Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Cognitieve Neuropsychologie > HC 2 > Flashcards

HC 2 Flashcards

1
Q

Why should we use EEG?

A

-Reaction time is the ultimate result of sensory, decision and motoric processes.

-We don’t know what happens in the brain during these processes. EEG helps determine the stadia with this.

-EEG can time course these stadia with precision of miliseconds.

-EEG can inform us about cognitive processes if there is no behavioural response.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What is an advantage of EEG compared to fMRI?

A

There is high temporal resolution, because of the distinction in stadia of informationprocessing. This is very hard or near impossible when using slow hemodynamic signals (fMRI).

For appliances that require real-time control, the high temporal resolution is needed.

ERPs allow us to measure all the different stadia, while in fMRI there are collapsed into a single time slice.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What is measured by EEG?

A

The electrical signal that is produced by cerebral activity. The most important one being the postsynaptic potential in the apical dendrites from cortical pyramidneurons.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Why do we not measure action potentials with EEG?

A

Action potentials only go in one direction. They are all or none responses and always excitory. This means that they cannot be summed up and they also don’t last long.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Why are post-synaptic potentials better picked up than action potentials by the EEG?

A

-They are great at responses
-Last longer
-Weaker in amplitude
-When travelling together they create dipoles at pyramidal cells
-Can be inhibitory or excitory
-Can be summed up

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Why can neurons from the amygdala not be measured with the EEG?

A

It is important that the potentials go in the same direction, which is not the case for the amygdala. This structure has neurons where the sum is near 0, because the potentials cancel each other out.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What are the requirements for a strong EEG signal?

A

They have to summed over many neurons, meaning:

-Timing, they have to be harmonized
-Position of the neuron, when they are aligned in the same orientation, there is a more powerfull EEG, if not then the signal gets neutralised.

In this way, positive and negative potentials don’t cancel each other out when they get summed.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Which cells have the right properties for a strong EEG signal?

A

Pyramidal Cells in the cortex.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What are dipoles?

A

It is a seperation charge over distance. It is essential for EEG, because dipole orientation provides differentiation among sources.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What does an EEG set-up look like?

A

The EEG set-up looks like:

-Participants sits in front of the stimulation computer
-EEG is measured while the participant fixates on the screen
-The EEG signal goes through filters and amplifiers
-The marker codes and also the filtered and amplified EEG signal is put into a digitization computer

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What are triggers (markers)?

A

They are the stimuli that are marked with a certain code, for example congruent or incongruent and they precede the responses, which also have their own code.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What is a mastoid?

A

It is the thickest part of the skull and is usually used as a reference sensor in EEG.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

How is EEG measured?

A

The voltage level between two sensors is measured. This is usually between one sensor on the scalp and a reference one.

The positiveness or negativeness of a voltage level determines how the signal looks. In other words: this results in rhythmic fluctations in voltage.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Name the reference and ground electrodes and where are they located?

A

Ground electrode: On the forehead

Reference:
Tip of the nose
Nasal cavity
Earlobe
Mastoid

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What is a reference electrode?

A

The fundamental principle is: always think of ERPs as a difference between the active and reference sites.

It provides a biological baseline.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

How should you place the reference electrode?

A

It should be in a convenient location:
-Not biased towards a certain hemisphere
-Easy to attach
-Not distracting
-Frequently used by other investigators so that waveforms can be easily compared

The best compromise according to Luck in most cases is the average of mastoids (or earlobes), but other researchers believe average reference is the best.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

What is the difference between the international 10-20 system and 10-10 system?

A

The distance between each sensors and the amount of electrodes. The 10-20 system has less sensors and the 10 and 20 refers to distances between adjacent electrodes, which are either 10% or 20% of the total distance of the skull (front to back or left to right or circumference of the head).

The use of percentages guarantees that the location of a particular electrode is the same across participants, independent of size of the head.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

What do the abbreviations stand for in electrode placements?

A

Fp= Frontal Pole
F= Frontal
C= Central
P= Parietal
O= Occipital
T= Temporal

Left: Odd numbers
Right: Even numbers
Midline: z for zero

19
Q

How do we lower resistance of the signal?

A

SIgnals have to travel through the skull and scalp, which results in a high resistance. You can lower it with conductive gel.

