Executive processes & dysexecutive disorders Flashcards
What are executive functions?
Functions that regulate & control cognitive processing
How do behavioural deficits link to executive functions?
Behaviour deficits stem from difficulties with executive functioning
Name 3 tests of executive processes.
- Tower of Hanoi/London
- Verbal/category fluency task
- WCST
What do you do in the Tower of Hanoi task?
3 rods, one holding a stack of different coloured disks
You must move the entire stack to another rod following numerous rules:
- only move one disk at a time
- a disk can only be moved if it is the uppermost disk on the stack
- no disk may be placed on top of a smaller disk
How do people with frontal lobe damage do on the ToH task?
Have difficulty
Problems with planning (= combining components to complete a task)
Shallice (1982) found that lesions in WHICH area of the brain cause difficulties on the ToH task?
Left anterior lesions
Which researcher/s found that patients with PFC lesions performed worse than health controls on the ToH task?
Goel & Grafman (1995)
Goel & Grafman (1995) say that patients (with PFC lesions) have difficulty on the ToH task not because of planning deficits but because of…
An inability to resolve a goal-subgoal conflict
What does a verbal/category fluency task involve?
Must generate as many words beginning with a letter/in a category
How does damage to the frontal lobe affect performance on verbal/category fluency tasks?
Make less responses than healthy controls (3-4 words per min vs. 12+ words per min)
Repeat words
What did Baldo et al. (2000) find about verbal/category fluency tasks?
People with frontal lobe lesions are impaired (make less responses) compared to healthy controls
The individual does not have an over-learned programme for generating items from a category, so what must they do when doing a verbal/category fluency task?
Must run their own retrieval strategies whilst ensuring that items come from the correct category & aren’t repetitions
What does the WCST test?
A person’s ability to follow rules, use feedback & amend their actions
What does the WCST involve?
There are 4 ‘key’ cards - the participant must match other cards to each key card (depending on colour of shapes, number of shapes on cards, types of shapes on cards)
Pps discover sorting rules using correct/incorrect feedback from the experimenter
What sort of responses do healthy people make in the WCST?
Learn quickly, eventually acquire all rules, make few errors
What sort of responses do people with frontal lobe damage make in the WCST?
They learn the first rule but don’t change - make perseveration errors based on the old rule
What did Nelson (1976) find that patients with frontal lobe damage did on the WCST?
Even when they are told that the rule has changed, they still perseverate
Which researcher/s found that patients with frontal lobe damage were significantly more impaired than patients with non-frontal lobe damage?
Robinson et al. (1980)
What did Robinson et al. (1980) claim the WCST could be used for?
Distinguishing patients with frontal & non-frontal lesions
According to Shallice (2002), patients with frontal lobe damage have an impaired…
Supervisory Activating System
What does a person do/what can a person not do if their Supervisory Activating System is impaired?
Once a strategy has been adopted it keeps running because they can’t interrupt & change their ongoing activity
What happens if there isn’t a well-established current activity & the SAS is damaged?
The system remains inert or is captured by another stimulus
What sort of behaviours do people with a damaged SAS produce?
Distractible & facetious behaviour
Show utilisation behaviour
What is utilisation behaviour?
The presentation of objects implies the order to grasp & use them (Lhermitte, 1983)
What balance is disturbed if an individual is showing utilisation behaviour?
The balance between their dependence on & independence from the outside world is disturbed
When a person is showing utilisation behaviour, what inhibitory function is suppressed?
The inhibitory function of the frontal lobes on the parietal lobes is suppressed
Who proposed the SAS model?
Norman & Shallice (1986)
According to the SAS model, which 2 processes manage the functioning & control of schemas?
- Contention scheduling system
2. Supervisory activating system
What happens in the Contention Scheduling System (SAS model)?
Prior learning lets an activity run automatically (with little interference from the activity)
Sometimes activities come into conflict & one must be prioritised
The CS ensures that the correct schema is activated & prevents other competing actions from being executed simultaneously (through inhibition)
In the Contention Scheduling System (SAS model), when are schemata initiated?
When the level of activation (of the schemata) reaches a threshold
If a schema encounters many activations, what does it mean for the future?
We will have easier future access to that schema & greater suppression of the activation of schemata that are connected to it
What happens to schemas that are concurrently run together many times?
They are strengthened with use & take less attentional control
The CS (SAS model) is…
a) slow, voluntary, irregular in activating schemata
b) fast, automatic, consistent in activating schemata
b) The CS is fast, automatic & consistent in activating schemata
What does the Supervisory Activating System (SAS model) have control over?
The Contention Scheduling System
What does the Supervisory Activating System (SAS model) do?
Monitors conscious, deliberate planning of actions, novel situations that can’t be solved by previously-learnt schemata, & when preventing error is critical
Monitors the activation of an appropriate schema, suppresses inappropriate schemata, & adjusts to solve problems that existing schemata failed to resolve
What does the SAS (SAS model) do when there is no existing schemata related to a presenting issue?
