Cognitive, Executive Functions, WEEK 5 Flashcards
1
Q
What are executive functions?
A
- EF are the “conductor of the brain orchestra” > EF coordinates the activity of all other brain modules > enables us to perform flexible, purposeful + goal-directed behaviour > helps us do complicated things
Needed to optimise performance in situations that require coordination between several cognitive processes. - To complete a complicated task like an experiment, you need your to coordinate functions so you follow the instructions correctly, select correct response + do the right mental manipulations to ensure you do the task correctly
- Supervisory, controlling, or meta-cognitive (thinking about thoughts > high level mental processes), not specific to one domain (memory, perception, language, motor)
- Linked to distinction between automatic (bottom-up behaviour, like bottom up attention) and controlled behaviour ( requires executive functions > needs top down conscious decision)
- Strong link to the prefrontal cortex (pfc)
2
Q
Evolutionary development of frontal lobes
A
- The prefrontal cortex is towards the front of the frontal lobes
- Comparison of different brains show how they may have changed through evolution > more of the brain is devoted to the prefrontal cortex thus more devoted to executive functions and that kind of processing than other animals
3
Q
Anatomy of PFC
A
- 3 important surfaces in PFC = Lateral, Medial and Orbital
- Lateral surface of a lobe = the side of the lobe Dorsolateral = top of the side of the lobe Ventrolateral = bottom of the side
- PFC is connected to almost all of the rest of the brain
- Medial surface of PFC = in the middle of the PFC > if you were to split the two hemispheres apart, the middle of the PFC is the medial surface
- Orbital surface of PFC = the part at the very very front (the tip almost just above your nose)
- Lateral surfaces of PFC seem to be more involved in “cold” control processes, things like cognitive aspects of EF while medial and orbital surfaces seem more involved in processes associated with emotion + social regulation of behaviour > “hot” control processes
4
Q
EF in practice
A
- Norman and Shallice (1986) identify five general situations requiring executive functions
- Situations involving planning or decision making
- Situations involving error correction or trouble-shooting
- Situations where responses are not well-learned or contain novel sequences of actions
- Situations judged to be dangerous or technically difficult
- Situations that require the overcoming of a strong habitual response or resisting temptation
- These 5 situations cover complicated behaviours > things involving planning, reasoning, problem-solving
- The link between PFC and EF become clear as e.g. you don’t see your dog doing problem solving or very complicated behaviours, dogs + other animals do many different methods of doing things till they achieve it. On the other hand, EF in humans help us plan and think ahead which helps us find solutions
5
Q
Executive Function: Planning and Decision Making
A
-The Towers of London task tests this by making the ppts rearrange coloured discs to match the target discs > your mind is trying different methods out and imagining hypothetically how to correctly go about the problem to solve it
-The task works in peoples my mind by planning and rearranging where different discs can go and planning many moves ahead (move them around in your head) and this leads to making an appropriate decision
- People don’t solve this task one move at a time (move one then think about the next one) > typically people plan out their moves then carry out the action so they know what they will do
- Here we are planning a series of actions to achieve a goal which is complicated and in the future > how EF is linked to towers of London and planning and decision making
- Dorsolateral PFC is particularly active in the functional imaging taken during the towers of London task + damage to the PFC results in poor performance to the towers task.
^Indicates a link between the PFC (especially dorsolateral PFC) and the ability to plan ahead + make decisions about actions in the future
6
Q
EF: Error Correction, Trouble-shooting & Task Switching
A
- Wisconsin Card Sorting Test > This task requires a shift in strategy following an unexpected rule change
- presented with 4 cards above your own card, each card has a certain shape, a certain amount of the shapes and a certain colour. Your job is to match your own card to a card above based on either them having the same shape, the same colour or the same amount of shapes (number). You are NOT told which criteria to look for, you just have to guess and think about which criteria’s it could be (criteria being looked for changes every few rounds)
- you hold the particular rules needing to be applied and hold it in mind + keep repeating it > when you get negative feedback (says wrong) then you know the rule has changed + hold this in mind and decide what other rule it could be and try it > if this one is wrong then 2 rules have been ruled out and it must be the 3rd
- 3 possible tasks of correcting behaviour when an error has been made (rule has changed + has to be corrected by trying a different task) > If rule changes, then you need to recognise this has happened, choose one of the other options, switch to the task (if it doesn’t work switch to the other task) > this is a lot of error correction, trouble shooting and task switching
- Trouble shooting meaning trying to work out what other behaviour would be an appropriate response in this circumstance
- Task switching meaning for example switching from colour to focusing on number etc..
