Problem 6 Flashcards
Cognitive subtraction
Compares the activity of the brain in a task that utilizes a particular cognitive component to the activity of the brain in a baseline task that does not use this
–> one can thus infer which regions are specialized for this particular cognitive component
How did petersen figure out which regions are involved in spoken words ?
By comparing the passive viewing of written words with reading aloud the word
–> both experimental and baseline tasks involve visual processing the word but only experimental involves spoken output
How did peterson figure out which regions are involve with retrieving the meaning of written words ?
By comparing a verb-generation task (see cake but say eat) with reading aloud (see cake say cake)
–> both experimental + baseline tasks involve visual processing, word recognition + spoken output but only experimental involves understanding the meaning
How did petersen figure out which regions are involved with recognizing words ?
By comparing brain activity when passive viewing the word cake with passively viewing a cross
–> both experimental + baseline tasks involve visual processing but only experimental involve visual word recognition
Assumption of pure insertion
Assumes that adding a different component to a task does not change the operation of other components
–> disadvantage of cognitive subtraction
e.g.: it could be that th amount of visual processing that ideal with written words is not the sam as for non-linguistic vision
Interaction
Refers to the effect that one variable has on another
–> thus the addition of an extra component in the task may potentially change the operation of other components in the task
Why are baselines so important to functional imaging ?
Because without it the regions of activity can not be meaningfully interpreted.
–> thus a good cognitive theory of the elects that comprise task must be established so an appropriate baseline can be selected
Efference copy
Refers to a motor signal that is used to predict the sensory consequences of an action
–> explains why we can’t tickle ourselves because we know what this would mean
Categorical design
Measures differences in brain activity between 2 or more conditions
Functional specialization
Implies that a region responds to a limited range of stimuli/conditions and that this distinguishes it from the responsiveness of other neighboring regions.
Functional integration
Refers to the way in which different regions communicate with each other
Block design
Presenting stimuli sequentially within a condition and then alternating the grouped conditions (based on similar stimuli)
–> AB block design in which a cycle corresponds to two epochs
Event related design
Linking the BOLD response to specific events, such as the presentation of a stimulus or the onset of a movement
–> a clear signal can be obtained by averaging over repetitions of these events
THUS: allows the researcher to present experimental and control trials randomly, ensuring that participants are in a similar attentional state during both types of trials
What is the advantage of block designs over event-related ones?
More power
–> more able to detect significant but small effects
What are the advantages of event related designs over blocked ones ?
- Enable a much wider range of experimental designs
2. Are more closely related to the typical design structure of most cognitive psychology experiments
Factorial design
Involves letting the subject perform a task where the cognitive components are intermingled in one moment and separated in another instance of the paradigm
–> allows tests for interactions between each component thus alternative + solution to subtraction
Conjunction analysis
Requires identifying a set of tasks that have a particular component in common
–> looking for regions of activation that are shared across several different subtractions
THUS: problem of interaction is reduced
Behaviorally driven fMRI
Letting the subject lay inside the MR scanner doing nothing, and observe variations of the BOLD response related to spontaneous activity, or ‘resting state’
–> often measured by other methods such as galvanic skin response
Mixed design
Refers to a combination of block + event related design
–> can provide info related to maintained vs transient neural activity during paradigm performance
Maintained neural actiivty
Brain regions exhibiting task-related info processing
Transient neural activity
Brain regions exhibiting item related pattern of info processing
Parametric design
Is based on the idea of increasing the cognitive demand associated with a particular cognitive task w/o modifying its intrinsic nature
–> increase in BOLD effect = increase in cognitive demand
What are the disadvantages of Cognitive subtraction ?
Why?
- Assumption of pure insertion
- -> adding new component to a task may lead to interaction - Interactions
- -> makes the imaging data ambiguous
Why do functional imaging data sometimes disagree with lesion data?
- Imaging data imply that a brain region is used in a given task
- -> lesion data suggest that this region is not essential to task - Vice versa
Mental clock test
Subjects are asked to imagine pairs of times that are presented acoustically
–> then judge at which of the times the clock hands from the greater angle
