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The role of the posterior prefrontal cortex in task preparation
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Jan Derrfuss Birte Forstmann Hannes Ruge Iring Koch Nachshon Meiran Orit Rubin Markus Ullsperger Thomas Knösche D.Yves von Cramon
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The fronto-lateral cortex
inferior-frontal junction (IFJ) dorsolateral ventrolateral
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Neuronal correlates of task-switching
Dove et al. (2000)
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Processes involved in task-switching
Cognitive processes involved in task-switching preparation related control processes task preparation reduces switch-costs execution related control processes even with optimal preparation there are residual costs
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The task-cueing paradigm
By presenting a cue in advance to the task one can separate cue-related and target related processes. preparation cue task Cue-target interval (CTI)
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Separating task preparation from execution-related control
A number between 20 and 40 (not 30) was displayed. Magnitude task: Is the number greater or smaller 30? Parity task: Is the number odd or even? A cue indicated which task to execute. magnitude task parity task
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Experimental paradigm
with preparation without preparation only preparation null Fixation 0-200 ms Cue ms Target ms Response 33 33
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Demonstration of a trial
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Behavioral results Reaction time (ms) 750 800 850 900 950 1000 1050
without preparation with repeat switch
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Cue-related activation
IFJ IFj preSMA r=.57 Brass & von Cramon (2002)
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Conclusion The IFJ and the preSMA are involved in task preparation.
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Open question Are these areas involved in the encoding of the cue or the updating of the task representation?
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Decomposing components of task preparation
By assigning two cues to each task one can dissociate cue encoding from task-set updating = magnitude judgment = parity judgment cue repetition cue switch meaning switch
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Decomposing components of task preparation
within-trial manipulation of cue-related processing task Processing related to cue 1 cue 2 long CTI short CTI
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Experimental paradigm
cue repetion cue switch meaning switch single cue Fixation 0-200 ms Cue 1 (100 ms) Cue 1 (100 ms) CCI=700 CTI=60/700 33 Target Cue 2 (100 ms) Response CTI=60/700 33 33 33 33 33 Target Response
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Demonstration of a trial
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Behavioral results short CTI long CTI Meaning- switch repetition
Cue-switch Meaning- switch repetition Cue-switch
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Meaning-switch versus cue-switch
IFJ Intra-parietal sulcus Inferior frontal gyrus z > 3.1 Brass & von Cramon (2004)
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Signal change analysis
cue- repetiton switch meaning- left IFJ cue- repetiton switch meaning- IPS
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Signal change analysis
preSMA cue- repetiton switch meaning-
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Who comes first? abstract task representation
concrete task representation
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Who comes first?
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Who comes first? Brass, Ullsperger, Knösche & Phillips (in preparation)
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Conclusions The IFJ and the IPS are related to the activation of task representations. There is a hierachical order of prefrontal and parietal cortex in task preparation.
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Manipulating the association of cue and task
integrating information over time distinguishing relevant from irrelevant information
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Manipulating the association of cue and task
magnitude parity Task cues switch repeat Transition cues
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The paradigm Transition Cue 9 1 Task Cue Transition Cue 6 Task Cue 7
Parity Task Parity Task Parity Task Magnitude Task
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Behavioral results 2A 2B Forstmann, Brass, Koch & von Cramon (submitted)
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fMRI results 2B 2A * * Forstmann, Brass & von Cramon (submitted) 3.1
5.1 3.1 2A * Forstmann, Brass & von Cramon (submitted)
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The selection of task-relevant information
congruent incongruent neutral red green xxxx
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Cue dimensions form dimension color dimension Parity task magnitude
no Task form dimension color dimension
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Cues task A task B congruent incongruent neutral congruent incongruent
form dimension relevant A A A B B B irrelevant A B NO B A NO color dimension relevant A A A B B B irrelevant A B NO B A NO
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Demonstration of a trial
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Design Block Block order Instruction
1 warm up trial + 32 experimental trials + 4 null-events Block Block order form color
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Behavioral results Brass & von Cramon (submitted)
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Possible contrasts Incongruent/congruent (bivalent) versus neutral (univalent) selection of task-relevant context Incongruent versus congruent selection of conflicting task representations
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Incongruent/congruent vs. neutral
Brass & von Cramon (submitted)
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Conclusions Cortical areas more anterior in the prefronal cortex come into play, whenever the information in the environment does not directly indicate the relevant task-set.
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General conclusions The IFJ and the IPS play a crucial role in task preparation. Activation in the IFJ precedes activation in the IPS. Whenever the cue does not directly indicate which task to execute, activation shifts anterior in the prefrontal cortex.
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of three cortical domains
The IFJ at the junction of three cortical domains premotor domain task-rules are an abstraction from stimulus-repsonse rules language domain language domain task-rules are represented in an abstract language-like format prefrontal domain task-rules are required for high-order cognitive control
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The BOLD-response Slower Rise and Start of Negative Fall in ~10 s
Event Rise and Fall in ~10 s
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Neuronal correlates of task-switching
If + left hand, if + right hand Basis Task frequent Response Critical Task seldom Dove et al. (2000)
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Neuronal correlates of task-switching
Dove et al. (2000)
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Neuronal correlates of task-switching
Dove et al. (2000)
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Fast versus slow responses in the long CTI
IFJ CTI Brass & von Cramon (2002)
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Fast versus slow responses in the long CTI
IFJ Brass & von Cramon (2002)
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Cue-target versus cue-only
IFJ Brass & von Cramon (2002)
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Paradigms on cognitive control
Task-switching Participants have to alternate between different task-sets Stroop interference task A relevant but non-dominant stimulus dimension has to be enforced against a irrelevant but dominant stimulus dimension. Verbal n-back task Information have to be coordinated in working memory.
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Results of within-subject comparison
Overlap of activations in Stroop, task-switching and n-back Derrfuss, Brass & von Cramon (submitted)
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Who comes first? 33 cue switch meaning trigger
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Signal change analysis
magnitude task parity task magnitude task parity task neu con incon neu con incon neu con incon neu con incon color form color form neu con incon neu con incon neu con incon neu con incon Brass & von Cramon (submitted)
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