20
Q

What does a ground electrode do?

A

It reduces electrical environmental noise.

21
Q

What does an amplifier do?

A

It simply amplifies a signal.

22
Q

What is AD conversion?

A

AD means analogue to digital. We converge the analoque signal (sample rate) to visual. Analogue EEG signal is digitized (numbers) to have time series that represent the voltage values.

23
Q

What is the sampling frequency?

A

The rate of digitization in Hertz (Hz).

24
Q

What is aliasing?

A

It is under sampling, so faster signals are perceived as non-moving. It overlaps frequency components resulting in a sample rate below the Nyquist rate.

25
Q

What is the Nyquist-Shannon sampling theorem?

A

The sample rate should be at least 2x the fastest frequencies in the signal.

26
Q

What is the AD-level?

A

Resolution is the amount of information in each sample.

27
Q

What are the different frequency bands?

A

Delta: 0-4Hz
Deep sleep

Theta: 4-7Hz
Deep meditation

Alpha: 8-12Hz
Eyes closed, awake

Beta: 12-30Hz
Eyes opened, thinking

Gamma: 30-100Hz
Unifying consciousness

28
Q

What is an oscillation?

A

It is a vibration of periodic reversal of movement direction.

29
Q

What is time-domain?

A

Signals measured in time. Raw data needs to get converted into ERPs (event-related potentials). In short:

-We want epochs
-Delete the rest
-Take the average of all the epochs => p300

Small and large waves cancel each other out, what remains are waves that are similar.

30
Q

What is an epoch?

A

The signal that is 1 second after the stimulus, we are only interested in this part.

31
Q

What are ERPs?

A

EEG changes that are time locked to sensory, motor or cognitive events that provide safe and noninvasive approach to study psychophysiological correlates of mental processes.

They are tiny and embedded in noise that is 20-100uV.

They provide us a conitnuous measure of activity at each moment in time. This allows us to measure the brain processes that occur between the stimulus and the response instead of just measuring the behavioral response that comes at the end of these processes.

32
Q

What is the importance of clean data?

A

Averaging is a key method to reduce noise. The quality of the ERP or ‘noisiness’ is expressed as the signal to noise ratio (S/N ratio).

To increase the S/N ratio, we need to increase the number of trials.

33
Q

What is usually presented on papers regarding ERPs?

A

Papers usually don’t show single-subject ERP waveforms. Instead, they usually take single-subject averaged ERP waveforms and average them together into a Grand Average waveform.

However, for statistical analysis, single-subject waveforms are used.

34
Q

What is generally thought about ERPs?

A

Early peaks= more sensory processing

Later peaks= more cognitive, deeper processing

35
Q

Which waves are highly sensitive to physical properties of the stimulus?

A

C1, P1 and N1.

36
Q

What are some examples of event-related potentials?

A

-N170
-Mismatch negativity
-N400
-P600
-LPP

37
Q

What is N170?

A

A face-specific component that responds more to faces (higher amplitude) than to non-faces. Activity originates from the occipital electrode sides and is somehow stronger on the right hemisphere.

38
Q

What is mismatch negativity?

A

MMN is evoked automatically by a change in a sequence of sounds.

39
Q

What is N400?

A

The ERP ‘component’ that is related to meaning. It is bigger when the word’s meaning doesn’t fit the context.

40
Q

What is P600?

A

The ERP ‘component’ that is related to form (syntactic violations). It is bigger when a word is not of the expected type for a position in a sentence.

41
Q

What is LPP?

A

ERP component related to emotion. It is the late positive potential and primarily reflects arousal and not valence.

42
Q

What are the meanings of vertex, nasion and inion?

A

Vertex= highest point of the skull

Nasion= where the top of the nose meets the ridge of the forehead

Inion= The external occipital protuberance of the skull

43
Q

What is the meaning of ‘gain’?

A

The voltage gain. It is the ratio of output signal voltage to input voltage of an EEG channel. It is often expressed in decibels.

44
Q

What is the meaning of impedance?

A

It is typically measured by passing a small alternating current between two or more electrodes connected to the skin. Thus, the measured impedance reflects contributions from more than a single electrode. It is the resistance.

Cognitieve Neuropsychologie (13 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions