Executive functioning

Dr. Elizabeth Sheppard

Developmental Cognitive

Neuropsychology (C8CLDC)

Child Clinical Neuropsychology

(C8DCHN)

Objectives: Be able to explain what is meant by executive functions

(defining/problems) Give examples and explain cognitive tests used to test EF Discuss the strengths and limitations of EF measures in

adults and children Explain how EF develops in typical children Discuss the extent to which adult models of EF can be

applied to children using evidence from typically developing children and children with acquired brain lesions

What are Executive functions?

Set of processes that underlie flexible goal-directed behaviour (e.g. planning, inhibitory control, attentional flexibility,working memory), Bianchi (1922)

High-order control processes Domain general i.e. operate across cognitive

systems/ modalities This definition is provisional & under-specified –

we don’t know much about this area of cognition!

How many components of Executive abilities are there?

Lezak 1995 - Suggests there are 4 components of Executive function: Volition Planning Purposeful behaviour Effective performance

Stuss 1987 - Identifies a number of associated skills necessary for goal-directed behaviour Ability to shift from one concept to another Ability to modify behaviour in light of new info Ability to synthesise & integrate isolated details into coherent

whole Ability to manage multiple sources of information Ability to make use of relevant acquired knowledge

Anderson et al. (2001) propose 3 separable but unified components of EF:

1.)  Attentional control: selective attention and sustained attention

2.)  Cognitive flexibility: working memory, attentional shift, self-monitoring, and conceptual transfer

3.)  Goal setting: initiating, planning and organisation, generating and implementing strategies for problem solving, and strategic behaviour

How many components of Executive abilities are there?

What is Executive Dysfunction (dysexecutive syndrome)?

1.) Behavioural features - Poor self-control, impulsivity, erratic careless responses, poor initiation of speech, inflexibility (Lezak, 1995) Case of Phineas Gage – quiet family man

– yard long spike forced through his head Memory, language & motor functions in

tact Complete personality change

What is Executive Dysfunction (dysexecutive syndrome)?

2.) Cognitive features – People with Executive Dysfunction exhibit poor performance on tasks which require one to use Executive Abilities Tasks developed for use with adult

participants with brain injuries Large range of tasks tapping into various

aspects of EF

Measures of EF - Wisconsin Card Sort

Cards vary along several dimensions

Sort & given feedback – infer rule

Experimenter changes rule

Change strategy & infer new rule

Involves problem solving & cognitive flexibility

Measures of EF - Tower of Hanoi

Move all hoops from left peg to right peg without putting larger hoop on top of smaller

Involves attentional shifting, planning, inhibition

Measures of EF - Stroop Task

Read colour words

Either congruous or incongruous

Take longer if incongruous

Involves selective attention & inhibition

RED

BLUE

GREEN

YELLOW

RED

BLUE

GREEN

YELLOW

Measures of EF - Verbal Fluency Task

Generate as many words as possible in one minute that begin with the letter ‘ N ’?

Requires the use of a self generated strategy Time limit imposed

Measures of EF - Rey Figure Test

Copy figure as accurately as possible

Accuracy score measures spatial organisation

Organisational strategy score measures strategic decision making

Memory test also used sometimes

Measures of EF - Self-ordered Pointing task

Present series of arrays with a number of different elements

Point to different element in each array until all pointed to

Spatial location of elements changes in arrays

Involves working memory and strategic planning

Problem with measurements

Some question over reliability of measures e.g. WCST (Pennington et al.)

Discriminant validity = the ability to discriminate between distinct constructs Tasks tap multiple EF components so unclear

which EF causes poor performance Tasks also involve non-EF processes so are

poor at differentiating between EF deficits and non-EF deficits

What is executive dysfunction?

3). Biological features The “Frontal Metaphor” Association noted between tasks which

involve EF processes and damage to the pre-frontal cortex

Neuropsychologists may say an individual’s symptoms “look frontal”, without knowing the nature of the brain damage

Studies documenting effects of frontal lesions report heterogeneous range of tasks & behaviours disrupted

But… all require goal-directed behaviour, usually in novel contexts e.g. Cohen & Servan-Schreiber, 1992

Patients with lesions fail despite understanding goal of task due to perseveration, impersistence, intrusions of task irrelevant behaviour or lack of initiative

Cannot be attributed to more basic deficit in memory, perception or language comprehension

What is executive dysfunction?

What is executive dysfunction?

Evidence from neuroimaging and neuroanatomical studies suggests that EF processes are associated with the PFC (Rakic, Bougeois, Zecevic, Eckenhoff & Goldman-Rakic, 1986)

Strong evidence from PET scan studies showing association between WCST and activity in the PFC in normal and schizophrenic patients (Weinberger et al. 1994)

How does executive function relate to IQ?

