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Executive Functions. Nathan Spreng Cognitive Neuroscience: Psy393 August 8, 2005. Preliminary issues. Lecture slides & email Last exam Paper – download problems? www.library.utoronto.ca/resources Final Exam: Tuesday August 16, 2-5pm Room: SF 3202 Basic frontal lobe neuroanatomy.

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executive functions

Executive Functions

Nathan Spreng

Cognitive Neuroscience: Psy393

August 8, 2005

preliminary issues
Preliminary issues
  • Lecture slides & email
  • Last exam
  • Paper – download problems?
    • www.library.utoronto.ca/resources
  • Final Exam: Tuesday August 16, 2-5pm
    • Room: SF 3202
  • Basic frontal lobe neuroanatomy
lecture outline
Lecture Outline
  • PFC and overcoming the “default mode”
  • Attributes of executive functions
  • Goal Directed Behaviour
  • Video
  • Supervisory System
  • Capgras case study
  • Video (?)
default mode
Default mode
  • Default mode:
    • inflexible stimulus-response linkages
    • promotes automatic reactions and immediate gratification
    • sensitive predominantly to the internal milieu
    • remains resistant to modification by context or experience
    • Preference for sameness and certainty
    • Which promotes stimulus bound or stereotyped behaviour
    • Ego-centric, here-now perspective.
  • More conspicuous in sub-mammalian species, children, FL patients
  • Remains in latent form for healthy normals
default mode1
Default mode
  • The principle physiological function of the PFC is to suppress and transcend the default mode
    • introducing circuitry where neuronal responses can become contingent rather than obligatory
  • Stimulus - Response:
    • one-to-one relationship
  • One-to-many response options afforded by the PFC, tolerates greater uncertainty, diversity and choice
frontal lobes
Frontal Lobes
  • Four core functions:
  • Working memory & attention
  • Inhibition of distraction, perseveration, and immediate gratification
  • Ability to encode context and perspective
  • Dynamic mapping of significance
executive function attention
Executive Function: Attention
  • Enables on-line holding of information.
  • Incorporates info into a stream of consciousness
  • Maintenance of convergent information from different modalities
  • Shifting attention from external events to their internal representations
  • On-line manipulation of information
    • important role in the voluntary scanning and reorganization of mental content
  • Enables one to transcend stimulus bound thought that is reflexive and environmentally based towards a selective and deliberate consciousness
executive function future perspective
Executive Function: Future Perspective
  • PFC mediates shifts in time so that intended actions and their consequences can be apprehended from the vantage point of the future.
  • PFC neurons in monkeys fire in anticipation of reward (Hikosaka and Watanabe, 2000)
  • PFC activation in estimation of temporal intervals in humans (Coull and Nobre, 1998)
    • shifting awareness to the inferred future
  • Enables the prediction of consequences for contemplated behaviours, essential for planning, sequencing and foresight
    • -impaired in PFC damage
executive functions1
Executive Functions
  • Plan actions towards a goal
  • Use information flexibly
  • Realize consequences
  • Draw inferences
  • Independent of IQ
slide12
Frontal lobe damage produce deficits in:
    • Initiation, cessation and control of action
    • Abstract and conceptual thinking
    • Cognitive estimation and prediction
    • Cognitive flexibility and response to novelty
    • Goal directed Behaviours
initiation cessation control of action
Initiation, Cessation & Control of Action
  • “Psychological Inertia” (Luria, 1966)
    • Spontaneity and Fluency loss
    • Perseveration: repetitive behaviour unresponsive to feedback or reward
    • Environmental dependency syndrome (Lhermitte, 1983)
  • Separation of knowledge and actions
psychological inertia
Psychological Inertia
  • Tasks assess ease and fluidity of concept generation
  • Verbal Fluency: words starting with “s”
    • L-PFC sensitivity
    • repetitions, halting speech
  • Non-verbal Fluency: figures with 4 straight lines
    • R-PFC sensitivity
executive functions2
Executive functions
  • Shifting concepts
  • Part-whole relations
  • Integrating isolated ideas
  • Handling simultaneous sources of information
  • Use of feedback
  • Translation of knowledge to action
shifting sorting tests task demands
Shifting & sorting tests -task demands-
  • Find a rule that can be used to group or sort disparate stimuli
  • Shift attention to see the stimuli in a new way
sorting tests sub processes
Sorting tests – sub-processes
  • Identification and generation of concepts
  • Hypothesis testing
  • Maintenance of attention
  • Resistance to interference
  • Utilization of feedback to guide behavior
  • Inhibition of perseveration
  • Shifting of cognitive set
  • Perceptual, motor processes
wisconsin card sorting test grant berg 1948 milner 1963
Wisconsin Card Sorting Test(Grant & Berg, 1948; Milner, 1963)
  • Wisconsin Card Sorting Task (WCST)
    • no explicit rules
    • learn from feedback
    • must shift to new contingencies (10 correct)
  • Test characteristics
    • Administration methods
      • Nelson, 1976:"Having failed to grasp the test requirements, bewilderment frequently turns to distress as responses are negatively reinforced on a basis that to the patient appears totally arbitrary (if not perverse)."
    • Measures
      • Categories, Perseverations, Loss of Set
wisconsin card sorting test
Wisconsin Card Sorting Test
  • Measures:
  • Categories, Perseverations, Loss of Set
wisconsin card sorting test1
Wisconsin Card Sorting Test
  • What frontal subregions are implicated?
    • DLPFC: Milner (1963)
    • Medial frontal: Drewe (1974)
    • Orbitofrontal: Stuss et al. (1983)
  • Posterior lesion effects
wisconsin card sorting test2
Wisconsin Card Sorting Test
  • Is it sensitive and specific to frontal function in healthy adults?

