Quiz 1 Flashcards
1
Q
purpose of AEPs
A
Evaluate auditory system (AS) function and detect neural dysfunction
Objective, physiological responses to sound; useful for all ages & cognitive levels
2
Q
aep is useful for
A
Newborns (NBHS)
Difficult-to-test patients
Comatose or sedated patients
Monitoring auditory development (e.g., with HAs/CIs)
3
Q
what are AEPs
A
Electrical brain responses to sound (stimulus-locked)
Recorded via scalp electrodes
4
Q
measurement axis of aeps
A
Measured in microvolts (µV) (Y-axis) over milliseconds (ms) (X-axis)
Time x-axis (ms
Amp y-axis (microvolts)
5
Q
what is a rate study
A
Neural synchrony test
tests as under stress
6
Q
what is normal abnormal in rate study
A
High rate (90/s)
Normal: Wave V remains
Abnormal: Wave V disappears or shifts
Retro or ansd
7
Q
First human EEG (Berger)1929
A
1929
8
Q
First AEPs (Weaver & Bray: CM)
A
1930a
9
Q
ABR and ECochG development (Jewett, Williston, Coats, Eggermont)
A
1971–74
10
Q
AER Classification
A
By time epoch (latency)
Stimulus Type
Electrode Location
by source
11
Q
describe epoch (latency) of aep
A
ECochG → very early
0 - 1.5
Cochlea & distal 8 N
CM, SP, N1
ABR → early
1.5 - 12
Aud N & BS
MLR (AMLR) → middle
12 - 50
Thalamus & Aud cortex
ALR
50 - 300
Primary and Secondary Cortex
P300
>300
Higher-level cortical (cognitive) areas
Primary and association areas
12
Q
Exogenous
A
(ABR, ECochG): Response driven by stimulus; good for sleeping/unconscious patients
13
Q
Endogenous
A
(P300): Requires attention/awareness
14
Q
what goes under stim type
A
exo and endo
15
Q
what are electrode locations
A
far and near field
16
Q
describe far field
A
Standard recordings (ECochG, ABR, etc.)
electrodes are at a distance from the generator
17
Q
describe near field
A
Only with special setups (e.g., transtympanic ECochG, IOM)
electrodes are near the generator
18
Q
one in the ™ would be better and produce larger amps than one on the ear lobe or in the ear canal
A
true
19
Q
source
A
receptor potentials
neurogenic
20
Q
receptor potentials
A
Cochlear hair cells (ECochG, OAEs)
21
Q
neurogenic
A
Nerve & brainstem (ABR, MLR)
22
Q
AER Measurment Process
A
Stimulus → Ear
Neural response → scalp electrodes
Signal amplified & filtered
Converted (analog → digital)
Averaged → waveform displayed
23
Q
what is a din pin
A
Standard connector for analog audio signals, helps transfer to digital for analysis
24
Q
Components of AERs
A
ECochG
ABR
MLR
ALR
MMN
25
ecochg
Measures cochlea & distal auditory nerve
Components:
CM (~1 ms)
SP
AP = ABR Wave I
Recorded near the cochlea (ear canal or ™)
26
abr
Measures neural synchrony in the brainstem
Abnormal in ANSD (normal OAEs, abnormal ABR)
Waves I–V:
Wave I = ECochG AP
Wave V = most robust; used for threshold estimation
Latency: ~<15 ms
Infants have poorer morphology due to neuromaturation
27
MLR
Middle latency response
Peaks: Na, Pa
Origin: thalmus and primary aud cortex (A1)
Larger amp than earlier responses
28
ALR
Auditory late responses
Reflect conscious sound perception
Require awake state
Include primary & negative peaks
29
MMN
Mismatch Negativity
Negative waveform at ~250 ms
Indicates automatic detection of sound change
30
Clicks
pros: BB, rapid, abrupt onset, short duration, high intensity, strong response
cons: Not frequency-specific
31
tonebursts
pros: Frequency-specific , short duration
cons: Smaller response better threshold estimation
32
speech
pros: Natural, engages cortex
/ba/ /da/
cons: Complex & variable
More realistic stimuli
33
Factors Affecting AEPs Overview
Stimulus Factors
Acquisition Factors
Non-Pathologic Subject Factors
Waveform Analysis
34
what are the stim factors
stim type
duration and rise time
polarity
intensity
rate and interstimulus interval (ISI)
35
what are the acquisition factors
electrode setup
amp
filters
signal averaging
artifact rejection
36
what are the non-pathological subject factors
age
temp
state of arousal
meds
gender
37
what are the waveform analysis
presence
abs latency
interpeak
amp
interaural
morphology
reproducible
polarity
38
Broadband, short duration → great neural synchrony, poor frequency specificity (used in ABR & ECochG)
clicks
39
Frequency-specific, longer rise time → better frequency targeting, less synchrony (used for threshold ABR)
tonebursts
40
Used for complex or cortical responses (e.g., ASSR)
speech/am/fm tones
41
very short duration; better synchrony, poor frequency specificity
click
42
short durations
good for synchrony, poor for frequency specificity
43
long durations
good for frequency, poor for synchrony
44
what are the polarities
rarefaction
