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Neuro-cognitive bases of task control Leipzig, June 5th, 2004. Neural Substrates of Rule Retrieval & Implementation. Silvia A. Bunge. Department of Psychology & Center for Mind and Brain University of California, Davis. http://mindbrain.ucdavis.edu/content/Labs/Bunge/. - PowerPoint PPT Presentation
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Neural Substrates of
Rule Retrieval & Implementation
Silvia A. Bunge
Department of Psychology & Center for Mind and Brain University of California, Davis
http://mindbrain.ucdavis.edu/content/Labs/Bunge/
Neuro-cognitive bases of task controlLeipzig, June 5th, 2004
Cognitive Control Laboratory, UC Davis
• How do we suppress interference and override inappropriate responses? • Brain, 2001
• Neuron, 2002• NeuroImage, 2002• Neuropsychologia, 2003 (Hazeltine)• J Cog Neurosci, 2002 (Ochsner)
• How do we represent goals and rules for behavior?• J Neurophys, 2003• In prep.
• How do basic control processes give rise to higher cognitive functions?
• PNAS, 2000 (dual-task performance)• Cerebral Cortex, in press (integration)
Much of our behavior is guided by rules
Unspoken rulesfor social interaction
Explicit, symbolic rules
Retrieving and Using Rules for Behavior
• Rule retrieval and maintenance
• Long-term storage of rules
• Maturational timecourse of rule use in children
• Brain regions subserving rule retrieval vs. switching
• Neural changes underlying the development of rule use?
Retrieving and Using Rules for Behavior
• Rule retrieval and maintenance
• Long-term storage of rules
• Maturational timecourse of rule use in children
• Brain regions subserving rule retrieval vs. switching
• Neural changes underlying the development of rule use?
PFC and Rule Representation
Wallis, Anderson & Miller, 2001
abstract• PFC neurons maintain rule representations
Asaad et al., 1998; White & Wise, 1999
• BUT: spared rule articulation Shallice and Burgess, 1991
• PFC lesions: deficit in learning and implementing rulesMilner, 1963; Petrides 1985; Passingham, 1993
• knowledge vs. implementation vs. strategic retrieval: Sylvester & Shimamura, 2002 Gershberg & Shimamura, 1995
Candidates for Abstract Rule Maintenance
– DLPFC : ‘context’ maintenanceO’Reilly, Braver & Cohen, 1999 Macdonald et al., 2000: instruction-related activ. of DLPFC in Stroop task
What about maintenance of sets of response contingencies?
– VLPFC : learn & use simple S-R associationsPetrides & Milner 1982; Toni 1999; Passingham 2000; Murray 2000
Response
Simple2 Right
Sample/Probe
Task Rules
Compound1Left
Right
Compound2 Right
Left
Simple1 Left
Trial Structure
Time (sec)
7 - 15
+
Delay1
0.5
Sample
2.0
+
Delay2
1.5
Probe
1.0
Cue
Rule retrieval
Rule maintenance
Bunge, Kahn, Wallis, Miller & Wagner, J Neurophys, 2003
- Regions involved in rule representation: compound > simple- Abstract: not dependent on cue type (shape/verbal)
Rule Retrieval
Compound > SimpleCue period
Bunge, Kahn, Wallis, Miller & Wagner, J Neurophys, 2003
Posterior middle temporal:rule storage?
L anterior VLPFCrule retrieval?
Abstract Rule Maintenance
0.2
0.4
Pe
ak a
mpl
itud
e
0
SimpleCompound1Compound2
0.2
0
0.4
ShapeVerbal
post. VLPFC
Rule sensitivity Cue sensitivity
parietal
Summary
PosteriorMiddle temporal:
rule storage? anterior VLPFC:
rule retrieval?
L posterior VLPFC, parietal:
rule maintenance
Bunge, Kahn, Wallis, Miller & Wagner, J Neurophys, 2003
DLPFC:- rule-sensitive during cue period, but p > .001-not rule-sensitiveduring delay
Retrieving and Using Rules for Behavior
• Rule retrieval and maintenance
• Long-term storage of rules
• Maturational timecourse of rule use in children
• Brain regions subserving rule retrieval vs. switching
• Neural changes underlying the development of rule use?
Posterior MTG: Action Knowledge Store?
Martin & Chao, 2001
• active when view/name/imagine/retrieve info about manipulable objects (e.g. tools)
Questions
Posterior middle temporal gyrus
1st UCD study!
• PFC involvement in retrieval of recently learned vs. well-learned rules?
• general role in storing action-related knowledge, including rule meanings?
