Task 6 Flashcards
What is cognitive subtraction ?
-> Compare brain activity in task that uses a particular cognitive component to brain activity in baseline task
Why is a baseline activity so important ?
-> Brain is always active thus “activity” can only be meaningfully interpreted relative to a baseline
What are the assumptions of cognitive subtraction ?
- Need to find d 2 tasks (experimental vs. baseline) that differ in terms of a small number of cognitive processes
- Pure insertion: adding an extra component doesn’t affect the operation of earlier components
What is the Problem of cognitive subtraction ?
-> Pure insertion does not exit = Interaction !
What is a factorial design ?
- > Identify a set of tasks (3 ) that has one particular component in common and a baseline
- > use multiple subtraction
How do we identify an interaction in the factorial design ?
- > is the difference btw A & B more/less than difference btw C & D?
- > Formula = (A-B) - (C-D)
How to identify an main effect according to the factorial design ?
-> (A+B) - (C+D)
Why is the factorial design better then cognitive subtraction ?
-> Problem of interaction / pure insertion can be reduced
What is meant by conjunction analyis ?
-> focusing on commonalities instead of differences (filter out the differences
What is meant by Contrast analyis ?
-> focusing on differences instead of commonalities (filter out similarities)
What is mant by Parametric design ?
- > increasing the cognitive demand (difficulty level) associated with a particular cognitive task
- > The more the bold lvl changes in one area the more more necessray this area is
What are the benefits of the Parametric design?
-> No baseline is needed
What are the cons of the Parametric design ?
-> Increasing a parameter over a certain limit can involve recruiting other cognitive processes that are not necessarily present at lower levels
What is meant by functional intergration studies ?
-> Tries to identify how activity in different regions is interdependent
What is meant by the resting state Paradigm ?
- no task, just chill
- Change in brain activity is noise
- in brain regions that are functionally connected, the noise levels tend to correlate together -> can identify networks
Define the goal of the block design:
- Where neuronal activity is located
What is the method of the block design ?
- > Stimuli that belong together in one condition are grouped together
- > combine the bold reponse
What are the Pros of the block design?
- > More statistical power !!-> Bold signal is higher* / higher HRF magnitude
- > SNR is high
- > shorter
what is the con of the block design ?
- > Some events can not be blocked
- > can not specify how a specific stimuli effects the bold activity
- > Often confounding due to training effects and lack of attention / anticipation
What is meant by the ISI ?
- > inter stimulus interval
- > Determine the onset of each stimuli
- > Unimportant for Block design vs Very important for event related design
What is the Method of the Event related design ?
- > Stimuli that belong to different conditions are separated
- > 3 Types
What is meant by the SLOW ISI event releated design ?
- > wait long enough for HRF to recover to the baseline (15 seconds)
- > Clear bold repsonse but task would be way to long
What is meant by the RAPID event releated design ? Also name pro and cons:
-> do not wait (smaller then 15 seconds
-> Usually use jittering = ISI varying between 2-6 seconds
BUT
-> Danger of Bias = Which means that the current HRF can be effected by previous HRF
-> Higher statistiacl power
What is meant by the randome ISI event releated design ?
-> Radnome ISI intervals
What are some benefits of evet related design ?
- > more experimental designs are doable
- > Less fatique / prediction
- > more attention
- > less sensitive to head motion
What is the goal of the event related design ?
-> to identify differences in region of interest
What are the con of event related design ?
- > More noise due to bias
- > Less statistical power
- > Longer designs
What is meant by behaviourly driven designs ?
- > Used for measuring activity which can not be stimulated (patient has to do naothing)
- > Example hallucination -> press button
- > We measure the variation of bold response to spontaneous occurring signal
What is meant by reverse inference ?
-> Mental states is inferred from brain activation
Descripe characteristics of activation Maps:
- > Colour
- > Or no colour
What is meant by coloured areas in activation maps ?
- > Areas surviving statistical threshold
- > Areas are either non common areas -> contrasting between two conditions
- > Or higher / greater / maximal activity -> in comparison to a certain baseline
What is meant by non coloured areas in activation maps ?
- > Either common areas between two conditions
- > Non active areas
- > Or non significant areas
How do we construct an activation map ?
Within subject analysis / First lvl
Between subject analysis / Secon lvl
What is happening during within subject analysis ?
- > Use an active and a reference vector for comparing deviance in bold signal
- > determined by threshold
What is happening during between subject analysis ?
- Activity is averaged across partcipants
- And a voxel based transformation starts (talairch 3 D model)
How long does a block design go?
exceeds usually the hemodynamic response function ( between 15 - 30 Seconds)
What does behaviorally controlled mean ?
-> In a task the person has to do something and report on it so we know that he actually doing it
Explain jittering:
- > The next stimuli is presented before the hemodynamic response goes back to baseline
- > not a fixed time allways between 2-6s
- > Based on lineraiy assumption
- > decomposing the rapid event related design since we have multiple time frames
