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HESP630- Electrophysiology > Final Exam > Flashcards

Final Exam Flashcards

1
Q

What are the benefits of a 2-channel recording?

A
  • Can get ipsilateral and contralateral waveforms

- Can get a horizontal montage

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2
Q

In patients with ANSD, why would cortical responses be present when the ABR is absent?

A
  • Cortical responses result from slow changes–post synaptic potentials
  • Brainstem responses occur because of fast action potentials, which require more neural synchrony.

ANSD results in neural dyssynchrony, thus the cortical responses would be present but the brainstem responses wouldn’t be.

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3
Q

What is the sensitive period for maximal plasticity for cochlear implantation in children?

A

3 years. 3.5-7 years there is a lot of variability. >7 years, you’re screwed.

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4
Q

How quickly does the P1 latency reach normal levels in children who are early implanted?

A

5 months

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5
Q

What consonants are evaluated in infants with hearing aids using the HearLab system?

A

/m/, /t/, /g/

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6
Q

What is the recommended MLR analysis for diagnosis of APD (according to Weihing et al, 2012)

A

Ear effect and electrode effect.

Less variability for electrode effect.

Ear effect:
(RA + RB)/2 (LA + LB)/2

Electrode effect:
(RA+LA)/2 (RB+LB)/2

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7
Q

What is the maturational time course of the cortical components going from infant to adult?

A

P1 and N2 are more prominent in children

Gradually shifts to P2 and N1 becoming prominent in adults. Latencies become adult-like around adolescence

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8
Q

Describe how you obtain an MMN (Mismatch Negativity)

A

Oddball paradigm–> present 1 regularly occurring stimulus and then an oddball (say 1 out of every 4). Subtract oddball from regularly occurring stimulus and get curve. Take area under the curve (difference waveform) as your MMN.

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9
Q

Why can’t the late responses be used for clinical disgnosis?

A

Highly variable

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10
Q

What measurement of the AN-CAP are you monitoring during VIIIth nerve surgery?

A

N1 (which is the same as wave I in ABR and AP in ECochG) [auditory nerve]

Wave I= distal end of the auditory nerve and Wave II= proximal end of the auditory nerve.

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11
Q

Why is ABR sensitivity for tumor detection so low (80%)? What can be done to increase sensitivity?

A

Only testing mid/high frequencies (2000-4000 Hz) with ABR. Thus, if the tumor affects low frequency region of the auditory nerve, then the ABR won’t pick it up. Can use stacked ABR to increase sensitivity.

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12
Q

What can be done to prevent phase cancellation of the low frequency components of the ABR?

A

Stacked ABR. Line all the waves up by wave V so that you obtain using HP noise.

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13
Q

Why is it so important to minimize physiological noise when obtaining stacked ABRs?

A

With stacked ABR, you’re measuring amplitude not latency after you line up all the wave Vs. Thus, if someone is noisy, it can cause a spurious increase in amplitude.

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14
Q

What analysis is used for evaluating the frequency energy of a response?

A

Fourier analysis [Fast Fourier Transform (FFT)]

FFT finds the amplitude energy of simple sine waves that make up a complex waveform.
Speech sounds- frequencies coded as timing differences in waveforms- can look at differentiation in terms of timing differences/phase

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15
Q

List 2 ways to analyze phase representation

A
  1. Time- look at timing differences between waveforms

2. Phaseogram- calculates radian differences automatically

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16
Q

What is the primary requirement for evoked potentials to be viable in a clinical setting?

A

Replicable/reliable waveforms

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17
Q

In what circumstances is it important to identify Wave I?

A
  • Neurodiagnostic ABR

- Wave I permits calculation of interwave latency values

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18
Q

What is the best recording setup to elicit a click-evoked wave I? Why?

A

Horizontal–> Because you have better alignment of the dipoles (same dipole)

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19
Q

Why can a contralateral recording help separate waves IV and V in the response?

A

With ipsilateral, you get a fused wave IV and V because the pathway doesn’t go through the LL.

With contralateral, go through LL and IC.

*Crossover of signal–will be measuring from 2 places/allows for better separation of the two waves.

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20
Q

What are the components of the ECochG? Which component reflects the DC component?

A
  1. Cochlear Microphonic (CM)–> closely resembles the sound stimulus. Reflects the alternating current, which mainly originates from the OHCs
  2. Action potential (AP)–> Generated by fibers of the auditory nerve.
  3. Summating potential (SP)–> a separate peak preceding the AP. May appear as a ledge or hump on the beginning of the AP. Arises from the cochlea.

SP reflects the DC component of hair cell receptor potential.

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21
Q

Why is ECochG used for diagnosis of ANSD?

