fMRI experimental design L2.1

Question 1

What are the three main types of experimental designs in fMRI?

Answer 1

1. Categorical
2. Factorial
3. Parametric.

Question 2

What are the three main ways to arrange stimuli in fMRI experiments?

Answer 2

1.Block design
2. Event-related design
3. Mixed design.

Question 3

When designing an fMRI experiment, what are important considerations?

Answer 3

• test specific hypotheses
• manipulate experience/behaviour to get best detectable neural changes
  -tolerable by participants

Question 4

what factors can be manipulated in a fMRI experiment?

Answer 4

• Stimulus type (e.g., audio/visual),
• stimulus timing (block or event-related)
• participant instructions (implicit vs. explicit tasks).

Question 5

What is a Categorical design in fMRI experiments?

Answer 5

It is based on cognitive subtraction and seeks differences between distinct cognitive states.

Question 6

What is the main concept behind Factorial design in fMRI?

Answer 6

manipulates more than one factor at the same time and looks at interactions between these factors

Question 7

what is parametric design in fMRI?

Answer 7

explores systematic changes in brain response based on varying task performance ( e.g reaction times and difficulty levels)

Question 8

what is a Block design in fMRI?

Answer 8

repeating experimental conditions within a block and changing with control/baseline blocks

Question 9

advantages and disadvantages of block design in fMRI

Answer 9

advantages:
1. simple to design and analyse
2. statistically powerful
3. flexible for parametric and factorial designs

disadvantages:
1. can be predictable leading to habituation and reduced response as it might not allow extraction to responses to specific stimuli

Question 10

what is event-related design in fMRI?

Answer 10

each stimulus is a separate epoch (event) to its possible to analyse brain activity to specific events
- mimics format of behaviour study better than blocks
- allows for more complex/less predictable experiments but in turn more complex to design/analyse

Question 11

Advantages and disadvantages of event-related design in fMRI

Answer 11

advantages:
- mimics behavioural studies
- allows post-hoc sorting of responses (correct vs incorrect)
- flexibility: allows for more complex and varied experiments

disadvantages:
- needs more complex design so can’t do simple experiments
-less statistical power unless there’s lots of well separated events ( but this is long)

Question 12

what is a mixed design in fMRI?

Answer 12

combination of block and event-related designs,giving flexibility and sustained activity while getting results

Question 13

what are the challenges with mixed design in fMRI?

Answer 13

while its possible to separate short term and long term events doing it is very hard

Question 14

what is cognitive subtraction in the context of categorical design?3

Answer 14

is the subtraction of brain activity during the rest or control condition form the brain activity during task
- AKA comparing the ‘task’ vs ‘rest’

Question 15

how does factorial design explore interactions between factors?

Answer 15

examines the effect of one factor (e.g motion) on the response to another factor like attention, through main effects and interaction terms

Question 16

what does parametric desing allow researchers to model?

Answer 16

systematic brain responses to changing task attributes such as reaction times, difficulty levels or learning effects

Question 17

what is the difference between block and event-related design in fMRI?

Answer 17

block = continuous exposure to stimuli
event= shows stimuli as discrete,separate events

Question 18

what are some alternatives to task-based fMRI when designing experiments?

Answer 18

• resting-state fMRI
• arterial spin labeling (ASL)
• EEG
  -MEG
  -fNIRS

Question 19

what are some common pitfalls when designing an fMRI experiment?

Answer 19

testing too many hypotheses at once and designing an experiment that people cant tolerate or complete

Question 20

what is the benefit of using more naturalistic stimuli in fMRI experiments?

Answer 20

thy elicit more realistic and ecologically valid brain repossess compared to static or controlled stimuli

Question 21

what is the importance of a baseline in fMRI?

Answer 21

baseline conditions allow for comparison against the task condition to detect changes in brain activity during the experimental task