11. Executive Brain

What are executive functions?

control processes that enable an individual to optimise performance, requiring coordination of basic cognitive processes, not tied to a specific cognitive domain (such as memory, language, perception)

What are examples of executive functions?

problem solving, overcoming habitual responses, task-switching, multi-tasking

Where are executive functions linked to?

the prefrontal cortex

What brain area is problem solving linked to?

dorsolateral PFC, ventrolateral PFC

What area is overcoming habitual responses linked to?

anterior cingulate cortex

What brain area is multi-tasking linked to?

Polar PFC

What brain area is task-switching linked to?

orbitofrontal/ ventromedial PFC

What are the principles of problem solving?

giving a participant an endpoint (goal) and a starting point; participants must generate a solution of their own

What is task-setting?

generating a soloution

What is the test for problem solving?

tower tests e.g tower of london (more moves, higher complexity)

Describe the methods of the neural correlates study for problem solving (Ruocco et al., 2014)?

38 healthy participants, trait deliberation: the tendency to think carefully before acting, used fNIRS, scarborough adaptation of ToL - "Can you solve this in exactly 2 moves?"

Describe the findings of the neural correlates study for problem solving (Ruocco et al., 2014)?

Found increased left dorsolateral PFC activation when solving problems - even higher in individuals with high trait deliberation.

What is a habitual response?

a response that we engage in automatically

What is overcoming habitual responses related to the concepts of?

response inhibition & impulsivity

What is response inhibition?

reducing the likelihood or a particular thought or action

What is impulsivity?

a behavioural tendency to make immediate responses or seek immediate rewards

What are the tests for overcoming habitual responses?

stroop test or Go/No-Go test

What is the suggested explanation for stroop tests?

reading the word is habitual so generates an incorrect response which must be inhibited, incorrect response competes with the less habitual task of naming the ink colour - possibly take longer to answer & make errors

Describe the study on stroop tests (Alexander et al., 2007)?

38 healthy controls and 42 patients with frontal lesions, stoop task and fMRI for lesion location and reaction times. found slow reaction time and decreased correct responses with lesions in: ACC, presupplementary motor areas and dorsolateral areas

Neural correlated for pre-SMA?

motor responses

What happens when we make an error?

human and non human primates are slower and more accurate after making an error - error detection + compensation

What is the evidence for the role of the anterior cingulate cortex (ACC) in error detection?

ACC lesions in monkeys > error + 1 is not slower or more accurate, EEG evidence of a response in the ACC to errors

What is error-related negativity?

an event-related potential component in EEG detected when an error is made (Gehring et al., 1993)

What is the neural correlates for detecting errors?

after an error, relatively large negative deflection in EEG signal 'appears to have its origins in ACC', brain areas responsible for change in behaviour - lateral PFC

What are some of the proposed theories for the role of the ACC?

strategic control processes to reduce response conflict in top down manner? evaluative processes just to detect response conflict (different neural correlates for control)?

Describe the methods for the study on whether ACC has a strategic or evaluative role (Carter et al., 2000)?

fMRI of 12 healthy controls, modified stroop test, hypotheses for ACC activity - H1: strategic control (high response conflict and strategic control > low strategic control and high response conflict) H2: evaluative response conflict (low strategic control and high response conflict > low and low, low strategic control and high response > high strategic control & response)

Describe the findings for the study on whether ACC has a strategic or evaluative role (Carter et al., 2000)?

found that ACC activity modulated by response conflict even when strategic control processes are low, ACC activity greater for highest response conflict not for highest strategic control, evaluation of response conflict not control processes

What are the subregions of the anterior cingulate cortex & what are they implicated in?

dorsal region - executive functioning, ventral region - emotional processing

What did Rushworth et al. (2007) argue about the function of 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

What does overcoming habitual responses require?

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 - also known as 'set-shifting', related to the concept of perseveration: failure to shift away from a previous response

What are the tests for task-switching?

