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Electrophysiology > Lecture 1 > Flashcards

Lecture 1 Flashcards

1
Q

What are the fast-latency responses?

A
  1. the auditory brainstem response (ABR)
  2. the auditory steady-state response (ASSR)
  3. the frequency-following response (FFR)
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2
Q

You can get fast-latency responses when people are ____.

A

sleeping

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3
Q

What are the cochlear responses?

A
  • OAEs
  • EcochG
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4
Q

What are the 4 parts of an OAE?

A
  1. spontaneous (SOAE)
  2. transient (TEOAE)
  3. distortion product (DPOAE)
  4. stimulus frequency (SFOAE)
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5
Q

What are the three parts of an EcochG?

A
  1. compound action potential (CAP)
  2. summating potential (SP)
  3. cochlear microphonic (CM)
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6
Q

Where are responses coming from with an EcochG?

A

Cochlea and AN

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7
Q

What does EcochG stand for?

A

Electrocochleographic

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8
Q

What are the cortical auditory evoked responses?

A
  • auditory middle-latency response
  • auditory slow and late-latency response
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9
Q

What are the middle-latency responses?

A
  • transient MLR
  • 40 Hz ASSR
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10
Q

What are the slow and late-latency responses?

A
  • P1-N1-P2 complex
  • Mismatch negativity (MMN)
  • P300 response
  • N400 response
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11
Q

True or false: cortical auditory evoked responses are commonly used in audiology?

A

False: used more in psychology

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12
Q

Are objective measures or behavioural measures superior for testing brain activity?

A

behavioural

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13
Q

What are the two ways to measure brain activity?

A
  1. Hemodynamic / Metabolic
  2. Electrical (EEG) or magnetic (MEG)
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14
Q

What are the tests used with measuring Hemodynamic / Metabolic activity?

A
  1. PET
  2. fMRI
  3. Optical
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15
Q

Describe the Hemodynamic / Metabolic approach

A
  • rich blood supply to brain
  • thinking requires blood
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16
Q

Hemodynamic / Metabolic: spatial and temporal resolution

A
  • spatial resolution is very good
  • temporal resolution is poor (slow because you are looking at something that happens after the fact)
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17
Q

Explain oxygen rich vs. oxygen poor blood

A

oxygen-rich and oxygen-poor blood has different magnetic properties, BOLD or T2* imaging based on loss of magnetization related to use of oxygen released (by blood) to cells that are firing

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18
Q

What are the tests used with measuring electrical or magnetic activity?

A
  • electrical (EEG)
  • magnetic (MEG)
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19
Q

Describe the electrical or magnetic approach

A
  • neurons have electrical properties that can be directly recorded (single unit)
  • electrical activity of many neurons sums to create voltage changes at the scalp (e.g. ABR/MLR/ERP)
  • electrical activity also creates magnetic fields that can be measured at the scalp (MEG)
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20
Q

electrical or magnetic: spatial and temporal resolution

A
  • spatial resolution is poor (because looking at what multiple neurons are doing, not a single one)
  • temporal resolution is very good
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21
Q

What are some differences between electrical and magnetic imagine?

A
  • Magnetic imaging is very expensive
  • Magnetic instead of electrical because nothing is distorted by the scalp
  • Electrical imagine isn’t expensive and is used often in clinic
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22
Q

Optical imaging of changes in ____ with tonal stimulation in the chinchilla

A

Blood flow

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23
Q

What is the hemodynamic approach typically used for?

A
  • Used for studying the structure and function of the cortical networks involved in speech perception and language
  • Used for studying high level things (networks, how different parts of the brain are involved in different things)
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24
Q

Why is the hemodynamic approach not used in audiology assessment?

A
  • poor temporal resolution
  • expensive
  • invasive
  • requires compliant subject (awake)
  • although referrals may be indicated (e.g., MRI)
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25
Q

What is the electrical/magnetic approach typically used for?

A

used for estimating hearing thresholds, detecting space-occupying lesions, assessing neural integrity and timing at multiple levels (cochlea to cortex)

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26
Q

the ____ approach is used extensively in audiological clinical assessment.

A

elecetrical/magnetic

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27
Q

Name 4 reasons why electrical/magnetic approaches are common in audiology clinic assessments

A
  1. excellent temporal resolution
  2. inexpensive and clinically available
  3. non-invasive
  4. little compliance is needed
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28
Q

why is the electrical/magnetic approach used in audiological clinical assessment?

A
  • excellent temporal resolution
  • inexpensive (i.e., EEG), clinically available
  • non-invasive
  • little compliance required
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29
Q

What setting are electrical/magnetic approach most commonly used in?