WCST vs. sensorimotor control

(Berman et al., 1995)

wisconsin card sorting test3
Wisconsin Card Sorting Test
  • Sensitive to diffuse injury and certain posterior damage
  • With proper controls
    • Perseveration sensitive to DLPFC and superior medial frontal damage
    • Set loss sensitive to inferior medial and right DLPFC damage
  • Task sensitivity modulated by examiner-provided structure
  • Not a proxy for frontal function in healthy participants
psychological inertia1
Psychological Inertia
  • Environmental dependency syndrome (Lhermitte)
  • Utilization behavior
  • Actions impelled by the physical or social environment
  • Excessive dependency on the immediate environment
    • stereotyped responses
    • ignoring context.
  • Interferes with behavioural flexibility and individual autonomy (free will).
neuroimaging
Neuroimaging
  • Go/No Go
  • go trial: push button
  • no-go: withhold response (more difficult if rare)
  • fMRI
    • R-DLPFC (BA46/9)
    • R-VLPFC (BA44)
    • Anterior Cingulate (ACC)
abstract v concrete thinking
Abstract v Concrete Thinking
  • Modified WCST
  • Conceptual sorting criteria
  • 2 groups, 8 dimensions
    • water/land, triangle location, etc.
    • 2 groups, 8 dimensions Conceptual sorting criteria
  • Deficit in sorting into meaningful piles even with concrete clues
cognitive estimation prediction
Cognitive Estimation & Prediction
  • Cognitive estimation deficits: deducing judgment from known information
    • Prices
    • Time to complete
    • Prioritizing becomes difficult
  • Intact knowledge base (Semantic memory)
  • Prediction impaired for social and ToM
cognitive flexibility and response to novelty
Cognitive flexibility and response to novelty
  • FL deficits when...
    • Learned behaviour must be overridden
    • Environmental information doesn’t guide behaviour
goal directed behaviours
Goal Directed Behaviours
  • Staying on task
  • Sequencing
  • Shifting Set & Strategy Modification
  • Using information to guide behaviour
  • Self-monitoring
staying on task
Staying on task
  • Prerequisite for success
  • FL patients wander off...
  • DLPFC: maintenance of attention
    • establishes task relevancy
sequencing
Sequencing
  • Determining steps to achieve a goal
  • Recognition v Recency
    • TL v FL
  • Self-ordered pointing
sequencing1
Sequencing
  • Tower of London (Shallice, 1982)
    • Move balls one at a time
    • Desired position
    • Minimum moves
  • FL lesions, L > R deficit. Aimless moves
  • Neuroimaging: DLPFC, L > R activity
shifting set strategy modification
Shifting Set & Strategy Modification
  • Conceptual or perceptual shift deficits
    • Changing directions midway through
    • sorting task
  • Switching: FL region determined by task demand
  • Involves inhibition of previous set
  • Formation of new set

(Dias et al, 1997; Slamecka, 1968; Owen, 1991)

shifting set strategy modification1
Shifting Set & Strategy Modification
  • A Respond according to shape
  • B Respond according to shape
    • Shapes replaced with novel exemplars
    • Intradimentional
  • C Shift to other dimension (lines)
    • Previously relevant dimension must be present to evoke deficits
  • D Reversal of reward contingencies (within dimension)

(Dias et al, 1997; Slamecka, 1968; Owen, 1991)

shifting set strategy modification2
Shifting Set & Strategy Modification
  • L-PFC shifts attention between perceptual dimensions
  • OFC reverses stimulus-reward associations within perceptual domains
  • Mechanisms of on-line processing are independent of inhibitory control in PFC
  • Impairment of inhibitory control is restricted to novel situations
  • PFC areas involved in
    • suppression of previously established response sets
    • not involved in the acquisition of these response sets

