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electrophysiology > midterm > Flashcards

midterm Flashcards

1
Q

describe the amplitudes of a response in correlations with latencies

A

the shorter the latency, the smaller the amplitude.

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2
Q

describe how the frequency spectrum is related to latency

A

the shorter the latency the higher the frequency spectrum

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3
Q

how does stimulation rate relate to latency

A

the shorter the latency, the faster the stimulus rate.

does this mean: the faster the stimulation rate the shorter the latency?

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4
Q

how are latency and variability relate?

A

the shorter the latency, the smaller the variability

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5
Q

how does electrode position relate to latency?

A

small shifts in electrode location can alter waveform morphology. the shorter the latency, the more far-field the response.

what does far-field response mean?

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6
Q

how susceptible is a response to a “state” change?

A

the shorter the latency, the less susceptible to changes in the subject’s state.

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7
Q

describe the rate of maturation in relation to latency

A

the shorter the latency, the more rapidly maturation proceeds

what the fuck does this mean?

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8
Q

name the 4 stimulus factors used when recording bioelectrical fields

A
  • earphones
  • type (tonegs, clicks, speech)
  • intensity
  • stimulation rate
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9
Q

name 2 subject factors when recording bioelectric fields

A
  • age

- awake or asleep state

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10
Q

name 5 main recording factors when recording bioelectric fields

A
  • Electrodes (impedance, montages)
  • Differential Amplification
  • A - D conversion (amplitude resolution, sampling rate, time base)
  • Averaging
  • Filtering (high pass, low pass, slope)
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11
Q

what is a major challenge in ABR?

A

maximizing the detection of the signal!

a sound-evoked electrical signal is small/extraneous biologic and environmental noise is high

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12
Q

One of the recording factors in recording bioelectric field is electrodes. name some variations in the electrodes that can make a difference.

A

impedance
montages

-what is ‘montages’?

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13
Q

One of the recording factors in recording bioelectric field is A-D conversion. name some variations in A-D conversions that can make a difference

A
  • amplitude resolution
  • sampling rate
  • time base
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14
Q

One of the recording factors in recording bioelectric field is filtering. name some filtering variations

A
  • high pass
  • low pass
  • slope
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15
Q

What does latency mean?

A

point in time relative to stimulus onset

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16
Q

what does trigger mean?

A

beginning of time window. signals averager to enable alignment of all stimulus presentation sweeps

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17
Q

what is a pre-stimulus interval?

A

the period between trigger and stimulus.

-enables assessment of non-stimulus-related brain activity.

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18
Q

what is rate? (in terms of a stimulus)

A

the number of stimulus repetitions per second

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19
Q

what is ISI?

A

interstimulus interval

-time from offset of one stimulus to onset of the next

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20
Q

what is SOA?

A

stimulus onset asynchrony

-time from onset of one stimulus to onset of the next

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21
Q

what is stimulus measured in?

A

level or intensity. its measured in dB SPL or dB nHL

dB nHL: referenced to normal threshold for that particular stimulus
dB SPL: usually measured as peak SPL

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22
Q

what is the goal of ABR (in terms of stimulus)?

A

to collect the responses as quickly as possible to minimize test time
-you are limited by the fact that the repetition rate must be slow enough to eliminate the adaptation of the response you are recording

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23
Q

does stimulus rate matter? why?

A

Rate matters. Once the rate is super fast (ex 66.6/sec). If your pt has some kind of a problem that is effecting the auditory response to sound, if you stress the system and you see that the system cant keep up it becomes clinically useful and provides a red flag if the pt. isnt keeping up.

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24
Q

what are some things to consider when picking a stimulus rate?

A
  • stimulate as fast as possible; save time
  • adaptation
  • latency and time epoch of the response of interest
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25
Q

Is there an ANSI standard for stimulus intensity?

A
  • No ANSI Standard:
    1. often referenced to normal threshold for that stimulus expressed as dBnHL
  1. referenced to sound pressure level:
    if the stimuli are short (clicks, tone pips), we measure the sound pressure level of the peak of the stimulus, and express the level as peSPL.
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26
Q

what are some stimulus transducers?

A

headphones
insert earphones
loud speakers
bone vibrators

-the type of earphone can affect the quality of the click and therefore the response

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27
Q

what are some characteristics that are associated with using insert earphones?

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 does not extend into recording epoch
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28
Q

define condensation

A

headphone diaphragm is displaced outwardly. the TM is displaced medially

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29
Q

define rarefaction

A

the headphone diaphragm is displaced inwardly and the TM is displaced laterally

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30
Q

name the pathway of recording evoked potentials

A
  • neurons
  • sum (cancel or add)
  • send out a field
  • travels up through the tissue of the brain
  • through the dura
  • through the skull
  • through the scalp
  • to the electrodes
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31
Q

what are some electrode characteristics

A
  • material which conducts electricity (gold, tin, platinum)
  • impedance/resistance-opposition to current flow
  • it is important to have
  • —-low impedance (more current flow, better response)
  • —-balanced impedance across electrodes (equal contribution from each electrode
  • voltage = current x impedance
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32
Q

stimulation rate

A

the shorter the latency the faster the rate

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33
Q

variability

A

the shorter the latency the smaller the variability

34
Q

electrode position

A

(degree to which small shifts in electrode location alter waveform morphology)
the shorter the latency the more far-field the response

35
Q

susceptibility to state changes

A

the shorter the latency the susceptible to changes in subject state

36
Q

rate of maturation:

