Lecture 3A: Executive Functions

Define executive functions

Integrative (take information from all other parts of the brain) cognitive functions that determine goal-directed and purposeful behaviour (execF is not relevant during default mode activities/non-goal-directed tasks) and are supra ordinate (other info from the brain is combined in a coordinated way) in the orderly execution of daily life functions (execF is integral for occupational participation/performance)

Exec functions are top-down control processes that coordinate lower level processes in an intentional and effortful way

Can see it as a conductor that coordinates a coherent and desirable symphony

• the essence is self-regulation and goal-direction (PURPOSE OF EXEC F)

What are the three main components of executive function?

1. Working Memory

   1. Maintaining and manipulating information is an executive function

2. Cognitive Flexibility

   1. Changing perspectives

      1. ability to hold many different thoughts at once

      2. switching between tasks

   2. Adapting to change

      1. changing plans when something goes wrong

      2. solving problems in creative ways

   3. Deficits of cognitive flexibility

      1. Rigid thinking: unwilling/unable to consider other perspectives

      2. Inability to change plans/actions when something goes wrong

3. Inhibition

   1. Impulse control

      1. Suppressing behaviours that don’t help achieve the goal

         1. Deficits result in making inappropriate comments, risk taking, road rage, easily distractible, inability to filter out irrelevant information

      2. Resisting acting impulsively and resisting temptations

         1. controlling and inhibiting motor actions

   2. Interference control

      1. Filtering out distracting things, cognitive distractions, focusing, controlling all the interferences (more cognitive)

What are the three models in which we can understand executive functions?

1. Buffer

   1. Exec F acts as a buffer between stimulus and response

   2. Pausing, taking time and space to consider alternative courses of action

   3. Refer to the box turtle example

   4. Allow you to think so that you don’t do the most impulsive thing

2. Goal-management - theory of goal neglect

   1. Goals guide behaviours

      1. Goals are integral to exec f

      2. The goal is selected, then a set of actions necessary to achieve the goal is formulated and triggered. The plan is continued but checking back periodically to see if the plan is working

   2. Dysfunctional exec F do not look goal-oriented

      1. They can tell you their plans in detail, and may follow it to a point, but then they abandon their plans at some point (goal neglect)

      2. May not initiate a task because they can’t formulate a goal

      3. Can recognize they are making an error but they are unable to correct it

3. Novel vs Routine - supervisory attentional system

   1. Novel activities captivate our attention

   2. There is an executive functioning distinction between novel and routine tasks

      1. Not much exec F is necessary for routine tasks because we don’t have to pay attention, but it is REQUIRED for novel situations (unexpected or new)

      2. We have to think about what behaviours have to be used here to achieve the goal

How much of the cortical area of the brain is occupied by the frontal lobe? Where to they end?

Almost 1/3

End at the central sulcus (it is everything anterior to the central sulcus

What are the three main areas of the frontal lobe? What aspects of executive functioning area associated with each area?

1. Dorsolateral - “cold” executive functions involved in GOAL-DIRECTION

   1. upper and side parts

   2. Responsible for planning, abstract reasoning, and cognitive flexibility

   3. Deficits: cognitive rigidity, concrete thinking, poor planning, goal-neglect

      1. difficulty making decisions, inability to stay oriented on goal,

   4. Damage is often caused by TBI

2. Dorsomedial - inhibition

   1. includes the anterior cingulate and the supplementary motor area

   2. Damage to this area results in problems with starting and stopping (poor initiation and response inhibition)

3. Orbitofrontal

   1. The part that sits on top of the skull

   2. Dr. Zorro example - carved initials into the patient’s stomach after surgery

      1. later diagnosed with dementia (frontaltemporal dementia) characterized by early degeneration of the orbitofrontal aspects

      2. This area is associated with personality behaviour

      3. Deficits: out of character behaviour, irritable, inappropriate, risky things, lack of insight, coarse, vulgar, enraged, lie about themselves, environmental dependency

How does the case study of CW help us understand the interconnected nature of the frontal lobe and the rest of the brain

Had a lesion in the cerebellum

• had motor issues, dysarthria, other symptoms characteristic of cerebellar lesion

But he also exhibited hallmark symptoms of frontal lobe dysfunction

• problems understanding what others mean

• acts without thinking

• difficulty planning ahead

• Easily distracted

Takeaway: Injury to any part of the brain will likely result in some sort of deficit to executive functioning in some way

• can range from mild to moderate, depending on what systems are involved

What disorders result in damage to the frontal lobe?

