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Executive Functions Nathan Spreng Cognitive Neuroscience: Psy393 August 8, 2005.

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Presentation on theme: "Executive Functions Nathan Spreng Cognitive Neuroscience: Psy393 August 8, 2005."— Presentation transcript:

1 Executive Functions Nathan Spreng Cognitive Neuroscience: Psy393 August 8, 2005

2 Preliminary issues Lecture slides & Last exam Paper – download problems? – 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 Find a rule that can be used to group or sort disparate stimuli Shift attention to see the stimuli in a new way Shifting & sorting tests -task demands-

17 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 Sorting tests – sub-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 Is it sensitive and specific to frontal function in healthy adults? WCST vs. sensorimotor control (Berman et al., 1995)

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 doesn’t 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 > R deficit. Aimless moves Neuroimaging: DLPFC, L > 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 (Dias et al, 1997; Slamecka, 1968; Owen, 1991) 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)

34 Shifting Set & Strategy Modification (Dias et al, 1997; Slamecka, 1968; Owen, 1991) 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

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 Contention Scheduling (3) Trigger Data Base Special-purpose Cognitive Subsystems (1) Perceptual System Supervisory Attentional System (4) Schema Control Units (Action) (2) Supervisory Attentional System 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 Attention Categories of Tasks ·Sustaining ·Concentrating ·Sharing ·Suppressing ·Switching ·Preparing ·Setting

47 Supervisory System Energize a Schema Inhibit a Schema Adjust Contention Scheduling Monitor Goal Fulfillment If-then Logic E I C M L

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

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

50 ab c c E I C M L Sustaining Attention a. Energize task schema b. Inhibit competing schema c. Monitor responses on and off tasks

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 E I C M L a b c d d

53 Fractionating the SAS ProcessGoalPutative localization SustainMitigate schema decayR Frontal ConcentrateActivate one schema, inhibit othersAnterior cingulate SharingActivate two schemasOrbitofrontal, ACG Suppress Inhibit selection of inappropriate schema DLPFC (L?) SwitchActivate recently inhibited schemaDLPFC, medial PFC Prepare Submaximal activation for later response DLPFC Set Consistent mobilization of most appropriate schema across sessions L DLPFC Stuss et al. (1995)

54 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

55 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

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

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