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Psychology - CN > Lecture 5- EEG > Flashcards

Lecture 5- EEG Flashcards

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1
Q

Who was EEG invented by?

A

Hans Berger (1873-1941)

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2
Q

When was the first EEG result published?

A

1929

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3
Q

What unit of electrical activity is measured?

A

Microvolts (millionth of a volt)

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4
Q

What are ERPs?

A

measure of potential fluctuations time locked to an event

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5
Q

What is the spectral content of EEG?

A

analyses the type of neural oscillations that can be observed in EEG signals in the frequency domain

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6
Q

Advantages of EEG

A 
Cheaper
Portable
Very high temporal resolution (milliseconds)
Tolerant to movement 
Silent
Simple to conduct 
Can detect covert processing 
Can elucidate stages of processing rather than just the end result
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7
Q

Disadvantages

A

Low spatial resolution
Poorly measures neural activity occuring below upper layers of brain
Time intensive
signal:noise is poor
Brain have many folds therefore opposite potentials across a sulcus can cancel out (MEG would still work because magnetic field is orthogonal)

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8
Q

Explain volume conduction ?

A

Ions of a similar charge repel each other

When many ions are pushed out of many neurons at the same time, they push their neighbours and so on, in a wave

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9
Q

How does volume conduction influence the EEG signal?

A

When the wave reaches electrode, they push or pull on the electrons inside the metal

The difference in push/pull voltage between an electrode and a reference electrodes is measured by a voltmeter = EEG signal

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10
Q

EEG activity reflects the ____ of activity of many neurons with a similar ____ ____

A

synchronous

spatial orientation

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11
Q

Why might ions from cells not line up and not create a detectable wave?

A

Because the cells have not have similar spatial orientation

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12
Q

What cells are thought to produce most EEG signal? Why?

A

Pyramidal neurons - they are well aligned and fire together.

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13
Q

Why is activity from deep sources difficult to detect?

A

Because voltage field gradients fall off with the square of the distance

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14
Q

Synchronous activity of a large number of neurones can give rise to macroscopic _____

A

oscillations

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15
Q

What is impedance measure in? How is it different resistance?

A

ohms

Has a phase component

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16
Q

How to reduce impedance?

A

Using conductive gel Wiggling electrodes

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17
Q

What’s the recommended max level of impedance

A

below 5 kOhms is considered good

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18
Q

What is the most common framework for setting up electrodes?

A

10-20 system

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19
Q

What is the elctrode in the top-middle of the head?

A

Cz

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20
Q

the Nasion and Inion are equidistant to which electrode?

A

Cz

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21
Q

High-pass filter fillters out ___ artifact. For example _____

A

Slow artifacts e.g. electrogalvanic signals and movement artifacts

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22
Q

Low-pass filter filters out ____ signals

A

electromyographic (signals from muscle movement)

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23
Q

What is applied to remove artifacts caused by electrical power lines?

A

Notch filter

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24
Q

EEG display can be set up in different ways to represent difference between voltage at 2 electrodes. These are different forms of _____.

A

Montage (e.g. sequential, referential, average reference, laplacian)

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25
Q

What kind of analysis can help remove artifacts (e.g. blink detection)?

A

Independent Componant Analysis (ICA)

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26
Q

How are ERPs analysed?

A

By averaging over many trials/sites

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27
Q

P100?

A

basic visual response (occipital)

28
Q

N100

A

basic auditory response (frontal)

29
Q

N170

A

reflects face stimuli

30
Q

P300

A

reflects decision making

31
Q

Lateralized Readiness Potential (LRP)

A

indicator of motor planning

32
Q

What part of the ERP is analysed and quantified?

A

Peak amplitude
Latency
Area under deflection
(And/Ors)

33
Q

Multivariate Analysis in EEG adds what component?

A

Temporal

34
Q

Fourier analysis is the principle that…

A

Any waveform can be broken down into or constructed from the sum of sine waves of different frequencies

35
Q

Fourier analysis can tell you the separate ____ and at what _____ composed your waveform

A

frequencies

amplitudes

36
Q

What is the Fourier Spectrum?

A

Plots amplitude as a function of frequency

37
Q

What are the frequency bands found in EEG?

A 
Delta <4Hz
Theta 4-7Hz
Alpha 7-14Hz
Beta 15-30Hz
Gamma >30Hz
38
Q

Delta

A

<4Hz – sleep, some attention tasks

39
Q

Theta

A

4-7Hz, similar to alpha

40
Q

Alpha

A

7-14Hz - resting, tiredness, attentional lapses

41
Q

Beta

A

15-30Hz - motor behaviour

42
Q

Gamma

A

> 30Hz - long range neural synchronisation

43
Q

What is steady state?

A

Use an oscillating stimulus at a frequency that can then make the brain oscillate at that particular frequency.

Measure the steady-state evoked potential - the amplitude at the stimulus frequency

44
Q

Head and contour plots?

A

Plots the EEG signal across the scalp

Typically show the distribution of activity across electrodes at specific point in time

45
Q

The processes of inferring from the distribution of activity across electrodes where in the brain the signal originated is called…?

A

Source localization

46
Q

Special equipment is required to combine EEG with MRI or MEG because….

A

Too much metal!

47
Q

In regard to the N and P waves of the EEG, N and P stand for…

A

Positive and negative

48
Q

An EEG waveform measures the change over time of the ____ between ____ ____ on the scalp

A

Voltage between two points on the scalp

49
Q

A contour plot shows…

A

the distribution of activity across sensors at a specific point in time

50
Q

If a large number of neurons are all firing at once, this will produce an ___ ____ and an accompanying ____ ___

A

Electrical dipole

Magnetic field

51
Q

Nearby electrodes are often ___ ___ with each other

A

highly correlated

52
Q

Opposite potentials across a ___ can cancel each other out

A

sulcus

53
Q

In EEG we are measuring difference in electrical charge, this is called ___ or ____ _____

A

Voltage

Potential difference

54
Q

In EEG there must always be a ____ electrode

A

reference

55
Q

The voltages we measure are usually in the order of ___ of ____

A

tens of microvolts

56
Q

A microvolt is a _____ of a volt

A

Millionth

57
Q

Electrodes are typically made of?

A

Silver/silver chloride

58
Q

What does a multimeter do?

A

Manually measures impedance

59
Q

Because EEG signals are so small, we need to ___ them
But what else will be ___?
____ also digitise the EEG signals

A

Amplify
Noise
Amplifiers

60
Q

The true signal we are interested in can be revealed by?

A

averaging over multiple trials and/or multiple subjects

AND/OR

average over several electrodes to get a
global signal for a particular region

61
Q

Blinks show up on the _____ at the bottom of the plot

A

electro-oculogram (EOG)

62
Q

The positive and negative components of a waveform are known as ______

A

deflections

63
Q

Using steady-state, we can measure the neural response to some stimulus as a function of its ____

A

intensity

64
Q

Clinical applications of EEG

A 
Epilepsy
Migraine
 Movement disorders	(e.g.	Parkinson’s)
Psychiatric disorders
Diagnosing brain death, coma etc
65
Q

How can we relate EEG responses to subjective experience?

What can be used to derive an underlying model that explains data from both measures?

A

Do psychophysical tasks whilst measuring EEG

Computational modelling

66
Q

Neurofeedback?

A

Way of monitoring your own internal mental state

May or may not work

67
Q

Frequency vs time plots

A 
time = x
frequency= y 
amplitude = colour

Psychology - CN (9 decks)

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