condensation
alternating
45
rarefaction
Stapes moves away from ™ → shorter latency, larger waves
46
condensation
Stapes moves toward/inward TM → longer latency
47
alternating
Averages both; masks ANSD, so don’t use for diagnosing ANSD
48
describe intensity changes
↑ Intensity → ↓ Latency, ↑ Amplitude, better morphology
More syncrhonized neural firing
↓ Intensity → ↑ Latency, ↓ Amplitude, poorer morphology
Fewer neurons firing
49
units of intensity
dB SPL, dB HL, dB SL, dB nHL (used in ABR)
50
High rate (>30/s)
↑ Latency, ↓ Amplitude, more neural fatigue
Shorter interstimulus levels
51
low rate
(<20/s): ↓ Latency, ↑ Amplitude, clearer waveforms
ABR standard: ~27.1/s
52
abr standard rate
~27.1/s
53
what is interstimulus interval (ISI)
time bw each stimulus
= 1000 ÷ rate → Must be > neuron refractory period
(Short = weak/missing waves; Long = strong, clear waves)
1s/rate
54
TDH-39/49 (Supra-aurals)
1–4 kHz peak, less ideal for ABR
55
ER-3 inserts
Preferred for ABR; better control, reduced resonance & crossover
56
Why use inserts for clicks?
Clicks are broadband; inserts provide cleaner delivery and reduce ear canal resonance and crossover
57
goal of stim type
Create large, synchronized neural responses via abrupt-onset stimuli (e.g., ABR, ECochG rely on neural synchrony)
58
short duration
Better synchrony, larger responses, worse frequency specificity
Click & brief tonebursts
59
long duration
Better frequency specificity, worse synchrony & smaller responses
long/continous tones, tonebursts, pips, speech
60
Abrupt, rapid onset, short duration; broadband (1000–4000 Hz or 2-4 kHz on audio); standard duration: 100 µs (0.1 ms)
click
61
Frequency-specific; used with specific rise/fall times and plateau
tonebursts
62
stim for ABR (for threshold estimation)
tonebursts
63
stim for ECochG & ABR (onset responses)
clicks
64
ABR is an onset response →
synchrony > duration
65
what is duration
total length of stimulus
66
what is rise time
time to reach full intensity
67
duration/rise time & effect of clicks
Very short (~100 µs)
Maximizes synchrony; broadband
68
duration/rise time & effect of tonebursts
Short rise/fall times + plateau
mroe frequency specificity
69
duration/rise time & effect of pure tones
Long rise time
Highly frequency specific; less synchrony
70
what is 202 envelope
500 Hz tone
2 ms rise, 2 ms plateau, 2 ms fall = 8 ms total duration
Common for toneburst ABR
71
blackman window
Used to reduce spectral spread (improves frequency specificity)
72
Short rise =
better synchrony (ABR)
73
Longer rise =
better frequency specificity (thresholds)
74
better synchrony, worse frequency specificity
click
75
better frequency specificity, lower synchrony
toneburst
76
what polarity dont we use if we want to diagnose ansd
alternating
77
what is polarity
When delivering the stimulus it is how the transducer diaphragm is moving
78
rarefaction
Stapes moves away from TM→ shorter latency, larger amp
79
condensation
Stapes moves toward TM → longer latency, smaller amp
80
alternating
Averages both → don't use for ANSD, may cancel response
81
what happens with increased intensity
↓ Latency, ↑ Amplitude, better waveform
More intense = more neurons firing = stronger, earlier signal
82
what happens with decreased intensity
↑ Latency, ↓ Amplitude, poor morphology
83
intensity units
dB nHL = normal hearing level (used in ABR)
dB peSPL = peak equivalent SPL; used for short-duration stimuli (e.g., clicks)
84
intensity at cochlea is influenced by
Transducer type
Ear canal size
Middle ear function
85
what is rate
stimuli per second
86
what is ISI
Interstimulus Interval
time between stimuli = 1000 ÷ rate (ms)
1s/rate
87
20/s ISI
1000/20 = 50ms
88
10/s ISI
1000/10 = 100ms
89
81.1 ISI
1000/81.1 = 12ms
90
ISI must match neuron recovery time
TRUE
91
Fast neurons
(ants 🐜) = ABR/ECochG = short recovery
92
Slow neurons
(sloths 🦥) = MLR/Late AEPs = long recovery
93
ISI > refractory period
clear waves, strong response (neurons fully recover)
94
ISI < refractory period
egraded/missing response (neurons have incomplete recovery)
95
Wrong rate can mimic pathology → always match stimulus to neural population
TRUE
96
inserts vs supras
Inserts (ER-3)
Adds ~0.9 ms delay to latencies
Reduces stim artifact (clearer wave I)
Greater IA, better fit
Always report transducer used
Supras (TDH-39)
No added delay
May blend artifact with Wave I
Risk of ear canal collapse
Must subtract .9ms if comparing to inserts
97
stim generator
produces as
98
transducer
delivers the sound
99
electrodes
Pick up brain’s response (placed on scalp, ear, etc.)
