most important aspect for electrocochleogram for determining ___________
cochlear pathologies
81
CM and SP have no appreciable _________ relative to stimulus onset
latency
82
N1 peak exhibits a ________ msec latency
1.5 msec
83
the AP latency _________ and amplitudes _________ with increasing stimulus amplitude
decreases; increases
84
latency is ________ to high freq sounds than to low freq sounds of same intensity
shorter
85
what are the clinical uses of electrocochleography (ecog)
- 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

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