Lots:

• Stroke

• Alzheimers

• MS

• Depression

• Parkinson’s

• ALS

• Aging

• TBI

• Schizophrenia!!!

• PTSD

  • May recover emotionally and have coping mechanism developed from therapy but cognitive issues may remain

  • May impede the ability to use strategies learned in CBT because exec F is dysfunctioning - can’t find the things you learned in the moment, can’t organize it

Anything that involves the frontal lobes… everything involved the frontal lobes…

What are some challenges to assessing executive functions of the frontal lobe accurately?

Challenges:

• Other factors can be impacting exec F (lack of sleep, pain, stress)

• Tests have to be complex enough to uncover a deficit (must be novel)

• Examiners often act as the frontal lobes of the subject

  • In a testing situation, the patient is being guided, being controlled

  • The best way to examine exec F is out in the community

  • Environment shouldn’t be too controlled

• Variability in performance = hallmark of frontal lobe damage

  • performance isn’t going to be the same day to day

How can we assess working memory?

Assess the ability to retain information (to concentrate) and manage multiple tasks at once

Digit span/Alpha span

• Give them a set of digits or letters and ask them to say it back to you both forward and backward

How can you assess for cognitive flexibility/control of action?

Assess the ability to flexibly alter behaviour based on changing contingencies

Wisconsin card sorting test

• Assess how well they are able to adapt and problem solve on the fly as the criteria changes without you informing them

• Set up card on table and ask them to sort them based on where they think they fit

According to colour, shape, or number

Examiner holds the rule as to what the category is and doesn't tell the patient

• Observe whether the individual can adapt based on the criteria the examiner has selected

• Criteria changes after every 10 correct (also doesn't tell the patient)

 

• refer to slide for details

How can we assess for inhibition?

Assess ability to withhold habitual responses or responses to highly salient environmental stimuli

Stroop Colour-Word Interference Task

• First: name the colour as quickly as possible (colour only)

• Second: name the colour as quickly as possible (colour AND word)

• Can they inhibit prepotent responses?

  • dysexecutive = very slow

What is the multiple errands task?

a series of 8 tasks to be done in a shopping area (eg. Mall)

• 6 simple tasks

• 7th is a command to be at a certain place in the mall 15 mins after starting

• 8th is the task of writing 4 pieces of information on a postcard

• Other general rules involved as well (eg. do not enter a store more than once)

This is a functional, real-world assessment that looks at goal-directed behaviour

What are some rehab implications regarding executive function assessment?

Exec F is difficult to assess/measure in a laboratory/clinic

• real-world assessment is best

Deficits in exec F may impact other rehab interventions not related to the exec F dysfunction

The intervention options available vary widely based on the nature of the deficit

General unawareness and unconcern are to be expected

Deficits are most apparent in NOVEL SITUATIONS

• if we assess in the clinic, how can we generalize it?

What is the development of executive function in children?

It is VERY difficult (if not impossible) to measure executive function in children

But we also know that executive functioning is highly correlated and predictive of school performance, social functioning, and physical/mental health

Inhibition begins developing at 6 months, and working memory at 3 years

from 7-9 years old onward, cognitive flexibility begins developing

What is the last region of the brain to fully mature?

The prefrontal cortex (at 24+ years old)

• increased myelination and white matter tract development until full maturity

• In teenage years, risk-taking is commonly seen, and can often be attributable to maturing frontal lobes

what is the purpose of executive function?

Self-regulation and goal-direction