Task 4 - MEG & EEG Oscillations

Question 1

What is a more direct method of measurement? EEG or fMRI?

Answer 1

EEG

Question 2

What is a field of research that benefits highly from the temporal resolution of EEG?

Answer 2

E.g. Implicit Racial Bias

Question 3

When determining waveforms, EEG signals are often ____ or _____.

Answer 3

Stimulus-locked; Response-locked

Question 4

Describe Ito et al.’s racism experiment.

Answer 4

Oddball paradigm: Presenting positive objects paired with either white or black faces -> Black faces had a larger P3 response as they were perceived as more different from positive stimuli

Question 5

The fact that our attitudes towards certain faces influences basic perception is shown by…

Answer 5

That N170 is sensitive to face evaluation.

Question 6

How does ECoG improve on EEG?

Answer 6

It has better spatial resolution

Question 7

What exactly does EEG respond to?

Answer 7

post-synaptic potentials that change extracellular membrane potentials

Question 8

When are alpha waves often observed and what frequency do they correspond to?

Answer 8

~10Hz

Observed at rest

Question 9

What is often referred to as a good location for the reference electrode in EEG?

Answer 9

Mastoid Bone

Question 10

How can a waveform be quantified?

Answer 10

Frequency (Hz)
Amplitude (Microvolt)
Phase (Degrees)

Question 11

What happens in a Fourier Analysis?

Answer 11

When multiple frequencies act at the same time, Fourier analysis can disentangle them and show what frequencies are present how strongly.

Question 12

What are the X and Y axes in a frequency spectrum?

Answer 12

X: Frequency
Y: Amplitude

Question 13

What is the name of the MEG equivalent of ERP?

Answer 13

ERF - Event related field

Question 14

Name two crucial differences in the information obtained from EEG/MEG studies vs RT studies.

Answer 14

• RT can only capture end results, whereas EEG and MEG show the whole process.
• EEG and MEG can also be analyzed when there is no reaction to be measured.

Question 15

What anatomical feature is one reason why dipoles are large enough to be measured?

Answer 15

Cortical Organization in Columns

Question 16

What is an important reason, that setting up MEG equipment is very costly?

Answer 16

You need to shield the entire room from the earth’s magnetic field.

Question 17

As opposed to EEG, MEG can only detect ____ dipoles.

Answer 17

tangential

Question 18

Which measurement techniques have the inverse problem?

Answer 18

Only MEG

Question 19

Which subcortical structure is often said to be the motor of cortical oscillations?

Answer 19

The Thalamus

Question 20

What are some alternatives to making use of a reference electrode?

Answer 20

• Using the average as reference

- Laplacian Transformation - average potential difference between each electrode and the nearest four electrodes

Question 21

When are delta waves often observed and what frequency do they correspond to?

Answer 21

1-4 Hz

present during sleep

Question 22

When are theta waves often observed and what frequency do they correspond to?

Answer 22

4-8Hz
drowsiness
when present in the frontal lobe: focused attention and mental effort

Question 23

When are beta waves often observed and what frequency do they correspond to?

Answer 23

13-30Hz

During attention

Question 24

When are gamma waves often observed and what frequency do they correspond to?

Answer 24

36-44Hz
Associated with arousal
Often occur in bursts

Question 25

When investigating waveforms, what is a very important parameter of one’s setup to consider?

Answer 25

Sampling rate

Question 26

What theorem says, that sampling rate should be at least two times the highest frequency under investigation?

Answer 26

Nyquist Theorem

Question 27

What is Aliasing?

Answer 27

When a signal is sampled at a rate that is too low, and introduces irreparable distortion to the digital waveform.

Question 28

What is the affective congruency effect?

Answer 28

Affective target words are categorized more quickly when preceded by a prime word of the same valence.

Question 29

What neural mechanism explains the affective congruency effect?

Answer 29

Readiness Potentials

Question 30

What is a different name for the Laplacian transformation?

Answer 30

Radial Current Flow

Question 31

What is the reason and effect of a taper transformation?

Answer 31

It reduces amplitudes at both ends of an epoch to zero in order to keep variance stemming from other epochs low.