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EEG Flashcards

1
Q

what did Richard canon find out? and when?

A

Electrical phenomena in
animal’s brains (1875)

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2
Q

what did Adolf beck find out? and when?

A

Recordings of oscillatory
electrical brain activity in
response to different types of stimulation (visual, auditory) (1890)

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3
Q

who discovered Electrical phenomena in animal’s brains?

A

Richard canon

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4
Q

who discovered Recordings of oscillatory electrical brain activity in response to different types of stimulation (visual, auditory)

A

Adolf beck

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5
Q

who recorded the first human electroencephalogram? and when?

A

Hans berger 1929

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6
Q

who reported the first alpha waves? and what else did they report?

A

Hans berger
First report of alpha waves (~8 12 Hz) and their
suppression when the subject opens the eyes

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7
Q

electric

A

changes in membrane potential

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8
Q

chemical

A

synaptic transmission

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9
Q

intracranial measurements

A
  • intraparenchimal recordings
  • electrocorticography (EcoG)
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10
Q

extra cranial measurements

A
  • magnetoencephalography (MEG)
  • electroencephalography (EEG)
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11
Q

how is the temporal resolution of EEG?

A

excellent

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12
Q

on what time scale can EEG measure?

A

Measuring electrical (or magnetic) potential on a sub
millisecond scale

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13
Q

how is spatial resolution in EEG? and why?

A

low
-> because of volume conduction
-> difficulty recording activity from deep sources
->inverse problem

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14
Q

what is volume conduction?

A

The spreading of electrical
current from the source to the receiver while crossing
different media

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15
Q

is volume conduction an issue with MEG?

A

no

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16
Q

what is difficult to record with EEG and why?

A

Difficult to record activity
from deep sources
> Electrical field spreads as a
function of distance
> The activity from neural
populations with different
orientations cancels out

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17
Q

what is the inverse problem?

A

Estimate the location of brain activity given the pattern of activity measured on the scalp
> ill-posed problem: impossible to solve perfectly

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18
Q

what are the advantages of EEG? (4)

A
  • High temporal resolution
    (milliseconds)
  • Directly measures electrical activity of the brain
  • (relatively) mobile and non
    invasive
  • (relatively) cheap
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19
Q

what are disadvantages of EEG? (3)

A
  • Poor spatial resolution
  • Very weak signal (small
    signal to noise ratio)
  • Difficult to measure deep
    structures
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20
Q

where is electric potential measured from?

A

Electric potential is measured from an array of electrodes placed
on the scalp with respect to a reference point (different possible locations, but mostly also on the scalp)

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21
Q

how is the position of the electrodes on the scalp?

A

standardized

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22
Q

what is the system for the electrode placement?

A

> 10- 20 system

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23
Q

what is the most common number of electrodes? and why?

A

64 -> good trade off

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24
Q

how many electrodes can be used?

