EEG and MEG / ERP's ARTICLES

Question 1

What is the primary advantage of ERPs over modern neuroimaging techniques?

Answer 1

The primary advantage of ERPs is their high temporal resolution, allowing measurement of brain activity on a millisecond scale.

Question 2

What fundamental brain activity does ERP measure?

Answer 2

ERPs measure postsynaptic activity of neural ensembles rather than individual neuron action potentials.

Question 3

Which ERP component is associated with preparatory cognitive activity?

Answer 3

The Contingent Negative Variation (CNV).

Question 4

Why is the 10/20 electrode placement system important in ERP studies?

Answer 4

It standardizes electrode placement, making ERP findings easier to integrate and replicate across studies.

Question 5

What are the C1, P1, and N1 components responsible for?

Answer 5

These components reflect the early stages of sensory and perceptual processing in the brain.

Question 6

Define the term ‘inverse problem’ in the context of ERP analysis.

Answer 6

The inverse problem refers to the difficulty of localizing neural generators of ERP effects from scalp recordings due to multiple possible solutions.

Question 7

What does the N2pc component indicate?

Answer 7

It is associated with the deployment of covert attention to visual field targets.

Question 8

Name two methods to improve the signal-to-noise ratio in ERP studies.

Answer 8

Collecting a large number of trials and ensuring a noise-free recording environment.

Question 9

How are ocular artifacts, such as eye blinks, addressed in ERP studies?

Answer 9

By using electrooculogram (EOG) recordings or excluding trials contaminated by artifacts.

Question 10

What is baseline correction, and why is it used?

Answer 10

Baseline correction involves subtracting the average prestimulus voltage from the entire waveform to isolate stimulus-related effects.

Question 11

Why do ERP researchers often use randomization in trial presentation?

Answer 11

To minimize anticipatory effects and ensure accurate stimulus-related waveform measurements.

Question 12

What is the P3 component known to reflect?

Answer 12

Working memory updating and categorization processes.

Question 13

What can cause distortions in ERP amplitude and timing?

Answer 13

Aggressive filtering during data processing.

Question 14

Why is it essential to use a sufficient number of artifact-free trials in ERP experiments?

Answer 14

To ensure reliable measurements of ERP components like C1, P1, and N1.

Question 15

What role does the alpha band play in ERP recordings?

Answer 15

Alpha activity is a major source of noise overlapping with early ERP components.

Question 16

What are the ERN and Pe components associated with?

Answer 16

Error processing and evaluation following a behavioral response.

Question 17

Why is the spatial resolution of ERP recordings limited?

Answer 17

The layers of tissue between the brain and the scalp distort the electrical signals.

Question 18

How do ERPs contribute to understanding cognitive processing?

Answer 18

They allow visualization of brain activity as it unfolds over time, from sensory input to behavioral response.

Question 19

What distinguishes stimulus-locked ERP waveforms?

Answer 19

They are time-locked to the presentation of a stimulus, reflecting sensory and cognitive processing.

Question 20

What is the role of the CNV in motor preparation?

Answer 20

It reflects the buildup of activity in anticipation of an expected stimulus.

Question 21

What do EEG and MEG primarily measure in the brain?

Answer 21

EEG measures electrical fields, while MEG records magnetic fields generated by neuronal activity.

Question 22

What is a major difference between EEG and MEG in terms of sensitivity to neural sources?

Answer 22

EEG is sensitive to both radial and tangential sources, whereas MEG primarily detects tangential components.

Question 23

What condition must neurons meet to generate detectable EEG/MEG signals?

Answer 23

Neurons must be active synchronously and spatially organized to form a functional entity.

Question 24

What is the ‘forward problem’ in EEG/MEG studies?

Answer 24

Calculating scalp electric or magnetic fields from known neuronal sources.

Question 25

What is the ‘inverse problem,’ and why is it challenging?

Answer 25

Estimating neuronal sources from scalp recordings; it has multiple solutions without specific constraints.

Question 26

How do EEG and MEG signals differ in terms of spatial distortion?

Answer 26

MEG signals experience less spatial distortion than EEG due to the properties of surrounding tissues.

Question 27

What role do neuronal oscillations play in cognitive processes?

Answer 27

They facilitate information coding, modulate attention, and enable communication between neuronal populations.

Question 28

Name the primary EEG/MEG frequency bands and their general functional associations.

Answer 28

Delta (<4 Hz): Deep sleep and unconscious processes.
Theta (4-8 Hz): Memory and navigation.
Alpha (8-13 Hz): Relaxation and inhibition of irrelevant stimuli.
Beta (14-30 Hz): Active thinking and motor planning.
Gamma (>30 Hz): Perception and consciousness.

Question 29

What is ‘phase-locking value’ (PLV) used for in EEG/MEG studies?

Answer 29

To measure functional connectivity between brain regions by analyzing the consistency of phase relationships.

Question 30

What is the significance of gamma oscillations in perception?

Answer 30

They play a key role in forming neural representations and supporting the binding of sensory information into coherent perceptions.

Question 31

How can neuronal synchrony be achieved according to EEG/MEG studies?

Answer 31

Through oscillations that align neuronal activity, facilitating effective communication and coordination.

Question 32

What is Independent Component Analysis (ICA), and how is it used in EEG/MEG?

Answer 32

A preprocessing method to separate EEG/MEG signals into statistically independent components, often used for artifact removal.

Question 33

Why are EEG/MEG signals more distorted when passing through the skull?

Answer 33

The skull and other tissues have varying electrical resistivities that affect the signal.

Question 34

What is ‘functional connectivity’ in the context of EEG/MEG?

Answer 34

The statistical association between activities of different brain regions, as inferred from signals.

Question 35

What is ‘effective connectivity’?

Answer 35

The causal influence one brain region exerts over another.

Question 36

How do EEG/MEG oscillations differ in spatial extent across frequency bands?

Answer 36

Lower frequencies (e.g., delta) engage broader spatial domains, while higher frequencies (e.g., gamma) are more localized.

Question 37

What is the role of cross-frequency coupling in cognitive processing?

Answer 37

It integrates information across different oscillatory frequencies, such as gamma modulated by theta rhythms.

Question 38

What distinguishes induced from evoked EEG/MEG activities?

Answer 38

Induced activities are not precisely time-locked to an event, whereas evoked activities are.

Question 39

How are EEG and MEG used together with fMRI in neuroscience?

Answer 39

To combine the temporal resolution of EEG/MEG with the spatial resolution of fMRI for a comprehensive view of brain activity.

Question 40

What is the ‘binding hypothesis’ associated with gamma oscillations?

Answer 40

It suggests that synchronization in the gamma band integrates neural assemblies to form unified percepts or actions.