Executive Functions

1
Executive Functions

• Nathan Spreng
• Cognitive Neuroscience Psy393
• August 8, 2005

2
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

3
Who is the Central Executive?
4
Lecture Outline

• PFC and overcoming the default mode
• Attributes of executive functions
• Goal Directed Behaviour
• Video
• Supervisory System
• Capgras case study
• Video (?)

5
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

6
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

7
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

8
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

9
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

10
Fuster J., 2003
11
Executive Functions

• Plan actions towards a goal
• Use information flexibly
• Realize consequences
• Draw inferences
• Independent of IQ

12

• 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

13
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

14
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

15
Executive functions

• Shifting concepts
• Part-whole relations
• Integrating isolated ideas
• Handling simultaneous sources of information
• Use of feedback
• Translation of knowledge to action

16
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

17
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

18
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

19
Wisconsin Card Sorting Test
Measures Categories, Perseverations, Loss of Set
20
Wisconsin Card Sorting Test

• What frontal subregions are implicated?
• DLPFC Milner (1963)
• Medial frontal Drewe (1974)
• Orbitofrontal Stuss et al. (1983)
• Posterior lesion effects

21
Wisconsin Card Sorting Test
WCST vs. sensorimotor control (Berman et al.,
1995)

• Is it sensitive and specific to frontal function
  in healthy adults?

22
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

23
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).

24
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)

25
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

26
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

27
Cognitive flexibility and response to novelty

• FL deficits when...
• Learned behaviour must be overridden
• Environmental information doesnt guide behaviour

28
Goal Directed Behaviours

• Staying on task
• Sequencing
• Shifting Set Strategy Modification
• Using information to guide behaviour
• Self-monitoring

29
Staying on task

• Prerequisite for success
• FL patients wander off...

• DLPFC maintenance of attention
• establishes task relevancy

30
Sequencing

• Determining steps to achieve a goal
• Recognition v Recency
• TL v FL
• Self-ordered pointing

31
Sequencing

• Tower of London (Shallice, 1982)
• Move balls one at a time
• Desired position
• Minimum moves
• FL lesions, L gt R deficit. Aimless moves
• Neuroimaging DLPFC, L gt R activity

32
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)
33
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)
34
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)
35
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

36
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

37

• Video

38
Theoretical Account of Executive Functions
39
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)

40
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

41
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)
42
Supervisory Attentional System
Supervisory Attentional System (4)
Schema Control Units
Contention Scheduling (3)
Trigger Data Base
Perceptual System
(2)
Special-purpose Cognitive Subsystems (1)
(Action)
Shallice (1981)
43
Four Components of the Supervisory System
1) Cognitive units or modules 2) Schemata 3)
Contention scheduling 4) Supervisory
(attentional) processes
44
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

45
Schema interactions
46
Seven Anterior AttentionCategories of Tasks

• Sustaining
• Concentrating
• Sharing
• Suppressing
• Switching
• Preparing
• Setting

47
Supervisory System
E I C M L

• Energize a Schema
• Inhibit a Schema
• Adjust Contention Scheduling
• Monitor Goal Fulfillment
• If-then Logic

48
Anterior Attention System
Supervisory System
E I C M L
Schemata
Perceptual Information
Effector System
49
Sustaining attention

• Definition
• Attention to relevant events occurring at a
  relatively slow rate over prolonged periods of
  time

50
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
51
Concentrating Attention

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

52
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
53
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)
54
Capgras Syndrome

• Misidentification of people as other people, or
  locations as other locations
• (Stuss Alenxander, 19791999)
• Reduplicative Paramnesia Subjective certainty
  that a familiar place or person has been
  duplicated

55
Capgras Syndrome

• CT
• Diminished density
• Bilateral frontal
• Right temporal (including amygdala)
• Enlarged ventricles
• (R gt 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

56
Capgras Syndrome

• Reports disorientation
• New family has replaced the old
• with notable similarity
• Desertion of previous wife not distressing
• kind enough to find replacement

57
Capgras Syndrome
Demonstrates implausibility but cannot change
feeling
58
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