Executive Functions Flashcards
define executive functions
collective of top-down cognitive processes that assert themselves when non-automatic processes are insufficient or inappropriate in a given situation (Burgess & Simon, 2005)
e.g novel, difficult, requiring attention, multiple cognitive processes need to be coordinated, shifting between different processes
what functions are considered to be executive
task initiation: impairment results in a reduction of self-generated action and procrastination that results in apathy, akinetic mutism, abulia and decreased fluency. Tests of verbal and non-verbal fluency.
sustained attention: impairment in staying on task that results in distraction. Tests of continuous performance
response inhibition: acting without thinking resulting in disinhibition. Tests such as stroop or go/no-go where prepotent responses should be inhibited
error monitoring: lack of awareness when wrong response made resulting in an inability to learn from mistakes due to an unawareness of them being made. WCST perseveration
cognitive flexibility/ set-shifting: rigid thinking resulting in perseveration and inflexibility. WCST
WM: difficulty holding information online to perform tasks, poor problem solving following instructions. Digit span, corsi blocks.
Multi-tasking: difficulting co-ordinating actions simultaneously e.g multiple errands
Planning and prioritisaiton: disorganisation, difficulty making decisions, completing tasks e.g tower of Hanoi
social/ emotional regulation: poor social skills, empathy. ToM
strategic retrieval from episodic memory: incorrect or inappropriate recall for the context, resulting in confabulation. Word list learning.
Is there a general model to explain the many different executive functions?
Norman & Shallice 1980
when greater control is necessary, the supervisory systems acts on schemas
SAS biases the schema selection process when an action is ill-learned, novel, critical, dangerous or when planning is required
what is the dysexecutive syndrome?
A term coined by Baddeley (1986) to describe dysregulation of executive functions, or in his model of WM the central executive, caused by damage to the frontal lobes.
Associated with both behavioural and cognitive components
behavioural:
global hypoactivity (apathy), global hyperactivity (distractability, impulsivity, disinhibition), perseverative stereotyped behaviour with inflexibility, impaired error monitoring, emotional and social dysregulation (loss of empathy)
cognitive:
response initiation, suppression, switching, information generation, rule duedction/problem solving/ planning, sustained and focused attention, working memory, strategic retrieval from episodic memory, theory of mind
How have patient studies informed the idea of a dysexecutive syndrome
Focal lesions
The Modern Phineas Gage (Mataro et al., 2001)
- bilateral prefrontal damage
- apathetic (difficulty initiating, maintaining and completing tasks); restless and impatient; poor planning
- impaired on WCST, verbal fluency and luria motor learning and maintenance
Patient EVR (Eslinger & Domasio 1985)
- large orbitofrontal meningioma resected
- personality changes, impulsive, fixated on simple tasks, impaired decision making and organisation, total disruption of personal life
- passed standard EF tests such as WCST
Manohar et al., 2021
- bilateral orbitofrontal and vmPFC damage
- disinhibited and disorganised behaviour, apathy and impaired error monitoring
- performed better than patients with unilateral lesions and healthy controls on a gambling task where particiapnts had to decide which of two options was most likely to win and how much to bet on this outcome
- did not show anchoring biases to previous bets and alternative option value (unrestrained by contextual biases)
Frontal resection patients (Milner & Petrides, 1984)
- make perseveration errors in WCST
- have problems with recency judgements, planning and self-generated action, unable to organise memories and be flexible with behaviour
neurodegenerative disorders
behavioural variant fronto-temporal dementia (bvFTD)
bilateral frontal atrophy or anterior temporal atrophy
3 of
- behavioural disinhibition
- apathy/ inertia
- loss of sympathy/ empathy
- perseverative, stereotyped, compulsive, ritualistic behaviour
- hyperorality and dietry changes
- executive function deficits with sparing of memory and visuospatial abilities)
Alzhimer’s - behavioural variant (Ossenkoppele et al., 2015)
- dysexecutive deficits caused by AD pathology
- more often cognitive than behavioural, with the most common behavioural presentation being apathetic
- voxel-wise contrasts of patients vs controls highlights atrophy in bilateral temporoparietal regions and limited atrophy in frontal cortex (particularly compared to bvFTD)
- difficult to distinguish form bvFTD need biomarkers and often not confirmed until post-mortem