Traffic Signs: study phase
• Each sign viewed 1 time for 4 sec • Signs in ‘New-Trained’ category explained 4 times
Old Merge (U.S.A.)
• 14 Americans with 4+ yrs driving experience in U.S. • no experience driving abroad
Trained
Untrained Expressway entrance (Germany)
Wait for counter-traffic (Italy)
New
Traffic Signs: fMRI
5 sec
+
variable…
5 sec
+
variable
“Whenever a new sign appears on the screen, think about its meaning.”
• no response requirements
Traffic Signs: post-test
Explain meaning
• Accuracy
Button press:High/Low/Guess
• Confidence judgement
Behavioral Results
Correct identification
Pro
port
ion
of t
rials
• Old vs. New-Trained: don’t differ much in terms of knowledge (only experience)
N = 14
New-Untrained
New-Trained
Old
0
0.4
0.8
* ***
High Low Guess
Confidence judgement
0
0.4
0.8
Pro
port
ion
of t
rials
• New-Untrained signs are familiar but not meaningful
“Passive” viewing of traffic signs
• Left VLPFC is active during task performance • follow-up analyses: activation doesn’t depend on knowledge or amount of experience
p <.001
All conditions > fixation
Recovering rule meaning: Posterior Middle Temporal Gyrus
Retrieve+ > Retrieve-
p < .001Posterior MTG
• Bilateral middle temporal gyrus is engaged for meaningful signs, regardless of amount of experience
Retrieve+ > Retrieve-
Left parahippocampal cortex:• retrieval of meaningful signs• more active for signs with richer associations
p <.001
Recovering rule meaning: Medial Temporal Lobes
Parahipp.
Old > New-Trained
p <.005
Retrieve+
Conjunction
p <.0001
Controlled rule retrieval
• Right VLPFC (BA 47) is more active during correct retrieval of rules with weaker than stronger associations
Retrieve+
New-trained > Old
p < .005
R insula (anterior VLPFC)
Summary
L & R posterior middle temporal:
• Retrieve+ >Retrieve-
rule storage
R anterior VLPFC:• New-Trained > Old
(Retrieve+)
controlled rule retrieval
L parahippocampal c.:• Retrieve+ >Retrieve-• Old > New-Trained (Retrieve+)
Automatic rule retrieval
Retrieving and Using Rules for Behavior
• Rule retrieval and maintenance
• Long-term storage of rules
• Maturational timecourse of rule use in children
• Brain regions subserving rule retrieval vs. switching
• Neural changes underlying the development of rule use?
Development of rule use
• Developmental improvements in:
• representation of rules w contingencies (Zelazo et al., 2003)
• rule maintenance over a delay (Diamond, 1991)
• flexible rule-switching (Kray et al., 2004)
• These functions may mature at different times (Crone et al., in press)
Behavioral study: Development of rule use
rule retrieval: bivalent vs. univalent targets
• rule maintenance:500 vs. 4500 ms cue-target delay
• rule switching vs. rule repetition
Crone & Bunge, in prep.
• 8-year-olds (N = 16)• 13-year-olds (N = 20)• Adults (N = 20)
Univalent targets
Bivalent targets
Summary of behavioral findings
• no group differences in accuracy for rules with univalent targets (see also Zelazo, 2003)
• 8 & 13-year-old children less accurate for bivalent rules than adults, and show disproportionally larger RT increases for bivalent > univalent rules
Crone & Bunge, in prep.
• Rule switches less accurate than rule repetitions, but no group diffs
• 8-year-olds had proportionally larger switch costs than 13-year-olds or adults when switching to a bivalent (but not univalent) rule.
Different developmental trajectories:• rule switching is mature by 13• rule retrieval is not mature by 13
Rule retrieval (bivalent vs. univalent targets)
Rule switches vs. repetitions
Retrieving and Using Rules for Behavior
• Rule retrieval and maintenance
• Long-term storage of rules
• Maturational timecourse of rule use in children
• Brain regions subserving rule retrieval vs. switching
• Neural changes underlying the development of rule use?
