L8a the executive brain

What is termed the brain’s ‘conductor’

executive functions

What are executive functions

control processes that enable an individual to optimise performance

What is required to perform executive functions

coordination of basic cognitive processes

What makes executive functions distinct from other cognitive processes

not tied to a specific cognitive domain such as memory or language

Are executive functions supervisory and controlled functions or receptive and uncontrolled functions

supervisory, controlled functions

Name the 4 main categories of executive functions

problem solving, overcoming habitual responses, task-switching and multitasking

What brain region are executive functions most associated with (PFC)

prefrontal cortex

Which 2 PFC subregion are associated with problem solving?

Dorsolateral PFC and ventrolateral PFC

Which PFC subregion is associated with task-switching?

Orbitofrontal/ventromedial PFC

Which 2 PFC subregion are associated with overcoming habitual responses?

Pre-SMA and anterior cingulate cortex (ACC)

Which PFC subregion is associated with multi-tasking?

Polar PFC

What is fluid intelligence (Gf) vs crystallised intelligence (Gc), according to Cattell

the ability to reason and solve novel problems vs knowledge accumulated from culture and education

Where does Gf originate from

Spearman’s general intelligence factor g

What do tests assessing fluid intelligence aim to minimise

cultural and educational influences

Two tests of fluid intelligence

Raven’s Progressive Matrices and Cattell’s Culture Fair Intelligence Test

What kind of test is Raven’s Progressive Matrices

non-verbal reasoning test

What does a non-verbal reasoning test involve

participates identify the missing piece in a pattern or sequence

What knowledge/skill does Raven’s Progressive Matrices rely on to assess fluid intelligence

abstract pattern recognition rather than language/learned knowledge

What does Cattell’s Cultural Fair intelligence Test involve

series completion, classifications, matrices, all using abstract shapes and patterns

What is the Multiple Demand (MD) system (set of which brain regions, 3 tasks, regardless of what?)

a set of frontal and parietal brain regions consistently recruited during complex, novel, and sequential tasks, regardless of cognitive domain

For what 4 kinds of tasks is the MD system recruited for

attention, cognitive control, multi-step problem solving, comparing hard vs easy tasks

What does the MD system explain about cognitive tasks and brain regions

why they active overlapping PFC-parietal regions

What ability does the MD system provide a neural basis for

general problem-solving ability through flexible allocation of processing

What are two types of evidence supporting the MD systems in non-human primates and in humans

electrophysiology and fMRI

These are the six key brain regions of the MD system – name 1 to 6

posterior inferior frontral sulcus (IFS), anterior insula/frontal operculum (AI/FO), pre-supplementary motor area (pre-SMA), dorsal anterior cingulate cortex (ACC), intraparietal sulcus (IPS), rostrolaterial pre-frontal cortex (RPFC)

Fedorenko et al used fMRI with individual-subject functional localisation instead of group-level analyses – why is this?

to avoid artificial inflating overlap in brain areas due to variability in brain structure

Two aims of Fedorenko et al’s approach was to located the MD in each individual and tap into the MD system – how was each aim achieved

by using one localiser contrast (to locate MD) and test responses to 7 diverse demanding tasks (tap into MD system)

What was a key task design and why was this done

hard vs easy conditions to isolate cognitive demand

Complete the main finding of Fedorenko et al – the first two responses are cortex areas, the second set of responses is the difficulty of the task (think which task MD becomes more active for) and the last response is what this suggests about the MD

frontal, parietal, hard, easy, domain-generality

Why does this individual-level evidence strengthen existence of a real MD system (consider previous issues with group-level analyses)

demonstrates that overlap is true and exists within individuals (not artificial)

Define the principle of problem solving (experimental)

giving a participant an end-point (goal) and a starting point in which they must generate a solution of their own (also known as task-setting)

What is an example problem solving test

tower tests

Ruocco et al wanted to study trait deliberation (tendency to think carefully before acting) using an adapted tower test – what was this adaptation and what neuroscience method was used

just answer yes or no, don’t need to do the task. Used fNIRS

What area of the PFC was activate when solving problems

left dorsolateral PFC

How did trait deliberation influence this activation

activation was higher in individuals with high trait deliberation

What two concepts explain/are related to habitual responses

response inhibition and impulsivity

What are two tests of overcoming habitual responses (we’ve looked at these plenty, think back to authoritarianism in personality module)

stroop test and go/no-go test

What are the two behavioural outcomes in the Stroop task that reflect inhibition failure?

