EEG & Eye-Tracking - Lecture 5

Question 1

What type of neural activity does EEG primarily measure?

Answer 1

EEG measures differences in electric potential resulting from postsynaptic potentials (EPSPs and IPSPs) generated by spatially aligned and synchronous cortical neurons.

Question 2

Why are pyramidal cells particularly suitable for EEG measurements?

Answer 2

They are spatially aligned, perpendicular to the cortical surface, recurrently connected, and receive synchronous inputs.

Question 3

Name one primary limitation of EEG.

Answer 3

EEG is limited to measuring cortical activity and cannot effectively localize subcortical sources due to the “inverse problem.”

Question 4

How does MEG differ from EEG in terms of signal origin?

Answer 4

MEG detects the magnetic fields created by neural currents, which are less distorted by the surrounding brain tissue compared to the electrical potentials measured by EEG.

Question 5

What are common artifacts in EEG recordings, and how are they mitigated?

Answer 5

Common artifacts include eye blinks, muscle tension, and 50 Hz mains interference. Mitigation techniques include Independent Component Analysis (ICA), filtering, and proper subject preparation.

Question 6

What are Event-Related Potentials (ERPs), and how are they computed?

Answer 6

ERPs are changes in EEG amplitude evoked by a stimulus, computed by averaging epoched time series across multiple trials to eliminate noise.

Question 7

What is the importance of frequency domain analysis in EEG?

Answer 7

It decomposes EEG signals into frequency bands (oscillations) that reflect different functional roles, such as attention and motor control.

Question 8

Explain the significance of a time-frequency spectrum in EEG analysis.

Answer 8

A time-frequency spectrum shows how the amplitude of oscillations changes over time, revealing dynamics that may cancel out during simple averaging.

Question 9

What is the “inverse problem” in EEG source localization?

Answer 9

It refers to the challenge of determining the exact neural sources of EEG signals due to the ambiguity of mapping observed scalp potentials back to their cortical origins.

Question 10

List two advantages and two disadvantages of EEG.

Answer 10

Advantages: High temporal resolution & noninvasive nature.

Disadvantages: Poor spatial resolution & susceptibility to noise.

Question 11

What physiological features are measured in eye tracking?

Answer 11

Saccades, gaze fixation location and duration, and pupil diameter.

Question 12

Describe the two types of eye tracking systems.

Answer 12

Head-mounted systems: Attached directly to the participant for close measurement.

Remote systems: Measure eye movements from a distance without physical contact.

Question 13

What are saccadic eye movements, and why are they used in research?

Answer 13

Rapid jumps of the eyes between points of focus, used to minimize the influence of hand movement artifacts and study cognitive processes.

Question 14

How can pupil diameter indicate cognitive load?

Answer 14

Pupil dilation is influenced by the sympathetic nervous system, reflecting arousal, effort, or stress, which are proxies for cognitive load.

Question 15

What is the attention Drift Diffusion Model (aDDM)?

Answer 15

A cognitive model integrating response times, accuracy, and fixation data to show how gaze impacts evidence accumulation for decisions.

Question 16

How does gaze fixation duration differ between experts and novices?

Answer 16

Experts typically fixate more efficiently on relevant information, while novices display less selective fixation patterns.

Question 17

Explain the concept of the pupil light response (PLR).

Answer 17

A largely reflexive response of pupil constriction and dilation to changes in light, which can also be modulated by cognitive factors such as visual attention.

Question 18

How can eye tracking data be confounded, and what are common artifacts?

Answer 18

Confounds include variations in light, eye blinks, and participant fatigue. Artifacts include difficulties caused by glasses, dark irises, or medication affecting pupil diameter.

Question 19

What role does the Locus Coeruleus play in regulating pupil diameter?

Answer 19

It is a key regulator of noradrenaline, linking pupil size changes to arousal and cognitive effort.

Question 20

How can eye tracking aid in understanding dyslexia?

Answer 20

Eye tracking reveals atypical patterns such as increased multiple fixations on words and shifted fixation points, suggesting reliance on sublexical processing rather than orthographic recognition.