Executive functions Flashcards
Executive Function
Complex processes by which an individual optimizes his/her performance in a situation that requires the operation of a number of cognitive processes. [In short it is about controlling your behavior to reach your goals]
What is wrong about Phineas Gage?
He had a Prefrontal Cortex damage. After this damage his personality changed , he became more impulsive and he started experiencing problems in following plans. ( Cognitive Neuroscience Folklore)
Stability and Plasticity Dilemma
To reach your goals there has to be a balance between stability and plasticity. For stability; you have to stick your plans so that you can pursue them without distraction. However, you need certain amount of plasticity in case of any changes in the situation. PFC helps you to reach this balance !
Homunculus Problem in Executive Functioning
Who controls and monitors your behaviors? Is there a little man inside of your brain? No, there is no little man thinking inside (This is the homunculus problem) rather control may be the outcome of multiple competing biases (top down and bottom up).
Prefrontal Lobotomy (Yey or Nay)
Moniz (a doctor I think) was really into the prefrontal lobotomy (severing connections between PFC and limbic system) and it was executed more than 80.000 cases of schizophrenia and depression. Although they argued that patients became happy (?) after the lobotomy, they also became duller and apathetic. - And probably they got worse in tasks require planning and set shifting.
Wisconsin Card Sorting Task
This task can be used as a measure of executive functioning. Basically, there are different rules to sort the cards (color, number, shape) and the participant should figure out which rule he/she needs to adhere. During the experiment, experimenter changes the rules of the sorting randomly and rather than explicitly saying the new rule, just say “wrong” when participant tries to sort cards by using previous rules. The goal of the participant is learning the new rule and changing his/her behavior according to it.
Task Set and Set Shifting
Task Set : The way that you can solve a problem or the way that you can reach your goal.
Set Shifting : When the rules of the game is changed or the situation changes, you may need a new task set to reach your goal. Suppressing the old task set and shifting to a new one is called “set shifting”.
Perseveration
While healthy humans (people without PFC lesions) can change their task sets when the rules of the game are changed (like in the Wisconsin Card Sorting Game), people with PFC lesion stick to their old task sets. Although their behavior does not solve the problem anymore, they just keep doing it which is called “perseveration”.
Tower of London Task
It is a task that measures executive functioning (Especially “planning”). In the task there is a “start position” and a “target position”. Participant’s goal is that reaching the target position ASAP (with less trial-error). Participant should plan his/her behavior to do this with minimum number of moves. [It is difficult since some of your movements should go against to your goal first to reach your goal in the end]. People with PFC lesion do this with a lot of moves which shows that they can’t plan beforehand but try to reach their goals by relaying on trial-error.
Executive Control Models
(PS: Look at the page 8 in the slides).
Executive control model shows how the perceptual information used to reach your goals. “Trigger data base” part decides what to do in each condition. After that part, information goes to “Scheme Control Units”. In here there is a competition (which one is going to be used) between Contention Scheduling (Which is used for routine operations) and “Supervisory Attentional System” (which is necessary to decide what to do in a novel, non-routine situation). At the end information reaches “Effector System” (purpose processing unit involve in schema operation in both action and thought).
Bias Signals from PFC
PFC is not an essential part in stimulus-response pathways. (without PFC you can still perform). BUT, without PFC, your stimulus-response chains will be hard-wired, without no flexibility. Therefore, PFC controls the way how a certain stimulus creates a certain response. (so it biased the action due to the certain stimuli and it has a “modulatory function”)
Stroop Test and PFC Relationship
During the Stroop test, both name of the word and the color of the word are activated. You need to suppress one of them to reach your goal. (If you need to say the color of the word, you should suppress the urge to say the name of it- which is difficult since we are over-trained to read things-Top down bias-). For the goal setting part, PFC is crucial.
Switch Cost and Inhibition
During Stroop test or other tests like this, if you switch between two tasks (like saying the name of the word to saying the color of the word) there will be a slowing of response time due to discarding the previous schema and setting up the new one. This is called switch cost. Switch cost is caused by “inhibiting the old task” rather than setting up the new one. So if the previous task is easy (like saying the names of the word in Stroop task) people are faster in switching.
Inhibition = Reduced spiking rate at the synaptic level and more negative post synaptic membrane potential.
Action Plans in Primate Lateral PFC (is action plan coded due to the stimuli characteristics or planned behavior)
When cell spikes are measured, researchers found that BOTH stimuli and the response are important. There is a coding of cue-response relation in cell. Cells act differently due to different stimulus and different behavior. [Difference not caused solely by the stimulus or response, It is affected by the combination of both]
Action Plans in Human Lateral PFC
fMRI studies show that both “Parietal Cortex” and PFC are important in action plans of humans. Two of them have a role in establishing the map between the stimulus and behavior.
Free Will and Libet Experiment
The famous experiment is about measuring the time differences between “readiness potential”, “my decision to move” and the actual movement. Participants are free to move their hands whenever they want. Before doing any movement, our muscles get ready to move (this is readiness potential) and this potential is measured by EEG during the experiment. The key point of the experiment is that, participants should say when they decided to move their hands (they used a chamber full of dots moving around it, participant says the place of the dot when they’ve decided to move their hand). When they looked at the time difference between participant’s decision (-200 ms before movement) and readiness potential (-500 ms before movement), It seems like our muscles are getting ready to move before we decide moving. So do we say that our brain knows what we are going to do before we decide ? Is this mean that there is no free-will and everything is deterministic ? Be critical and don’t jump into the conclusions. The debate still continue. Further research showed that we can predict the behavior by looking at Lateral Frontopolar Cortex and Medial Frontopolar cortex although not perfectly. What does that mean? Does predicting something (your behavior) means that you have no control over it ?
