dysexecutive syndrome Flashcards
sub-regions of the frontal lobes
- Primary motor cortex - production of skilled movements.
- Premotor cortex - organisation of more complex actions
- Prefrontal cortex - controlled behaviour
- dlPFC - inhibition, planning, working memory
- vlPFC/vmPFC - emotional control/regulation
- FPC - most abstract forms of human cognition
role of pre-frontal cortex in cognition
- Consensus that the frontal lobes mediate “higher” cognitive functions, and the co-ordination and strategic use of other cognitive resources.
- These are commonly referred to as “executive functions”:
- Organizing, planning, prioritizing
- Making decisions, thinking strategically
- Deploying attention, focusing, following a plan
- Monitoring performance, actions
- Multi-tasking, task switching, inhibition
- Problem-solving, abstract thinking, integration of knowledge
- Working memory, prospective memory, future thinking
- Regulating emotions, appropriateness to the context
- Damage causes “dis-executive syndrome”
common causes of prefrontal damage
· Traumatic brain injury (TBI)
· Stroke or rupture of aneurysm of anterior communicating/cerebral artery
- Tumour e.g., miningioma
clinical syndrome
Phineas Gage (1823-1860):
· 1848 - 25 years old, railroad construction foreman
· An accident caused penetrating head injury - a metal bar went up through his eye and skull.
· A few hours later he was able to speak to the doctors
· Two weeks later his memory for familiar people and recent events was intact.
· Survival for another 11.5 years.
· Haemorrhage and infections damaged particularly the ventromedial prefrontal cortex.
· Harlow, 1848
- Miller, 1993
clincial syndrome 2
· After the accident, Harlow reported ‘‘he is fitful, irreverent, indulging at times [. . .], manifesting but little deference for his fellows, impatient of restraint or advice when it conflicts with his desires [. . .], devising many plans of future operations, which are no sooner arranged than they are abandoned. [. . .] In this regard his mind was radically changed, so decidedly that his friends and acquaintances said he was ‘no longer Gage’.”
· PG also developed a ‘‘great fondness for pets and souvenirs, especially for children, horses and dogs – only exceeded by his attachment for his tamping iron [which caused the injury], which was his constant companion during the remainder of his life”.
- These cognitive and behavioural changes are consistent with more recent evidence from patients with damage to the ventromedial prefrontal cortex.
clinical syndrome 3
· Utilisation behaviour - the tendency to grasp common objects when presented, and perform the function commonly associated with the object. Indicates lack of appropriateness to the context, impulsivity.
- Individuals with prefrontal damage find it difficult to resist the impulse to use the objects in front of them, even when these actions are not appropriate to the situation.
clinical syndrome 4
· “executive dis-functions”:
- Inability to organise and plan
- Distractibility
- Inability to inhibit prepotent responses, impulsivity
- Inability to switch/shift focus
- Inability to solve complex problems, think in abstract ways
- Inability to make farsighted decisions
- Inability to envision future situations
- Inability to respond the context appropriately.
testing executive functions
· Wisconsin card sorting test (WCST):
- Tests: set-shifting, rule abstraction, flexible thinking
- 3 possible ways of categorising stimuli: number, colour, shape
- Task: learn what is the correct rule to categorise stimuli based on feedback
- Individuals with prefrontal damage get “stuck”, carrying on sorting by a rule even if told it was wrong.
- This behaviour is referred to as perseveration (Milner, 1963)
stroop test
- Tests: selective attention, response inhibition
- Individuals with prefrontal damage cannot inhibit the more prepotent, automatic response of reading the words, despite knowing their task it to name the colour of the ink the word is written with.
hayling test
- Tests: response inhibition and strategy generation
- A series of sentences are read with the last word missing
- “The captain wanted to stay with the sinking…”
- “He posted the letter without a…”
- Part A: complete the sentence with an appropriate word - “ship”/”stamp”
- Part B: complete the sentence with an unrelated word - e.g., “chair”/”blue”
- Individuals with prefrontal damage cannot inhibit the automatic response of completing the sentence with the obvious word.
- They also cannot generate a strategy to find unrelated words (e.g., listing words belonging to a certain category).
testing executive functions 2
· Some individuals will perform well on tests of general IQ, attention and even traditional tests of executive function but…
· They are disorganised in their daily life - e.g., poor at making a plan and sticking to it.
· Most lab-based tests are very structured vs real life situations are not well structured.
· Tests need to be open-ended, require multi-tasking and planning.
- Ecologically valid tests predict functioning in “the real world”.
the mutliple errands test
· Shallice and burgess, 1991
· Tests: planning, strategy thinking, problem-solving
· Perform 8 tasks written on cards to be used as reminders during the test
- 6 simple tasks (e.g., buy a brown loaf, buy a packet of throat pastilles)
- A seventh task requires the subject to be at a certain place 15 minutes after starting
- An eighth task requires to obtain four sets of information and write them on a postcard (i.e., the name of the shop in the street likely to have the most expensive item; the price of a pound of tomatoes; the name of the coldest place in Britain yesterday; the rate of the exchange of the French franc yesterday).
- Takes place in the real world (in a small shopping precinct near the hospital previously unknown to the patients)
- Requires to obey various rules:
Only go into each shop once
Only use a watch to assist you
Stay within a certain area
Spend as little money and time as possible
- Control participant
- Individual with prefrontal damage
· Errors typically made by an individual with prefrontal damage:
- Plan formulation or modification
* Going to Post Office before all relevant information obtained (Cases 1-3)
* Failure to look at watch at start (Case 3)
* Generation of inappropriate criteria
- Marker creation or triggering
* Going out of bounds (Cases 2, 3)
* Attempt not to pay for item in shop (Case l, 2)
* Looking in irrelevant shops (Cases 1, 2)
- Evaluation and goal articulation
* Posting postcard without all information (Cases 2, 3)
* Failure to keep a check of money (Cases 2, 3)
* Thinking finished when had not (Case 1)
supervisory attentional system (SAS)
· Norman and Shallice, 1986
· Action is either automatic or under attentional control.
· Automatic (e.g., making a cup of tea):
- Can be executed without awareness or deliberate attention
- Attention can be automatically drawn to an object
· Controlled (e.g., learning to drive a car):
- Involve planning or decision making
- Involve troubleshooting
- Involve novel sequences of actions
- Are dangerous or technically difficult.
- Require the inhibition of habitual/overlearned responses
problems with SAS result
· Perseveration - once activated, schemas persist in absence of any SAS input.
· Distractibility - when no single schema is dominant, the SAS would normally inhibit responses.
· The model provides reasonable accounts for the performance of dysexecutive patients on standard tests:
- Utilisation behaviour: SAS required to inhibit action schemas relevant to the object
- WCST: SAS required to shift responding from previous category
- Stroop: SAS required to prevent inhibit “read” response
- Hayling: SAS required to inhibit dominant sentence completion
- The model does not easily address more complex planning/ decision making/ multitasking situations.
EVR
· Damasio & Eslinger, 1985
· Age 32 - Father of two, active in local community, promoted to senior
· position in accountancy firm, “role model” for siblings
· Age 35 - after brief period of visual disturbances and personality change,
· large tumour removed from ventromedial frontal cortex
· WAIS-R IQ – 125, above average performance on all subtests an
· intelligence battery and traditional tests of frontal lobe function
· BUT…
- * Spent family savings
- * Continually fired from increasingly unskilled jobs
- * Wife divorced him
- * Remarried against advice, divorced 2 years later
- * Could spend entire days “getting ready for work”
- * Deciding where to dine out could take hours
- EVR’s fundamental deficit is in decision making
