Task 6 Flashcards
What is the Blocked design?
- stimuli from a given condition are presented consecutively together
- allows for the comparison of different conditions (which are presented in different blocks, that result in different levels of recollection)
What are principles of the Blocked design?
- cognitive engagement in a task is maintained, by presenting stimuli sequentially within a condition
- alternattion of two conditions: AB block
What are advantages of the Blocked design?
- in fMRI has more power to detect small effects than event-related designs
- allows for high experimental control
- can yield higher signal to noise ratios, due to the longer duration of each condition
What are disadvantages of the Blocked design?
- cannot be used if things need to occur infrequently/ unexpectedly
- cannot be used if one doesn´t know how to group things together
What is the event-related design?
stimuli from 2+ conditions are resented randomly, or interleaved
what are the advantages of the event-related design?
- ability to detect transient variations in hemodynamic responses
- less sensitivity to head motion artefacts
- can be used to assess pratcie effects
- allows for randomisation of conditions
- time between stimulus representations can be varied (= good for attention levels, since it reduces the predictability)
What are the disadvantages of the event-related design?
- time-consuming
- challanging to present a large number of trial types within a single experiment
What is the behaviourally driven design?
- alternative to the paradigm used in conventional designs
- observing subjects spontaneous activity/ resting state as variations of the BOLD response
- the design is intrinsically dependent on each subject’s performance, and the inter-subject variability, number of events per condition and consequently the statistical power of the study is largely unknown beforehand
What strategies are there?
- subtraction method
- factorial design
- parametric design
- conjunction analysis
What is the subtraction method?
- images “active” condition - images “control” condition
- based on pure insertion assumption and absence of interaction (-> assumption is often violated)
What are activation maps?
- based on processing steps
- activation maps evolve around a single subject
- first level analysis: brain areas that meat a statistical threshold
How are activation maps computed?
How are activation maps interpreted?
What is the study by Wagner (1998)?
- hypothesis:
> experiment 1 (block design)
> - fMRI design:
- control conditions:
What is the first experiment in the study by Trojano at al (2018)? AND ROEFS
- hypothesis:
- fMRI design:
- control conditions:
What is the factorial design?
- when cognitive conditions are processed in a factorial manner then it can be tested for interactions
- relies upon neuropsychological evidence for precise definition of the task components (= should be intermingled in one and separated in another moment
What is the parametric design?
- the cognitive task is performed at different difficulty levels, without modifying its intrinisc nature
- increase in the BOLD effect, when cognitive demand is increased (= implies an association)
- technique allows for an analysis separating these areas from other brain regions (= otherwise baseline activity is included in the analysis)
What is the conjunction analysis?
- variation of the factorial design: at least two or more conditions of the fMRI paradigm share the cognitive component of interest
- not based on detecting differences, but commonalities between conditions (common patterns of BOLD in each condition)