Wisconsin Card Sorting Test (WCST), Iowa Gambling Task

What is a schema?

a structured body of prior knowledge that captures common patterns across related experiences

What is the Wisconsin card sorting test?

task is to match cards to 1 of 4 reference cards whose symbols vary in: shape, number, colour. but subjects not specifically told these variations

What do reaction times in Wisconsin card sorting test tell us?

minimal change in RT between no-switch and no-switch trials, big difference in RTs between no switch and switch trials (the switch cost) - related to activity/integrity of left dorsolateral PFC

What is the switch cost?

a slowing of response time due to discarding a previous schema and setting up a new one

Describe the study by Meuter & Allport (1999) on the switch cost?

16 bilinguals, numeral naming, measured response latency when switching from first to second language or second to first. found all ppts showed slower language naming in second language overall (harder task), bilinguals slower at switching from second language (hard) to first (easy), the switch cost is greater when discarding a complex schema to set up a simple one (related to left dorsolateral PFC)

What is the Iowa Gambling task?

subjects given a loan and each round chose a card from 1 of 4 decks, receive either gain or loss - decks have different returns over the entire task: A&B start good become bas and C&D start okay become good

Describe the neural correlates study on Iowa Gambling task?

ppts with ventromedial PFC lesions, measured net choice of advantageous decks. health controls switch from bad to good decks, those with lesions fail to switch from bad to good, show intact performance on other tests of executive function

What can executive function control processes be divided into?

hot - stimuli related to reward (food, money) , cold - purely cognitive stimuli (sensory dimensions)

What is reversal learning?

learning that a previously rewarded stimulus or response is no longer rewarded - by default: 'hot' control process

Describe the method of the study on marmoset monkeys for hot and cold control processes neural correlates (Dias et al., 1996)

respond by matching cards to examples (adapted Wisconsin card sorting), reward their responding to a certain item in one dimension, regardless of the other dimension, lesions in either: orbitofrontal/ventromedial prefrontal cortex, lateral prefrontal cortex. post lesion training wither reversal learning (see same stimuli, only rewarded for different shape, must reverse learning that circle is rewarded) and dimension set shift (see all new shapes and lines, now only rewarded for certain line, must learn new rule)

Describe the findings of the study on marmoset monkeys for hot and cold control processes neural correlates (Dias et al., 1996)

a double dissociation: suggests dissociable neural correlates for control of responses to reward-related (hot) bs purely cognitive (cold) stimuli. Hot stimuli - orbitofrontal/ventromedial cortex - connections with posterior affective areas, cold stimuli - lateral frontal cortex - connections with posterior sensory/motor areas

Describe the study on Iowa Gambling Task & Reversal learning?

ppts with ventromedial PFC lesions, perform fine on other tests of executive function but fail to switch from bad to good decks - could be failure of reversal learning - early in game decks a and b rewarded but late C & D rewarded: when early game gains are equivalent to bad and good decks, patients with ventromedial PFC perform as controls.

What is multi-tasking?

carrying out several tasks in succession; requires both task-switching and maintaining future goals while current goals are being dealt with

Describe the patient evidence study on multi-tasking by Volle et al., (2011)

45 ppts with lesions, fMRI prospective memory & voxel-based lesion-symptom mapping. found lesions in right polar prefrontal region: deficit in time based prospective memory tasks, deficit in using prospective memory for estimating long time durations and/or in the self-retrieval of one's intention to act (important for multi-tasking)

What is prospective memory?

the processes that allow for the realisation of an intention after a delay

What did the multi-tasking neural correlates study find on polar PFC?

maintaining current episodic control and a pending context

What did the multi-tasking neural correlates study find on anterior lateral PFC?

using episodic control to switch to a different context

What did the multi-tasking neural correlates study find on posterior lateral PFC?

· Learned contextual information (rule set) guides response

What did the multi-tasking neural correlates study find on premotor cortex?

Simple stimulus-response mappings