100
amplifier
Boosts tiny electrical responses
101
filters
Remove background noise/artifacts
102
signal averager
Repeats and averages to enhance true responses, includes artifact rejection
103
trigger system
Aligns stimulus with the brain response (response delay)
104
processor & display
Analyzes and shows/prints the final waveform
105
electrodes
Detects AEPs and sends it to the system
Proper setup - minimizes noise, ensures accurate latency & amplitude
106
Disc/Cup Electrodes
Scalp recordings
different sizes
reusable
107
disposable electrodes
pre-gelled and adhesive
single use
costs more, design limited, has expiration dates
108
Ear Canal Electrodes
Tiptrode/Tymptrode
ecochg
insert into ear canal
wire elctrode with silastic tubing with gel
109
Transtympanic electrodes
ECochG, CI candidacy testing
Inserted through the eardrum to record from promontory
110
Subdermal Needle Electrodes
OR, intraoperative monitoring
Penetrates skin for strong signal; gel-tipped
111
1 channel recording
3-4 electrodes
1 ear at a time
1 waveform
abr threshold testing and screenings
slower
112
2-channel recordings
4+electrodes
records both at once or ipsi and contra
2 waveforms
neurodiagnostic testing, ANSD evals, & retro investigations more detailed
faster
113
cz
top of head
114
fz
forhead midline
115
A1/A2:
Left/Right earlobe or mastoid
116
M1/M2
Left/Right mastoid
117
odd numbers
left
118
even numbers
right
119
non-inverting polarity
Cz or Fz (active) → signal is kept in original form
120
inverting
A1/A2 or mastoid (reference) → signal is flipped 180° (mirror image)
121
why do we invert
Cancels out noise (EEG) by subtracting the inverted reference signal → leaves only the AEP
122
what is the purpose of filters
Improve signal clarity by removing unwanted electrical noise
Allow specific frequency ranges through, block others
123
types of filters
high pass
low pass
band pass
band reject
124
high pass filter
passes highs and blocks lows
100 Hz HPF → blocks <100 Hz
125
low pass filter
passes lows and blocks highs
3000 Hz LPF → blocks >3000 Hz
126
band pass filter
allows mid-range, frequencies within a range, blocks outside
Most common for ABR
30–3000 Hz for ABR
3-50 avoid - too restrictive
127
band reject filter
Blocks specific frequency (e.g., 60 Hz hum) Blocks a specific frequency range, lets others pass
60 Hz notch filter
128
Normal EEG noise
<30hz
129
neuromuscular activity noise
100–500 Hz (partial overlap with AEP)
130
power line/lignts
60 Hz (sinusoidal wave)
131
ABR signal (main energy)
~100–3000 Hz
132
what is filter slope
Describes how sharply unwanted frequencies are attenuated
Measured in dB per octave (e.g., 12 dB/oct)
133
Steeper slope =
sharper cut-off (important for later AEPs)
134
Amplifier
Boosts tiny brain signals (<1 µV) to readable levels
135
gain
how much stronger the signal is after going through the amplifier
~100,000x original signal
Needed because wave V is around 0.5 µV
136
Electrode Setup Tips
Place electrodes on different areas (e.g., Cz and A1) to maximize CMR
Avoid placing both on forehead → may cancel the AEP itself
137
what are artifacts
unwanted electrical activity
138
types of artifacts
Electrical: internal device noise
Electromagnetic: lights, phones
Electrophysiologic: patient movement, heartbeat
139
how to reduce artifacts
Turn off external devices
Ask patient to relax
Use artifact rejection setting (e.g., discard >10 µV trials)
140
Makes tiny brain signals large enough to read
amplifier
141
Boosts tiny AEP signals to visible level
amplifier
142
Cancels out shared noise bw electrodes
cmr
143
Cancels shared noise between electrodes
cmr
144
Blocks out random electrical noise
artifact rejection
145
Removes contaminated sweeps from averaging
artifact rejection
146
Repeats sounds & averages responses to boost the real signal and shrink the noise
signal averaging
147
Repeats & averages to enhance the true AEP
signal averaging
148
Tells the system when to start recording the brain’s response
triggering
149
Starts recording in sync with stimulus
triggering
150
subject factors
age
body temp
state of arousal
meds
muscle activity
gender
151
age & maturation
AEPs mature at different times:
