Peer mentoring Flashcards
What are the limitations of block design?
- highly predictable occurrence of stimuli
- inflecible for more complex tasks
- ecological validity
- cant seperate trials by performance
What are advantages of event-related design?
- flexibility and randomisation
- post hoc sorting
- can look at novelty and priming
- can look at temporal dynamics of response
What does a BOLD signal measure?
the magnetic properties of oxygenated v. deoxygenated blood
What is a limitaion of the block design in MRI studies?
it is highly predictable
What are the 6 preprocessing steps?
- high pass filtering
- motion correction
- slice time correction
- coregistration
- normalisation
- spatial smoothing
Ultimately we want to do statistics on GROUP activation maps. Thus, we must get all of the brains into a ‘standard space’. How do we do this?
Complex algorithms to warp each subject’s brain into the shape of a TEMPLATE BRAIN
What was the original standard based on?
The brain of a 60-year-old French Woman
Why do we no longer use the original standard?
her brain may not be representative of all brains
What standard do we use now for comparing brains?
Montreal Neurological Institute (MNI) space
How was MNI created?
352 scans on normal controls, all right-handed
Advantages of whole brain analysis?
■ No prior hypothesis about areas involved needed.
■ Includes the whole brain.
Disadvantages of whole brain analysis?
■ Can lose spatial resolution –> due to inter-subject averaging.
■ Can produce meaningless lists of areas. Hard to interpret.
■ Depends highly on statistics and selected threshold.
■ Multiple comparisons problem.
Advantages of region of interest?
- hypothesis driven
- avoids multiple comparison problem
- simple
- generalisable
Disadvantages of region of interest?
■ Easy to miss things going on elsewhere in the brain.
■ Not always simple how to define ROIs.
Limitations of fMRI
- data is correlative
- temporal resolution is low
BOLD signal is arbitrary… meaning what?
it has no stbale baseline
How fast is the BOLD signal?
it is slow. peaks 4-5 seconds after stimulus onset and about 16 seconds to return to baseline
What are the two types of designs that can be used in an MRI scan?
block design (long periods of alternating task performance) and event-related design- trials of different conditions are randomly intermixed
How do we analyse results?
- multiple regression
- multiple regression per voxel
- contrast
- threshold of p<0.05
What are the three major sulci?
central, lateral and parietal-occipital
Where are basic physiological and metabolic processes controlled?
by groups of neurons in the brainstem, including thalamus and hypothalamus
What are the types of functions controlled in this area?
respiration, digestion,, glucose, metabolism, arousal…
What are some specific groups of neurons?
- reticular formation (control of arousal and sleep)
- suprachiasmatic nucleus (circadian rhythm)
- ventromedial nucleus (blood glucose into body fat)
What is the function of the cirpus callosum?
to allow messages to travel between hemispheres