- The ventrolateral PFC is primarily activated during these trials where rules change > patients w/ damage to their PFC struggle with this task
7
Q
Patients with damage to PFC in the Wisconsin Card Sorting Test
A
- Patients with PFC damage fail to update the rule and exhibit perseveration behaviour (i.e. they keep responding using a previously correct response.) > perseveration is where you continue to perform a behaviour that is not/no longer appropriate.
- PFC seems important in correcting errors + troubleshooting those errors (identifying the error + choosing how to rectify it)
- DLPFC (red circle) responded during the feedback period, regardless of whether it was positive or negative feedback > DLPFC could be related to processing feedback, however because this area doesn’t care if feedback is -ve or +ve, it cannot be heavily involved in processing feedback because it cannot have much of an impact (something very involved in processing feedback would care about if the feedback is positive or negative so behaviour can be adjusted accordingly)
- Ventrolateral PFC (VLPFC; green circle) most strongly activated for negative feedback, suggesting the involvement of this region when there is a need to change the rule. > suggests VLPFC is interested in changing your behaviour or in processing that a rule has changed and so the response/behaviour should change too.
8
Q
EF: Overcoming Habitual Responses
A
- Stroop test > in this test you are presented with a word of a colour written on the screen and this is written in a colour too > ppts have to name the colour the word is written in
- People are slower to name the colour when the word is mismatched with the colour
- EF in this context are required to overcome a habitual response > if you see the word blue written in red, your mind automatically/habitually want to say blue but you need to inhibit this response to complete the task and perform the behaviour appropriately > perhaps the extra time it takes to respond is this processing
-Functional imaging and lesion studies suggest involvement of anterior cingulate cortex (ACC) and pre-SMA (Supplementary Motor Area) in overcoming habitual responses
-The anterior cingulate cortex is on the medial surface of the brain (anterior = towards the front > towards the front of the cingulate cortex)
Pre-SMA is just above the anterior cingulate cortex + is involved in motor actions (makes sense for stroop test because you need to respond out loud + need inhibitory control to stop saying what you habitually want to)
9
Q
Role of Anterior Cingulate Cortex in EF
A
- Involved in overcoming habitual responses
-Also involved in detecting errors + detecting when there is conflict between responses (when there is potential for an error to happen + tries to stop it before it actually does happen which is before feedback)
Evidence for this - Monkeys with lesions to ACC don’t trouble shoot after making an error + won’t try change behaviour, they preseverate
- In ERP’S, there are “error potential” at scalp when someone makes an error + knows they have > the error potential which is the recognition that an error has occurred may be coming from the ACC itself
- fMRI shows greater activity in ACC on error trial, but not this activity in ACC in the next trial which is error +1, here there is activity in the lateral PFC greatest on error+1 trial > suggests ACC is processing + detecting the fact an error has occurred but correcting the error + changing behaviour occurs in lateral parts of the PFC
10
Q
Non-Unitary models of EF
A
- Non-unitary models of EF are models which don’t assume EF to be one thing > there is a distinction between different types of processes within the prefrontal cortex
11
Q
Non-Unitary model: Theory of Working Memory (Petrides, 2000)
A
- creates a distinction between the maintenance of information in working memory and manipulation of information in working memory
- Working memory is the ability to hold things in your mind for a short amount of time to help do tasks
- Petrides theory indicates that the ventrolateral PFC is particularly involved w/ maintaining and retrieving memory > retention aspect of WM
- The dorsolateral PFC is more involved in manipulating, updating + monitoring information which is held in working memory
- This is evident in the Wisconsin card sorting task > the task involved requiring us to hold certain rules in mind using WM. So for example you maintain the rule of colour + keep doing this until you get negative feedback, this is when you manipulate or update the info in WM you are using > WM could be key to EF because it enables complex behaviours
12
Q
Supporting evidence for Theory of Working Memory
Self-ordered pointing task (Petrides & Milner, 1982)
A
- ppt shown set of images + have to point any random image in trial 1. In trial 2, they have to pick an image which they did not already select in trial 1. In trial 3, they have to pick an image they have not selected in trial 1 and 2. > in each trial the images move around
- Because images move around there is definitely a component of WM because as you go through you need to remember you have already chosen something and look for other things
- Patients w/ damage to PFC are impaired at doing this task > task about WM is particularly impaired in people with damage to PFC
- PET scans show that the periods of short-term maintenance of spatial info in the task, there is greater activity in the VLPFC, while when the ppt is maintaining + updating the new locations of the items, the DLPFC is more active > indicates a distinction and a presence of non-unitary element of WM.