A

ECochG allows you to see the cochlear microphonic. You would use rarefaction and condensation polarity to see the CM. The presence of a cochlear microphonic (CM) indicates ANSD because it informs OHC function. If ABR is abnormal and OAEs are present, CM may be present in patients without OAEs.

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22
Q

How is ECochG used for diagnosis of Meniere’s Disease?

A

Meniere’s Disease is characterized by abnormally large ECochG SP component. Repeatable SP and AP are recorded; AP amplitudes are calculated from a common baseline. The SP/AP ratio is calculated. Patient’s SP/AP ratio is compared in the suspected ear to the normal ear and to normative data. SP should be at least 1/2 AP in normal condition.

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23
Q

List 3 types of electrodes used in ECochG

A
  1. Tip trode–> placed in external ear canal but doesn’t touch TM
    Weakest but least invasive
  2. Tymptrode–> placed in ear canal and gently rests on the TM
  3. Transtympanic/Needle electrode–> placed through TM and rests on oval window
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24
Q

What might the absence of waves above I and II indicate?

A

Severe brainstem dysfunction that is incompatible with life. If get this result with someone in a coma, then this means that you are only getting a response from the auditory nerve and not the brainstem.

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25
Q

What might delays between waves I and III and III and V indicate?

A

Multiple Sclerosis

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26
Q

What does a prolonged separation between Waves I and III indicate?

A

Tumor on the auditory nerve

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27
Q

List advantages and disadvantages of toneburst ABR

A

Advantages:

  • Better estimation of NH
  • Tells about neural integrity
  • Absolute quiet not required

Disadvantages:

  • High level of skill required
  • Subjective interpretation of results
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28
Q

List advantages and disadvantages of ASSR

A

Advantages:

  • Automated
  • Avoid interpretation bias
  • Can test at high dB levels
  • Can test up to 4 frequencies at the same time
  • Good for severe to profound HL
  • Can test right/left ear at the same time

Disadvantages:

  • Overestimates hearing levels for normal hearing individuals
  • Patient needs to be completely still
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29
Q

How does ASSR compensate for neural adaptation?

A

A steady state stimulus will be ignored by the system. Thus, manipulation of the stimulus is desirable in ASSR. ASSR compensates by doing 100% modulation to turn the signal on/off and prevent the system from adapting.

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30
Q

What is the ideal modulation rate for measuring brainstem activity using ASSR?

A

> 60% but less than 100%. Usually around 80-90%

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31
Q

To get a response using ASSR, the ear must hear at the BLANK 1 frequency and the brain must respond at the BLANK 2 frequency.

A
  1. Carrier

2. Modulation

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32
Q

Sampling rate refers to the BLANK 1 scale and the bit rate refers to the BLANK 2 scale.

A
  1. Time

2. Amplitude

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33
Q

What low-pass setting should be used in infant hearing screening?

A

1500 Hz

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34
Q

What high-pass setting should be used in infant hearing screening? Why?

A

30 Hz; b/c infants have more low frequency energy in their responses. Do something higher (like 70-100 Hz) for adults

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35
Q

What advantages do chirps provide over clicks or tonebursts?

A

Chirps activate the entire BM at the same time. With tonebursts, you only get the basal end of the BM. With a chirp, it compensates for the tonotopicity of the BM and activates the low frequencies first, thus activating the entire BM.

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36
Q

List ways to optimize testing time when obtaining thresholds in babies.

A
  • Prepare the family by sending a letter outlining what the test is and why it’s important
  • Use a faster rate–> rates of 27.1 to 39/1/sec don’t degrade the response but don’t slow down testing time
  • Use ascending approach (if highly experienced tester)
  • Use 20-40 dB step sizes at suprathreshold levels with descending approach
  • No testing below minimum required intensity level (Ex. 20 dB nHL)
  • Don’t use step sizes less than 10 dB unless over 70 dB
  • Don’t repeat runs at suprathreshold levels
  • Test a high frequency first, then lowest frequency, then fill in the rest–> better in the highs (most likely where to see a SNHL) then fill in lows
  • Test assumed better ear first
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37
Q

Why are tonebursts used for ABR threshold estimation instead of pure tones?

A
  • Synchronous neural firing needed for brainstem response and this requires very brief stimuli
    Toneburst–> gated sinusoids (less than 1 sec)
    Continuous tone–> sinusoids with greater than 1 sec. duration. Gradual onset and offset so can’t use
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38
Q

What is the electrode montage for a 2-channel ipsi and contralateral recording?

A

Channel A:
Reference/negative- stimulus earlobe
Active/positive- High forehead (Fz)

Ground- low forehead

Channel B:
Reference/negative- contralateral earlobe

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39
Q

What is the electrode montage for a 1 channel horizontal recording?

A

Reference–> stimulus earlobe
Ground–> low forehead
Active–> reference earlobe

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40
Q

What is the electrode montage for an MLR recording?