ECochG → matures first
Then ABR, Middle Latency, and Cortical (last)
Maturation pattern:
Peripheral → Central
Caudo-rostral (tail → head)
Pre-term infants: Immature AEPs → maturation continues postnatally
152
body temp affects
Normothermia: Normal temp (37°C / 98.6°F) → no major AEP change
Fever or hypothermia (even ±1°C) → can affect latency/amplitude
153
Waveform Analysis Factors to analyze
Presence/Absence of expected waveforms
Absolute Latency
interpeak latency
amplitude
interaural difference
morphology
154
abs latency
Time (in ms) from stimulus onset to peak or valley
155
interpeak latency
vTime between two peaks (e.g., Wave I–V); used to assess neural conduction
156
amplitude
Measured in µV (microvolts)
Difference between peak & trough (most common method)
Larger = stronger response
157
interaural difference
Compare right vs. left ear responses; should be minimal
158
morphology
Shape, clarity, and reproducibility of the waveforms
159
latency
Time (ms) from stimulus to wave peak/valley
160
epoch
Recording time window after each stimulus
161
epcoch for abr
10–15 ms
162
why are epochs important
Wave Overlap: AEPs often overlap; use correct epoch to isolate desired response
163
polarity
direction of the wave (up or down)
164
polarity is influenced by
Electrode placement
Generator site
Stimulus polarity: rarefaction, condensation, or alternating
165
amplitude
Measured in microvolts (µV)
Most common: peak-to-following-trough
Smaller amplitude may still be clinically relevant if repeatable
166
what is the purpose and value of AEPs
Objective tool for detecting auditory disorders and hearing loss (HL)
Vital for infants, children, and non-responsive patients
167
what do AEPs support
Newborn hearing screening (NBHS)
Monitoring CNS development after HA/CI
Identifying neural dysfunction (e.g., ANSD, retrocochlear issues)
168
what are they useful for
Useful for patients who can’t complete behavioral testing:
Infants, comatose, uncooperative, or cognitively impaired individuals
169
what should you do before testing
Explain test clearly
Ensure patient is comfortable, quiet, and still (asleep is ideal)
Remove makeup, lotions; check medications
Skin prep:
Alcohol wipe → dry → Nuprep gel to reduce impedance
170
impedance
resistance to electrical current flow
171
Low impedance =
better signal quality
172
what are electrode impedance goals
Individual: ≤ 3–5 kΩ
Between electrodes: ≤ 2 kΩ
173
do we want balance across all electrodes
yes
174
high impedance could be
Reapply gel, re-prep, re-tape, or replace wires
175
10-20 system
Cz: Vertex (non-inverting/active) top of head
Fz/Fpz: Forehead and low forehead (Fpz often ground) noninverting
A1/A2: Earlobes (inverting/reference)
M1/M2: Mastoids (alternative references)
Odd numbers = left, Even = right, Z = midline
176
Secure placement + low impedance =
reliable data
177
Non-inverting (Active):
Vertex (e.g., Cz or Fz)
178
Inverting (Reference):
Earlobe or mastoid (e.g., A1, A2)
179
Ground:
Anywhere on the body (commonly Fpz)
180
1-channel recording
basic abr
181
2-channel
llows ipsilateral and contralateral recordings
Contralateral: typically no Wave I/III, but stronger Wave V
182
how to improve recordings
Use large ear tips to reduce sound leakage
Braid electrode wires, avoid wire tangling
Don’t mix electrode types/metals
Keep transducer wires separate from electrodes
In infants, avoid placing ground near heart
For bone conduction: keep electrodes far from oscillator
183
how to eliminate external noise
Turn off nearby electronics (e.g., phones, monitors)
Position preamp away from devices
Test in a quiet, shielded space
184
recording concepts
signal averaging
epochs
artifact rejection
185
signal averaging
Brain response is time-locked, noise is random
Repeat stimulus and average responses
Improves SNR (signal-to-noise ratio)
Helps detect small responses (~0.5 µV)
186
epochs
Short time window (e.g., 10–15 ms for ABR) after stimulus
Trigger pulse aligns system to stimulus onset
187
artifact rejection
Filters out:
Electrical (internal)
Electromagnetic (external devices)
Physiologic (muscle, heart)
Excludes responses over a set voltage threshold (e.g., 10 µV) to reduce contamination
