frontal lobes and executive function

7/31/2019 Frontal Lobes and Executive Function

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Executive functioning

What are Executive functions?

l Set of processes that underlie flexible goal-

directed behaviour (e.g. planning, inhibitory

control, attentional flexibility,working memory).

l Associated with the pre-frontal cortex area of

the brain.

How many components ofExecutive abilities are there?

l Lezak 1995 - Suggests there are 4 components of

Executive function.

l Stuss 1987 - Identifies a number of associated skills

necessary for goal-directed behaviour.

l Other authors also include focused and sustainedattention , strategy skills, self- monitoring, and the

ability to use feedback. (Glosser & Goodglass, 1990;

Levin et al. 1991; Mateer & Williams, 1991).


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1.) Attentional control: selective attention andsustained attention

l 2.) Cognitive flexibility: working memory,attentional shift, self-monitoring, and conceptualtransfer.

l 3.) Goal setting: initiating, planning andorganisation, difficulties generating andimplementing strategies for problem solving, andstrategic behaviour.

Definitions operationalised into 3

separable but unified componentsof EF:

What is Executive Dysfunction?

l Behavioural features- Poor self-control,

impulsivity, erratic careless responses, poor

initiation, inflexibility

l Cognitive features- Failure to carry out tasks

which require one to use Executive Abilities.l Main tasks developed from adults research on

patients who sustained injury to pre-frontal

region of the brain.

The Frontal Metaphor

l Association noted between tasks which involve

EF processes and damage to the Pre-frontal

cortex.

l Neuropsychologists may say an individuals

symptoms look frontal, without knowing the

nature of the brain damage.


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Are EF actually located in the Pre-frontal cortex (PFC)?

l Evidence from neouroimaging and neuroanatomical studies suggests that EF processesare associated with the PFC (Rakic, Bougeois,Zecevic, Eckenhoff & Goldman-Rakic, 1986)

l -There is strong evidence from PET scanstudies showing association between WCSTand activity in the PFC in normal andschizophrenic patients. (Weinberger et al.1994).

Why might damage to the PFCoccur?

l Congenital (developmental disorder)

l Acquired childhood

l Acquired adulthood

Tests of Executive functioning

l Wisconsin Card Sorting Task

l Tower of Hanoi/London

l Stroop

l Verbal Fluency

l Rey Figure Test

l Self-ordering Pointing


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Wisconsin Card Sort

Tower of Hanoi

Stroop Task

RED

BLUE

GREEN

YELLOW

RED

BLUE

GREEN

YELLOW


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Verbal Fluency Task

Generate as many words as possible in one

minute that begin with the letter N ?

l Requires the use of a self generated strategy

l Time limit imposed

Rey Figure Test

Self-ordered Pointing task


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Problem with measurements

l Multi-componential same poor performance,

but different reason. (Discriminant validity)

l Poor at differentiating between EF deficits and

non-EF deficits.

Why study Executive Functioningin children?

l Can inform us as to whether adults and children are

qualitatively different in terms of EF. (frontal metaphor)

l Some EF may be observable in childhood, and then

are no longer evident in adulthood.

l Gets around discriminant validity problem in adult tasks

which involve a number of EF processes.

l Can inform us about the typical development of EF

skills which can inform us about developmental

disorders that involve EF impairments.

Key questions

l How does EF develop?

- Stages

- Relationship between different EF processes

l Are children like adults in terms of EF?

-frontal metaphor

-look at typical and atypical developing children


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EF in Typical development

l Stages

Age 6- Competence with simple planning and organisedvisual search.

Age 10- Set maintenance, hypothesis testing, and impulsecontrol attained.

Adolescence- Complex planning, motor sequencing, andverbal fluency.

l Evidence suggests improvement in EF during childhoodcorresponds with growth spurts in frontal lobedevelopment (Anderson, Anderson, Northam et al; Bell & Fox,1992; Levin et al.,1991; Luciana & Nelson, 1998; Thatcher, 1991)

What does this tell us about EF?

l EF skills are not silent in childhood as

previously thought

l Relationship between frontal lobe and EF

ability provides further evidence of the role of

the PFC in EF

Relationship between different EFprocesses

l Beveridge et al. (2002) failed to find an

interaction between working memory and

inhibitory control in 6-8 year olds.

l Perner & Lang (2002) 3yr olds but not 4 yrs

olds show impairments on a task requiring

visual search and rule reversal, showingevidence of an interaction between this skills.


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What does this tell us about EF?

l Relationship between EF components is

complex and is still in need of investigation.

l Interaction effects highlight the importance of

adopting a developmental approach in

exploring EF functions.

Are children like adults?- Frontal lesions in childhood

l Williams & Mateer (1992) DR- 8:11, falling beam

- EEG & MRI showed damage to frontal region.

- Failure to maintain intellectual ability after injury

- Social & language problems, but Verbal and non-verbal

memory intact- Difficulty with acquisition of new information

- Little spontaneous activity

- Tantrums, aggression, unpredictable outbursts, impulsivity

Williams & Mateer (1992) Case 2

l SN age 11, fell from tree

-CT scan showed bilateral frontal lobe damage.

-Dramatic changes in VIQ and PIQ

- Problems with sustained attention, visuo-spatialplanning, & motor control

-inappropriate problem solving strategies, -Verbalreasoning and expressive vocabulary good, but notverbal inductive reasoning.

- Tantrums, aggressive, inappropriate laughter, eatingproblems


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Williams & Mateer (1992) Case 2

l Age 12-probs with mental flexibility, sustainingattention, verbal fluency, & perceptualorganisation.

l Age 13-Bi-frontal abnormalities evident (EEG)

Superior verbal ability, non-compliant behaviour

l Age 15- probs with inhibiting verbal responses,extreme literalness, compulsive attention todetail, directing attention, high distractibility.

Marlowe (1992) PL 3;11, lawn dart

l Age 5

- good intellectual levels

- good simultaneous but poor sequential processing

- Verbal processing excellent, but neededinstructions repeated extensively

l

Age 6- similar intellectual level (but reduced efficiency in learningnew info)

- A number of other cognitive deficits were evident: pooranticipatory behaviour, verbal understanding, visuo-spatialorganisation and production, distractable, inibitionproblems, perseveration.

What do childhood case studies tellus?

l Frontal lesions have dramatic and lasting

effects

l Suggests that effects of Frontal lesions are

NOT silent, temporary, or radically different

than adults. (support frontal metaphor)

l Severity and time of insult are important

-down stream effects


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Benefits of child research

l Adult tasks may require two or more Executive

processes.

l The severity EF problems may differ depending

on time of insult to the brain.

Summary

l Nature of EF

l EF associated with PFC

l EF tasks/problems (Disc. validity)

l Benefits of child research

l Similarities between adults/children

l Differences between adults/children

Neurodevelopmental implications

l Adult models can be applied to children

l Damage earlier results in more devastating EF

impairments (very little plasticity)

frontal lobes and executive function

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