A

hospital

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30
Q

Electricity is movement of charge from ____ potential to ____ (like water)

A

high, low

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31
Q

Rate of flow is current (I) measured in ____

A

amps

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32
Q

Resistance to flow (R) is ____

A

resistance

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33
Q

Potential difference (V) is measured in ____

A

Volts

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34
Q

sodium-potassium pump moves ____ outside cell and ____ inside cell

A

Na+, K+

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35
Q

How much energy in the brain does the sodium-potassium pump use?

A

70% is used to reserve this resting potential

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36
Q

The sodium pump in the brain allows cells to have ____ resting potential

A

negative

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37
Q

calcium pump keeps ____ outside of cell

A

Ca2+

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38
Q

membrane is more permeable to ____ (about 40x)

A

K+

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39
Q

how does the sodium-potassium pump work?

A
  • some potassium flows out (because of concentration gradient)
  • but then more positive charge outside of cell, so electrical force pulls against this, leads to charge of about –80 mV
  • leakage of Na+ changes this to about –65 mV
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40
Q

Where is resting potential?

A

-65mV

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41
Q

Neurotransmitters (e.g., glutamate) increase ____ of membrane to Ca2+ or Na+

A

permeability

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42
Q

What happens when the cell has a positive potential?

A

This triggers a closure of sodium channels and an opening of potassium channels, membrane potential swings back to negative, overshooting resting potential (hyperpolarized)

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43
Q

What are the two sides to the electric neuron?

A
  1. action potentials
  2. post-synaptic potentials
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44
Q

Explain action-potentials

A
  • the output side
  • all or none (digital or binary)
  • fast!
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45
Q

Explain post-synaptic potentials

A
  • the input side (what’s happening at the dendrites)
  • graded (analogue)
  • slow
  • it’s the sum activity of lots of other neural action potentials
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46
Q

Explain the action potential bb gun anaolgy

A
  • consider action potential like firing a BB gun (all or none)
  • Bob is getting shot with the BB gun repeatedly… a post-synaptic potential is Bob’s mental state (not all or none, changes more slowly)
  • once Bob gets to a certain point, he fires his BB gun!
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47
Q

What causes excitation?

A

inflow of Na+ into the dendrite or cell body due to neurotransmitter such as glutamate

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48
Q

A ____ is low potential

A

sink

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49
Q

A ____ is high potential

A

source

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50
Q

What happens to the post-synaptic potential during excitation?

A
  • the cell membrane more positive (source)
  • the surrounding extracellular fluid negative (sink)
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51
Q

Explain the dipole electric field in volume conductor

A
  • In the extracellular space, current flows from sources (+) to sinks (-)… i.e., towards places where neurons are being excited
  • It will take all possible paths and go to all possible places
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52
Q

The extracellular sinks and sources create voltage patterns that can be recorded at the ____

A

scalp

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53
Q

What way does current flow INSIDE the cell?

A

sink –> source

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54
Q

What does isotropic mean?

A

equal in all directions

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55
Q

what does anisotropic mean?

A

different properties in different directions

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56
Q

Is the extracellular space isotropic or anisotropic? Heterogenous or homogenous?

A
  • ansiotropic and hetergeneous
  • but linear at large scales (can ignore the fine details)
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57
Q

____ and ____ distort electric fields

A

Skull, scalp

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58
Q

the dipole field of a single neuron is too ____ to be recorded at the scalp

A

small (a lot of neurons need to work together and fire at the same time in order to get a response)

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59
Q

Far-Field

A
  • A couple cm away
  • Measuring on the scalp you are a few cm away
  • Can get larger responses when people are upside-down
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60
Q

Does EEG relate to a single neuron?

A

No, it relates to many neurons acting together

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61
Q

Explain spatial summation

A

In order to be detected without averaging, responses must occur in many neurons (at least 60 million) at roughly the same time

62
Q

How many mm thick is the cortex?

A

3-5 mm thick

63
Q

How many layers is the cortex?

A

6

64
Q

What cells make up the cortex and how are they aligned?

A

large pyramid cells, aligned in the same direction (in an open field)

65
Q

cortical pyramid cells form an ____ field

A

open

66
Q

true or false: both pyramid, thalamic cells, and axons form open fields?

A

false: pyramid cells do, but thalamic cells & axons don’t

67
Q

describe the orientation of neurons in an open and closed field

A

in an open field, they are all aligned parallel to each other

in a closed field, they are all tangled together

68
Q

Dipole fields must be aligned to sum at the ____

A

scalp

69
Q

Dipole fields must be temporally ____ to sum at the scalp

A

coincident

70
Q

What two things do you need to generate a far-field response?

A
  • spatial summation (which requires synchrony)
  • an open field
71
Q

What happens when many neurons work together, at the same time, in the same direction?

A

it creates a large dipole (battery) like a giant neuron

72
Q

Most large responses are from ____

A

post-synaptic potentials (coordinated patterns of excitation or inhibition)

73
Q

Do action potentials give rise to open fields?

