The Cognitive Neuroscience of Executive Function

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The Cognitive Neuroscience of Executive Function

• Adam Aron
• University of California, Los Angeles
• HBM 2006, Firenze, Italia

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What is executive function?
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PFC
Context 1 USA Context 2 Context 3 street
Look left Look right
PFC
Context 1 Context 2 UK Context 3 street
Look left Look right
Executive Function is The optimization, by
prefrontal cortex, of cognitive, sensory or motor
processing in posterior cortical and subcortical
modules
Miller and Cohen, 2001
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Overview

• What is executive function?
• Why is it relevant?
• How to go about studying it?
• Choosing a behavioral paradigm
• Developing a hypothesis
• Using multiple neuroscience methods
• Illustration the case of response inhibition

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Why is executive function relevant?
Lhermitte, 1983
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Different neural circuits for executive function
Fronto-hippocampal Fronto-parietal Fronto-amygdala
Fronto-striatal Fronto-subthalamic
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How to measure it?
Wisconsin Card Sort Test Stroop Eriksen
Flanker Task-Switching Reversal Learning Tower
of London/Hanoi Controlled Retrieval Response
Inhibition
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Good properties of a behavioral paradigm
Translational Ecologically valid Cognitively
specific/tractable Sensitive Cross-method
data Test-retest reliability
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Pitfalls in developing a neural hypothesis
Tasks which activate the frontal cortex usually
activate the same regions

Duncan and Owen, 2001
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Pitfalls continued
Neuroimaging activations cannot be taken to show
that a given brain region is sufficient or even
necessary for a given cognitive process, because

Activations can be epiphenomenal
Activations can be artifactual
It is known from animal studies that the activity
of single neurons can be modulated during a task
even when interference studies indicate that the
neurons of the area are not essential for the
task's performance.
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Solution base neural hypothesis on converging
evidence

especially evidence that the integrity of your
target region is necessary for task performance
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Illustration the case of response inhibition
Sasaki et al, 1989
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Measuring response inhibition behaviorally
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Go/No-Go imaging meta-analysis
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Frontal lobe lesion study

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Critical importance of right inferior frontal
cortex for response inhibition
medial orbital inferior middle superior

Aron et al, 2003
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Strong support from TMS
Chambers et al, 2006
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What does inferior frontal cortex act on?
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A model and a hypothesis
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fMRI study of response inhibition
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Go process activates fronto-striatal-pallidal-thal
amic-motor cortex regions
Aron Poldrack, 2006
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Go process activates fronto-striatal-pallidal-thal
amic-motor cortex regions
Effects of resonse inhibition on motor cortex
confirmed with TMS
Coxon et al, 2006
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Stopping activates right inferior frontal cortex
and subthalamic nucleus
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The challenge of connectivity
Structural equation modeling Dynamic causal
modeling
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Diffusion Tensor Imaging
Tractography Fractional-anisotropy/behavior
correlations
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White matter tract connects right IFC and
ipsilateral STN
-4mm 5mm
14mm

R

subthalamic nucleus
Inferior frontal cortex
Poldrack et al. in preparation
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Summary and Recommendations

• Do study executive functions - theyre
  interesting and relevant!
• Choose a behavioral paradigm with helpful
  properties
• Develop a neural hypothesis that is
  well-constrained by cross-method (especially
  lesion) data
• Think about connectivity