Quiz 7 Flashcards
what are the two strategies of functional imaging of blood flow and how do both of them similarly work
- Positron Emission Tomography (PET)
- Functional Magnetic Resonance Imaging (fMRI)
- neural activity consumes oxygen as well as generating electrical signals
- increase of blood flow to region, to compensate for increase oxygen consumption
- slow temporal resolution, but good spatial resolution (time taken for response is slow)
what is PET
- measures blood flow
- radioactive tracer injected into blood stream
- tracer takes 30 seconds to peak
what is fMRI
- measures blood oxygenation
- detects blood flow by exploring its magnetic properties
- change in info processing -> change in neural activation -> change in blood flow -> change in oxygenated and deoxygenated hemoglobin -> regional changes in MRI image
- limited temporal resolution (6 seconds) but better than PET
what does “region of the brain is active” mean?
- the brain is always all of the way active
- brain region is “active” if it is relatively more active during one condition compared to another (baseline)
explain an example of the PET and fMRI subtraction method
where does music appreciation take place?
- experimental: listen to music, control: listen to scrambled sounds
- brain imaging before music is playing, then during and see what changed
what is a connectivity analysis
reveals relationship between regions
what is the dependent and independent measure of functional imaging
dependent (data): brain regions
independent (conditions manipulated): behavior/ task performance
what is the dependent and independent measure of lesion deficit analysis
dependent (data): behavior / task performance
independent (conditions manipulated): brain regions
what is necessity vs sufficiency
is there a casual relationship between activity and behavior/cognition?
explain the pros and cons of fMRI and PET
pros:
- no special populations required
- fMRI: very good spatial resolution
- within-subject comparisons possible
- test wide range of questions
- fMRI: not just for localization of function- connectivity analysis and pattern analysis
cons:
- indirect measure
- reverse inference problems/correlational
- expensive
- poor temporal resolution
- PET: radioactive material unsafe if too frequent participant in studies
- fMRI: safe only if precautions are taken regarding magnet
- not appropriate for claustrophobics
why is fMRI > PET
- better spatial resolution (1 mm v. 10 mm)
- better temporal resolution (6 sec v. 30 sec) but neither is very good
- can use “event-related” and “blocked” design; blocked is only for PET
- no radioactivity (repeated PET scans not safe)
explain a double dissociation task in neuroimaging
do visual short-term memory and verbal short term memory involve different cognitive processes?
-phonological loop (repeating words to self) vs. visuo-spatial sketchpad (visualizing pictures)
1) 2-back task: was this letter seen 2 back?, search task: is this the letter M?
. PET subtraction verbal method
PET activation in 2-back task
- PET activation in search task (control)
= brain areas related to verbal memory
2) spatial WM task: circle where the dot was on previous card, control condition: shows where dot is always
. PET subtraction: spatial working memory
PET activation in memory task
- PET activation in control task
= brain areas related to visual memory
Different parts of the brain light up
diagnosing visual agnosia
- inability to recognize objects
- how do you test for visual agnosia?
- how do you ensure that they don’t just have Alheizmers disease and have forgotten the names of objects?
what are the two types of visual agnosia
apperceptive and associative
what is apperceptive agnosia
- difficulty in forming initial “percept” - cannot put visual information into whole
- cannot copy even simple figure
- cannot name objects visually