fMRI study
• Goal: 60 subjects, ages 8-25
• Current N: -17 adults (ages 18-25) - 9 adolescents (ages 13-17) - 9 children (ages 8-12)
CUE (1 sec)DELAY (.5 sec)TARGET (2.5 sec)
BLOCKED Scan
Bivalent1 Rest
(20 trials)
Univalent
(20 trials)
. . . Rest
MIXED Scans
• 90 trials intermixed• 30 trials/rule; ** rule switch vs. repetitions
Minimal differences in performance across age groups: good baseline for developmental diff’s
Retrieving and Using Rules for Behavior
• Rule retrieval and maintenance
• Long-term storage of rules
• Maturational timecourse of rule use in children
• Brain regions subserving rule retrieval vs. switching
• Neural changes underlying the development of rule use
Neural basis of task-switching• fMRI studies variably implicate medial PFC/parietal/lateral PFC (Dove 2000; Sohn 2000; Brass 2002; Dreher 2002; Bunge 2003; Sylvester 2003)
• lateral PFC:
• TMS of medial PFC or parietal cortex impairs switching (Rushworth 2001, 2002)
• not reliably observed in fMRI studies (e.g. Braver 2003; Bunge 2003)
• active at onset of switch & repeat trials (Dreher 2002; Braver 2002)
• rule retrieval (Bunge et al. 2003, in prep; Brass et al., 2003)
• involved in rule retrieval rather than switching per se?
• perseveration on WCST more common w/ damage to medial
than lateral PFC (Stuss 2000)
Rule retrieval vs. switching: Partially overlapping regions?
Bivalent > Univalent rules
Rule switch > repetition (bivalent rules)
Both
p < .00516 adults
A closer look…
Bivalent > Univalent rules, excluding Switch trials
Rule switch > repetition (bivalent rules)
p < .00516 adults
- L anterior VLPFC (insula; BA 47)
- L parietal (BA 7/40), L pre-SMA (BA 6), R pre/motor, basal ganglia
500
550
600
650
700
750
REPETITION SWITCH
Median RT
UNIVALENT BIVALENT
Effect of Rule Type on Switch Costs
0
0.5
1
1.5
2
2.5
3
3.5
4
4.5
5
REPETITION SWITCH
% ERRORS
UNIVALENT BIVALENT
Bivalent vs. Univalent targets:- slower, less accurate- greater switch costs
Effect of Rule Type on Switch-Related Activation
Switch > Repetition
p < .00116 adults
Bivalent rules
Univalent rules
N.S.
Effect of rule switching is evident for bivalent rules
Tentative summary: adult fMRI data
• rule retrieval and rule-switching may be neurally separable
• BUT mechanisms affecting rule retrieval influence rule-switching, and vice versa:
• task-switching is taxed more when switching to a bivalent rule than to a univalent rule
• rule retrieval is taxed more when trials are mixed than blocked
- rule retrieval: VLPFC- switching: parietal (7/40), pre-SMA (BA 6), pre/motor, b.ganglia
Retrieving and Using Rules for Behavior
• Rule retrieval and maintenance
• Long-term storage of rules
• Maturational timecourse of rule use in children
• Brain regions subserving task switching vs. rule retrieval
• Neural changes underlying the development of rule use?
Rule representation vs. task-switching
• Different developmental trajectories, based on differential maturation of regions involved in rule representation/switching? (Crone et al., in press; Crone & Bunge, in prep.)
Prediction: task switch-related activation (e.g., medial PFC/parietal) matures earlier than rule retrieval-related activation in VLPFC
Acknowledgements
UC Davis
National Science Foundation (A.W.)New Faculty Research Grant (S.B.)
Anthony WagnerItamar KahnEarl Miller
Jonathan Wallis
Eveline CroneSarah Donohue
Carter Wendelken Omri Gillath
Michael SouzaJesse Edelstein
Additional thanks to…
MIT
Funding
Ron MangunCharan Ranganath
Cameron CarterBarry GiesbrechtTamara SwaabRuss Poldrack
Mike CohenCraig Brozinsky
Subjects
Congruent
Incongruent
NO-GO
Neutral
Task
• 16 adults (9 males; ages 19 - 33; M = 24)
• 16 children (9 males; ages 8 - 12; M = 10)
Response selection
Behavioral results
Adults Kids
• Flanker accuracy: ≥ 98% for both groups• Increased interference-related slowing in children
Inco
ngru
ent
> N
eutr
al
Correlations with response selection efficiency Adults Children
Mag
nitu
de o
f ac
tivat
ion
Response selection efficiency
better worse
ADHD data
• correlated with fluid verbal ability (WISC-word attack)
Different approach to task?
In children, response suppression efficiency:
“right”
• NOT correl. w speed of processing or visuospatial skills
… related to intermediate step of verbalization?
• greater interference in children due to slower / less efficient (Ridderinkhof et al. 1997)S-R translation
Summary
Response Selection
• change in approach to task?change in approach to task?
• R VLPFC for adults; L VLFPC for children R VLPFC for adults; L VLFPC for children
Bunge, Dudukovic, Thomason, Vaidya & Gabrieli, Neuron 2002
Response selection AND response inhibition
• adults but not children recruited R VLPFCadults but not children recruited R VLPFC