Task 4 - MEG and EEG, oscillations and social cognition

Question 1

Magnetoencephalography (MEG)

Answer 1

• Non-invasive brain imaging technique.
• Measures the magnetic fields generated by neuronal activity.
• Uses superconducting sensors (SQUIDs) to detect tiny magnetic signals.

Question 2

FemtoTesla (fT)

Answer 2

• A unit of magnetic field strength used in MEG.
• MEG detects magnetic fields as small as femtotesla (1 fT = 10^-15 Tesla), which is extremely weak—about a billion times weaker than the Earth’s magnetic field.

Question 3

Mu-metal

Answer 3

A highly magnetic material used to shield MEG systems from external electromagnetic interference

Question 4

MEG vs. EEG

Answer 4

• EEG measures electrical potential, while MEG measures magnetic fields produced by it
• MEG more sensitive to currents that flow parallel to the scalp
• MEG has higher spatial resolution because magnetic field passes through skull better
• EEG much less expensive

Question 5

MEG and EEG Oscillations

Answer 5

• Both MEG and EEG measure brain oscillations, which are rhythmic patterns of neural activity
• These oscillations are organized into frequency bands that are associated with different cognitive states and processes

Question 6

Delta

Frequency Bands in MEG/EEG

Answer 6

(0.5–4 Hz): Deep sleep, unconscious states

Question 7

Theta

Frequency Bands in MEG/EEG

Answer 7

(4–8 Hz): Light sleep, relaxation, memory encoding

Question 8

Alpha

Frequency Bands in MEG/EEG

Answer 8

(8–12 Hz): Relaxed wakefulness, eyes closed.

Question 9

Beta

Frequency Bands in MEG/EEG

Answer 9

(13–30 Hz): Active thinking, focus, motor activity.

Question 10

Gamma

Frequency Bands in MEG/EEG

Answer 10

(30–100 Hz): High-level cognitive functions, attention, memory

Question 11

Frequency

Answer 11

The number of oscillations (cycles) per second (Hz).

Question 12

Amplitude

Answer 12

The strength or intensity of the oscillation (height of the wave).

Question 13

Phase

Answer 13

The position of the wave relative to a reference point in time

Question 14

Power

Answer 14

Power in EEG/MEG refers to the energy contained in a signal at a specific frequency or over a frequency band.
There is absolute power and relative power.

Question 15

Fast Fourier Transform (FFT)

Answer 15

Instead of looking at how the signal changes over time, FFT shows the frequencies that make up the signal.

It tells us which brainwave frequencies (e.g., Alpha, Beta, Gamma) are present and how much power they have.

Question 16

Absolute power

Answer 16

Absolute power refers to the raw power (amplitude squared) of a specific frequency band in EEG. It is measured in microvolts squared (µV²) and represents the actual strength of brain activity at a given frequency

Question 17

Relative power

Answer 17

Relative power expresses the power of a specific frequency band as a percentage of the total power across all frequency bands. It tells us how dominant a frequency band is compared to the entire EEG spectrum.

Question 18

Frequency analysis

Answer 18

• Breaks EEG signal into frequency components, showing the power distribution across different frequency bands.
• Uses Fourier Transform (FFT) to analyze frequency content.

Question 19

Time Frequency Analysis

Answer 19

• Analyzes EEG signal by examining both time and frequency, capturing how frequency content changes over time
• Provides time-frequency representation, showing when specific frequencies occur

Question 20

Implicit racial attitudes

EEG study

Answer 20

• Showed white participants white faces, black faces & positive images in context of negative image
• White elicited larger P2 & N2 (conflict monitoring) than black faces

Question 21

Intergroup attitudes affecting face processing

EEG study

Answer 21

When no intergroup competition: favour own group members& are indifferent to outgroup members
Larger N170 for ingroup

When intergroup competition: enhanced processing of outgroup faces as they may be threatening/otherwise noteworthy
Larger N170 for outgroup