Slower reaction times and increased errors.

What did Alexander et al use to relate lesion location to reaction times to stroop task in patients with frontal lesions vs healthy controls

fMRI

Lesions in which three brain areas are associated with slow reaction time and decreased correct responses to Stroop test, suggesting their role in inhibiting habitual responses

ACC, pre-SMA, and dorsolateral areas

This is the Go/No-Go task, what 2 things does it seek to measure with errors on no-go trials (explored previously)

response inhibition and impulsivity

Picton et al tested response inhibition and impulsivity (false alarms) in healthy controls vs patients with frontal lesions – what 3 lesion locations specifically within the superior medial frontal lobe were associated with more false alarms

ACC, pre-SMA and dorsomedial PFC

Recall the 3 common lesion areas found in the Stroop test and go/no-go test

dorsolateral PFC, pre-SMA and ACC

Recall the 3 common impairments found in the Stroop test and go/no-go test

slower reaction times, more false alarms, and more errors

Of the 3 common lesion areas, which is associated with problem solving (think back to tower tests brain activation)

dorsolateral PFC

Of the 3 common lesion areas, which is associated with response inhibition

pre-SMA

What is the status of the role of ACC

remains debated but possible evidence for its role in error detection

How do humans and non-human primates behave after making an error and what 2 things does this reflect

slower and more accurate, error detection and compensation

How did monkeys with ACC lesions behave after making an error

weren’t slower or more accurate

Gehring et al investigated error-related negativity – what is this?

an event-related potential component in EEG detected when an error is made

What occurs in the EEG signal when an error happened

large negative deflection

What brain area does this ERP component appear to originate in (supporting earlier debates)

ACC

ACC might then be active during error detection but which brain region is responsible for the change in behaviour (being more accurate) – we know the answer already

PFC

So there is agreement that the ACC is part of an error prevention network but what are the two competing theories for its role (different executive functions)

strategic control vs evaluation

What is the aim of strategic control processes

to reduce response conflict in top-down manner

What is the aim of evaluative processes

to detect response conflict

Wolpe et al using a single-case lesion study, comparing a 74-year old patient with a focal pre-SMA lesion to a 52 health age-matched controls – what task did they perform and what did it require

stop-signal task (part of go/no-go task) requiring participants to stop a potentially already-initiated action when a stop signal appears

Two reaction times were measured for this study – what were these two RT

stop-signal RT and go RT

Wolpe et al also used the Drift Diffusion Modelling, which estimates what 3 parameters

threshold, drift rate and non-decision time

What does threshold measure, and what does high vs low scores signal

how much evidence is needed before acting, high signals caution while low signals impulsive

What does drift rate measure

how quickly evidence accumulates towards a decision boundary

What does non-decision time measure (2 things)

stimulus encoding (time needed to perceive the stimulus) + motor output (time to execute the final motor response)

Did patient should low or high decision threshold in this study

abnormally low

What differences existed between drift rate and non-decision time, if any?

no differences

What can be interpreted from lower threshold (3 subsequent impacts on behaviour/actions)

faster action initiation (requiring less evidence) -> harder to inhibit actions -> causes more error/stopping failures

What conclusion can be drawn about the role of the pre-SMA’s function due to this patient’s behaviour (who has a pre-SMA lesion)

dynamic threshold modulation – mechanism for controlling voluntary action and contributing the MD system

What should the pre-SMA normally do to modulate the decision threshold

increase the decision threshold when stopping might be required

What is task-switching (set-shifting)

discarding a previous scheme and establishing a new one

What is perseveration and how does it relate to task-switching

failure to shift away from a previous response - a behavioural consequence of impaired task-switching

