Experimental Designs in fMRI

Question 1

What is an independent variable in an experiment?

Answer 1

The variable manipulated in an experiment to generate changes in the measured response.

Question 2

Define dependent variable.

Answer 2

The measured variable of interest in an experiment.

Question 3

Differentiate between categorical and continuous variables.

Answer 3

Categorical variables have discrete values, while continuous variables have an infinite number of values.

Question 4

What is the purpose of an experimental design in fMRI?

Answer 4

It organizes an experiment to effectively test research hypotheses, especially crucial in fMRI due to its high cost.

Question 5

How is internal validity defined in a study?

Answer 5

Internal validity is achieved if a study produces one and only one explanation of the results.

Question 6

Explain external validity in the context of a study.

Answer 6

External validity refers to the generalizability of results beyond the research context, from sample to population, from one study to another, and from a study to the real world.

Question 7

What is the impact of extraneous variables on internal validity?

Answer 7

Extraneous variables interact with the independent variable and its manipulation, worsening internal validity.

Question 8

Describe the trade-off between internal and external validity.

Answer 8

There is a trade-off between internal and external validity, increasing one will decrease the other, necessitating a balance.

Question 9

What characterizes an experimental condition?

Answer 9

An experimental condition contains tasks or stimuli relevant to the research hypothesis.

Question 10

What is the purpose of a control condition (baseline)?

Answer 10

A control condition provides a standard for comparison with experimental conditions, ensuring they are not too distant or similar.

Question 11

What is the pure insertion assumption in subtraction designs?

Answer 11

It assumes that a specific cognitive process can be inserted into another set of cognitive processes without altering their nature.

Question 12

How is a conjunction design used in fMRI studies?

Answer 12

It isolates the same process by multiple separate comparisons and tests for common activation in several independent contrasts.

Question 13

What is the aim of parametric designs in fMRI?

Answer 13

Parametric designs vary a stimulus parameter of interest on a continuum, offering flexibility in testing relations between BOLD and the parameter.

Question 14

What does a factorial design with categorical factors allow in different studies?

Answer 14

It allows the verification of the pure insertion assumption in different studies, modeling interaction between factors.

Question 15

What is PPI, and what factors does it involve?

Answer 15

Psychophysiological Interactions (PPI) is a parametric factorial design involving a psychological context and a physiological source, requiring knowledge about neurobiological plausibility.

Question 16

How do block designs capture brain responses?

Answer 16

Block designs examine responses to a series of similar stimuli, capturing sustained tonic responses.

Question 17

Differentiate between epoch and event-related models in block designs.

Answer 17

Epoch models involve sustained periods of stimulation, while event-related models consist of impulses.

Question 18

What are advantages of block designs in fMRI experiments?

Answer 18

Block designs are simple, minimize task switching, are robust to uncertainty in timing, and allow straightforward analysis.

Question 19

What is a disadvantage of event-related designs compared to block designs?

Answer 19

Event-related designs are less efficient for detecting effects than block designs.

Question 20

What is the problem of multicollinearity in fMRI data analysis?

Answer 20

Multicollinearity occurs when regressors in the design matrix correlate with each other, making the interpretation of GLM results challenging.

Question 21

How are adaptation and refractory effects employed in fMRI studies?

Answer 21

They are used as indices of brain function, with repetition suppression revealing brain regions associated with adaptation.

Question 22

What is reverse inference in fMRI?

Answer 22

Reverse inference involves inferring the occurrence of a process based on the activation of a certain brain region, which is logically invalid for various reasons.

Question 23

What criticism is associated with brain-behavior correlations in fMRI studies?

Answer 23

Some argue that reported brain-behavior correlations are impossibly high, potentially misleading interpretations.

Question 24

How is susceptibility artifact defined in fMRI?

Answer 24

Susceptibility artifacts result from differences in magnetic field strength near substance interfaces of different magnetic susceptibility.

Question 25

How does the presentation of a brain image influence scientific reasoning, according to McCabe & Castel (2008)?

Answer 25

Participants are more likely to judge a statement as valid when a brain activation map is included in the article.

Question 26

What is a notable advantage of fMRI?

Answer 26

FMRI is non-invasive and does not require ionizing radiation, making it safe for repeated use.

Question 27

What is a limitation of fMRI in terms of time resolution?

Answer 27

fMRI has low time resolution, but it can be combined with EEG to address this limitation.