Effects of adult frontal lesions on IQ appear to be negligible (Kolb & Wishaw, 1990)

Frontal lobes may be important for fluid intelligence but less important for crystallised intelligence

Duncan et al. (1995) – patients with frontal lesions showed disparity between scores on Wechsler IQ test & Culture Fair IQ test; those with lesions elsewhere/ no lesions did not

Why might damage occur to the PFC? Acquired adulthood Acquired childhood Congenital (developmental disorder)

Why study Executive Functioning in children? Are adults and children qualitatively different in

terms of EF? (frontal metaphor) Some EF behaviours may actually be evident in

childhood but redundant in adulthood (Smith et al., 1992)

Gets around discriminant validity problem in adult tasks – simpler tasks can be used.

We need to know about typical development of EF skills to help us understand developmental disorders that involve EF impairments.

Stages of Executive development

Frontal lobes originally thought to be functionally silent during childhood – EFs not measurable until second decade

This has been refuted now – e.g. Diamond & Doar argue cognitive skills necessary for EF are demonstrated in young children

Studies have shown frontal activity during even infancy e.g. Chugani et al. (1987) – measured local cerebral

metabolic rates of glucose & found evidence of frontal activation in infants of 6 months

Stages of Executive development

Older children make age-related gains on battery of EF tasks Levin et al. (1991) – gains in concept

formation, mental flexibility, planning & problem solving

Researchers agree that EF skills produce stage-like development

Some EFs appear to mature earlier than others – supporting multidimensional nature

Stages of Executive development

Welsh, Pennington & Groisser (1991) Studied children aged 3-12 yrs on various EF

measures – argue for 3 distinct developmental stages Age 6- Competence with simple planning and

organised visual search. Age 10- Set maintenance, hypothesis testing, and

impulse control attained. Adolescence- Complex planning, motor sequencing,

and verbal fluency In general, greatest development occurs in

middle childhood with slower development continuing later

EF development and frontal lobe development

Evidence for direct link between frontal development & EF from studies of object permanence in monkeys

Object permanence requires working memory & inhibition – develops in children around 7 months

Diamond & Goldman-Rakic

(1989) – animals with lesions

to parietal lobes passed A

not B task; those with frontal

lesions did not

EF development and frontal lobe development Evidence suggests improvement in EF during childhood

corresponds with growth spurts in frontal lobe development Bell & Fox (1992) – EEG changes in frontal lobes during

1st year of life correlate with length of delay for response in delayed response tasks

However, some argue EF maturation reflects integrity of cerebral development throughout the brain; or EF maturation dependent on emergence of other cognitive abilities (see Anderson et al.)

Skill learning approach (similar to interactive specialisation account) – frontal cortex consistently involved in acquisition of new skills & knowledge from early on in life & plays role in organising other parts of cortex (e.g. Thatcher, 1992)

Children with acquired frontal damage – case studies

If children with frontal lesions different from adults, problems for ‘frontal metaphor’

Children with acquired frontal damage are rare so case study approach used for studying frontal injuries in children

Therefore, note that limitations of case studies apply here Lack of consistent measures across cases Ascertainment biases (bias in sampling – non-random)

Nevertheless case studies produce fairly consistent findings

N.B. Very important to consider cases within developmental perspective

Children with acquired frontal damage – case studies

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

Children with acquired frontal damage – case studies

Williams & Mateer (1992) - SN age 11, fell from tree- CT scan showed bilateral frontal lobe damage.- Dramatic changes in PIQ- Problems with sustained attention, visuo-spatial planning, & motor control- Inappropriate problem solving strategies, -Verbal reasoning and expressive vocabulary good, but not verbal inductive reasoning. - Tantrums, aggressive, inappropriate laughter, eating problems

Children with acquired frontal damage – case studies

Age 12-probs with mental flexibility, sustaining attention, verbal fluency, & perceptual organisation.

Age 13-Bi-frontal abnormalities evident (EEG). Superior verbal ability, non-compliant behaviour

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

Children with acquired frontal damage – case studies

Marlowe (1992) - PL 3;11, lawn dart Age 5 - good intellectual levels - good simultaneous but poor sequential processing - Verbal processing excellent, but needed instructions

repeated extensively Age 6 - similar intellectual level (but reduced efficiency in learning

new info) - A number of other cognitive deficits were evident: poor

anticipatory behaviour, verbal understanding, visuo-spatial organisation and production, distractible, inhibition problems, perseveration.

What do childhood case studies tell us?

