Task 6 - Design and analysis of neuroimaging experiments

Question 1

Subtraction method (fMRI)

Answer 1

• Compares brain activity during a task condition with a control condition
• Subtracts the brain activity of the control condition from the task condition to isolate specific cognitive processes

Question 2

Conjunction analysis (fMRI)

Answer 2

• Statistical technique used to identify common brain regions activated across different experimental conditions or groups.
• Reduces issues related to pure insertion, highlights shared cognitive processes.

Question 3

Parametric design (fMRI)

Answer 3

• Varies the intensity or amount of a cognitive process to examine its effects on brain activity.
• Measures brain activity as a function of changes in a parameter (e.g., stimulus intensity, task difficulty)

Question 4

Blocked Design in fMRI

Answer 4

Experimental conditions are grouped into blocks (e.g., task vs. rest) and repeated for several cycles.

Question 5

Event-Related Design in fMRI (erfMRI)

Answer 5

Individual events or trials are presented sequentially with varying intervals between them (e.g., a visual stimulus followed by a task).

Question 6

Advantages of a Blocked Design

Answer 6

• High statistical power
• Good for detecting sustained brain responses (e.g., attention)
• Easier to detect brain activity due to repeated conditions.

Question 7

Disadvantages of Blocked Design

Answer 7

• Less ecological validity (artificial block structure)
• Expectation effects (participants anticipate conditions)
• Not suitable for short-lived brain responses.

Question 8

Advantages of Event-Related Design

Answer 8

• Higher ecological validity (real-world-like tasks)
• Measures short-term brain responses
• Flexible and captures individual events effectively.

Question 9

Disadvantages of Event-Related Design

Answer 9

• Lower statistical power (requires more trials)
• More challenging to control timing intervals
• May need larger sample sizes for sufficient data.

Question 10

Rapid erfMRI

Answer 10

• Presenting rapid, sequential stimuli to figure out how the brain responds to stimuli in quick succession
• Captures brain activity with high temporal resolution

Question 11

Mixed Design in fMRI

Answer 11

• Combines both blocked and event-related designs within the same experiment.
• Purpose: To capture both sustained brain responses (from blocks) and transient responses (from events)

Question 12

Advantages of a Mixed Design

Answer 12

• Offers a balance between high statistical power (blocked) and capturing dynamic responses (event-related).
• Useful for complex cognitive tasks that require both sustained and momentary brain activity analysis.

Question 13

Disadvantages of a Mixed Design

Answer 13

• More complex data analysis due to the combination of different designs.
• Longer scan time required for the combination of both designs.

Question 14

Behaviorally Driven fMRI

Answer 14

• Refers to using behavioral data (e.g., response time, accuracy) to drive the analysis of fMRI data
• Provides context for brain activity by linking neural responses to specific behavioral actions

Question 15

Hypothesis

Example study: Wagner et al.

Answer 15

• Activation in the left prefrontal and temporal cortices during verbal encoding predicts the likelihood of later memory retention
• Semantic processing leading to better recall than nonsemantic processing due to greater brain activation.

Question 16

fMRI design

Example study: Wagner et al.

Answer 16

Combined both a blocked and an event-related design

Question 17

Control conditions

Example study: Wagner et al.

Answer 17

Blocked: Subjects looked at a fixation point on the screen while not performing any tasks
Event-related: Had periods with no words presented (rest periods)