Executive Function Flashcards
What are executive functions?
The ability to plan actions to reach a goal, guide, or control behaviour towards the goal
— use information flexibly, think abstractly, make references
Must be exerted in situations when there is no existing plan/ template/ experience for how to act
Required when typical responses must be overridden or inhibited
AKA Cognitive control
Cognitive control
A term indicating a process in which someone is guiding their own thoughts and actions
How many functions contribute to the performance of executive abilities?
More than one, therefore, it’s difficult to link each function to a specific brain region
Executive deficits
Most commonly observed after damage to the frontal lobe, including the white matter area connecting frontal regions to other area
— difficulties in executive functioning can occur despite normal functioning in other “intellectual processing areas”
The lateral prefrontal cortex
- Dorsolateral
- Ventrolateral
- Orbitofrontal
- Premotor
(check slides to practice labelling location)
Goal-directed behaviours
- guiding behaviour towards a goal is multifaceted
- losing a facet can derail the entire plan
- completing a task requires a number of skill
- functions rely on a pattern of activity within overlapping portions of the frontal lobe + the degree it interacts with other brain regions
Skills needed to complete a task
- staying on task
- sequencing information
- modifying strategies
- using knowledge in your plans
- monitoring actions
Creating and maintaining a goal
- required for executive functioning
- most basic prerequisite for meeting a goal is staying on task
- those with frontal lobe damage have issues staying on task
Creating and maintaining a goal: Task sets
Task set: process that designated which information is task relevant
Stroop test can test this: a cue 1.5 seconds before the stimulus says what information should be identified
Lateral prefrontal cortex becomes active during the cue period, before the stimulus
—– greater degree of activation causes a less competing colour name causing slowed responses
Prefrontal areas help us stay on task
Sequencing and Planning
- to reach a goal, you need to know what steps need to be taken and what order to take them in
»> requires knowing what comes before and after, what’s been a accomplished, what needs to be performed
»> dorsolateral prefrontal regions may be important in sequencing items because they support executive processes that act on information maintained in working memory
Self-Ordered Pointing Task (slides)
(6 items are given on a screen, participant must pick any item they haven’t picked before, items change location each time)
- reveals deficits in sequencing
- observed after frontal lobe damage, notably laterally
- regions also active neurologically-intact individuals when they must make a recency judgement
Choosing a Sequencing Strategy
- Another important aspect is the ability to choose which sequence/ strategy allows a goal to be attained
- Patients with frontal lobe damage are less likely to report they are using strategies
- One way to assess strategy is the Tower of London Task (move balls to the goal position in as little moves as possible/ in recommended number of moves)
Task-switching
- reaching a goal is not always linear
— there are often things that require task-switching - The neuropsychological test used is the Wisconsin Card Sorting Test (WCST) (told to sort cards in a certain way, then told to sort in another way)
—– neurologically intact people adjust their responses accordingly in this test
—— A variety of brain areas are activated during the WCST: Dorsolateral Prefrontal Cortex, Ventrolateral prefrontal cortex, inferior parietal lobe, temporoparietal association cortex, the basal ganglia
Task-Switching and the Brain
A variety of brain areas are activated during the WCST:
- Dorsolateral Prefrontal Cortex, Ventrolateral prefrontal cortex, the inferior parietal lobe, temporopariteal association cortex, the basal ganglia
Task switching is likely directed by an executive control system that is independent of the systems that perform each individual task
Frontal lobe damage and task switching
patients with left frontal lobe damage have a specific deficit in task-switching
Increasing activity in this area (the left DLPFC) via transcranial direct current can augment task-switching abilities
- inferior frontal junction is also implicated in task-switching
Psychological Intertia
Hard to start an action, once engaged, hard to stop
- damage to medial frontal areas, including the supplementary motor area and anterior cingulate
- regions of the medial prefrontal cortex may be involved in determining how much effort will be exerted to reach a goal
Inhibition: Go? No-Go Task
Person responds by pushing a button when certain stimuli appear and withholding to other stimuli
- difficult when No-Go trials are rare, because Go is expected
- Witholding a response has consistently been found to engage a right-sided network of frontal brain regions
Inhibition: Stop-Signal Task
The person must respond to a stimulus as quickly as possible
In some trials, quickly after the stimulus is presented another signal occurs quickly that indicates you should stop
- activiates similar right-side networds of brain regions
- Both this and go/no-go involve the dorsolateral prefrontal cortex, the anterior cingulate, the SMA (pre-SMA), insula, and parietal regions
Self-Monitoring and Evaluations and Brain Damage
The ability to evaluate one’s own behaviour is affected by frontal lobe regions
— metacognitive awareness is distrupted by patients with left OR right frontal lesions
— frontal damage impairs the ability to detect errors and modify ongoing behaviours to take a corrective action (especially right)
Error-Related Negativity
Occurs ~100ms after an error
Amplitude increases under conditions in which response accuracy is emphasized
The larger the error, the larger the ERN
A variety of converging evidence suggests that the ERN component arises from rostral regions of the anterior cingulate cortex (ACC)
Self Monitoring and Evaluation
We have a set of brain mechanisms that helps to monitor our performance and detect error
- Theory: the anterior cingulate detects that an error has been made
—– but, even when someone is not aware they made an error, an ERN (Error-Related Negativity) can be detected
—– It could be the ERN is providing an undifferentiated signal that something is amiss
Awareness of an error is indexed by error positivity (Pe)
Error Positivity (Pe)
Frequently follows ERN by about 200-300 ms
— likely generated by the insula, which is associated with interoception
Increases when there’s awareness of an aerror
Introception
The ability to sense the physiological condition of the body
ERN in people with ADHD and Anxiety
Anxious people have an increase ERN
Those with ADHD have decreases in ERN and Pe
