Executive Functions

What was untrue about the Gage story?

• Gage did not mistreat his wife or children; in fact, he had a family and maintained relationships.

• He worked successfully for many years as a coach driver in Chile, showing he still had social skills and reliability.

• Many claims about his personality becoming completely irresponsible or erratic are exaggerated or unverified

What is the silent lobes?

• Assumed that frontal lobes could be disconnected from the rest of the brain with little consequence

• Gage could walk and talk just fine

What was psychosurgery for?

• Treating psychiatric patients 

• Not to cure the patient of their illness but to make the patient behaviour more controllable

Why did Freeman push for lobotomies?

• Disconnect the CEO and make the patient more controllable - return them to a surgically induced childhood

What were the consequences of lobotomies?

• Struggled with complex behaviours, the executive functions

How is the anatomy of the frontal cortex functionally distinguished?

• Primary motor

• Premotor

• Prefrontal regions

What are the subregions of the prefrontal cortex

• Dorsolateral region

• Rostral or fronto-polar

• Ventrolateral 

The frontal cortex develops…

• Last in the brain and is large compared to other mammals

How much larger is the human prefrontal cortex (PFC) compared to great apes?

• 3.5 times larger

How large is the human PFC compared to the rest of the human cortex?

• 29%

• Making it large relative to other cortical areas

What are cortical convolutions?

• Folds and grooves in the brains outer layer (cortex) that increase its surface area

How does the frontal cortex connect with other brain regions?

• Connected with temporal and parietal regions that process multimodal inputs, which is critical for integrating information

Why are these connections in the FC important for goal-directed behavior?

• Allow the frontal cortex to maintain goal-directed behavior through multimodal integration.

What structures enable rapid communication across the brain?

• Long-range white matter tracts, including the inferior frontal occipital fasciculus, which supports semantic language processing and goal-oriented behavior

What is needed to be aware of what is being processed in a region of the brain?

• In order to be aware, a direct one to one connections must be made between it and the frontal lobes via white matter tracts

Why might we not be conscious of what is being processed in visual area V1?

• Frontal cortex lacks direction connections to V1, we cannot be consciously aware of the info processed there

What are executive functions?

• Abstract reasoning

• Decision making

• Impulse control

• Planning ahead

• Multitasking

• Cognitive flexibility

• Error correction

• Etc

What are the four domains of executive functions

1. Inhibitory control: suppress impulses

2. Set shifting: task switching/mental flexibility 

3. Working memory updating: capacity to hold and manipulate info in mind while adding new info (Remembering a phone number while also keeping track of a new address you just heard)

4. Planning: ability to think ahead and organize steps to achieve goal

What is unity and diverse model of executive functions?

• Breaking down these higher order functions into diverse categories that also connect with one another

Is standard intelligence affected by frontal damage?

• No

Is intelligence correlated with executive function?

• No

• (convergent vs divergent thinking)

What is convergent thinking?

• Asking “what is the capital of Australia?”

• One right answer - you either know it or dont know it, you converge on one answer

• IQ tests often asks these questions

What is the main focus of executive functioning?

• Less about arriving at an answer and more about flexibility and the capacity to come up with novel solutions, even if and especially when you don’t know, or there isn’t one single answer

What is divergent thinking?

• Generate many different ideas or solutions from a starting point, often in creative or unconventional ways

What is the stroop task?

• Measure how well one can inhibit their prepotent responses (automatic response)

• Participants are asked to not read the word that is written (prepotent response) but instead to say what the colour actually is

What is Lucri’s tests on inhibition?

• “If I tap once, you tap twice”

• The patient must suppress the automatic response to mimic the examiner and instead follow the opposite rule

• Frontal lobe damage struggles to stop themselves from automatically copying actions

What is Lucria test on motor sequences?

• “Fist, edge, palm” test

• Patient must maintain and execute a specific sequence of movements

• With more repetitions, the sequence becomes difficult to hold for frontal patients, and they show difficulty maintaining the order over time

What errors do frontal lobe patients show in verbal fluency tests?

• Inertia: being slow to get started and slow to continue (related to marked reduction in spontaneous speech)

• Perseveration: getting stuck on a word and repeating it

• Rule breaking: writing proper nouns or plurals even instructed not to

• Poor strategy use: fail to cluster words that share meaning, or phonemically, etc

What is a way to measure set-shifting or mental flexibility?

• Wisconsin Card Sorting task

What is the Wisconsin Card Sorting task?

• Patient’s task is to sort a deck of cards into 4 piles

• However the patient is not told how to sort them - only info they get is feedback on whether the card they place has been sorted correctly or not

What happens after when the patient successfully sorts the cards?