A

max 256

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25
what are pro/cons of more electrodes?
- more spatial accuracy - more time to prepare
26
where are additional electrodes placed and why?
Additional electrodes placed on the face to record EYE MOVEMENTS
27
how are the additional electrodes placed?
> Horizontal electrooculogram HEOG ): to the corner of the eyes > Vertical electrooculogram VEOG ): above and below the eye
28
what is the equipment? (9)
- cap - electrodes bundles - gel - flat electrodes - amplifier - battery pack - trigger box - computer to record EEG data + software - computer to administer the task (if needed)
29
what is the EEG procedure? (3 steps?
- step 1: place cap on the participant's head - step 2: add gel in each hole of the cap - step 3: insert electrodes
30
what is the goal of data cleaning?
Remove all the noise and keep only the signal coming from the brain
31
what are you filtering out?
* Low frequencies (drifts) * High frequencies (muscle contraction) * Line noise (50 Hz)
32
what are parts of preprocessing?
- filtering - referencing - interpolarting bad channels
33
what is referencing?
Change in voltage with respect to this reference (external electrodes, average of all channels, one specific channel)
34
what is interpolating bad channels?
Correcting data from one electrode based on the average of its surroundings
35
what is epoching?
epoching is a procedure in which specific time-windows are cut from the continuous EEG signal
36
what is the independent component analysis (ICA)?
Decomposes the signal in independent parts explaining a portion of variance
37
what does clean data look like?
The largest sources of noise have been removed, the signal from the brain is retained
38
what is univariate?
- (activation-based) - Comparing levels of activation across conditions, usually averaging across recording units
39
what is multivariate?
- (information based) - How spatially distributed activity patterns contain task relevant information
40
examples of multivariate
-Decoding (machine learning) - Representational similarity analysis - ICA, PCA..
41
what does each portion of recorded data contain? (ERPs)
- signal and noise
42
what cancels out the noise?
averaging across trials
43
difference between signal and noise?
signal: similar in each trial noise: randomly fluctuates across trials
44
what can you see after many many trials?
Scalp recorded systematic neural signal generated by a specific neuroanatomical module when a specific computation is performed
45
what did hallowed and Paulin Davis record? and when?
Recordings of sensory ERPs (1939)
46
who recorder sensory ERPs?
Hallowell and Pauline Davis (1939)
47
who recorded the first cognitive ERP? and when?
Grey Walter (1964)
48
what did grey walker find?
First cognitive ERP -> Contingent negative variation
49
what is contingent negative variation (CNV)?
- Condition A (No-Go): Passive viewing - Condition B (Go): Press a button upon detection of the target stimulus
50
what does contingent negative variation reflect?
Reflecting preparation for the upcoming target
51
sensory & perceptual ERP components (2)
- Visual P1 - N170
52
what is P1? and what does it reflect?
Large positive component, most prominent at lateral occipital electrodes, peaking roughly 100 ms post stimulus . Reflects visual processing
53
what is N170?
Lateralized posterior negative peak associated with face processing
54
what is the motor ERP component?
Readiness potential Negative deflection preceding a movement , maximal above (contralateral) motor areas.
55
where is P1 most prominent?
most prominent at lateral occipital electrodes
56
when does P1 peak?
peaking roughly 100 ms post stimulus
57
cognitive ERP components (3)
- P300 (and subcomponents) - mismatch negativity - error-related negativity
58
what is P300 sensitive to?
Sensitive to target probability , peaks over frontal electrodes
59
what is mismatch negativity?
Negative wave maximal at midline scalp sites, ~ 200 ms post a deviant stimulus
60
where does mismatch negativity occur?
at midline scalp sites
61
when does mismatch negativity arise?
scalp sites, ~ 200 ms post a deviant stimulus
62
what is error-related negativity?
Negative deflection at frontal and central sites with onset immediately following an erroneous response
63
where is error-related negativity?
Negative deflection at frontal and central sites
64
when is error-related negativity?
with onset immediately following an erroneous response
65
what are oscillations?
The recorded data can be decomposed in signal (s) and noise
66
what is the phase (oscillations)?
the angle at a given time
67
what is the frequency?
the cycles per second (width)
68
what is the amplitude?
how low/high the oscillation is
69
what does the highest frequency you can look at depend on?
depends on your sampling rate
70
frequency bands (5)
- delta - theta - alpha - beta - gamma
71
what is Delta associated with?
Associated with some sleep stages
72
Hz of delta
1-4 Hz
73
what is theta associated with?
Hippocampal theta associated with learning and memory, midfrontal theta with cognitive control
74
Hz of theta
4- 8 Hz
75
what is alpha associated with?
Thought to inhibit the cortex not in use (i.e. gatekeeping), for example in attention
76
Hz of alpha
8 - 12 Hz
77
what is beta associated with?
Linked to waking consciousness, active concentration, motor processing
78
Hz of beta
13 - 30 Hz
79
what is gamma associated with?
Involved in conscious perception, WM and attention
80
Hz of Gamma
30 - 70 Hz
81
where is alpa amplitude suppressed?
Alpha amplitude is suppressed in parietaloccipital electrodes contralateral to the attended location
82
effects of cue validity contralateral - ipsilateral
60% - 80% - 100&
83
what is machine learning?
Tries to learn how the brain responds to different conditions
84
what is the goal of machine learning?
The goal is to correctly predict to what condition new, unseen data belong to
85
3 steps of decoding in ML
1) Train classifier on a subset of labeled data 2) Test classifier on new unlabeled data 3) repeat many times
86
very large multidimensional data space
Need to be careful of multiple comparisons problem and implement specific statistical measures
87
EEG is a ... technique to ...
Great technique to study fast cognitive dynamics, not ideal for ‘where’ questions
88
Rich, complex, and multidimensional data that can be analyzed in many ....
ways depending on the research question. Need to be careful with statistical testing

RM (15 decks)

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