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Principles > Experimental Designs in fMRI > Flashcards

Experimental Designs in fMRI Flashcards

1
Q

What is an independent variable in an experiment?

A

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

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2
Q

Define dependent variable.

A

The measured variable of interest in an experiment.

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3
Q

Differentiate between categorical and continuous variables.

A

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

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4
Q

What is the purpose of an experimental design in fMRI?

A

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

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5
Q

How is internal validity defined in a study?

A

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

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6
Q

Explain external validity in the context of a study.

A

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.

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7
Q

What is the impact of extraneous variables on internal validity?

A

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

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8
Q

Describe the trade-off between internal and external validity.

A

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

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9
Q

What characterizes an experimental condition?

A

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

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10
Q

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

A

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

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11
Q

What is the pure insertion assumption in subtraction designs?

A

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

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12
Q

How is a conjunction design used in fMRI studies?

A

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

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13
Q

What is the aim of parametric designs in fMRI?

A

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

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14
Q

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

A

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

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15
Q

What is PPI, and what factors does it involve?

A

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

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16
Q

How do block designs capture brain responses?

A

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

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17
Q

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

A

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

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18
Q

What are advantages of block designs in fMRI experiments?

A

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

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19
Q

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

A

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

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20
Q

What is the problem of multicollinearity in fMRI data analysis?

A

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

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21
Q

How are adaptation and refractory effects employed in fMRI studies?

A

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

22
Q

What is reverse inference in fMRI?

A

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.

23
Q

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

A

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

24
Q

How is susceptibility artifact defined in fMRI?

A

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

25
Q

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

A

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

26
Q

What is a notable advantage of fMRI?

A

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

27
Q

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

A

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

28
Q

Why is fMRI considered an indirect measure of neural activity?

A

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

29
Q

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

A

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

30
Q

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

A

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

31
Q

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

A

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

32
Q

How does susceptibility artifact occur in fMRI?

A

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

33
Q

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

A

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

34
Q

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

A

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.

35
Q

What is the purpose of multiple comparison correction in fMRI?

A

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

36
Q

What are the advantages of block designs in fMRI experiments?

A

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

37
Q

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

A

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

38
Q

Why is fMRI considered an indirect measure of neural activity?

A

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

39
Q

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

A

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

40
Q

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

A

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

41
Q

What is a notable advantage of fMRI?

A

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

42
Q

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

A

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

43
Q

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

A

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.

44
Q

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

A

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

45
Q

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

A

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

46
Q

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

A

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

47
Q

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

A

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

48
Q

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

A

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.

49
Q

Why is multiple comparison correction important in fMRI data analysis?

A

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

50
Q

What are the advantages of block designs in fMRI experiments?

A

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

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