• Experimenter switches the sorting rule but does not tell the patient

• Continue to tell them whether its right or wrong

• Patient has to figure out the new rule

• Common for patients to give up - indicative of that inability to self regulate behaviour and emotional responses appropriately 

What does the Wisconsin Card Sorting measure?

• Set-shifting: capacity to shift mental sets by counting the number of categories the patient successfully sorts and what kinds of errors they make

• Perseveration: if they sorted by colour, they may continue to do so after the rule changes even though they are now told it’s wrong

• The dissociation between knowing and doing (example - frontal patients will know certain behaviours are socially inappropriate but they are unable to inhibit these behaviours

What is the interesting aspect of persecution in the Wisconsin Card Sorting task?

• Interestingly though, patients are often able to communicate what the sorting categories are, they can tell you that the cards are supposed to be sorted by number, colour, and shape, but they can’t put that knowledge into action

What is the Tower of London task?

• Given a starting position of these coloured balls on pegs, a goal position, and the number of moves you are allotted to get there

• Frontal patients find it difficult to plan, and will exhibit that trademark impulsivity, often moving the first ball very quickly without actually putting much forethought into how to complete the task

• Perseverative errors 

What is the Rey-Osterrieth Figure Copy test

• Again, measures planning abilities and organizational steps

• Where would you start for something like this? A good strategy is to start with the “bones” of it – the rectangle, the triangle, the lines that sort of act as axes – this makes it easier to place the smaller details and ensure that enough space is left for everything.

One is traumatic brain injury?

• Consequence of frontal lobe damage

• Result of acceleration-deceleration injuries such as crashes, falls, fights, or sports impact injuries

What are the 2 main mechanisms of traumatic brain injury?

• Impact itself: The brain area hit first is the coup, and the opposite side hit by the brain’s movement is the countercoup, these areas are more prone to damage (brain shifts)

• Brain shift by velocity of impact: cause axons to tear - diffuse axonal shearing, happen all over the brain

Which area of the brain is more prone to damage?

• Orbitofrontal cortex

• Due to their proximity to bony protrusions inside the skull

What is impulsivity and disinhibition include?

• Little forethought

• Inappropriate social behaviour

• Short fuse

• Hyper - hypo sexual arousal

• Increased reckless behaviour

• Increased drug use

What is Chronic Traumatic Encephalopathy? (CTE)

• Enough repeated exposure to traumatic brain injuries

• Tissue loss that results from enlarged ventricle space and sulcal widening

• Poor ability to sustain attention, impulsive and aggressive behaviour, increased risk of depression and suicidal ideation

What is Utilization Behaviour?

• Related to the typical patterns of frontal damage

• Patients feel compelled to use objects placed in front of them for their designed purpose in inappropriate situations 

  • A patient sees a toothbrush on a table and immediately starts brushing their teeth, even if it’s in the middle of a meeting

Why was the technique in the Utilization Behaviour strange?

• Would sit in front of the patient, put objects on the table and say nothing

• Reasonable that the patient may have just assumed they were meant to do something with the objects and just did it. Maybe they were just guessing at what they were supposed to do

What patient behaviors couldn’t be easily explained by expectation alone in the Utilization Behaviour?

• put glasses on his face even though he already had glasses on

• insisted as they passed by the hospital chapel that they needed to stop and pray.

• Some of the behaviours were imitative as well – if L’Hermitte did it, then the patients would feel compelled to do the same

What are examples of meaningful interactions with objects in the Utilization Behaviour task?

• A pack of cigarettes was placed on the table; a smoker with UB lit one, while a non-smoker offered the pack to L’Hermitte

• A former nurse patient followed L’Hermitte around the hospital and insisted on giving him a shot when passing a table of saline-filled needles

Why do patients feel a compulsive need to use objects or imitate behaviors?

• Related to mirror neurons

How do mirror neurons contribute to learning through imitation?

• Such as a baby sticking out their tongue when an adult does, suggesting that mirror neurons help us learn motor behaviors

How do mirror neurons contribute to learning through motor learning?

• Trying to acquire a high level motor skill, like dance or martial arts, useful to watch others first

• When dancers watched videos of their trained dance style, their dorsal premotor brain activity was highest. This doesn’t mean they were learning, but it suggests they were mentally mimicking the movements, like a mental rehearsal.

How do mirror neurons contribute to learning through theory of mind?

• Social contexts

• TOM refers to our understanding that others have mental states, such as intentions, knowledge and beliefs

• Ability to infer the thoughts and feelings of others

Which region of the brain shows theory of mind?

• Temporo-parietal cortex and the inferior frontal cortex

• Show mirror neuron like properties

What is working memory?

• Ability to hold info in the mind over short periods of time

• Executive function aspect is the ability to manipulate and update this store with new info as it becomes available to achieve goals

• Goal driven