Topic 10 - Executive Function

Executive Function Def

Conductor for other brain regions; Supervisory, controlling, or meta cog rather than domain specific (memory, perception, lang, attention, etc)

Required for controlled v auto behav + important in multitask and switching tasks 

What is Exec Funct req for? 

Controlled v auto behav + multitasking/task switching 

Where is executive functioning in brain?

Prefrontal Cortex

What animal has the most detailed frontal lobe?

Humans

Divisions of PFC (detailed)

1. VLPFC

2. DLPFC

3. Anterior PFC/Frontal Pole/Rostral PFC

4. Anterior Cingulate Cortex

5. Orbitofrontal Cortex

Ventro-lateral PFC (VLPFC) Left Hemi

Retrieval + maintained of semantic/linguistic info

Divisions of PFC (detailed)

Ventro-lateral PFC (VLPFC) Right Hemi

Retrieval + maintainace of visual/spatial info

Divisions of PFC (detailed)

Dorso-lateral PFC (DLPFC) Left Hemi

Selecting a possible range of responses + suppressing inapprop ones; Manipulating the contents of WM 

Divisions of PFC (detailed)

Dorso-lateral PFC (DLPFC) Right Hemi

Monitoring + checking of info held in mind, particularly in uncertainty (info organization); Vigilance + sustained attention 

Divisions of PFC (detailed)

Anterior PFC, Frontal Pole, Rostral PFC

Multitasking; Maintaining future goals while currently performing other tasks or subgoals

Divisions of PFC (detailed)

Anterior Cingulate

Monitoring in situations of response conflict + error detection; Detection of errors + response conflict (potential errors)

Activity greatest on an error trial

Divisions of PFC (detailed)

Orbio-frontal Cortex

Executive processing of emotional stim (eg. evaling risks + rewards); Behav resp mediated by the emotional component 

Divisions of PFC (detailed)

Medial or Cingulate PFC

Motivation conduct

Divisions of PFC (detailed)

Petrides’ Theory of Working Memory

Says there are 2 distinct WM processes in the PFC

1. VLPFC (lower) → Maintainance of info

2. DLPFC (higher) → Manipulation of info

VLPFC in Petrides’ Theory of Working Memory

Lower; Maintenance of info 

DLPFC in Petrides’ Theory of Working Memory

Higher; Manipulation of info

Self Ordered Pointing Task

Need to point at a pic then point at a dif pic; Requires maintenance + manipulation of info

PFC Damage + Self Ordered Pointing Task 

Impairs performance on self ordered pointing task 

Domains where Exec Funct are Important

• Task setting + prob solving

• Overcoming potent or habitual responses

• Task switching

• Multtasking

Tower of Hanoi Task 

Need to place rings in largest to smallest order at the very end in the least amount of moves possible; Prob solving for exec funct

PFC Damage + Tower of Hanoi Task

Results in poor performance

Does Tower of Hanoi activate PFC?

Yes, in healthy controls

Stroop Test 

Name the ink color not the word written; Requires inhibition 

Incongruent trials harder than congruent trials 

What does Stroop Test activate in brain?

Anterior Cingulate + pre SMA

Stop Signal Task Def

Speeded RT with rare “no go” cases; Requires inhibition

Stop Signal Task Part of Brain 

Pre SMA (right lateral PFC if the task is hard)

What does PFC Damage do to inhibition + impulsivity?

Does NOT impair movement of execution of actions but DOES make actions disorganized/inapprop for current goals

Leads to failure to inhibit potent/habitual responses, so actions are driven by habits and/or objects in the environment rather than controlled goal driven behav (impulsivity); Preservation + utilization behav

Preservation

Repeating an action that has already been performed + is no longer relevant

PFC Damage

Utilization Behav 

Impulsive actions on irrelevant objects in environ 

PFC Damage

Wisconsin Card Sorting Test (WCST) Def

You place a card + get feedback (right/wrong), and you infer a rule from the feedback; Sometimes the rule randomly switches, so must recog that the rule changes + infer new rule 

Used to assess cog reasoning + exec funct/PFC damage; Tests task switching for exec funct

Wisconsin Card Sorting Test (WCST) Types of Errors 

1. Perseveration Errors 

2. Non-Preservation Errors

Perseveration Errors

Continuing to use an old rule even after feedback that card placement was wrong; Reflects how quickly ppl can switch tasks/adapt to changing rules

Wisconsin Card Sorting Test (WCST) Types of Errors 

Non-Perseveration Errors

Other errors; Reflects how quickly ppl learn rules, random errors + luck

Wisconsin Card Sorting Test (WCST) Types of Errors 

What does WCST conflate?

1. Rule inference

2. Unpredictable switches

What does task switching reflect the cost of?

Inhibition of the old task

Is there a greater switching cost from a hard to easy task or easy to hard task? 

Greater cost for hard to easy task

Ex. 2nd lang to first lang 

Task Switching Brain Areas

Lateral + medial PFC

What part of the brain does switching responses (like left/right button) activate?

Medial PFC (pre SMA)

What part of the brain does switching attended stim (shape/color) activate? 

Lateral PFC

6 Element Task

Have to do 6 open ended tasks (math, writing, names of pics, etc) in 15 min; There is not enough time to do all of the tasks but told to try all of them + there are restrictions on the order of tasks

Requires multitasking

6 Element Task + PFC Damage

Do very poorly

• Some do okay on individual tasks

• Some switch too often

• Some spend too much time planning + taking notes

Is the PFC needed for actions that cannot be done on autopilot? 

