the executive brain Flashcards
what is executive function?
control processes that enable
an individual to optimise performance, requiring
coordination of basic cognitive processes
like a conductor
how are EF domain general?
Not tied to a specific cognitive domain
what are the supervisory EFs?
Problem solving
Overcoming habitual responses
Task-switching
Multi-tasking
disorder used be called… but are now linked to…
‘frontal lobe disorders’
prefrontal cortex (PFC)
what are the 3 surfaces of the PFC?
orbital
lateral
medial
what areas within the orbital surface are involved in EF?
BA 11:
- Orbitofrontal/ ventromedial PFC
- Task switching
BA10:
- Polar PFC
- Multi-tasking
what areas within the lateral surface are involved in EF?
BA 46/9:
- Dorsolateral PFC
BA 44/45:
- Ventrolateral PFC
=Problem solving
what areas within the medial surface are involved in EF?
BA 24:
- Anterior Cingulate Cortex
- Overcoming habitual responses
what is the principle of problem solving?
Giving a participant an end-point and a starting point; participants must generate a solution (task setting)
what test is used for problem solving?
Tower test: Tower of London
“how to get from initial to goal position?”
Describe the Ruocco Tower test study for problem solving:
- 38 healthy ps
- trait deliberation: think before act
- fNIRS
- Scarborough adaptation of ToL
what were the results of the Ruocco Tower test study for problem solving?
Increased left dorsolateral PFC activation when solving problems
Even higher in individuals with high trait deliberation
what is a habitual response?
one that we engage in automatically
what concepts are ‘overcoming habitual responses’ related to?
Response inhibition:
- Reducing the likelihood of a particular thought or action
Impulsivity:
- A behavioural tendency to make immediate responses or seek immediate rewards
what tests are used in ‘overcoming habitual responses”?
Stroop test
Go/no go test
explain the Stroop test in terms of habitual response:
reading the word is habitual (fast), so when it is incorrect it must be inhibited
incorrect responses compete with the less habitual task of naming the colour (slow)
describe the Alexander et al. stroop test for ‘overcoming habitual responses’:
- 38 healthy ps
- 42 ps with frontal lesions
- fMRI
- measure reaction time
what were the results of the Alexander et al. stroop test for ‘overcoming habitual responses’?
Slow reaction time and decreased correct responses with lesions in:
anterior cingulate cortex, presupplementary motor area, and dorsolateral areas
what is the go/no go test?
habitual responding is due to frequency of different stimuli
eg. respond habitually when ‘go’ more frequent
what do errors on ‘no-go’ trials show?
measure of response inhibition
behavioural marker of impulsivity
describe the Picton Go/no go test for overcoming habitual responses’:
38 healthy ps
43 ps with frontal lesions
‘go’ was more frequent
what were the results of the Picton Go/no go test for overcoming habitual responses’?
Lesions in superior medial frontal lobe associated with more false alarms:
-Dorsomedial PFC
-Anterior cingulate cortex (ACC)
-Pre-supplementary motor area (pre-SMA)
‘Overcoming habitual responses’: what happens when we make an error?
Humans and non-human primates are slower and more accurate after making an error.
Suggesting: error detection + compensation
what is error-related negativity?
an event-related potential component in EEG detected when an error is made
- relatively large negative deflection in EEG signal
- origins in ACC
What brain region is responsible for the change in behaviour (more accurate)?
Lateral PFC
what are the 2 theories for the role of ACC in error detection?
- Strategic control processes to reduce response conflict in top-down manner? (strategically controlling the likelihood of making an error)
- Evaluative processes just to detect response conflict
describe the Carter et al. study for role of ACC in error detection:
fMRI of 12 healthy ps with Modified Stroop test
congruent = low response conflict (colour same as word)
incongruent = high response conflict (different)
manipulated strategic control process = cue to expect congruency
high strategic control process = expecting incongruency
what were the results of the Carter et al. study for role of ACC in error detection?
- ACC activity was not regulated by trial type during high strategic control trials regardless of response conflict
- greatest activity of ACC for high conflict trials in low strategic control condition (when expected to be congruent, but was not)
what does the Carter et al. study for role of ACC in error detection suggest?
that the ACC does evaluation of response conflict not strategic control processes
what are the 2 subdivisions of the ACC?
