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Basic principles in neuroimaging > 5. EEG > Flashcards

5. EEG Flashcards

1
Q

Who invented EEG?

A

Hans Berger

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2
Q

(EEG) opposite potentials in a sulcus can…

A

cancel each other out

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3
Q

In EEG we are measuring…

A

a difference in electrical charge (this is called voltage)

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4
Q

(EEG) voltages are ____ measures across the head

A

relative

  • there must always be a reference electrode
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5
Q

a microvlot is ____ of a volt

A

a millionth

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6
Q

The voltages we measure with EEG are ___, typically in the order of tens of ____

A

voltages, tiny, microvolts

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7
Q

What is the nasion?

A

EEG cap placement reference point:

  • just above the bridge of the nose (between eyes)
  • From the Cz electrode to the Nasion should be 50% of the distance of the semicircle
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8
Q

What is the inion?

A

EEG cap placement reference point:

  • The bump at the base of the skull
  • From the Cz electrode to the inion should be 50% of the distance of the semicircle
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9
Q

impedance is measured in…

A

ohms (Ω)

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10
Q

How can impedance be reduced?

A

By using conductive gel or paste

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11
Q

what is impedance?

A
  • a measure of the overall opposition of a circuit to current
  • It is like resistance, but it also has a phase component
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12
Q

___ impedances are considered good

A

<5kΩ

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13
Q

(EEG) any noise introduced before the amplifier…

A

will be amplified too

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14
Q

Applying a ____ can sometimes make the EEG waveforms easier to interpret

A

smoothing filter (e.g. low pass filter)

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15
Q

What are some of the methods used to precisely record on the EEG trace when a stimulus was shown

A
  • triggers based on sound/light signals

- using digital connections between computers

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16
Q

In many experimental paradigms, one computer records the EEG while a different computer…

A

displays some stimuli

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17
Q

(EEG) the true signal we are interested in can be revealed by…

A

averaging over multiple trials and/or multiple subjects

  • we might also avg over several electrodes to get a global signal for a particular region
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18
Q

EEG artifact removal:

Various labs use different rejection criteria:

  • e.g. removing trials where some measure exceeded ____ of the mean
A

±3SE

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19
Q

What is independent components analysis (ICA)?

A

Independent component analysis attempts to decompose a multivariate signal into independent non-Gaussian signals.

  • A simple application of ICA is the “cocktail party problem”, where the underlying speech signals are separated from a sample data consisting of people talking simultaneously in a room
20
Q

What is an ERP

A

Event related potential (ERP) is the measured brain response that is the direct result of a specific sensory, cognitive, or motor event

21
Q

negative voltages are plotted ____ in ERP

A

upwards

22
Q

What is used to quantify ERPs?

A
  • Peak amplitude and/or latency

- or the area under deflection (peak)

23
Q

What is the Fourier analysis technique?

A

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

  • A convenient representation of this is to plot the amplitude (or power) as a function of frequency (y = amp / x = freq)
24
Q

(EEG) ____ plots represent how the Fourier spectrum changes over time

A

Frequency vs time plots:

y = freq / x = time

25
Q

Frequency band: Delta

A

<4Hz

  • sleep
  • some attention tasks
26
Q

Frequency band: Theta

A

4-7Hz
Is similar to Alpha:

  • resting, tiredness, attentional lapses
27
Q

Frequency band: Alpha

A

7-14Hz

  • resting
  • tiredness
  • attentional lapses
28
Q

Frequency band: Beta

A

15-30Hz

  • motor behaviour
  • concentration
29
Q

Frequency band: Gamma

A

> 30Hz

  • long range neural synchronization
30
Q

What technique can be used to make the brain oscillate at a particular frequency?

A

Steady state

  • presenting a stimulus oscillating at a desired frequency (sound, image, somatosensory)
31
Q

Where is the steady state EEG approach useful?

A

Working with children or animals (no communication required)

32
Q

What do head and contour plots show

A

typically the distribution of activity across electrodes at a SPECIFIC point in time

(heat maps for a given time)

33
Q

ERP: A basic visual response

A

P100 (occipital)

34
Q

ERP: A basic auditory response

A

N100 (frontal)

35
Q

ERP: Produced by face stimuli

A

N170

36
Q

ERP: Reflects decision making

A

P300

37
Q

ERP: An indicator of motor planning

A

Lateralized readiness potential (LRP)

38
Q

Where in clinical research is EEG used?

A
  • Epilepsy
  • Migraine
  • Movement disorders (e.g. Parkinson’s)
  • Psychiatric disorders
  • Diagnosing brain death, coma etc.
39
Q

How is EEG used in sleep research?

A

Different stages of sleep are associated with characteristic patterns of EEG activity

  • EEG can be used to investigate sleep disorders, and study consolidation of learning during sleep
40
Q

How is EEG used in basic sensory research?

A
  • Assessing hearing deficits, the efficacy of cochlear implants
  • Vision: steady-state EEG has become more popular

The advantage of basic sensory research is that it can be used on subjects who cannot respond to a behavioural task (e.g. very young children)

41
Q

EEG has excellent ____ resolution but poor ____ resolution

A

temporal, spatial

42
Q

fMRI has excellent ____ resolution but poor ____ resolution

A

spatial, temporal

43
Q

To use EEG with fMRI you need an MR-compatible EEG system…

A

without too much metal

44
Q

(EEG & MEG together) Because the magnetic field and electrical dipole are _____, measuring both simultaneously can…

A
  • orthogonal

- aid enormously in source localization

45
Q

What are the advantages of EEG?

A

+ Cheap (consumables cost

46
Q

What are the future uses of EEG?

A
  • Human-computer interaction
  • Gaming headsets
  • BCI/neurofeedback

Basic principles in neuroimaging (8 decks)

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