fMRI

Question 1

MRI mechanism

Answer 1

1 atoms have their normal spins
2 magnet aligns their spin
3 radio frequency pulse knocks over spins
4 original spins recover - different times
5 neural activity computed from recovery time

Question 2

T1

Answer 2

fat white
water dark

useful for:
- disruption BBB
- anatomical detail
- vascular changes

Question 3

T2

Answer 3

fat dark
water bright

• anatomical detail (CSF spaces)
• lesions

Question 4

fluid attenuated inversion recovery

Answer 4

T2 + free flowing water (CSF) dark
non free flowing water bright
fat dark

• lesions near ventricles (which T2 can’t)
• improves gray white difference sometimes

Question 5

gradient recalled echo

Answer 5

paramagnetic substances are dark
(blood, calcium, metals)

• hemorrhage detection

Question 6

what is fMRI based on?

Answer 6

BOLD contrast
different magnetic properties of oxyhemoglobin

Question 7

what are partial voluming effects

Answer 7

signal averaged over voxels
grey and white matter Sig may cancel each other out

Question 8

difference map

Answer 8

is first level result and the subtraction of two different processes
results In activation map

Question 9

difference univariate and multivariate analysis

Answer 9

uni: distinguishes conditions based on average activation in braun regions
- images are overlays of structural image and a statistical map indicating differences
multi: distinguishes conditions based on activation patters across braun regions
- decide cog state from brain activation pattern

Question 10

limitations

Answer 10

correlational approach
- region activated but
- necessary ?
- sufficient ?

reverse inference
- reasoning backwards from activity to cognition
- can only infer if brain region is truly selective
- difficult to isolate cog process