Under attentional control, a new schema may be created, assessed & implemented
The SAS (SAS model) is…
a) slow, voluntary, uses flexible strategies to solve problems
b) fast, automatic, has rigid solutions for problems
a) The SAS is slow, voluntary & uses flexible strategies to solve problems
What are ‘slips of action’?
Unintentional behaviours resulting from absent-mindedness or not paying attention
When do slips of action normally occur?
When we are doing an automatic & familiar task
What are the 2 modes of action control?
- Routine, well-practiced action sequences (e.g. driving to work)
- Novel/infrequently performed actions (e.g. taking a new route to work)
What activates action schemas?
Cues/triggers
What happens when action schemas are activated?
Leads to the performance of the action (represented by the action schema)
What is an action schema?
A sequence of actions you must perform to do an activity
What types of cues can activate an action schema?
- internally-generated thoughts
- objects in the environment
- physiological responses
- direct prompts
Are routine actions under the control of the CS or SAS?
CS
What causes trigger units to activate a schema?
Internal/external cues
What happens when the activation threshold of for an action is exceeded?
When the threshold is exceeded, the schema is selected, the action is initiated & competing schemas are inhibited
What is the basis of the CS?
Activation & inhibition of schemata
When an action is novel/infrequently performed, which system (CS/SAS) does it use? What does this system do?
The SAS - it applies extra activation/inhibition to select the required action schemas
Which area of the brain is the SAS located?
Frontal lobes
Which area of the brain is the CS located?
Posterior region
Which system (CS/SAS) is damaged after frontal lobe impairment?
The SAS
What types of behaviours occur after frontal lobe damage? Why?
Classic frontal behaviours occur because the CS is operation alone (isn’t moderated by the SAS, which is damaged due to frontal lobe damage)
Which behaviours would we expect to see if the SAS is damaged & the CS is operating alone?
Perseveration
Inertia/inappropriate action
Why does perseveration occur (SAS model)?
Occurs when a cue-schema response/association is well-learned or has been recently executed
Which test of executive processes shows perseveration in people with frontal lobe damage?
WCST
Why does inertia/inappropriate action occur? (SAS model)
Occurs when cue-schema links are weak
We can’t select a schema or alternate between actions
Our attention is easily captured by irrelevant aspects of the context
Which test of executive processes measures inertia?
Verbal fluency
Which 3 behaviours do executive process tests measure?
- Task switching
- Inhibition
- Updating
What is ‘planning’?
A complex executive task focused on future actions that you want to accomplish
What is prospective memory?
Completing an intended action that you can’t perform immediately
What actions are involved in a prospective memory task?
We must inhibit our current activity & switch to the PM task, then update our memory to encode whether you have/haven’t been successful
Miyake et al. (2000) compared pps performances on complex executive tasks (WCST, ToH) and simple executive tasks that tested a particular skill (RNG, operation span, dual tasking). Which 3 skills did every task measure?
Shifting, updating, inhibition
What did Miyake et al. (2000) find? (Compared complex executive tasks and simple executive tasks)
WCST performance was related to shifting/switching
ToH performance was related to inhibition
RNG performance was related to inhibition & updating
OS performance was related to updating
DT performance wasn’t related to any skill
Sylvester et al. (2003) used counter-switching & response in inhibition to examine the neural underpinnings of switching & interference. Pps were shown arrows pointing left/right. What did pps do in task 1?
Pps had to keep track of the number of left- & right-facing arrows in each block. They had to silently update their mental count for both arrows & then make a motor performance to initiate display of the next arrow.
What happened in switch & non-switch trials in Sylvester et al.’s (2003) study?
Switch trials - successive arrows pointed in different directions & required a switch in the counter to be updated
Non-switch trials - successive arrows pointed in the same direction
What decision did pps have to make at the end of each block of arrows in Sylvester et al.’s (2003) study?
Pps had to make a positive/negative decision about a probe that showed a left/right arrow & a possible count –> had to indicate whether their mental count agreed
What did task 2 in Sylvester et al.’s (2003) study involve?
‘SAME’ or ‘OPPOSITE’ was shown at the end of each block - if it was ‘SAME’, pps made responses compatible with the direction of the arrow shown at the end of the block (no inhibition), vice versa for ‘OPPOSITE’ (inhibition)
Which areas did Sylvester et al. (2003) find were activated in switch + inhibition trials?
Bilateral parietal cortex
Left dlPFC
Premotor cortex
Medial frontal cortex
Which areas did Sylvester et al. (2003) find were activated in switching only?
BA 7
BA 18
BA 19 (posterior area)
Which areas did Sylvester et al. (2003) find were activated in inhibition only?
BA 6 (premotor area) BA 10 (frontopolar area)
