Task 6

Question 1

Block design

Answer 1

• Stimuli from condition are presented consecutively together
• Stimuli that belong together are grouped together
• Maintaining cognitive engagement in a task by presenting stimuli sequentially within a condition
• Alternating this with other moments (epochs) when a different condition is presented

Question 2

Block design advantage

Answer 2

• More power because the ability to differentiate between conditions is better
• Relatively large BOLD signal change related to baseline
• More able to detect small changes
• Higher signal to noise ratio
• Required for studying. State-based processes
• Support subjects compliance when condition switching is disruptive

Question 3

Block design disadvantage

Answer 3

>

Involves subtraction method (which includes assumptions) 
Mainly used in PET 
People can anticipate what will happen -> this is going to affect the signal 
First few block attention is often high, but quite quickly attention goes down  so in a block design we cannot distinguish between differences within a block because the the BOLD response is elicited for the whole block and not a single component of the block do not get HR for a single trial  Minimally compatible with typical behavioral and electrophysiological method s may promote unintended subject strategies, anticipation, and habituation  requires pre-specification of a limited set of experimental comparisons

Question 4

Event-related design

Answer 4

-Stimuli from 2 or more conditions are presented randomly/interleaved

Question 5

Event-related design advantage

Answer 5

• Much wider range of experimental designs -> more suitable for cognitive experiments
• E.g. in some instances, there is no way of knowing in advance how events should be grouped
• Detect transient variations in hemodynamic responses
• Temporal characterization of BOLD: HRF
• Allows for randomization of the order of conditions
• One can vary time between stimulus presentation which reduces subjects ability to predict when and what will happen
• Requires participants to be constantly attentive
• Can be used to prevent practice effects
• Can provide estimates of the HR time courses
• Conditions can be categorized post-hoc -> even multiple post-hoc experimental contrasts are possible

Question 6

Event-related design disadvantage

Answer 6

• Overlap of BOLD signals might happen
• Less power then block design
• More difficult to detect small signal changes
• Smaller BOLD signals than in block design
• Smaller Signal to noise ratio -> bad for analysis
• Cannot be used to study state-based processes
• May be unsuitable when conditions have large switching cost (e.g. patients might not be able to switch that fast)
• More difficult to analyze

Question 7

Rapid erfMRI

Answer 7

• ISI is shorter than the duration of the HRF generated from previous stimuli
• Increased number of stimuli presented per time unit
• Enhanced statistical power (because more stimuli presented)
• BUT Reduces ability to estimate the HRF properties of a single stimulus
• > overlap
• Rule of thumb: ISIs should be varied with a minimum of 4s between consecutive stimuli

Question 8

Behaviorally driven design / resting state paradigm

Answer 8

• Let subjects lay inside MR scanner doing nothing, observe variations or BOLD response
• Participant merely lies back and rests
• Fluctuations in brain activity are little more than noise
• Identify sets of networks: fluctuations in activity tend to be shared

Question 9

mixed design

Answer 9

• Combination of block and event related designs can provide info about ‘maintained’ vs ‘transient’ neural activity
• Extracting brain regions exhibiting an item-related pattern pattern of info processing (transient) or task-related info processing (sustained)

Question 10

Factorial design

Answer 10

• Allowing for interaction between each component
• Subject performs a task where cognitive components are intermingled in one moment and separated in another instance
• Useful to investigate cognitive interactions

Question 11

Parametic design

Answer 11

• Variable of interest is treated as a continuous dimension rather than a categorical distinction
• Increasing cognitive demand of a particular task without modifying intrinsic nature
• Increase in BOLD would imply an association of an area to the intrinsic nature of the parameter being manipulated
• Measuring associations between brain activity and changes in the variable of interest (rather than measuring differences in brain activity between 2 or more conditions)
• Challenge: often increasing one parameter can involve recruiting other cognitive processes not necessarily present at low level of performance of the neural system

Question 12

Conjunction analysis

- Some kind of factorial design

Answer 12

• Identify set of tasks that has a particular component in common (you have to do that before even testing)
• Look for regions of activation that are shared across several different subtractions (instead of single subtraction)
• Baseline task still required
• problem of interactions can be reduced
• Helpful in studies where multimodal input or functions supporting a determined cognitive performance are the main interest
• Try to find out dame underlying cognitive processes for different tasks

Question 13

Functional integration

Answer 13

Functional specialization: region responds to a limited range of stimuli/conditions, this distinguishes it from responsiveness of other neighboring regions

Functional integration: way in which different regions communicate with each other

• Model how activity in different regions is interdependent
• Infer effective connectivity of functional connectivity between regions when performing a task