A 
C3 (Left top of head)--> Active
C4 (Right top of head)--> Active
Forehead: Ground
A1 (Left earlobe)--> Reference
A2 (right earlobe)--> Reference
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41
Q

For which stimulus is it easier to obtain thresholds- 500 Hz or 4000 Hz? Why?

A

4000 Hz–> low frequency energy gets cancelled out by phase cancellations

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42
Q

Why would you start with a click when doing a threshold ABR with babies?

A
  • Good assessment of neural integrity
  • Can tell you where to start testing tone bursts
  • You get waves I, III, and V
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43
Q

Describe how you would use evoked potentials to evaluate generalization of training.

A

Trained to discriminate /mba/ and /ba/ and they found that this training generalized to discriminating /nda/ and /da/. Larger MMN after training. MMN helps you become sensitive to subtle differences.

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44
Q

What areas of the cortex shows activation to stimulation in early and late-implanted children?

A

Early–> auditory cortex and parietal cortex

Late–> only parietal lobe

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45
Q

Why is stimulus rate important in diagnostics?

A
  • Increased stimulation rate may enable detection of subtle auditory neuropathology
  • With increased rate, the auditory system is stressed beyond its functional capacity
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46
Q

What increase in latency would you see with an increase in rate of 10/sec?

A

0.1 ms increase with every rate increase of 10/sec

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47
Q

How can you tell if you have post-auricular muscle effect in the MLR?

A

If it is before 20 ms, then it might be muscle artifact and not a response.

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48
Q

What happens to amplitude with increased sweeps?

A

Decreases b/c the noise contributes to the overall amplitude.

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49
Q

What are the benefits of a horizontal montage?

A
  • Better Wave I–need to see wave I if you want to see differences between wave I and III.
  • with ECocHG you can see the cochlear Microphonic when you do a horizontal recording
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50
Q

What happens to the response when you raise the low-pass filter?

A

Get artifact

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51
Q

How does filtering enhance signal detection?

A

Cut out cortical response by raising high pass filter to 100 and cut-out high frequency noise because brainstem only phase locks to about 2000 Hz

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52
Q

What conditions must be met for neural activity to be detected at the scalp?

A
  • More synchronous firing
  • Open field
  • Dipoles must be spatially aligned
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53
Q

What are the effects of hypothermia on ABR latencies?

A

Delayed

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54
Q

Why are MLRs, arising from Heschel’s gyrus, relatively small at the scalp?

A

Tangential dipoles

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55
Q

Describe the developmental trajectory of onset latencies for clicks or speech stimuli.

A

Decreases from infancy to 5 years of age. Flat from 5-8 years of age. Increases from 8 years of age to adult. Thus, latency is earliest at 5 years of age.

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56
Q

Why can’t the FFR be used for obtained threshold responses to speech stimuli?

A

Need a very brief stimulus to generate the synchronous neural firing necessary to generate an ABR at threshold. A clear FFR is only generated with stimuli that are presented at levels of at least moderate intensity.

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57
Q

What are the effects of sleep on the MLR?

A

MLR is affected by subject state! As a result, it isn’t good for testing babies.

Stage 2 sleep results in a reduction in amplitude.
Stage 4 (delta) sleep wipes out the ABR.
Stage 5 (REM) sleep results in a normal ABR.
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58
Q

What are potential uses for evoked potentials in the hearing aid fitting for both children and adults?

A
  • P1 latency decreases and follows trajectory and gets early post-HA use
  • Making sure that sounds are audible (HearLab) for children
  • Maybe brain isn’t coding sound correctly even though you are giving them appropriate amount of amplification and they don’t like their hearing aids.
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59
Q

When testing children with ABR, AAA guidelines suggest a filter slope of no more than BLANK.

A

12 dB per octave

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60
Q

True or False: According to Stevens et al Int J Audiol 2013, the nape to high forehead electrode configuration produced the greatest amount of noise.

A

True

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61
Q

Which of the following conditions is less likely to produce observable AEPs at the scalp?

A

Closed field

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62
Q

True or False: Far-field responses have increased spatial resolution.

A

False

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63
Q

True or False: Action potentials travel long distances without a reduction in amplitude.

A

True

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64
Q

ABR Wave I originates from which anatomic structure?

A

Distal end of the 8th nerve

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65
Q

Which of the following statements is true regarding Heschl’s Gyrus?

A

The neurons on either sides of the gyrus are oriented at an angle to each other.

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66
Q

Which of the following statements regarding signal averaging is true?

A

The noise is truly random

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67
Q

A filter which reduces a signal above a given frequency but lets lower frequency energy pass through is known as BLANK

A

A low-pass filter

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68
Q

Which of the following statements is true regarding rarefaction polarity?