(Dias et al, 1997; Slamecka, 1968; Owen, 1991)

guiding behaviour
Guiding behaviour
  • Environmental contingencies influence effective goal directed behaviour
  • ex: Telephone call while making dinner
  • Sub-goals interwoven
  • Neuroimaging hierarchical subgoals: OFC
    • 2 tasks performed in succession towards a general goal
    • baseline: task switch no retention
    • and holding info over delay
self monitoring
Self-monitoring
  • Is the goal being approached?
    • Diminished motivation
    • Error monitoring involved? (ACC)
      • error detecting
      • conflict monitoring
  • FL works with the ACC to monitor action and subjective (not absolute) detection of errors
theoretical accounts
Theoretical accounts
  • Feedback utilization (Luria)
  • Inhibition (Dias, 1996; Diamond, 1989)
  • Working memory (Goldman-Rakic, 1987; Kimberg & Farah, 1993)
  • Scripts & “managerial knowledge units” (MKU; Grafman, 1989)
  • Supervisory Attention (Norman & Shallice, 1986; Stuss et al, 1995)
controlled vs automatic processing
Controlled vs. Automatic Processing
  • Contention Scheduling
    • automatic processing
      • time & learning
      • role of FL diminishes with experience
  • Supervisory Attention System
    • effortful/controlled processing
      • where automatic processing would fail and must be overcome
      • novel events without processing schemes
      • when tasks are technically difficult
      • problem solving required
supervisory attention system
Supervisory Attention System
  • Modules: Basic cognitive operations
  • Schemata: Standard and routine programs for the control of overlearned skills in the modules
  • Contention Scheduling: The lateral inhibitory mechanisms that control competition between schemata
  • Supervisory System: General executive
    • Situations where incorrect response is liable to be produced by unmodulated contention scheduling
    • Situations in which no routine exists (novel).

Shallice (1982); Norman & Shallice (1980)

slide42
Supervisory Attentional System

Supervisory

Attentional

System (4)

Schema

Control

Units

Trigger

Data

Base

Contention

Scheduling

(3)

Perceptual

System

(2)

Special-purpose

Cognitive

Subsystems (1)

(Action)

Shallice (1981)

four components of the supervisory system
Four Components of the Supervisory System

1) Cognitive units or modules

2) Schemata

3) Contention scheduling

4) Supervisory (attentional) processes

four components of the supervisory system1
Four Components of the Supervisory System

1) Modules: Basic cognitive operations

2) Schemata: Standard and routine programs for the control of overlearned skills in the modules

3) Contention Scheduling: The lateral inhibitory mechanisms that control competition between schemata

4) Supervisory System: General executive component - top down processing

seven anterior attention categories of tasks
Seven Anterior AttentionCategories of Tasks
  • Sustaining
  • Concentrating
  • Sharing
  • Suppressing
  • Switching
  • Preparing
  • Setting
supervisory system
Supervisory System
  • Energize a Schema
  • Inhibit a Schema
  • Adjust Contention Scheduling
  • Monitor Goal Fulfillment
  • If-then Logic

E I C M L

slide48
Anterior Attention System

Supervisory System

E I C M L

Schemata

Perceptual

Information

Effector

System

sustaining attention
Sustaining attention
  • Definition:
  • Attention to relevant events occurring at a relatively slow rate over prolonged periods of time
slide50
Sustaining Attention

a. Energize task

schema

b. Inhibit competing

schema

c. Monitor responses

on and off tasks

E I C M L

a

b

c

c

concentrating attention
Concentrating Attention
  • Definition
  • Attention when task is demanding and relevant events occur too quickly rather than too slowly
slide52
Concentrating Attention

a. energize task

schema

b. decrease inhibition

among similar

schema to allow

high activity levels

in several schema

c. monitor responses

on tasks for minutes

d. If-then logic

d

E I C M L

a b c

d

fractionating the sas
Fractionating the SAS

Process

Goal

Putative localization

Sustain

Mitigate schema decay

R Frontal

Concentrate

Activate one schema, inhibit others

Anterior cingulate

Sharing

Activate two schemas

Orbitofrontal, ACG

Inhibit selection of inappropriate

Suppress

DLPFC (L?)

schema

Switch

Activate recently inhibited schema

DLPFC, medial PFC

Submaximal activation for later

Prepare

DLPFC

response

Consistent mobilization of most

L DLPFC

Set

appropriate schema across sessions

Stuss et al. (1995)

capgras syndrome
Capgras Syndrome

Misidentification of people as other people, or locations as other locations

(Stuss & Alenxander, 1979;1999)

Reduplicative Paramnesia: Subjective certainty that a familiar place or person has been duplicated

capgras syndrome1
Capgras Syndrome
  • CT
  • Diminished density
    • Bilateral frontal
    • Right temporal (including amygdala)
  • Enlarged ventricles
    • (R > L)
  • Significant cognitive impairment, including executive functioning and memory;
  • Slow recovery
  • 10 months after injury: first weekend visit
    • wife - new hair cut, new car
    • teenage kids - a year older
capgras syndrome2
Capgras Syndrome
  • Reports disorientation
  • New family has replaced the old
    • with notable similarity
  • Desertion of previous wife not distressing
    • kind enough to find replacement
capgras syndrome3
Capgras Syndrome

Demonstrates implausibility but cannot change feeling

capgras syndrome4
Capgras Syndrome
  • Years later:
    • Maintained belief of second family
    • Neuropsychological testing: normal IQ, memory, language, basic attention; impaired on “frontal tests”
  • Why?
    • Executive functioning impairment
      • Failure of personal evaluation or validation of the situation
ad