Question 28

Why is fMRI considered an indirect measure of neural activity?

Answer 28

It measures changes in blood flow and oxygenation, which indirectly reflect neural activity.

Question 29

What is a potential issue with the heavy dependence on choosing a good baseline condition in fMRI studies?

Answer 29

Too close to active conditions may result in false negatives, while too far may lead to false positives.

Question 30

What term describes the correlation between regressors in the design matrix in fMRI analysis?

Answer 30

The problem of multicollinearity arises when regressors correlate with each other.

Question 31

What does fMRI evidence need to be supported by to establish causality?

Answer 31

fMRI evidence needs further converging causal evidence, such as from neuropsychology or transcranial magnetic stimulation (TMS).

Question 32

How does susceptibility artifact occur in fMRI?

Answer 32

Susceptibility artifacts result from differences in the magnetic field strength near interfaces of substances with different magnetic susceptibilities.

Question 33

According to Lilienfield et al. (2015), why should certain terms be avoided in neuroimaging literature?

Answer 33

The use of certain terms may lead to wrong interpretations and assumptions, affecting both popular and scientific reception.

Question 34

What is reverse inference in fMRI, and why is it considered logically invalid?

Answer 34

Reverse inference involves inferring a process based on the activation of a brain region, but it is logically invalid due to the lack of a one-to-one correspondence in the mind-brain relationship.

Question 35

What is the purpose of multiple comparison correction in fMRI?

Answer 35

Multiple comparison correction is essential in neuroimaging data to account for the high number of statistical tests and reduce the risk of false positives.

Question 36

What are the advantages of block designs in fMRI experiments?

Answer 36

Block designs are simple, minimize task switching, have maximum efficiency, and are robust to uncertainty in timing.

Question 37

What is a limitation of event-related designs compared to block designs?

Answer 37

Event-related designs are typically less efficient for detecting effects than block designs.

Question 38

Why is fMRI considered an indirect measure of neural activity?

Answer 38

fMRI measures changes in blood flow and oxygenation, which are indirect indicators of neural activity.

Question 39

What is the main criticism associated with brain-behavior correlations in fMRI studies?

Answer 39

Some argue that reported brain-behavior correlations are impossibly high and may not accurately reflect underlying cognitive processes.

Question 40

According to McCabe & Castel (2008), how does the presentation of a brain image influence scientific reasoning?

Answer 40

Participants are more likely to judge a statement as valid when a brain activation map is included in the article.

Question 41

What is a notable advantage of fMRI?

Answer 41

fMRI is non-invasive and does not involve ionizing radiation, making it safe for repeated use.

Question 42

What is a limitation of fMRI in terms of time resolution?

Answer 42

fMRI has low time resolution, but it can be complemented by combining it with EEG.

Question 43

Why is the choice of a good baseline condition crucial in fMRI studies?

Answer 43

The choice of a good baseline condition is crucial as being too close to active conditions may lead to false negatives, while being too far may result in false positives.

Question 44

What term describes the correlation between regressors in the design matrix in fMRI analysis?

Answer 44

The problem of multicollinearity arises when regressors in the design matrix correlate with each other.

Question 45

What does fMRI evidence need to be supported by to establish causality?

Answer 45

fMRI evidence needs to be supported by further converging causal evidence, such as findings from neuropsychology or transcranial magnetic stimulation (TMS).

Question 46

What are susceptibility artifacts in fMRI, and how do they occur?

Answer 46

Susceptibility artifacts result from differences in magnetic field strength near interfaces of substances with different magnetic susceptibilities, affecting brain regions proximal to these interfaces.

Question 47

According to Lilienfield et al. (2015), why should certain terms be avoided in neuroimaging literature?

Answer 47

Certain terms may lead to incorrect interpretations and assumptions in both popular and scientific reception.

Question 48

What is the logical issue associated with reverse inference in fMRI?

Answer 48

Reverse inference involves inferring a process based on the activation of a brain region, but it is logically invalid due to the lack of a one-to-one correspondence between mind and brain.

Question 49

Why is multiple comparison correction important in fMRI data analysis?

Answer 49

Multiple comparison correction is crucial to account for the high number of statistical tests in neuroimaging data, reducing the risk of false positives.

Question 50

What are the advantages of block designs in fMRI experiments?

Answer 50

Block designs are simple, minimize task switching, have maximum efficiency, and are robust to uncertainty in timing.