The Executive System and its Disorders: A Brief Visit

1. The Executive System and its Disorders: A Brief Visit www.neuro.spc.org/rawnsley Vaughan Bell vaughan@backspace.org Outline • What is the executive system ? • How does it break down ? The dysexecutive syndrome: • Affect and social judgment • Executive memory • Abstract thinking and intentionality • Relation to psychopathology

2. What is the Executive System ? • It’s not intelligence ! IQ paradox ? • It is mainly concerned with the co-ordination of other cognitive resources. • It is a dynamic, ‘online’ system, that may only fully engage some aspects in real world situations. • Involved in handling novel situations where routine activation of behaviour would not be sufficient for optimal performance. • Involved in making actions and thought processes less effortful the more we experience them. • This means the role of the executive system will change when the same person is tested in the same task on different occasions.

3. Handling of Novel Situations • Norman and Shallice (1980) outline five types of situation where routine activation would not be sufficient: 1) Those that involve planning or decision making. 2) Those that involve error correction or troubleshooting. 3) Situations where responses are not well-learned or contain novel action sequences. 4) Dangerous or difficult situations. 5)Situations which require the overcoming of strong habitual response or resisting temptation.

4. Dysexecutive Syndrome • Despite the fact that the executive system may seem particularly abstract… • … we do know a good deal about how it may break down after brain injury. • As we shall see, the pre-frontal cortex (PFC) is particularly associated with the executive system. • Although the relationship is not clear cut.

5. Problems with Affect and Social Judgement Damasio et al (1994) • Phineas Gage was one of the earliest reported cases of frontal lobe damage causing personality changes. • We now know that problems with emotional control and decision making are not uncommon in dysexecutive patients. • Patient EVR, a ‘modern day gage’ provides a similar example.

6. Theories of Affect of Social Judgement • Damasio (1998) - Somatic marker hypothesis. • Rolls (1996) - Role of orbito-frontal cortex (OFC) in socially mediated stimulus - response behaviour. • Baron-Cohen (1995) sees this sort of impairment in terms of an impaired ‘theory of mind’ • Blair and Cipolotti (2000) - mediates how past experience is used in ‘here and now’ social cognition

7. Executive Memory Baddeley (2000) • In Baddley’soriginal and revised memory models the executive system is an essential component for the co-ordination of memory resources. • Parkin (1997)has argued for the role of the executive system in episodic encoding. • Damage to the executive system can have dramatic effects on memory function, e.g. patient JB.

8. Abstract Thinking & Intentionality • The ability to conceptualise abstract problems and executive tasks to a predetermined plan involves a complex set of mechanisms. • Executive deficits can result in problems with: • temporal organisation (planning) • rule attainment • action selection • Deficits in this area can be tested with, for example, the Tower of London task, Six Elements Task, Multiple Errands task.

9. Stroop Test: Executive Inhibition XXXX XXXX XXXX XXXX XXXX XXXX XXXX XXXX XXXX XXXX XXXX XXXX XXXX Red Green Blue Yellow Green Red Green Blue Yellow Green Red Blue Yellow Taylor et al (1997)

10. Action Mediation • Another dramatic failure of executive inhibition is utilisation behaviour. • Patients are unable to prevent themselves from carrying out actions that are triggered by their environment. • For example, a patient may find it hard to pass a door without trying to open it. • Shallice et al (1989): failure of supervisory process. • See also, action slips. • Executive system is also involved in action initiation and breaks down in akinetic mutism.

11. Unitary Models of the Executive System • Duncan (1995) has proposed the executive system is equivalent to Spearman’s g and fluid intelligence. • Norman and Shallice (1980) have proposed a comprehensive model… • This model outlines a selection-for-action system which mediates the selection of schema selection... • …with the ability to intervene where necessary.

12. Relationship to Psychopathology: Schizophrenia • Executive deficits found in schizophrenic patients: • Planning, Cognitive flexibility and control, Working Memory, Problem solving, Response inhibition, Organisation, Fluency, Monitoring • However, to argue that symptoms of schizophrenia are caused by executive impairment is more difficult. • It seems that there is a generalised intellectual decline (Goldberg and Gold, 1995) • Along with other possible neurocognitive problems: • e.g. dementia, negative features, movement disorders, amnesia, incoherent speech, visual agnosia • (Frith, 1992)

13. Relationship to Psychopathology: Schizophrenia • However, Frith (1992) argues that the major underlying deficit in schizophrenia is one of metarepresentation; this seems heavily executive. • That is, the ability to have representations of representations, of the world, our thoughts, actions and intentions and those of others. • Impairment in generating intentions could lead to poverty of action, perseveration, inappopriate action. • Impairment in monitoring willed intentions could lead to delusions of alien control, auditory hallucinations, thought insertion / removal. • Impairment in monitoring the beliefs and intentions of others could lead to delusions of reference, paranoia, certain kinds of incoherence, third person hallucinations.

14. Relationship to Psychopathology: Depression • A Disruption to the parallel functional network linking prefrontal to subcortical regions has been implicated in psychiatric disorders including major depression (Austin and Mitchell, 1995) • Certainly, executive function is know to occur in depression, especially as it becomes more severe (Austin et al, 1999) • It has been thought this might just be an epiphenomenon due to lack of motivation. • However, executive deficits may persist after recovery of mood disorder, suggesting these that may be implicated in its aetiology (Austin et al, 2001).

15. Conclusion • The executive system is concerned with the co-ordination of other cognitive resources. • It may break down, impairing: • Affect and social judgment • Executive memory • Abstract thinking and intentionality • Executive performance can be impaired with mental illness. • And some symptoms may be a secondary result of this impairment. • Although such a causal relationships is not clear in every psychopathology.