Yes

Ex. Actions that are involved in the interruption of ongoing behav or setting up novel actions/cog procedures 

PFC’s Supervisory Attentional System (SAS)

Overrides automatic or environmental driven behav; Objects have action schemas (like a hammer/nail), and tasks/scripts are a hierarchal collection of obj schemas

SAS selects which schemas/scripts to use based on top down (goals) + bottom up (sensory info)

Top Down Info

Goals

PFC’s Supervisory Attentional System (SAS)

Bottom Up Info

Sensory info

PFC’s Supervisory Attentional System (SAS)

What do PFC lesions do to SAS?

Weaken SAS, which causes

• Preservation

• Difficulty setting up new schemas

• Utilization behav (making sensory info win)

Issues with SAS Model 

• Some PFC patients with grossly disorganized real world behav pass standard tests

• Some patients pass some tests, but not others (eg. multitasking impaired but not stroop)

• Maybe tasks arent perfect

Lateral PFC

Cognitive, “cold” tasks; Monitoring, error correction

Orbito Frontal PFC

Emotional, “hot” tasks

Lateral PFC Left Side

“Task setting”, open ended tasks, switching rules

Lateral PFC Right Side 

“Task monitoring”, sustained attention, keeping on task 

Posterior PFC

Simple stim → Response mapping

Ex. Red stim → left button press

Anterior PFC

Complex mappings, multitasking’ Active when holding a goal in mind while performing a subgoal

Ex. red stim → left button press, but only if stim is also a vowel

WCST Like Task 

Train ppl that certain shapes are rewarded + then reverse which shape is rewarded; Basically shift what dimension to attend to 

Req reversal learning + set shifting 

WCST Like Task for Orbito Frontal PFC Lesion

Poor reversal learning (emotional)

WCST Like Task for Lateral PFC Lesion

Poor set shifting (cognitive)

3 Main Divisions within PFC (Broad)

1. Lateral PFC (cognitive)

2. Medial PFC (social)

3. Orbital PFC (emotional)

Main Site of Exec Function 

Frontal Lobes 

Lateral Division of PFC

~Cognitive

3 Main Divisions within PFC (Broad)

Medial Division of PFC

~Social

3 Main Divisions within PFC (Broad)

Orbital Division of PFC

~Emotional

3 Main Divisions within PFC (Broad)

Somatic Marker Hypothesis

Emotional events (like a risky situation) store somatic markers in memory, which are stored in the orbiofrontal + ventromedial frontal cortex

Retrieving that emotional event reinstates the somatic marker + guides any behav (making a response more or less likely)

Could be conscious or unconscious

Where are somatic markers stored according to Somatic Marker Hypothesis?

Orbitofrontal + ventromedial frontal cortex

Iowa Gambling Task 

Can choose from a good or bad deck; The bad deck has big rewards and big penalties, resulting in net loss but the good deck has small wins and small penalties resulting in net gain 

Orbito-frontal Damage + Iowa Gambling Task 

Do not learn to avoid the bad deck, unlike normal controls + do not develop anticipatory skin conductance response, only have them AFTER loss

What tasks are orbio-frontal damage patients impaired on?

Impaired on gambling/Iowa Gambling Task, but not WM, stroop, WCST

What tasks are lateral PFC damage patients impaired on?

Impaired on WCST + stroop but not on gambling/iowa gambling task

Criticisms of Somatic Marker Hypothesis/Gambling Task 

• Players may be making a conscious decision rather than an unconscious decision based on the skin conductance resp 

• Deficits may be due to reversal learning (bad decks initially receive large reward on first trial; and same frontal patients generally unimpaired if first trial omitted) 

Multiple Demand Network Def

Tests of exec funct + fluid intelligence use the same brain regions (aka multiple demand network); Regions that are active whenever you do a task that is NOT automatic

Multiple Demand Network Areas

• Lateral PFC

• Parietal Lobe

• Anterior Cingulate

PFC Damage + Multiple Demand Network

Impairs performance on exec funct and fluid intelligence (stroop, planning, wm, task switching) BUT NOT on crystallized intelligence (like vocab, general knowledge, facts)

Left Lateral PFC Damage Patients 

Generally helps set up tasks/rules

So have trouble on task setting (esp tower of hanoi + open ended WCST) + task switching (take longer to switch rules than controls but faster than right PFC damage)

Right Lateral PFC Damage Patients 

Generally helps with monitoring tasks/staying on rules

So have trouble with task monitoring/keeping on task + task switching (worse than left PFC patients bc likely to use old rule) + worse than left PFC at predictable WCST

Likely to make more random errors + revert to old rule in WCST than left PFC

Worse than left on predictable WCST (told the rule + when switches occur) 

TMS of Left Dorsolateral PFC (LDLPFC)

Disrupts random digit generation

3 Roles of Right PFC

1. Monitoring (relating current info to task + checking whether info is valid)

2. Sustained Attention

3. Inhibiting Responses (eg. no go task) but could be failure to monitor

So active generally for externally presented info (perception tasks) + internally generated info (memory task)

When is Right PFC most active?

In conditions of uncertainty (like tip of the tongue, low confidence)

How is PFC ordered?

Hierarchally ordered

Damage to Anterior PFC

Impairs multitasking but not other exec funct tasks

When is Anterior Cingulate most active?

On error trial

Anterior Cingulate + Error Potential/Error Related Neg

An ERP wave that occurs after making an error; Prob originates from anterior cing 

Is the PFC the only single source of exec function?

No