A

the shorter the latency the more rapidly maturation proceeds

37
Q

Amplitude

A

the shorter the latency the smaller the amplitude

38
Q

amplitude of subcortical potentials

A

less than 10 mV

39
Q

amplitude of cortical potentials

A

greater than 10 mV

40
Q

amplitude of abr

A

.2 mV

41
Q

amplitude of MLR

A

1 mV

42
Q

amplitude of LLAEP

A

1-10 mV

43
Q

spectrum

A

the shorter the latency the higher the frequency specturm

44
Q

frequency spectrum of ABR

A

30-1500 Hz

45
Q

number of averages of ABR

A

2000

46
Q

number of averages of MLR

A

1000

47
Q

number of averages of LLAEP

A

100

48
Q

frequency spectrum of MLR

A

10 - 100 Hz

49
Q

frequency spectrum of late potentials

A

.1-30 Hz

50
Q

frequency spectrum of EEG

A

1-12 Hz

51
Q

condensation

A
  • headphone diaphragm displaced outwardly

- TM displaced medially

52
Q

Rarefaction

A
  • headphone diaphragm displaced inwardly
  • RETRACTION
  • TM displaced laterally
53
Q

impedance/resistance - opposition to current flow

A

important to have:

  1. low impedance (more current flow, better response)
  2. balanced impedance across electrodes (equal contribution from each electrode)
54
Q

Voltage =

A

current * impedance

55
Q

common mode rejection ratio (CMRR)

A

reducing the noise by subtracting the “common mode” the current that is common to the two electrodes (expressed in dB)

  • rejection ratio - used by equipment manufacturers and expressed in dB
  • better to have bigger than smaller ratio
56
Q

Strategies for avoiding electrical noise

A 
matched electrode impedances 
differential amplification
grounding
shielding 
filtering 
separate power cords from input to averager 
stimulus rate - not at multiples of 60
57
Q

Why do we do ABRs?

A

diagnose hearing loss
CNS lesions / disorders
language - based learning problems (e.g. dyslexia)
auditory processing disorders
developmental delay
attention deficit disorder
central function with peripheral hearing loss (hearing aids, cochlear implants)
at-risk infants, autism, Alzheimer’s disease
impact of aging, hearing loss

58
Q

Three types of Gamma waves

A

at rest
induced
evoked

59
Q

induced gamma waves

A

response to a stimulus NOT time locked

  • not phase-locked, jittery latency
  • varies from trial to trial
    • cannot average across many responses as you average it out
    • time-frequency analysis is needed: average the power across trials
60
Q

evoked gamma waves

A

response to a stimulus is time locked
- depend on synchrony
- dynamic
- reflect response patterns across population of neurons
Dendrites - postsynaptic potentials (PSP)
Axons - action potentials (AP)
Evoked Responses - reflect both PSP and AP

61
Q

exogenous EP components

A

sensitive to stimulus manipulations

62
Q

endogenous EP components

A

sensitive to psychological state of subject

- if they’re asleep, paying attention etc.

63
Q

What are the three cochlear responses and their latencies?

A 
Cochlear Microphonic (CM) 0
Summating Potential (SP) 0 
Otoacoustic Emissions 0
64
Q

What are the three brainstem and their latencies?

A

Auditory Brainstem Response (ABR) 1-12
Frequency Following Response (FFR) 6+
Brainstem Response to Complex Sounds (cABR) 6+

65
Q

What are the middle latency responses and their latencies (MLR)?

A

Na, Pa, TP41, Nb, Pb, (P1) 10-60

66
Q

What are the event related potentials and their latencies?

A 
N1, N1b (N100), N1c (N150) (all from auditory cortex), P2, N2, Sustained negativity 80-250
Elicited with oddball paradigm
mismatch negativity (MMN) 150-275
Nc 400-700
Processing negativity Nd 60-700
P300, P3a, P3b 250 - 350 
N400 - 400
67
Q

Electrocochleaography (ecochg) - where does the electricity around the cochlea come from?

A
  • potential difference across hair cells
  • dendrite potentials in 8th nerve
  • action potentials along 8th nerve
68
Q

Amplitude of cortical vs subcortical potentials

A

The shorter the latency the smaller amplitude

  • subcortical: < 10 mV
  • cortical: > 10 mV
69
Q

What is latency?

A

point in time relative to the stimulus onset

70
Q

What is a trigger?

A

beginning of time window, signals averaged to enable alignment of all stimulus presentation sweeps

71
Q

What is a pre-stimulus interval?

A

period between trigger and stimulus, enables assessment of non-stimulus-related brain activity

72
Q

Which has shorter recovery times, brainstem (earlier) or cortical (later) responses?

A

earlier responses have shorter recovery times than later

73
Q

What are Gamma waves and what are their frequency?

A
  • 31-120

- hyper brain activity which is great for learning

74
Q

What are beta waves and what are their frequencies?

A
  • 13-30

- here we are busily engaging in activities and conversation

75
Q

What are alpha waves and what are their frequencies?

A

8-12 Hz

very relaxed, deepening into meditation

76
Q

What are theta waves and what are their frequencies?

A

4-7 Hz

drowsy and drifting down into sleep and dreams

77
Q

what are delta waves and what are their frequencies?

A

.5-3 Hz

deeply asleep and not dreaming

78
Q

Exogenous

A

sensitive to stimulus manipulations (EP)

79
Q

Endogenous

A

sensitive to physiological state of the subject (EP)

80
Q

Where does electricity around the cochlea come from?

A
  • potential difference across hair cells
  • dendrite potentials in 8th nerve
  • action potentials along 8th nerve
81
Q

What are electric currents in the cochlea measured with?

A

electrocochleaography (ECochG)

electrophysiology (1 decks)

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