A

Not really

74
Q

do post synaptic potentials need to be precisely aligned to add up? why or why not?

A

no, they are slow

75
Q

do action potentials need to be precisely aligned to add up? why or why not?

A

yes, because they are very quick (about a msec)

76
Q

ABR is composed of ____

A

action potentials

77
Q

are most large responses from pre or post synaptic potentials?

A

post synaptic

78
Q

With an EEG we are looking at ____ activity

A

spontaneus

79
Q

Is stimulus needed for an EEG?

A

No

80
Q

What is the EEG recording?

A

The scalp-recorded EEG is a pattern of voltage changes reflecting primarily post-synaptic activity (not action potentials)

81
Q

What is the EEG picking up?

A
  • only a small number of neurons are spiking at any given time
  • post-synaptic potentials are slow and wide-spread
  • the pyramid cells in the cortex produce open fields
82
Q

With the EEG, oscillations likely reflect what?

A

Thalamocortical circuit dynamics

83
Q

Explain the input/output of the brain

A
  • The brain is a system that oscillates without input, not just input-output
  • Only 5-10% of input is coming from the outside
  • The brain is highly inwardly focused
84
Q

All sensory input passes through the ____

A

Thalamus (except olfaction)

85
Q

Sensory input targets pyramidal neurons in layer ____ of the thalamus

A

IV

86
Q

What % of connections in layer IV are from other parts of the cortex?

A

90-95%

87
Q

Are there more outgoing (corticothalamic) neurons or more incoming (thalamocortical) neurons?

A

10x as many outgoing

88
Q

The brain is a complex system that is only perturbed by ____ input

A

external

89
Q

What are the 5 rhythms of EEG?

A
  1. Alpha
  2. Beta
  3. Gamma
  4. Delta
  5. Theta
90
Q

Alpha occurs at which frequencies?

A

8-12 Hz (around 10 Hz)

91
Q

Beta occurs at which frequencies?

A

13-20 Hz (around 20 Hz)

92
Q

Gamma occurs at which frequencies?

A

> 20 Hz (big peak around 40 Hz)

93
Q

Delta occurs at which frequencies?

A

0.5-3 Hz (slow waves when deeply sleeping)

94
Q

Theta occurs at which frequencies?

A

4-7 Hz (between delta and alpha)

95
Q

What does gamma stimulate?

A

cortical columns

96
Q

What does theta influence?

A

memory, communication, and syllabic rate

97
Q

Eyes closed vs. eyes open EEG

A

Eyes closed
- A huge peak around 10Hz (alpha)
- When eyes are closed you aren’t processing visual information
- If asked to visualize something when eyes closed, alpha can decrease

Eyes open
- Flattens out (decreases as you go up in frequency)
- Lose alpha because they are processing what they are seeing

98
Q

Where is alpha in the brain?

A

Alpha is everywhere in the brain (but prominent over visual cortex)

99
Q

Where is beta in the brain?

A

beta is mostly motor and sensory cortex

100
Q

What do the O, P, C, F, and Fp mean on an EEG?

A

O = occipital (can see that alpha is big until eyes are open)
P = parietal
C = central
F = frontal
Fp = frontal pole (forehead)

101
Q

When eyes are closed, there is lots of ____, the brain is very ____

A

alpha, synchronized

102
Q

When the eyes are open, ____ goes away, there is ____

A

alpha, desynchronization

103
Q

What is the main clinical use of EEG?

A

tracking sleep

104
Q

What are the stages of sleep?

A

stage 1: very similar to being awake
Stage 2: k complex and bursts of spindles
Stage 3: slow waves and spread out in time (delta waves)
Stage 4: more than 50% of what you are looking at is delta waves

105
Q

One year after Berger’s discovery of EEG, the first auditory evoked response was recorded from the auditory nerve of a ____

A

Cat

106
Q

auditory evoked responses refers to ….

A

electrical stuff occurring in response to sound

107
Q

what did Pauline Davis note in EEGs when patients were stimulated with a loud sound?

A

k-complex

108
Q

why do we think Pauline Davis named the k-complex the k-complex?

A

thought that someone knocked on the door then she discovered it

109
Q

Who are the father and mother of auditory evoked responses?

A

Hallowell Davis and Pauline Davis

110
Q

why was progress in auditory evoked response studies slow?

A
  • becuase the spontaneous EEG was much larger than activity evoked by auditory stimuli
  • harder to get and record
111
Q

all early work with auditory evoked responses included what? like how did people study it?

A

looking at electrical responses from the cochlea using invasive electrodes (usually placed on the round window)

112
Q

how close/far does an electrode have to be for it to be considered near vs far field?

A
  • near field = electrode is in/on the structure
  • far field = several cm away
113
Q

What are the pros of near-field recording?