Dorsal region implicated in executive functions
Ventral region implicated in emotional processing
what does Rushworth et al. argue about the ACC?
function of the ACC is to assess the value of responses
i.e., whether an action is likely to elicit a reward or punishment
Overcoming habitual responses requires monitoring response conflict to avoid making errors that might elicit punishment/be of lower value?
what is task switching?
discarding a previous schema and establishing a new one
‘set-shifting’
task switching: perseveration
failure to shift away from a previous response
Not ‘preservation’ but related
what tests are used in task switching?
Wisconsin Card Sorting Test (WCST)
Iowa Gambling Task
describe the Wisconsin Card Sorting Test (WCST):
match card to 1 of 4 reference cards whose symbols vary in: Shape, Number, Colour
say they are correct based on number, then switch and say incorrect, because based on shape = switch trial
what is the switch cost in task switching?
a slowing of response time due to discarding a previous schema and setting up a new one
Big difference in reaction times between No-switch and Switch trials
depend on complexity of schemas?
what study to predict either a higher Switch Cost for complex–>simple, or simple–>complex?
WCST Study: Meuter & Allport
16 bilinguals, numeral naming
Measured response latency when switching between languages
what were the results of the SCST bilingual study?
All ps. showed slower naming in L2 overall
Bilinguals are slower at switching from L2 (hard) to L1 (easy)
The Switch Cost is greater when discarding a complex schema to set up a simple one
Related to the (left) dorsolateral PFC
what study to test task switching when tasks are inherently of different values?
Iowa Gambling Task:
given loan, receive gain or loss based on card choice
A+B = start good, become bad – need to switch AWAY
C+D = start okay, become good – need to switch TO
describe the IGT study:
ps with ventromedial PFC lesions
Measured net choice of advantageous decks
results of IGT study
Healthy controls learn to switch from ‘Bad’ decks to ‘Good’ decks
Individuals with ventromedial PFC lesions:
- Fail to switch from ‘Bad’ decks to ‘Good’ decks over time
- but show intact performance on other tests of executive function (Stroop, WCST)
what are ‘hot’ EF control processes?
stimuli related to reward (food, money)
what are ‘cold’ EF control processes?
purely cognitive stimuli (sensory dimensions)
what EF are ‘cold’ control processes associated with?
Task-switching (also known as set shifting):
- Discarding a previous schema and establishing a new one
what EF are ‘hot’ control process associated with?
Reversal learning:
- Learning that a previously rewarded stimulus or response is no longer rewarded
describe the adapted WCS task on marmoset monkeys:
reward responding to certain item in one dimension(circle shape), regardless of other (lines)
then given lesions in either:
- Orbitofrontal/ventromedial prefrontal cortex
- Lateral prefrontal cortex
what was the post lesion training for moneys in WCS
either:
- reversal learning: same stimuli but different shape rewarded (not circle)
- dimension (set) shift: all new stimuli, only rewarded certain line dimension. learn new rule = task switch
what were the dissociation findings of the monkey WCT study?
double dissociation:
Suggests dissociable neural correlates for control of responses to reward-related (‘Hot’) vs. purely cognitive (‘Cold’) stimuli
what were the neural correlate findings of the monkey WCT study?
‘hot’ stimuli: orbitofrontal/ventromedial cortex
Cold’ stimuli: lateral frontal cortex
what does the IGT study tell us about reversal learning?
because those with ventromedial PFC lesions fail to switch to ‘good’ decks,
suggests that the ventromedial PFC is doing something involving reversal learning which enables task switching when there’s reward (hot)
what is multitasking?
carrying out several tasks in succession; requires both task-switching and maintaining future goals while current goals are being dealt with
what is the difference between task-switching and mulititasking?
In task-switching one goal is substituted for another
In multi-tasking several goals are maintained at the same time
what is prospective memory?
processes that allow the realisation of an intention after a delay
describe the Volle et al. study on multitasking:
45 ps with lesions
fMRI prospective memory paradigm
Voxel-based lesion-symptom mapping
“OGonly” = ongoing task (semantic/lexical)
what were the findings of the Volle et al. study on multitasking?
hierarchically ordered executive system:
posterior –> anterior gradient for simple–> complex tasks
describe the hierarchically ordered executive system:
Premotor cortex:
- simple stimulus response mappings
Posterior lateral PFC:
- contextual info guides response
Anterior lateral PFC:
- switch to different contexts
Polar PFC:
- complex multi-tasking
Lateral PFC
Problem-solving
Task-switching
‘Cold’ cognitive control processes
Polar PFC
Multi-tasking
Medial PFC (ACC)
Response conflict?
Orbital PFC
Task-switching – reversal learning
‘Hot’ cognitive control processes
