executive function iii ref: theories: gazzaniga pp. 526-529

Executive Executive Function IIIFunction III

Ref: Theories: Gazzaniga pp. 526-529 Ref: Theories: Gazzaniga pp. 526-529

Prefrontal Cortex: 3 Major RegionsPrefrontal Cortex: 3 Major RegionsDorsolateral Dorsolateral

Prefrontal CortexPrefrontal CortexKey role in executive functionKey role in executive function

Social/emotional mediation of Social/emotional mediation of behaviourbehaviour

Anterior CingulateAnterior Cingulate

Orbitomedial Orbitomedial

Prefrontal CortexPrefrontal Cortex

Evaluating own behaviourEvaluating own behaviour

TodayToday

• Review of dorsolateral PFC, anterior cingluateReview of dorsolateral PFC, anterior cingluate

• Discussion of orbitomedial PFCDiscussion of orbitomedial PFC

• Theories of executive functionTheories of executive function

Dorsolateral PFCDorsolateral PFC

• Key role in Working MemoryKey role in Working Memory

• Other Functions:Other Functions:

1.1. Initiation, cessation of actionInitiation, cessation of action

2.2. Dynamic filtering (e.g. Stroop task)Dynamic filtering (e.g. Stroop task)

3.3. Task switching (e.g. Trail making test)Task switching (e.g. Trail making test)

4.4. Flexibility - response inhibition, Flexibility - response inhibition, cognitive flexibility (e.g. alternate cognitive flexibility (e.g. alternate

uses test)uses test)


• Strongly activated in highly demanding tasks e.g divided attentionStrongly activated in highly demanding tasks e.g divided attention

• Also especially active when errors occurAlso especially active when errors occur

• Generally, participates in situations requiring close Generally, participates in situations requiring close monitoring, monitoring, where there is where there is response conflictresponse conflict

• Acts in tandem with dorsolateral PFC to ensure that the necessary Acts in tandem with dorsolateral PFC to ensure that the necessary attentional resources are effectively deployedattentional resources are effectively deployed

Orbitomedial PFCOrbitomedial PFC• Social and Emotional Mediation of BehaviourSocial and Emotional Mediation of Behaviour

Phineas GagePhineas Gage: Before the accident he had : Before the accident he had

been their most capable and efficient been their most capable and efficient

foreman, one with a well-balanced mind, foreman, one with a well-balanced mind,

and who was looked on as a shrewd smart and who was looked on as a shrewd smart

business man. He was now fitful, business man. He was now fitful,

irreverent, and grossly profane, showing irreverent, and grossly profane, showing

little deference for his fellows. He was also little deference for his fellows. He was also

impatient and obstinate, yet capricious and impatient and obstinate, yet capricious and

vacillating, unable to settle on any of the vacillating, unable to settle on any of the

plans he devised for future action. His plans he devised for future action. His

friends said he was "No longer Gage."friends said he was "No longer Gage."

Orbitomedial PFC: FeaturesOrbitomedial PFC: Features Two key features of damage to orbitomedial PFC:Two key features of damage to orbitomedial PFC:

1.1. No initiative, flattened affect: (“pseudodepression”)No initiative, flattened affect: (“pseudodepression”)

Elliott: After removal of a brain tumour that bilaterally invaded the Elliott: After removal of a brain tumour that bilaterally invaded the

brain's orbital surface, Elliott performed well on standard IQ tests and brain's orbital surface, Elliott performed well on standard IQ tests and

even outperformed most age-matched control subjects on the WCST. even outperformed most age-matched control subjects on the WCST.

Nonetheless, he had great difficulties coping with the real world. He Nonetheless, he had great difficulties coping with the real world. He

lost his job, and eventually went bankrupt. As striking as Elliott's lost lost his job, and eventually went bankrupt. As striking as Elliott's lost

sense of social norms was his personal detachment from his problems. sense of social norms was his personal detachment from his problems.

He had no difficulty recounting the minutest details of his many He had no difficulty recounting the minutest details of his many

failings, but spoke of them as if he were a dispassionate observer.failings, but spoke of them as if he were a dispassionate observer.

Patient Y: A high velocity missile had entered the patient's left temple and Patient Y: A high velocity missile had entered the patient's left temple and

emerged through the right orbit. Prior to injury, Patient Y had been quiet, emerged through the right orbit. Prior to injury, Patient Y had been quiet,

intelligent, proper, and hard-working. Subsequent to this injury, he was intelligent, proper, and hard-working. Subsequent to this injury, he was

outspoken, facetious, brash and disrespectful. There was no evidence of self-outspoken, facetious, brash and disrespectful. There was no evidence of self-

pity, although he frequently made rather morbid jokes about his condition. pity, although he frequently made rather morbid jokes about his condition.