Frontal lesions have dramatic and lasting effects Suggests that effects of frontal lesions are NOT silent,

temporary, or radically different than adults (support frontal metaphor)

Severity and time of insult are important

- down stream effects Some of the symptoms are similar to those for

developmental disorders (e.g. conduct disorder, ADHD), although they do not meet all criteria – seems to support frontal metaphor for developmental disorders

Summary

EFs – multi-componential processes underlying flexible goal-directed behaviour

EFs associated with PFC Number of EF tasks/ but problematic –

discriminant validity Child research gets around this to some

extent Case studies suggest EFs similar in children

and adults

References

Anderson, V., Northam, E., Hendy, J., & Wrennall, J. (2001). Developmental Neuropsychology: A Clinical Approach. Hove: Psychology Press.

Bell, M. A., & Fox, N. A. (1992). The relations between frontal brain electrical activity and cognitive development during infancy. Child Development, 63, 1142-1163.

Bianchi, L. (1922). The Mechanism of the Brain and the Function of the Frontal Lobes. Edinburgh: Livingstone.

Chugani, H. T., Phelps, M. E., & Mazziotta, J. C. (1987). Positron emission tomography study of human brain functional development. Annals of Neurology, 22, 287-297.

Cohen, J. D., & Servan-Schreiber, D. (1992). Context, cortex, and dopamine: A connectionist approach to behavior & biology in schizophrenia. Psychological Review, 99, 45-77

Diamond, A., & Doar, B. (1989). The performance of human infants on a measure of frontal cortical development: The delayed response task. Developmental Psychology, 22, 271-294

Diamond, A., & Goldman-Rakic, P. (1989). Comparison of human infants and rhesus monkeys on Piaget’s AB task: Evidence for dependence of dorsolateral prefrontal cortex. Experimental Brain Research, 74, 24-40.

Duncan, J., Burgess, P., & Emslie, H. (1995). Fluid intelligence after frontal lobe lesions. Neuropsychologia, 33, 261-268.

References

Glosser, G., & Goodglass, H. (1990). Disorders in executive control functions among aphasic and other brain-damaged patients. Journal of Clinical and Experimental Neuropsychology, 12, 485-501.

Kolb, B., & Wishaw, I. Q. (1990). Fundamentals of Human Neuropsychology. New York: W H Freemont & Company.

Levin, H. S., Culhane, K. A., Hartmann, J., Evankovich, K., Mattson, A. J., Howard, H., Ringholz, G., Ewing-Cobbs, L., & Fletcher, J. M. (1991). Developmenal changes in performance on tests of purported frontal lobe functioning. Developmental Neuropsychology, 7, 377-395.

Lezak, M. (1995). Neuropsychological Assessment. (3rd edn.). New York: Oxford University Press.

Luciana, M., & Nelson, C. (1988). The functional emergence of pre-frontally guided working memory systems in four-to-eight year old children. Neuropsychologia, 30, 273-293.

Marlowe, W. B. (1992). The impact of a right prefrontal lesion on the developing brain. Brain and Cognition, 20, 205-213.

Mateer, C. A., & Williams, D. (1991). Effect of frontal lobe injury in childhood. Developmental Neuropsychology, 12, 95.

Rakic, P., Bourgeois, J.-P., Zecevic, N., & Goldman-Rakic, P. (1986). Concurrent overproduction of synapses in diverse regions of the primate cortex. Science, 232, 232-235.

Smith, S. D., Kates, M. H., & Vriezen, E. R. (1992). The development of frontal lobe functions. In S. J. Segalowitz & I. Rapin (Eds.). Handbook of Neuropsychology: vol 7. Child Neuropsychology. Amsterdam: Elsevier.

Stuss, D. T. (1987). Contribution of frontal lobe injury to cognitive impairment after closed head injury: Methods of assessment and recent findings. In H. S. Levin, J. Grafman, & H. M. Eisenberg (Eds.). Neurobehavioural Recovery from Head Injury. New York: Oxford University Press.

Thatcher, R. W. (1991). Maturation of the human frontal lobes: Physiological evidence for staging. Developmental Neuropsychology, 7, 397-419.

Thatcher, R. W. (1992). Cyclic cortical reorganisation during early childhood. Special Issue: The role of frontal lobe maturation in cognitive and social development. Brain and Cognition, 20, 24-50.

Weinberger, D. R., Behrman, K. F., Gold, J., & Goldberg, T. (1994). Neural mechanisms of future-oriented processes: In vivo physiological studies of humans. In M. M. Haith, J. B. Benson, R. J. Roberts, & N. F. Pennington (Eds.). The Development of future-oriented processes. Chicago: University of Chicago Press.

Welsh, M., Pennington, B. F., & Groissier, D. B. (1991). A normative-developmental study of executive function: A window on prefrontal function in children. Developmental Neuropsychology, 7, 131-149.

Williams, D., & Mateer, C. A. (1992). Developmental impact of frontal lobe injury in middle childhood. Brain and Cognition, 20, 196-204.

References