A

With rarefaction polarity, the TM is displaced laterally.

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69
Q

Which classification of evoked potentials is sensitive to the psychological state of the subject?

A

Endogenous

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70
Q

Which components are produced by a transient stimulus in the middle latency range?

A

Na, Pa, Nb

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71
Q

The cortex is more effective at producing relatively large scalp potentials for all but the following reasons:

A

The dipoles are oriented horizontally

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72
Q

Which of the following generalizations is true about early vs. late potentials?

A

The shorter latency potentials have less variability than the longer latency potentials.

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73
Q

For threshold measurement in infants, what recording window should be used?

A

25-30

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74
Q

When obtaining toneburst thresholds in infants, which rate is not so fast to degrade the response and not so slow to unnecessarily prolong testing times?

A

27.1 to 39.1/sec

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75
Q

What polarity is recommended for recording with a 500 Hz toneburst?

A

Alternating

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76
Q

Because the infant ABR is dominated by low frequency energy, what cut-off frequency is recommended for high-pass filter?

A

30 Hz

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77
Q

What are the recommended rise/fall and plateau times for a 2000 Hz toneburst?

A

1 ms rise/fall and 0 ms plateau

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78
Q

The click-evoked ABR estimates auditory function in which frequency range?

A

1000-4000 Hz

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79
Q

True or False: A disadvantage of using linear ramping for tone-burst testing is reduced frequency selectivity.

A

True

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80
Q

How many sweeps should be obtained when recording to a particular frequency and intensity level.

A

As many sweeps as are needed to produce a reliable response

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81
Q

What kind of ramping is recommended for toneburst ABRs?

A

Nonlinear Blackman

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82
Q

The advantages of earlobe rather than mastoid placement for the reference electrode include all but the following:

A

Wave I is larger for the mastoid placement

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83
Q

Reasons for starting the infant ABR with a click recording include all but the following:

A

The click signal is the least likely to produce a clear and reliable response

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84
Q

Mean narrowband chirp amplitude is how much larger than mean toneburst amplitude at 4000 Hz.

A

1.6

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85
Q

The following is true of the chirp stimulus:

A

Lower frequencies are presented before higher frequencies to compensate for the cochlear wave traveling way delay.

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86
Q

True or False: ASSR amplitudes are significantly larger in response to mixed modulation tones than in response to amplitude modulated tones alone.

A

True

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87
Q

True or False: Using ASSR, the lowest thresholds can be obtained in the first two weeks after birth.

A

False

88
Q

What is the best modulation frequency to use when testing infants with ASSR?

A

80 Hz

89
Q

True or False: A phase coherence value that is close to 1 indicates a high probability of a response being present.

A

True

90
Q

All but the following are advantages of ASSR over ABR

A
  • *Good predictor of thresholds close to normal hearing**
  • Better than click ABR for predicting thresholds for individuals with severe to profound hearing loss
  • Use of pure tones eliminates spectral splatter
  • Objective measurement
91
Q

When testing with ASSR, which of the following statements is true regarding the carrier frequency.

A

It is the area that is activated on the basilar membrane

92
Q

Which of the following conclusions did Hatton and Stapells (2011) make in their comparison of ASSRs obtained in infants using multiple or single stimuli in one or both ears.

A

The multiple stimulus ASSR technique is more efficient than the single stimulus ASSR technique.

93
Q

An appropriate modulation rate for eliciting a response from the thalamus or cortex would be:

A
94
Q

Advantages of ABR over ASSR would include all but the following:

A
  • *Minimal skill required**
  • Absolute quiet nor required
  • More accurate in newborns
  • Better for estimating normal hearing
95
Q

Why do you need to use modulated tones when testing with ASSR?

A

Steady signals will be ignored by the nervous system

96
Q

What modulation depth is being used when the stimulus is periodically turning on and off?

A

100%

97
Q

If a 500 Hz was modulated by frequency at 20%, what would the frequency range be?

A

450-550

98
Q

True or False: When you stimulate with different frequencies at the same time, you must use the same modulation frequency.

A

False

99
Q

True or False: With ASSR, a response occurs if the ear has hearing at the carrier frequency and the brain responds at the modulation frequency.

A

True

100
Q

True or False: Masking is not required when doing a bone-conduction ASSR.

A

False

101
Q

True or False: The ASSR can’t distinguish between SNHL and retrocochlear hearing loss.

A

True

102
Q

Which of the following analysis techniques is used to track how the response changes over time?

A

Sliding window analysis

103
Q

What duration do Skoe & Kraus (2010) recommend for post-stimulus period?

A

10-50 ms

104
Q

What were the cABR findings in children diagnosed with APD in the Rocha-Muniz et al (2012) article?

