The brain basis of cognitive control

The brain basis of cognitive control

Todd BraverCognitive Control and Psychopathology Lab,

Washington University

St. Louis

I do cognitive neuroscience

Cognitive Psychology + Neuroscience = Cognitive Neuroscience

What is that?


Study of knowledge and thinking

What is cognitive neuroscience?



Study of how the brain works



Study of how the brain thinks

The mystery of control• William James on will (1890)

“...wherever movement follows unhesitatingly and immediately the notion of it in the mind, we have ideo-motor action. We are then aware of nothing between the conception and the execution. In contrast, some acts require will, such that an additional conscious element in the shape of a fiat, mandate, or expressed consent is involved”

• The mind/body and homunculus problems– Is there a “controller” in our mind/brain– What is it? Is it made out of the same neural “stuff” of the rest of the brain– That’s what I want to find out: Why I am a cognitive neuroscientist

» A bit on my background…

• This is the domain of “cognitive control” (also called self-control, executive control)– Some subtopics: behavioral inhibition, sustained attention, working memory (goal-

maintenance), planning, multi-tasking» Real world examples

– How can these be studied in the lab?

Time for some demos!

• Tap your desk if the letter you see is anything but X

• If it is an X, DO NOT RESPOND

• Tap as fast as you can (it’s rapid paced)….

PCXKTFMBQXLH

Now let’s do some Stroop!

• Name the color of the Ink, ignore word name

• Answer as fast as you can….

YELLOW

Now some working memory

• Study word names, hold on to them over delay

• Check if the next word matches one of them– If so, say YES (quickly)

– If not, say NO (quickly)

+NAIL

TRAIN

GRAPE

SHIRTMOUSE

NAIL

+GRATE

ROCK

STEEL

FANGBREAD

TRAIN

What do these demos illustrate?

• First one: go-nogo– Behavioral inhibition: How can we stop ourselves from the impulse to

respond to the X?

– What causes us to fail (make an error)? How do we monitor & adjust performance based on failure?

• Second one: Stroop– Selective attention: How do we override the automatic tendency to attend to

word name, even when irrelevant?

– How do we respond and adjust to interference between word & color? Again, performance monitoring

• Third one: Short-term item recognition– Working memory: How do we maintain information in an accessible form

during delay?

– How do we decide which trial the target (probe) item belongs to? Current or previous? Using working memory to prevent sources of interference (i.e., familiarity)

Brain Mechanisms of Cognitive Control

• Studies of performance monitoring– What are brain circuits and computations that determine when

control is needed?

– i.e., to detect likelihood of errors, compensate for errors, or deal with sources of interference

• Studies of motivation– Why don’t people always exert optimal cognitive control? Does

it have a cost?

– How do increases in the (reward) value of cognitive control modify brain activity and behavior?

Gehring et al., 1993

• The ERN -- an error-specific brainwave– ERP: event-related (brain electrical) potential

Gehring et al., 1993

Compensatory Behaviors

Error CorrectionSubsequent Performance

ERN magnitude -> ERN magnitude ->

What is the inference from these findings?

Where is the ERN located in the brain?

The anterior cingulate cortex

Dorsal/Caudal

Ros

tral

/Ven

tral

Carter et al., 1998

Conflict Monitoring theory

The key points of the theory: • Errors are a special case of high conflict• ACC detects conflicts rather than errors per se

High Conflict

Low Conflict

What does conflict mean?

But also this was foundin the same ACC region

The Conflict-Control Loop

• What is the point of performance monitoring in the ACC?– To provide signals that indicate when control processes need to be adjusted– Control state needs to adapt to environmental demands & contingencies

» Low interference = low control (unbiased or bottom-up attention)» High interference = high control (focused attention)

Dorsal ACC & PFC form a feedback loop

Dynamically adjusts control in response to experienced conflict

(Botvinick et al., 2001 Psych Review)

How does PFC implement control?

Dorsolateral

Ventrolateral

• Active maintenance (Store words over delay)

• Of cognitive goals(Name color; nogo for X)

• To bias attention & action(Filter out words; slow down responding)

Computational Modeling of Conflict-Control Loop (Flanker task)

H H S H HS S S S SCompatible Incompatible

Evidence for ACC-PFC loop (Kerns et al., 2003)

ACC activity increases following conflict (incongruent) or error trialsIncreased PFC activity and decreased interference on subsequent trial

Take-Home Points• Performance monitoring & cognitive control might be

implemented in the brain through division of labor– ACC: When are control demands high?

– PFC: Modify control state (attention, goals, active maintenance) based on ACC demand signal

• ACC might respond to conflict rather than errors per se

– Conflict could be a good signal of control demand

– Doesn’t require knowledge of error

• This is a very active area of research!– Lots of new ideas, findings & theoretical accounts

Motivation & Cognitive Control• How come people seem to perform better when there is a lot at

stake?– Offering rewards seems to optimize behavior (e.g., gold stars, contests)– Does it work by modulating cognitive control state in the brain (e.g., PFC)?

• People seem to vary in their motivational levels – Some people seem to be very motivated by the prospect of rewards, others not

» Intrinsic motivation vs. extrinsic motivation – Do ‘reward-driven’ people do better on cognitive tasks, when rewards are present?

» Is it because they are more likely to utilize motivation to modify cognitive control?

We can answer these questions using brain imaging methodsFunctional Magnetic Resonance Imaging (fMRI)

fMRI Scanning

FMRI Principles

Increased Neural Response

Increased Local Cerebral Blood Flow

Decreased deoxyhemoglobin

Change in Magnetic Susceptibility

Change in fMRI Signal

Neuroimaging Activation Maps

Event-related fMRI

-0.1

0

0.1

0.2

0.3

0.4

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19

PERCENT MR SIGNAL

TIME (SEC)

Blood flow responses can be detected (and isolated) forindividual events of brief duration

Motivation Study design Verbal WM task

Performance & Reward-sensitivity

Group Average Individual

Differences

These are effects on non-incentive trials! A motivational context effect

Neural effects of motivation

Jimura, Locke, and Braver (2010)

Right DLPFC

No Reward

Reward

Sustained activity Trial-related activity

Motivational context shifts PFC activity dynamics from transient (late-trial) to sustained (+ early-trial). •What about individual differences?

Reward Sensitivity

Behavioral EffectsOf Motivational Context

No Reward

Reward

Shift in PFC activity dynamics statistically explains

Motivation-Personality-Behavior association

Right DLPFC

Individual Differences

Jimura, Locke, & Braver (2010) PNAS

A causal model

Jimura, Locke, and Braver (in preparation)

High Reward Sensitivity -> Proactive Control = Better Performance

Low Reward Sensitivity -> Reactive Control = Poorer Performance

Take-Home Points• Motivation seems to modulate cognitive control mode

– Proactive (sustained) mode might be optimized for obtaining rewards

– Sustained control helps maintain task goals and attention

• Individual differences– People that seem to care more about rewards are more likely to shift modes (PFC activity)

• Cognitive control might be costly– Might be penalties for using sustained control (effort biases)

» But Why?

– The way that control is implemented could be dependent upon estimates of task reward value

» Incentives might increase task reward value more for highly reward sensitive people

– ACC might also be involved here (determining cost vs. benefit of control)

The brain basis of cognitive control

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