When asked about how his injury had affected him, he showed some awareness When asked about how his injury had affected him, he showed some awareness

of some aspects of his problems (e.g. no sense of taste), but little concern, often of some aspects of his problems (e.g. no sense of taste), but little concern, often

commenting "To tell you the truth, it's a blessing this way".commenting "To tell you the truth, it's a blessing this way".

2.2. Lack of social restraint (“pseudopsychopathy’)Lack of social restraint (“pseudopsychopathy’)

Orbitomedial PFC: FeaturesOrbitomedial PFC: Features

Orbitomedial PFC: What does it do?Orbitomedial PFC: What does it do?

Somatic Marker Hypothesis (Damasio): Somatic Marker Hypothesis (Damasio):

• Orbitomedial PFC binds memories to their emotional and Orbitomedial PFC binds memories to their emotional and neurophysiological associationsneurophysiological associations

• normals: an “emotional” picture (e.g. accident victim) normals: an “emotional” picture (e.g. accident victim) evokes a learned emotional response. This is measurable.evokes a learned emotional response. This is measurable.

• P’s with Orbitomedial PFC lesions: can describe picture in P’s with Orbitomedial PFC lesions: can describe picture in detail, but no strong emotional responsedetail, but no strong emotional response

• Explains: flattened affect, lack of concern for social Explains: flattened affect, lack of concern for social conventionsconventions

Theories of Executive Function

• Problems with describing role of PFC in executive Problems with describing role of PFC in executive function: Many "Frontal" tasks are complex and can function: Many "Frontal" tasks are complex and can be described in >1 waybe described in >1 way

• Problem of circularityProblem of circularity

• Also terms such as “control” too vague to be testedAlso terms such as “control” too vague to be tested

• How can we describe what the frontal lobes do in a way How can we describe what the frontal lobes do in a way that is that is directly testabledirectly testable??

• Answer: we must develop a proper Answer: we must develop a proper theorytheory

Contention Scheduling TheoryContention Scheduling Theory

Two Major ComponentsTwo Major Components

SchemasSchemas::

• well-practised routines or action plans well-practised routines or action plans e.g. stop at red lighte.g. stop at red light

• are developed with are developed with practicepractice

• are "activated" by external stimuli OR internal cuesare "activated" by external stimuli OR internal cuese.g. stop at red light schema -> red lighte.g. stop at red light schema -> red light

• remain active until "switched off"remain active until "switched off"

SchemasSchemas

Supervisory Attentional SystemSupervisory Attentional System

Shallice and Norman (1989)Shallice and Norman (1989)


Supervisory Attentional System (SAS)Supervisory Attentional System (SAS): :

• overrides normal activation levels of schemasoverrides normal activation levels of schemas

• turns on, switches off schemas when no other cuesturns on, switches off schemas when no other cues

• creates program of action when no schema avail., creates program of action when no schema avail., or when task has special demandsor when task has special demands

• Schemas are stored in Schemas are stored in posterior cortical regionsposterior cortical regions

• The SAS is in The SAS is in prefrontal cortexprefrontal cortex


Explains:Explains:

• Inability to initiate or cease an actionInability to initiate or cease an action(psychological inertia, perseveration)(psychological inertia, perseveration)

• Difficulties dynamic filteringDifficulties dynamic filtering

• Poor task switchingPoor task switching

• Inability to inhibit habitual responsesInability to inhibit habitual responses

• Lack of cognitive flexibilityLack of cognitive flexibility

• Inability to formulate goalsInability to formulate goals

Contention Scheduling - ProblemsContention Scheduling - Problems

• Theory is highly cognitive. It proposes one central system Theory is highly cognitive. It proposes one central system - BUT PFC shows regional specialisation- BUT PFC shows regional specialisation

• Very powerful - predicts just about anything, so is difficult Very powerful - predicts just about anything, so is difficult to testto test

• Doesn’t deal with working memoryDoesn’t deal with working memory

AlternativesAlternatives

Miller & Cohen (2001):Miller & Cohen (2001):

• PFC PFC maintains patterns of activity that represent goalsmaintains patterns of activity that represent goals

• These patterns These patterns modulate processing in posterior cortexmodulate processing in posterior cortexe.g. resolve competition, inhibit inappropriate e.g. resolve competition, inhibit inappropriate

responsesresponses

• Similar to Contention Scheduling, but more anatomically-Similar to Contention Scheduling, but more anatomically-based, allows for the possibility of regional specialisation based, allows for the possibility of regional specialisation

• Also, gives a primary role to working memoryAlso, gives a primary role to working memory

• BUT still a problem with power??BUT still a problem with power??

ConclusionConclusion

• The executive functions of prefrontal cortex still poorly The executive functions of prefrontal cortex still poorly understoodunderstood

• Research is in its infancyResearch is in its infancy

• The next decade (even the next few years) is likely to The next decade (even the next few years) is likely to change this significantlychange this significantly

• Advances will depend as much on cognitive theories, as Advances will depend as much on cognitive theories, as they do on research technologythey do on research technology

executive function iii ref: theories: gazzaniga pp. 526-529

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