A

No differences in frequency encoding between children with APD and typically developing children

105
Q

With a conductive hearing loss, what happens to the waveform?

A

Latencies shift to become delayed (waveform moves to the right) and amplitudes remain same.

106
Q

True or False: Click ABRs are more sensitive to auditory impairments than ABRs elicited by speech

A

False

107
Q

Differences the encoding of speech syllables can be represented in the brainstem through all but the following:

A

Through differences in frequency energy.

108
Q

According to Anderson et al, 2010, how does noise affect speech-evoked brainstem responses in children who have difficulty hearing in background noise?

A

Delayed latencies in noise

109
Q

According to tonotopicity of the cochlea, what would be expected latencies for /ga/, /ba/, and /da/?

A

/da/ latencies would occur earlier than /ba/ latencies

110
Q

According to Skoe and Kraus (2010), what is the recommended stimulus presentation level for the cABR?

A

60-80 dB SPL

111
Q

True or False: cABRs can be elicited by both synthetic and natural speech stimuli.

A

True

112
Q

True or False: When testing with the cABR, duration of speech stimuli should be 40 ms or less.

A

False

113
Q

True or False: When testing with the cABR, optimal stimulus frequency would be greater than 300 Hz.

A

False

114
Q

True or False: Rocha-Muniz et al (2012) observed that the high frequency amplitudes were larger in children who are typically developing than in children who have been diagnosed with specific language impairment or auditory processing disorder.

A

False

115
Q

From elementary school to adolescent years, the following changes take place in the P300.

A

Latency decreases, amplitude increases

116
Q

True or False: Intersubject variance in the MMN is greater than intrasubject variance.

A

True

117
Q

True or False: The MMN is derived by adding the response waveform to the frequent stimulus to the response waveform to the rare stimulus.

A

False

118
Q

True or False: Attention to the rare stimulus is required to generate an MMN.

A

False

119
Q

True or False: The MMN can be generated in a newborn infant.

A

True

120
Q

True or False: Children with Specific Language Impairment have abnormal MMN responses.

A

True

121
Q

What AMLR recording parameters may produce a spurious PA?

A

Filter settings of 30 to 100 Hz

122
Q

Which of the following statements regarding sleep effects on AMLR is true?

A

A normal MLR can be obtained in Stage 5 sleep.

123
Q

If you have alcoholism in your family, which test might give you a clue that you are susceptible to becoming an alcoholic yourself?

A

P300

124
Q

True or False: When testing with MLR, electrode effect variance is smaller than the ear effect variance.

A

True

125
Q

True or false: The LLR amplitude increases with age.

A

False

126
Q

True or False: Larger LLR amplitudes in populations with clinical impairments may indicate over-allocation of neural resources.

A

True

127
Q

Which of the following statements is true regarding the P300.

A

It can be elicited with somatosensory stimulation

128
Q

True or False: The MMN reflects echoic memory.

A

True

129
Q

True or False: The amplitude of P2 is the primary measure of the MMN.

A

False

130
Q

According to Attias et al (2008), what was an important factor in the reduction or loss of the compound action potential.

A

Drilling the internal auditory meatus

131
Q

According to Attias et al. (2008), hearing preservation was accomplished in what percentage of small tumors?

A

77%

132
Q

What surgical approach is most effective for preserving facial nerve function?

A

Translabyrinthine

133
Q

True or False: Drugs have a greater effect on brainstem than on cortical function.

A

False

134
Q

Which of the following statements about the stacked ABR is not true as reported by Don et al (2012)

A

An interaural difference of 8% yields a sensitivity of 95% and a specificity of 88%

135
Q

Which of the following is a disadvantage of the retrosigmoid approach to removing vestibular schwannomas

A

Cerebellar retraction is a necessity

136
Q

Which near-field response is recorded during auditory intra-operative monitoring?

A

AN-CAP

137
Q

True or False: Use of mechanical stimulation can be used in facial nerve monitoring.

A

True

138
Q

What correction factors should you use in cases of hypothermia?

A

Subtract 0.2 ms from the wave I-V latency value for every degree of temperature below 37 degrees centigrade

139
Q

Which of the following statements regarding hypothermia is true?

A

When body temperature is less than 68 degrees fahrenheit the ABR disappears

140
Q

True or false: Wave V has an earlier latency and larger amplitude in women than in men.

A

True

141
Q

At what age are wave V click latencies the earliest?

A

early elementary school years

142
Q

If you subtract the waveform generated by a click plus 4 kHz high pass masking noise from a waveform generated by a click plus 8 kHz high pass masking noise, the derived waveform will contain energy corresponding to what frequency range?

A

4-8 kHz

143
Q

What is the primary measure of the stacked ABR?

A

Summed amplitudes from derived frequency bands.

