Neural Substrates of Rule Retrieval & Implementation

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

Acknowledgements

Eveline Crone, Ph.D.

Sarah Donohue Carter Wendelken, Ph.D.

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?

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


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


DLPFC:- rule-sensitive during cue period, but p > .001-not rule-sensitiveduring delay

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

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

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






• 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





• Brain regions subserving task switching vs. rule retrieval


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

Development of cognitive control

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

Response selection

Incongruent > Neutral

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

Right VLPFC

Selection Inhibition

Right VLPFC

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

Task-switch flanker experiment

Age

Proportion of correct trials

8 12 16

.88

.9

.92

.94

.96

.98

1

Spatial

Verbal

8 12 16

200

250

300

350

400

450

500

550

600

650

700

Spatial

Verbal

Age

Response Times (ms)

Pro

port

ion

corr

ect

RT

s (m

s)

Flanker + verbalFlanker + spatial

8 12 16Age

8 12 16Age

Neural Substrates of Rule Retrieval & Implementation

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