- Monkey studies with task similar to self-ordered pointing show that dorsolateral PFC is particularly important for updating (Petrides, 1995) > supports distinction of role of VLPFC and DLPFC
13
Q
Functional specialisation of PFC
A
- Is the PFC functionally specialised so that different parts of the PFC perform different things
- Frith (2000) – left DLPFC may be responsible for selecting a range of plausible responses > essentially setting the task options or “sculpting the response space“ / task-setting > what responses we could give?
- Frith et al. (1991) – left DLPFC active in “free will“ > choosing which finger to move or which word to say vs. being told what to do sees DLPFC being more active > our ability of doing something on our own w/o instruction may link to DLPFC
- TMS over the left DLPFC can induce people into being worse at making up random digits > people kind of perseverate when you ask them to make a list of random numbers, TMS makes it less random (perhaps is taking away freewill in some way) > harder to choose from a set of options > DLPFC may be functionally different from other parts of PFC + might be linked to higher level processes which would also link to consciousness
14
Q
More supporting evidence for right DLPFC
A
- N-back task: presented w/ images or letters one at a time and ppt has to say if this item is the same as the image presented n items before. E.g. if we set n at 2, we are asking if the image being shown now is the same as the one which was presented 2 items ago?
- Difficult task using a lot of the frontal lobe to get correct because you need to hold more things in memory depending on n > need to hold them in mind and update them with every new items and respond.
- Requires a lot of concentration, difficult to be able to multi-task doing it
- You have to hold the item in mind but also constantly update with the new each item (new image comes on screen, decide if it matches from n items ago but at the same time kick this item out of the WM + replace with the next item) > very complicated
- When ppts are in a scanner at the same time as doing the task, we see greater activity in the right DLPFC especially for 2 back and 3 back conditions
- Perhaps the more difficult N backs are conditions which require more monitoring of the contents in your WM, so maybe this is what the right DLPFC is for. However, the more difficult N backs also require more updating (which could be considered the hardest part) so right DLPFC could equally could be responsible for this > difficult to separate them
- Right DLPFC is certainly important for sustained attention, you need to pay attention to perform well
- Right DLPFC seems important for monitoring + sustained attention to not only external presented info (like perception tasks) and things out in the real world but also things we internally generate (like memory tasks and things in mind like minds eye)
- Consequently, right DLPFC seems very involved in complex memory judgement + confidence judgements (deciding whether you trust your memory for a particular event) > perhaps right DLPFC is more active in situations of uncertainty
15
Q
Theories of EF: Unitary Accounts
A
- Alternative of non-unitary is unitary accounts > this is the idea that there aren’t multiple executive functions which are supported by multiple different regions in PFC, there is one underlying function which is EF essentially > unitary
- Could be true as just because we give something a name and we say there could be two separate functions supported by certain areas, doesn’t mean this is true, that function could just be part of a larger function
- Evidence to support this is that if you perform well on one EF task like towers of London, you are likely to perform well on ALL EF tasks > performances are correlated with each other which suggests they are supported by one underlying process. > also all correlated with fluid intelligence, perhaps fluid intelligence is the underlying concept supporting these different functions
- When we look at single-cell recordings of the PFC in monkeys, we find that these individual cells change their role according to the kind of task which is being performed > important for unitary accounts because non-unitary accounts are saying that different executive functions occur in different parts of the PFC but, this evidence is indicating that a certain neurone in the PFC of the monkey is sometimes used for one EF and later used for another different EF
- suggests that PFC broadly is a set of parts of your brain which are capable of quite complex calculations + maintenance of info > depending on your task, you can employ different parts of PFC to help you solve that task using EF
- Could be that your brain selects whichever part of the PFC is available or most useful to help solve the task