144
Q

What are the 2 criteria for adequate electrode impedance?

A
  1. Low impedance

2. Balanced impedance across electrodes

145
Q

What is the effect of raising the low-pass filter?

A

Allowing more high frequencies deceases the amplitude because there is more noise that is let in

146
Q

What happens to the amplitude of the response when you increase the number of averages?

A

It decreases because you decrease the noise

147
Q

How does the frequency content relate to latency?

A

As latency increases, frequency content decreases.

148
Q

What are the advantages of using insert earphones when measuring evoked potentials?

A
  • practical, more comfortable for babies than large circumaural earphones
  • comfortable if reference electrode is earlobe
  • No ear canal collapse
  • Less electromagnetic stimulus artifact because sound source is separated from ear
  • Stimulus artifact doesn’t extend into recording Epoch
149
Q

Describe the effects of polarity on the ABR

A

8th nerve fibers fire when the BM is displaced upward but not downward. This happens during rarefaction but not condensation phase. So… brainstem latencies may be earlier with rarefaction polarity.

150
Q

What kinds of evoked potentials are more effected by subject state?

A

Endogenous

151
Q

List the 3 categories of EEG neural activity and define them.

A
  1. At rest– no stimulus
  2. Induced– response to stimulus NOT time locked
  3. Evoked–response to stimulus IS time locked
152
Q

What is a dipole?

A

(+) and (-) voltages separated in space

153
Q

What are the effects of geometric orientation of evoked potentials?

A

…….

154
Q

What is Nyquist’s Theorem and why is it important?

A

States that the sampling rate should be twice as high as the highest analog frequency. It is important because you want to get a precise measurement and extract all information. If you don’t do this you get aliasing.

155
Q

What conditions need to be met to detect voltage at the scalp?

A
  1. synchronicity–need neurons firing at the same time
  2. Dipoles need to be aligned–cortical ones are seen well. Orientation is okay but has to be aligned and oriented in same direction or else they will cancel each other out.
156
Q

What factors do you need to consider when choosing the amount of amplification?

A
  • Sampling rate
  • Bits
  • Gain (too much/too little)
  • Filters–> wider filder= larger recorded activity
  • Artifact rejection level
157
Q

What are the main two types of electrical activity that contribute to evoked potentials and how are they generated?

A

……

158
Q

How is the chirp stimulus different from a click stimulus?

A

Chirp compensates for temporal smearing by delaying the high frequencies relative to the lows. You want to use a chirp stimulus instead of a click because the chirp stimulates the whole region of the basilar membrane at the same time (a broad region) which results in a robust result.

159
Q

What kind of ramping should be used with the tone-burst stimuli and why?

A

Blackman ramping b/c there is more splatter with linear ramping.

160
Q

How do responses differ in response to a 500 Hz toneburst vs a 4000 Hz toneburst?

A

For the 500 Hz toneburst, the latency increases and the overall morphology is broader. For the 4000 Hz toneburst, the latency decreases and is more specific (not as broad).

161
Q

List reasons why it’s a good idea to start testing with a click stimulus.

A
  • Nice robust response under ideal circumstances
  • Get idea of neural conduction time because you can see if neurologically everything is ok
  • Wave I-V gives you information about the hearing loss
162
Q

What are some potential problems associated with bone-conduction testing?

A
  • Potential for large stimulus artifact (use alternating polarity to avoid this)
  • Output limitations
  • Large correction factor
163
Q

List ways to optimize efficiency during threshold ABR testing

A
  • Use faster rate (27.1 to 39.1/sec ideal b/c doesn’t degrade response or slow down testing time)
  • Use ascending approach (only if highly experienced)
164
Q

Which of the ABR waveform components is most important when obtaining thresholds and why?

A

Wave V- even when you decrease stimulus, you are more likely to see wave V than wave I.

165
Q

If you have to choose, which would be better for threshold with a baby whose parents are deaf–ASSR or toneburst ABR and why?

A

Depends on if hearing loss is sensory or neural/auditory neuropathy. If sensory use ASSR because it can distinguish b/w moderate and profound hearing loss (ABR is accurate to moderate HL) and child’s parents have SNHL. If neural/auditory neuropathy, use ABR b/c it can distinguish between sensory and neural HL (wave I/cochlear microphonic). ASSR can’t distinguish between cochlea/peripheral and retrocochlear hearing loss.

166
Q

What is the best modulation frequency for measuring responses from the inferior colliculus?

A

60 Hz+

167
Q

How much is the amplitude modulated for the ASSR and why?

A

100% because we are more sensitive?

168
Q

If you had to choose, which would be better for threshold testing with a 2 week old baby with a suspected mild unilateral hearing loss–ASSR or toneburst ABR and why?

