What are the two types of structural imaging techniques?
CT and MRI.
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What are the two types of functional imaging techniques?
PET and fMRI.
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What are the properties of CT scans (6)?
Moderately invasive, use x-rays, inexpensive, widely available, low spatial resolution, not useful for neuroscientific research.
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What are the properties of MRI scans (4)?
Non-invasive, uses radio frequency fields, extremely high spatial resolution, used for structural brain imaging in neuroscientific research.
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What are the properties of PET scans (6)?
Moderately invasive, uses radioactive isotopes, measure metabolic correlates of neural activity, high spatial resolution, low temporal resolution, expensive.
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What are the properties of fMRI scans (5)?
Non-invasive, measures metabolic correlates of neural activity, high spatial resolution, low temporal resolution, moderately expensive.
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What are the features of an MRI scanner (2)?
Incredibly strong magnets (1.5-7 tesla), no metal allowed.
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What is a BOLD signal?
A blood oxygen dependent level signal. Active neurons cause increases in blood flow to those parts of the brain.
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Why is a BOLD signal used in MRI scans?
Haemoglobin differs in its response to magnetic fields, depending on whether it is oxygenated or not.
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What is said to be a good baseline in an experimental design?
One that differs from the experimental condition only by the process of interest,
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What is a block design?
Intervals of task and rest.
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What are the disadvantages of block designs (4)?
High predictable occurrence of stimuli, inflexible for more complex tasks, blocking trials may decrease ecological validity, cannot separate trials by performance.
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What is an event-related design?
Trials of different conditions are randomly intermixed and occur close together in time.
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What are the advantages of event-related designs (5)?
Can design more complex/ novel experiments, randomization eliminates practice effects, allows post hoc sorting, rare/ unpredictable events can be measured, can look at temporal dynamics of response.
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How long does it take to collect a single volume (one slice) of data?
2-3 seconds.
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What is pre-processing of data?
Correcting for non-task related variability in experimental data, without consideration of the design.
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Why do we pre-process data?
To remove variability.
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What are the five steps to pre-processing data?
High pass filtering ---> Motion correction ---> Slice time correction ---> Co-registration ---> Normalization/ spatial smoothing.
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What do we use for standardized space?
MNI space, which is a combination of 352 MRI scans of right-handed people.
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What is multiple regression?
A way of determining the effect of a number of independent variables on a single dependent variable.
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What test does multiple regression use to test significance, and what threshold is applied to the given value?
A t-test, with a threshold of p< 0.05.
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What is whole brain analysis?
Examines the effects on a voxel by voxel basis across the whole brain.
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What are the advantages of whole brain analysis (2)?
Requires no prior hypothesis about which areas are involved, includes the entire brain.
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What are the disadvantages of whole brain analysis (3)?
Can lose spatial resolution with averaging, dependent on statistics and threshold, multiple comparison problems.
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What is region of interest analysis?
Focuses on one area of the brain.
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What are the advantages of region of interest analysis (4)?
Hypothesis driven so doesn't focus on meaningless areas, avoids multiple comparison problems, requires no further analysis, generalisable.
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What are the disadvantages of region of interest analysis (2)?
Easy to miss things in other areas, ROIs are not always easy to define.
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What are the advantages of fMRI data (1)?
We can find out how the brain carries out a particular function, so we can explore the mechanisms.
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What are the disadvantages of fMRI data (2)?
Its correlative, requires more evidence to determine causality.
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What are the limitations of mass univariate approach (3)?
Spatial smoothing causes loss of information, makes assumptions about the shape of neuronal activation, subtraction methods make assumptions about how the brain implements cognitive processes.
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Card 2
Front
What are the two types of functional imaging techniques?
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