fMRI

Question 1

front of the brain

Answer 1

anterior/rostral

Question 2

top of the brain

Answer 2

superior/dorsal

Question 3

back of the brain

Answer 3

posterior/caudal

Question 4

bottom of the brain

Answer 4

inferior/ventral

Question 5

what is the middle of the brain called?

Answer 5

medial

Question 6

how are the sides of the brain called?

Answer 6

lateral

Question 7

how can you name brain regions?

Answer 7

anatomical terms
functional terms

Question 8

how is the middle frontal gyrus named?

Answer 8

anatomical term

Question 9

how is the dorsolateral prefrontal cortex named?

Answer 9

functional term

Question 10

what can MRI be divided into?

Answer 10

structural MRI and functional MRI

Question 11

what does structural MRI measure?

Answer 11

structural properties of the brain:
grey matter
white matter
fibre tracts

Question 12

what does functional MRI measure?

Answer 12

functional properties of the brain

Question 13

what does functional MRI provide?

Answer 13

indirect measure of brain
activity

Question 14

what are the main parts of a MRI scanner? (5)

Answer 14

powerful magnet, RF coil, Computer and Monitor, RF generator and receiver, gradient coils

Question 15

4 steps of MRI

Answer 15

no magnet: atoms are randomly positioned
magnet on: mostly aligned
radio pulse: moved orthogonally
protons relax: release radio signal

Question 16

what happens in T1 relaxation time?

Answer 16

Proton spins will ‘relax towards their ’non-tilted’ alignment

Question 17

what happens in T2 relaxation time?

Answer 17

Proton spins will lose synch and become out of phase

Question 18

different tissues have …

Answer 18

different amounts of water – different magnetic properties – different relaxation time

Question 19

What is TR (repetition time)?

Answer 19

The time it takes to scan one volume of the brain

Question 20

basis for functional MRI

Answer 20

1. oxygen from lungs
2. oxygen bonds to hemoglobin
3. oxygen released to tissue cells

Question 21

what ae most fMRI studies based on?

Answer 21

the BOLD signal (Blood Oxygenation Level Dependent)

Question 22

what does BOLD stand for?

Answer 22

Blood Oxygenation Level Dependent

Question 23

what do metabolic changes in nerves require?

Answer 23

energy

Question 24

what is metabolism based on?

Answer 24

oxygen consumption, i.e. increased neural activity causes an increased demand for oxygen

Question 25

what does the drop of oxygen level lead to?

Answer 25

an increase of the local blood flow

Question 26

what does the compensatory mechanism do?

Answer 26

relative concentration of oxygenated hemoglobin increases

Question 27

how can oxygenated and de-oxygenated hemoglobin be differentiated?

Answer 27

oxygenated and de-oxygenated hemoglobin have different magnetic properties

Question 28

5 steps of fMRI

Answer 28

1) change of neuronal activity 2) oxygen consumption (initial decrease in oxygen level) 3) increase of local blood flow (increase of oxygen level) 4) changes of the magnetic properties of hemoglobin (causing local inhomogeneities in the magnetic field) 5) change in signal intensity

Question 29

BOLD response over time (3)

Answer 29

1) initial dip 2) main BOLD response 3) post stimulus undershoot

Question 30

what time span is the TR usually?

Answer 30

1 or 2 seconds

Question 31

how often does a volume happen?

Answer 31

every 1 or 2 seconds

Question 32

what is a volume?

Answer 32

scan of the whole brain

Question 33

what is the time series?

Answer 33

the sequence of all the scans

Question 34

what are the problems with motion?

Answer 34

- if the participant moves, voxels change their position - movement can cause artefacts if they are correlated with the design (e.g. when the participant always moves in a specific condition)

Question 35

what is the solution to the motion problem?

Answer 35

Rigid-body transformation -> Different images are re-aligned to a reference image

Question 36

what is co-registration?

Answer 36

alignment and overlay of functional image and structural image

Question 37

what is Spatial normalization?

Answer 37

warp images from different subjects on a template brain -> averaged activation

Question 38

what is smoothing?

Answer 38

Spatial smoothing replaces the signal of each voxel with a weighted average of that voxel’s neighbors

Question 39

what are the advantages of smoothing?

Answer 39

* While spatial smoothing decreases the spatial resolution of the measurement it reduces noise. * Furthermore, it makes averaging of functional activation across participants easier because it increases potential spatial overlap.

Question 40

what os statistical modeling of fMRI data?

Answer 40

time series of activation in a specific voxel

Question 41

what can the BOLD response be modeled with?

Answer 41

a specific response function, the so called HRF (Hemodynamic Response Function)

Question 42

what does HRF stand for?

Answer 42

Hemodynamic Response Function

Question 43

what does bold overlap refer to?

Answer 43

In some experimental designs, the BOLD response to specific stimuli might overlap.

Question 44

what does contrast refer to?

Answer 44

one can compare specific conditions and test whether there is a significant difference between the conditions in a specific brain area

Question 45

what is the block design?

Answer 45

the same stimulus type is presented repetitively in blocks

Question 46

what are the advantages of block design?

Answer 46

* gives a strong signal-to-noise ration * stimuli can be presented in rapid succession

Question 47

what are the disadvantages of block design?

Answer 47

* psychological not always possible * if trials are longer, the advantage of blockdesigns vanish

Question 48

what are slow event-related designs?

Answer 48

stimuli are presented with a long inter-trial interval to allow the HRF to return to baseline

Question 49

what are the advantages of slow event-related designs?

Answer 49

* Experimental conditions can be randomly mixed * HRF for each condition and even each stimulus can be determined

Question 50

what are the disadvantages of slow event-related designs?

Answer 50

* Inter-trial intervals are very long * Participants might get bored

Question 51

what are rapid event-related designs?

Answer 51

stimuli are presented with short inter-trial intervals that do not allow the HRF to return to baseline

Question 52

what are advantages of rapid event-related designs?

Answer 52

* Experimental conditions can be randomly mixed * HRF for each condition can be determined * Stimuli can be presented fast

Question 53

what are the disadvantages of rapid event-related designs?

Answer 53

* The HRF strongly overlaps therefore one can not easily determine the HRF for each condition and event