How does the Wisconsin Card Sorting Test (WCST) test task-switching

participants match cards to 1 of 4 cards varying in shape, number, and colour but the sorting rule changes without explicit instruction so participants have to infer the new rule from feedback

What is the “switch cost” in the WCST and what does it reflect

significant slowing of reaction time on switch trails relative to no-switch trials, reflecting the cognitive cost of discarding a previous schema and setting up a new one

Which brain region is the switch cost in the WCST related to – think about what the task requires (maybe problem solving)

left dorsolateral PFC

The Iowa Gambling Task also tests task-switching by giving participants an option of 4 decks of cards with different long-term returns. Decks A+B are initially rewarding but become costly while decks C+D become advantageous – what are participants required to do in this task

switch away from bad decks to good decks

Individuals with a lesion – in which brain area – failed to switch from bad decks to good decks across the task, compared to healthy controls (slightly different to WCST)

ventromedial PFC

What is odd about these individuals with ventromedial PFC lesions – behaviour in other tasks

show intact performance on other tests of executive function like Stroop and WCST

Executive function control processes can be divided into ‘hot’ and ‘cold’ – explain this distinction

‘hot’ refers to stimuli related to reward (food, money) while ‘cold’ refers to cognitive stimuli

Task-switching (WCST) and reversal learning (Iowa test) are related to which control processes

cold and hot, respectively

What double dissociation did Dias et al demonstrate in marmoset monkeys with hot and cold control processes – brain area impaired for which tasks

task-switching, reversal learning

What was Roca et al’s central question about frontal executive deficits

whether they are truly distinct impairments or explained by general fluid intelligence (g)

Were classic executive tests like WCST, Verbal Fluency, and Iowa Gambling Task explained by g or not

were fully explained by g, thus they don’t measure unique executive processes but general intelligence

Go/No-go task was one of many tasks that showed remaining deficits even after adjusting for g – what does this indicate about what they require

require specific executive abilities not reducible to g – an executive function distinct from fluid intelligence

Complete Roca et al’s findings

localisation, right anterior frontal

So fluid intelligence (g) can explain the performance on several classic executive tests – what idea does this challenge and propose instead

that all executive function tests measure distinct functions and instead many reflect general problem-solving ability

How does multi-tasking differ from task-switching

in task-switching, one goal is substituted for another whereas in multi-tasking, several goals are maintained simultaneously

What is prospective memory

the ability to realise an intention after a delay (related to multi-tasking because it requires maintaining future goals in mind while engaged in an ongoing task

Volle et al tested patients with right polar PFC lesions and other lesions (as well as healthy controls) at a prospective memory task – what two deficits did they find for right polar PFC lesions

time-based prospective memory tasks and using prospective memory for tasks

What two tasks were impaired when attempting to use prospective memory

estimating long time durations and/or the self-retrieval of one’s intention to act (both of which are important for multi-tasking)

We saw earlier that some executive tests which were not explained by g, were associated with right anterior frontal lesions – what does this new information contribute to this previous knowledge

that those unexplained tests required multi-tasking

Koechlin and Summerfield proposed a hierarchically ordered executive system – what is this system

poster to anterior gradient for simple to complex tasks

Complete the function of each brain area

episodic, pending, multi-tasking, episodic, switch, context, contextual, response, stimulus-response

What does a modular organisation of executive functions predict

that distinct, non-overlapping brain regions each support specific executive functions

What does a distributed organisation of executive functions predict

that executive functions emerge from flexible, overlapping networks (general intellectual ability)

What does lesion evidence vs neuroimaging evidence suggest about the modular vs distributed brain debate

supports specialisation vs supports flexibility and overlap

How might task complexity confound this debate

simple tasks may engage focal regions while complex tasks engage distributed networks

What is the overall conclusion of this lecture on executive functions

they are domain-general control processes with neural correlates in PFC (and multiple demand system?)

complete the overall conclusions for the different brain areas (executive function and hot/cold)

problem-solving, task-switching, cold, task-switching, reversal learning, hot, multi-tasking

What is the MD system proposed to be the neural basis for

fluid intelligence