A

Toneburst ABR would be better b/c ASSR has a lot of noise when patient is really young. Also, ASSR is more sensitive to severe to profound hearing loss and isn’t good to use for someone who is suspected to have a mild hearing loss. There was a study that showed that the results of ASSR aren’t very reliable in the first few weeks of life.

169
Q

How is phase analysis used in the ASSR?

A

Phase coherence is used to look for consistent locking to the phase of the stimulus, which confirms that the response is present.

170
Q

If you had to choose, which would be better for testing with a toddler suspected of having a retrocochlear hearing loss–ASSR or toneburst ABR and why?

A

Toneburst ABR b/c you can see the waveforms

171
Q

What limitations are there to testing 4 frequencies at once?

A

Level limitations becuase you can only go up so high and you have all this energy going into the ear so you won’t be able to present 110 dB simultaneously at 4 frequencies so you have to present one at a time when you go up. This is only the case when a severe hearing loss is suspected.

172
Q

What are the ramifications of overly restrictive filtering of the MLR?

A

May get false peaks (like 50-100 Hz)

173
Q

What type of surgical approach is used when hearing preservation is not an issue?

A

Translabyrinthine

174
Q

What is the recommendation for judging MLR as abnormal for APD diagnosis?

A

Using MLR electrode effect to see if there is a 50% difference between ears

175
Q

Describe normal developmental changes in the cortical response waveform.

A

Younger children generally have larger amplitude responses. It gets smaller with age (indicative of more efficient neural processing). In younger people, prominent peaks are P1 and N2. With adults, prominent peaks are P2 and N1

176
Q

What are the 3 auditory potentials that can be used to monitor the integrity of the cochlea and 8th nerve during surgery?

A
  1. ABR
  2. ECochG
  3. AN-CAP
177
Q

What kind of evoked potential is used for monitoring the facial nerve?

A

EMG of CN VII

178
Q

How would the P1 latency be used as a biomarker for management of ANSD?

A
  • P1– ability to perceive speech, actually hear sound
  • At infancy when tested: P1 normal (perceive speech ok, less likely to do CI right away); P2 abnormal (more likely to need to get CI right away)
179
Q

What is the neural mechanism underlying reduced plasticity after 7 years of age?

A

Cross-modal reorganization–> area in auditory cortex loses plasticity because those neurons are busy responding to other sources of stimulation (visual, vibrotactile, etc.)

180
Q

How would the P1 latency be used as a biomarker for management of severe to profound SNHL in kids?

A

P1 can be used as a biomarker for determining management of the kid, HA vs. CI. If the child receives a HA and you see a decrease in their P1 latencies, then HAs seem to be viable management option. If there is no decrease in P1 latency with HA, then audiologist may consider pursuing a CI to reduce the P1 latencies. For best results, a CI would be implanted before 3.5 years of age.

181
Q

How do the effects of noise on cortical responses differ for individuals with normal hearing or with ANSD?

A

Poor responses in noise for both people with normal hearing and ANSD at low levels. Response begins to decrease for ANSD before normal hearing at 80 dB in the normal hearing and the response is shifted, but no response at 80 dB in noise.

182
Q

What areas of the brain are activated by sound in an early, middle, and late implanted child?

A
  • Early implanted shows activity in auditory cortex and parietal cortex
  • Middle implanted shows……
  • Late implanted shows changes in parietal cortex
183
Q

In an early implanted child, how quickly would you expect the P1 latency to reach normal levels after hearing aid fitting or CI implantation?

A

Children who receive CIs under age 3 show delayed P1 latencies at hookup and then the P1 latencies decrease very rapidly at 1 week and 1 month after implantation such that they are within normal limits by 3-6 months after implantation. After the age of 7, the latencies aren’t so delated at hookup suggesting some development (albeit abnormal) and then there is some change in the initial over a month and then no change for over a year after implantation.

184
Q

Describe the relationship between P1 latency and early communicative development in young CI kids?

A

P1 latencies are in the normal range when pre-canonical and canonical babble are present.

185
Q

The following statements are true of short-latency responses:

A
  • They are unaffected by subject state

- They require synchronous neural firing

186
Q

Which of the following is true of a post-synaptic potential?

A

Slow membrane potential

187
Q

Which of the following statements is true regarding Heschl’s Gyrus?

A

The neurons on either sides of the gyrus are oriented at an angle to each other.

188
Q

Excessive noise spokes or small fluctuations in the waveform is the sign of what problem?

A

High-frequency electrical interference

189
Q

Which of the following is a solution for a bifid Wave I?

A

Change polarity

190
Q

Which 2 ABR peaks are often fused?

A

IV and V

191
Q

Which ABR peaks may be absent in a normal response obtained at a suprathreshold level?

