fMRI

Question 1

fMRI directly measures…
A: Neural events
B: Deoxygenated blood flow, correlated with neural activity
C: Oxygenated blood flow, correlated with neural activity
D: Oxygenated haemoglobin, correlated with neural activity

Answer 1

B: Deoxygenated blood flow, correlated with neural activity

Question 2

Which statement is false?
A: deoxygenated haemoglobin is
less sensitive (or paramagnetic) than oxygenated haemoglobin
B: When the oxygen is absorbed during neural activity,
the haemoglobin becomes deoxygenated
C: deoxygenated haemoglobin is
more sensitive (or paramagnetic) than oxygenated haemoglobin
D: fMRI measures the ratio of the two types of haemoglobin

Answer 2

A: deoxygenated haemoglobin is
less sensitive (or paramagnetic) than oxygenated haemoglobin
is FALSE.

Question 3

fMRI results are reported as the difference in ratio of ____

Answer 3

oxygenated and deoxgenated haemoglobin

Question 4

As a brain areas become active, the amount of blood being directed to the area ___

Answer 4

increases

Question 5

Although neural events occur at the ____ level, blood flow changes occur much more ____

Answer 5

millisecond; slowly

Question 6

Initial rise in blood flow may not be evident for several seconds and can peak __-__ seconds after event of interest

Answer 6

6-10

Question 7

Increase in oxygenated blood can represent a signal

change of as much as __, although typically around __

Answer 7

5%; 1%

Question 8

Because fMRI is ___, it can be used repeatedly within or across sessions with the same individual

Answer 8

non-invasive

Question 9

___ resolution is superior to all other brain imaging methods (e.g., better than PET, EEG, MEG), resolving activity estimates down to levels across the whole-brain of as little as ___

Answer 9

Spatial; 1mm3

Question 10

While signal changes associated with a particular cognitive operation (or event) must be repeated for ___ ___,
you can discriminate brain-wide activity for a series of ___ events

Answer 10

signal averaging; different

Question 11

fMRI provides you the ___ ___ to compare events based upon a subject’s performance

Answer 11

post-hoc flexibility

Question 12

Wagner et al. found that encoding-related activity could be seen in ___ and ___ regions

Answer 12

prefrontal regions (e.g., left inferior frontal gyrus) and hippocampal regions

Question 13

In Wagner et al.’s wordlist memory task, no difference between remembered vs. forgotten words was seen in lower-level perceptual regions (e.g., visual cortex), indicating that ___

Answer 13

while the words were viewed equally well, they were not remembered
equally well

Question 14

The standard contrast map in most fMRI studies identifies ___ that correlate with a experimental manipulation, but we still need to infer an area’s ____ contribution

Answer 14

regions of difference; functional

Question 15

True or false? fMRI is good at determining how brain activity (or changes therein) in one location is related to
another

Answer 15

FALSE. New analysis techniques are being developed to examine
‘connectivity’, with much interesting findings, but all currently lack the ability to determine relative timing and direction.
We still can’t tell which region activates another

Question 16

fMRI has __ temporal resolution.

Answer 16

poor

Question 17

Voodoo correlations: Vul et al. 2009 identified that many papers in social neuroscience suffer from ___. They find high correlations .7-.9 between BOLD activity and ___.

Answer 17

non-independence errors; measures of personality traits or self-reported scales.
The strength of these correlations was questioned because they are greater than the reliability of the underlying measures

Question 18

The voodoo correlations problem is caused by…

Answer 18

• Researchers initially identifying ROIs associated with a particular event (social distress) and a self-reported scale
• Then work out the average correlation coefficient for
  individuals in only those regions
• Biases analysis to regions where the correlation is likely
  to be highest

Question 19

Vul et al. identified the voodoo correlations problem in __% of the papers they surveyed.

Answer 19

54%

Question 20

Bennett et al. 2009 scanned a dead salmon during a picture viewing MRI study.
Using a standard parametric analysis, they identified ___

Answer 20

significant BOLD activity in voxels in the brain of the dead salmon

Question 21

Bennett et al.’s (2009) dead salmon problem is caused by:

Answer 21

Multiple comparisons.

• fMRI analysis involves comparing activity in two states (active vs rest) across each voxel in the brain
• There are over 40,000 voxels in a typical brain scan
• 40,000 comparisons completed with an alpha level of P >.05 will find 5% of voxels statistically active by chance

Question 22

Bennett et al.’s (2009) dead salmon problem highlights the need for ___

Answer 22

replication

Question 23

In __ images, artefacts, or loss of fMRI signal, occurs near junctions between ____, for example, around the sinuses, ear canals.
Makes it particular difficult to acquire reliable BOLD activity from regions
such as ____

Answer 23

T2; air and tissue; orbitofrontal cortex and subcortical regions

Question 24

List 5 fMRI design types.

Answer 24

• Block Design
• Slow ER Design
• Rapid Counterbalanced ER Design
• Rapid Jittered ER Design
• Mixed Design

Question 25

Subtraction designs are…

Answer 25

basic contrasts between task and control, or one type of task and another

Question 26

Issues with subtraction analyses

Answer 26

• Can have multiple comparisons/baselines
• Most common baseline = rest
• In some fields the baseline may be straightforward. For example, in vision studies, the baseline is often fixation on a point on an otherwise blank screen
• Be careful that you don’t try to subtract too much
• What are people really doing during rest?

Question 27

Problems with a rest baseline?

Answer 27

• For some tasks (e.g., memory studies), rest is a poor, uncontrolled baseline — memory structures (e.g., medial temporal lobes) may
  be DEactivated in a task compared to rest
• To get a non-memory baseline, some memory researchers put a low-memory task in the
  baseline condition — e.g., hearing numbers and
  categorizing them as even or odd

Question 28

5 advantages of event-related design?

Answer 28

1) Flexibility and randomization
- eliminate predictability of block designs
- avoid practice effects
2) Post hoc sorting (e.g., correct vs. incorrect, aware vs. unaware, remembered vs. forgotten items, fast vs. slow RTs)
3) Can look at novelty and priming
4) Rare or unpredictable events can be measured, e.g., P300
5) Can look at temporal dynamics of response
- Dissociation of motion artefacts from activation
- Dissociate components of delay tasks
- Mental chronometry

Question 29

Effect of adding trials: Averaging BOLD signal from an increasing larger
number of trials (from 4 to
144) results in…

Answer 29

a significant linear increase in the spatial extent of

statistical significant activity

Question 30

fMRI interaction problem: researchers claiming that __.

The presence of activity in one group vs the absence of it in another group does not tell you __.

Answer 30

one effect is larger than the other without testing them directly or performing an interaction analysis;
that there’s a difference between those groups if you don’t do an interaction analysis.

Question 31

BOLD overlap and jittering:
Closely-spaced haemodynamic impulses __.
Constant ITI causes problems.
Varying the timing of events allows you to __

Answer 31

summate;

separate, or deconvolve, the signal specific to a particular type of event.