A
  • can record post-synaptic potentials and spikes in individual neurons
  • can record in closed fields (spatial alignment of dipole fields not necessary)… e.g. thalamus, nuclei
  • can record very localized activity
  • much larger than far-field
    • e.g. CAP is 100 times larger at cochlear wall (e.g. promontory) than at earlobe or mastoid
114
Q

What are the cons of near-field recording?

A
  • invasive, often limited to animal studies
  • small-scale neural activity might not relate to perception and cognition
115
Q

What was the response averager?

A
  • From the 1950s
  • Made it possible to detect responses that were smaller than the background EEG activity
116
Q

What is a more modern example of response averaging?

A

face averaging

117
Q

what are the 2 assumptions of signal averaging?

A
  1. auditory responses should be time locked to stimulus
  2. background activity (EEG) should not be time locked
118
Q

with signal averaging, what are we trying to preserve and reduce?

A
  • trying to preserve time-locking
  • trying to reduce background activity
119
Q

since the auditory response should be the same after each stimulus, averaging the period after each stimulus should ____ this activity

A

preserve

120
Q

since the background activity should not be the same after each stimulus, averaging should ____ this activity

A

reduce

121
Q

Overall, what does averaging show you?

A

averaging shows you what stays the same on each trial

122
Q

Where do late potentials come from?

A

the cortex

123
Q

ABR refers to actions potentials that come from where?

A

The AN and brainstem

124
Q

what are the 5 ways we can classify evoked responses?

A
  1. latency
  2. stimulus dependence
  3. source tissue
  4. source location
  5. type of activity
125
Q

which classification type is the easiest and most common?

A

latency

126
Q

classify the following auditory evoked responses by short-, mid-, or long-latency:

ECochG
MLR
LLR
ABR

A

ECochG and ABR = short (<10ms)

MLR - mid (10-50ms)

LLR = long (50+ms)

127
Q

ABR is sometimes called the ____ latency response

A

fast (short = fast)

128
Q

Auditory Evoked Responses picture

A
129
Q

Need better resolution and more amplification to pick up ____ vs. ____

A

fast latency response (ABR) vs. long latency response

130
Q

What are 3 ways to describe potentials?

A
  • exogenous
  • endogenous
  • mesogenous
131
Q

what does exogenous mean and give an example

A
  • determined by stimulus
  • cochlear microphonic
  • AEPs
132
Q

what does endogenous mean and give an example

A
  • your reaction to something
  • N400 - response to a word that doesn’t make sense in the semantic context
  • ERPs
133
Q

what does mesogenous mean and give an example

A
  • partially determined by the stimulus, partially by perception/cognition
  • P1-N1-P2 complex
134
Q

is stimulus dependence an easy or hard way to classify?

A

hard

135
Q

what determines a response for endogenous?

A

attention

136
Q

what are the 2 things we observe in EEGs associated with auditory stimuli based on time locked changes?

A
  • AEPs
  • ERPs
137
Q

What are auditory evoked potentials (AEPs)? Give examples

A
  • responses that are determined by the stimulus (exogenous)
  • ECochG, ABR, MLR, ASSR (80 Hz and 40 Hz), FFR
138
Q

What are event-related potentials (ERPs)? Give examples

A
  • responses that relate to events
  • often relate to cognitive processes
  • affected by attention (endogenous)
  • LLR, MMN, P300, N400
139
Q

source tissue includes ____ activity, which includes what 3 things?

A

Neural
- Action Potentials
- Post-Synaptic Potentials
- Myogenic or Artifact

140
Q

What does source location refer to?

A

Where it occurs
- Planum Temporale,
- Heschl’s Gyrus
- Cochlear Nucleus

141
Q

what are the 5 types of potentials?

A
  • spontaneous
  • transient
  • sustained
  • steady state
  • induced
142
Q

What are transient potentials?

A

play a stimulus and get a response (happens once after the stimulus)

143
Q

What are spontaneous potentials?

A

no stimulus, measuring waves from the brain

144
Q

What are induced potentials?

A
  • changes in the spontaneous activity in response to a stimulus
  • play a sound and see changes in the alpha (induced change)
145
Q

What are steady-state potentials?

A

activity that follows the stimulus in some way

146
Q

What are sustained potentials?

A

EcochG, a pedestal response (constant positivity or negativity), does not fluctuate with the stimulus

147
Q

Onset and offset responses are ____

A

transient

148
Q

What is used for a neuropathy assessment?

A

EcochG

149
Q

What are ABR and ASSR used in?

A
  • peripheral hearing assessment (in babies)
  • neurological diagnosis
  • suprathreshold tests (discrimination)
  • speech-evoked responses
150
Q

true or false: EEGs in clinical audiology can also be used to detect hidden hearing loss and for advanced assessments?

A

true

Electrophysiology (8 decks)

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