A

II and IV

192
Q

According to Zack-Williams & Angelo, which of the following statements regarding sensitivity for detecting Meniere’s disease is true?

A

An SP/AP ratio >0.4 is found in 43% of individuals with Meniere’s

193
Q

Which of the following components of the ECochG requires an abrupt onset stimulus?

A

The action potential

194
Q

Which of the following is true about the summating potential?

A

It can only be recorded at high intensity levels

195
Q

When is masking necessary for ECochG testing?

A

Masking is never necessary

196
Q

Observation on a click-evoked ABR of a prolonged interval between waves I and V would be consistent with which of the following:

A

Retrocochlear pathology such as an acoustic neuroma

197
Q

Click-evoked auditory brainstem response are generally most closely correlated with behavioral thresholds for frequencies of:

A

2000-4000 Hz

198
Q

True or False: Brainstem responses require more amplification than cortical responses.

A

True

199
Q

True or False: According to Nyquist’s theorem, the sampling rate should be at least half the frequency of the highest frequency range in the stimulus.

A

False

200
Q

True or False: Low frequency sensorineural hearing loss affects the ABR to a greater extent than high frequency sensorineural hearing loss.

A

False

201
Q

True or False: An advantage of insert earphones is the reduction of stimulus artifact.

A

True

202
Q

What are the two criteria for adequate electrode impedance?

A
  1. Low impedance that is
203
Q

What aspect of dendritic orientation in the auditory thalamus prevents the generation of large far-field potentials?

A

The dendrites are oriented rather randomly and don’t allow the generation of large far-field potentials produced by the postsynaptic potentials.

204
Q

List 3 methods of classifying evoked potentials.

A
  1. Type of neural activity
  2. Latency (time)
  3. Stimulus
205
Q

Why can a contralateral recording help separate waves IV and V in the response?

A

With a contralateral recording, you are measuring the activity in the contralateral inferior colliculus (which does crossover). The electrical current in this arrangement is not going through the ipsilateral auditory nerve (which is responsible for originating wave I on the ABR). Thus, you are not going to see wave I on the auditory waveform. Furthermore, because of crossover of the signal that is seen in the ipsilateral inferior colliculus and the fact that you are measuring from 2 places in the auditory pathway, a separation in waves IV and V will be observed when doing a contralateral recording.

206
Q

List 2 benefits of combining a contralateral with a horizontal recording.

A
  1. You get an emphasized wave I with a horizontal recording that is lost with a contralateral recording b/c the horizontal montage measures electrical activity from the stimulated earlobe to the forehead and form earlobe to earlobe which strengthens wave I (from the auditory nerve) at the expense of a smaller wave V.
  2. You can compare the interpeak latency for retrocochlear pathologies.
207
Q

What are the possible consequences of applying too much amplification to a response?

A
  • Waveform is clipped

- Not enough points available to the A/D converter to represent the voltage extremes

208
Q

What are the possible consequences of applying too little amplification to a response?

A
  • Waveform is compressed
  • Too few points are being utilized to represent the maximum and minimum voltage values
  • Subtle morphological features are lost
209
Q

Name 3 strategies for avoiding 60 Hz interference.

A
  1. Not using a stimulation rate that is a perfect multiple of 60 (to avoid contamination)
  2. Shielding (trying to shield from electrical input)
  3. Filtering (to remove interference)
210
Q

What is averaging? Why is it important when measuring an auditory evoked response?

A

When stimulus-related changes in the EEG are consistent while the patterns of the spontaneous ongoing EEG are random. Therefore, if you average together the responses to the same stimulus presented many times, the amplitude of the evoked potential will grow and the amplitude of the random background EEG will be reduced to zero. This is important when measuring an auditory evoked response because it reduces the amplitude of the background EEG to zero.

211
Q

When would you use alternating or rarefaction/condensation polarities when testing with ECochG?

A

Alternating polarity would be used for recording SP component which cancels out the cochlear microphonic. A single polarity would be used when recording CM component (rarefaction and condensation separately).

212
Q

What might cause a large peak following Wave V?

A

Post-auricular muscle artifact

213
Q

List 2 sources of variability in recording ABRs.

A
  1. Fatigue from extended test sessions

2. From one test session to another

214
Q

What would cause a significant inter-ear wave latency difference in cases when retrocochlear pathology has been ruled out?

A

A conductive hearing loss. It results in a shift in the entire waveform and a change in the inter-ear wave latency

215
Q

What are the 3 components of ECochG and which is most often used in diagnosis of Meniere’s disease?

A
  1. Cochlear Microphonic (CM)
  2. Summating Potential (SP)
  3. Action potential (AP)

The Summating potential/action potential ratio is often used in the diagnosis of Meniere’s. IT is characterized by unusually large ECochG SP components.

HESP630- Electrophysiology (1 decks)

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