fMRI + MRI Flashcards
1
Q
overview
A
- f MRI has high spatial resolution, not high temporal
- offer brain to divided line Broadman + measure neurons in the area
2
Q
Anatomy
A
- Broadman’s areas of the brain
- Determined by postmortem studies
- Differences in structures = different function
3
Q
How does MRI work ?
A
- Atom nuclei have protons that spin around = magnetic properties
- when in a magnetic field protons align
- some align parallel, others antiparallel this signal can be measure
- Higher the field strength the better resolution
4
Q
Diffusion Tensor Imaging
A
- While matter connections + properties can be measured
- smaller temporal + spatial the resolution than fMRI
- indicates circuitry of brain
5
Q
comparing anatomy between groups - Taxi Driver study
A
- increased volume of hippocampus compared to controls
- Anatomical change related to specific skill of navigating London
6
Q
PET scans
A
- injected with radioactive isotope
- emits position meets an electron = annihilation event = energy released
- Not very good spatial resolution
7
Q
Brain Imaging in FMRI and MRI
A
- Helmet picks up small radio frequency signals emitted by protons
- processing signals allows construction of images
Image intensity is dependent on neural activity - changes seen in images is related to blood in brain
8
Q
Why Image intensity changes
A
1) Neural activity consumes oxygen
2) Initially leads to reduction in blood oxygenation
3) Blood supply reacts to oxygen reduction
4) provides more than at rest
5) Blood oxygenation changes magnetic properties of tissue
6) changes MRI signal
referred to as BOLD signal
9
Q
BOLD signal
A
- Initial dip (reduction in oxygenation)
- Is slow
10
Q
Block designs
A
- present 1 condition ( task stimulus)
- switch to alternative condition
-measure difference in images of condition - rest block after each active block
- captures fullness of BOLD response
11
Q
Motion
A
primary visual cortex (V1) responds to static + moving
- V5 ( MT) responds only to moving stimulus
12
Q
colour
A
- stimulus with either colourful or black + white squares
- V 4 responds strongly + selectively to colour
- McKeefry + Zeki
13
Q
fusiform face area (ffa)
A
- Kanwisher
- If show indivs with faces + contrast with block (objects) + rest period there was strong activity in FFA
14
Q
Lesion + FMRI studies
A
- good correspondence between FMRI in healthy + lesion overlap peaks in indius with achromatopsia + prosopagnosia
15
Q
Event related Designs
A
- measuring responses to events are important
- leave gaps between events to allow BOLD activity to return to baseline, however expensive
- However, leaving big predictable gaps means brain does something else which May alter activity
- solution = multivariate analyses, vary time between events
