Aud 720 Exam 2 Part 3

Front 1

goal of electrode placement and type

Back 1

consistently record a clear, complete, and sufficiently large EP

Front 2

effect of electrodes on EP

Back 2

may alter latency, amp, polarity, morphology of EP components

Front 3

two types of electrode recordings

Back 3

monopolar=one electrode in a pair is located far enough from generator to be inactive (incapable of detecting response)
bipolar=resposne conducted by both electrodes in pair

Front 4

what are electrodes arranged in

Back 4

a montage

Front 5

noninverting electrode

Back 5

where electrical activity is detected when connected to an amplifier or an evoked response system

does not undergo polarity reversal=just makes it larger

Front 6

inverting

Back 6

reference
undergoes polarity reversal

Front 7

ground

Back 7

used for reduction of electrical interference and artifact, used to get optimal response to ensure high quality recordings

Front 8

types of electrodes (list)

Back 8

dis type **
disposable electrodes
tiptrode (combo of electrode and insert phone)

Front 9

interelectrode impedance

Back 9

opposition to alternating current flow between one electrode and another

Front 10

how is inter electrode impedance measured

Back 10

with commercially available equip=small electrical current applied automatically to one electrode and amy of current reaching 2nd electtode is determined

Front 11

max desierable interelectrode impedance

Back 11

500 ohms; 5K

Front 12

what should you aim for for inter electrode impedance

Back 12

balanced and low (balanced=1-2 ohms)

Front 13

what can you do if no balanced

Back 13

1. reapply electrode (rescrub)
2. press on electrode for several moments
3. move electrode slightly
4. add more conducting pass
5. secure electrode with additional paste

Front 14

10-20 international electrode system

odd vs. even

z
F
C
P
O
T
A
M
Fz
fpz-

Back 14

odd=left
event=right

z-midline
F-frontal
C-coronal
P-parietal
O -occipital
T-temporal
A-earlode
M-mastoid
Fz-high forehead
fpz- unibrow

Front 15

typical montage for ABR

Back 15

noninverting electrode=Cz or Fz
inverting electrode=mastoid or earlobe
ground=opposite ear or mastoid t

Front 16

how do we distinguish what is evoked from noise?

Back 16

2 electrodes on diff places will detect same amount of electrical interference which is common to each electrode then
-differential preamp reverese polarity of input and subtracts input of noninvertiing =

Front 17

common mode rejection ratio

Back 17

measure of ability of preamp to reject similar activity at both inputs
-ratio of amp output when sig is presented to only one input relative to output when same sig is presented to both inputs

-varies w/ fq and electrode impedance

Front 18

artifact rejection

Back 18

based on sensitivity setting of amp, any sig detected by electrodes that excessed a disgnated present voltage is not sent to sig averaged (erase time period from memory)

Front 19

filtering

Back 19

objective to suppress preferentially those fq components of activity that contain particularly high amount of noise and energy

can effect amp and phase of input fq components

Front 20

ideal filter

Back 20

pass some input fqs (pass band) and totally suppress other fqs (stop band)

Front 21

high pass filter

Back 21

reject lower fqs and pass higher fqs

5-500 Hz

Front 22

bandpass

Back 22

rejects energy below a certain cutoff and above a certain cutoff=passing energy between 2 limits

100-15, 1500-3000

Front 23

low pass filter

Back 23

1000-8000 Hz

Front 24

effects of high pass pilfering

Back 24

as cutoff fq increases=amp reduces by about 50% and the latency progressively decreases

Front 25

effects of low pass filtering

Back 25

a decrease cutoff fq from 10000-300 Hz eliminates noise and enhances waveform analysis

Front 26

dangers of filtering

Back 26

remove important portions of response

waveform may consist of low/high fq components that will be affected differently by same filter

Front 27

waveform analysis (list)

Back 27

AEP waveforms
morphology
latency
amplitude
polaritiy
repeatiblity

Front 28

AEP waveforms

Back 28

sequence of peaks and valleys occurring w/in specific time period

Front 29

Morphology of waveform

Back 29

pattern of overall shape of waves, described w/ reference with expected norm (subjective parameter)

Front 30

latency

Back 30

time interval btwn exact moment of stim presentation and appearance of a change (peak or valley) msec

Front 31

amplitude

Back 31

microvolts

peak to following valley

Front 32

polaritiey

Back 32

direction, which way is up

depends on electrode location relative to generator of response and which electrode is plugged into positive and neg voltage inputs of differential amps

Front 33

response reliability

Back 33

two or more averaged waveforms where overlaid are very similar

Front 34

factors affecting repeatablitiy

Back 34

pt movement
muscle acitivity

Front 35

identifying waves

Back 35

clearly larger in amplitude than background noise

Front 36

approximate latencies

Back 36

I: 1/2 ms
II: 3/4 ms
V: 6/6 ms

Front 37

interwave latency values

Back 37

I-III: 2 ms
III-V: 2 ms
I-V: 4 ms

Front 38

Wave V/I ratio

Back 38

adult expect 2:1
child expect 1:1

Front 39

extra peaks

Back 39

OK

related to vertex-to-ipsi mastoid electrode array

most prominent in newborns

Front 40

bifid wave I

Back 40

wave I has 2 closes spaced peaks
not the end of the world

Front 41

most common fused peak

Back 41

IV/V

Front 42

fusion of wave IV and V

Back 42

more likely in cochlear path than normal ears

Front 43

abnormal patterns

Back 43

almost no limit

age and gender have effect

Front 44

stimulus parameters (list)

Back 44

frequency
duration
intensity
rate
polarity
mode of transduction
mode of stim presentation
masking

Front 45

frequency of stim depnds on

Back 45

stim intensity
EAA properties of transfused
ear canal and ME properties affecting sound transmission
integrity of cochlea

-\

Front 46

what is the relationship between duration of response and duration of stim

Back 46

direct

Front 47

methods for fq specific ABR

Back 47

mask fq regions not intended to be part of stim
-response to stim derived from other sources (method of subtraction)
-use of tonal stim

Front 48

notched noise masking of stim

advantage
disadvantage

Back 48

ad: no more time to record than tonal stim
dis: spread of low-fq component of masker into notch, broad small amp and sometimes indistinct morph of V
extra peaks

Front 49

tone burst stimulus

Back 49

permits fq specific ABR simply quickly and w/ relatively inexpensive instrumentation

Front 50

duration

Back 50

sum of rise time, plateau time, fall time

Front 51

stim intensity

Back 51

latency decreases and amp increases as intisity increases (expected but not always)

Front 52

what happens to a template at a higher fq

Back 52

skinner b.c less variability throughout the highs

Front 53

ISI

Back 53

interstim interval

interval btwn sucessess stim

Front 54

rate

Back 54

number stim per sec

Front 55

what rate has little effect on ABR

Back 55

up to 20/sec

Front 56

why rate effects

Back 56

cumulative neural fatigue and adaption and incomplete recovery

-rate effects slow and fast component

Front 57

polaritiy: condensation

Back 57

stim on produced by movmeem transducer diaphragm toward TM ((+) pressure wave)

Front 58

polaritiy:rarefraction

Back 58

pressure wave in (-) direction produced by moment of transducer diaphragm away from TM

Front 59

polarity alternating

Back 59

swathing between condensation and rarefaction

Front 60

masking

Back 60

present masking noise to nontest ear to attempt to ensure test ear is actually contributer

-just put 50 dB nHE in the other ear!!!