week 6 - executive functions Flashcards
what are executive functions?
‘conductor of the brain orchestra’
top most part of top down processing
they coordinate other brain modules to enable felxible, purposeful, goal-directed behaviour
why are executive functions needed?
needed to optimise performance in situations that require coordination between several cognitive processes
are executive functions specific to one domain?
no
supervisory, controlling or meta-cognitive (thinking about thoughts) rather than one specific domain (memory, perception, language, motor)
what are executive functions linked to?
linked to distinction between automatic (bottom up) and controlled behaviour (the latter requires execuitve functions)
strongly linked to the prefrontal cortex (PFC)
anatomy of prefrontal cortex
connection
PFC connected to almost all of the rest of the brain
anatomy of prefrontal cortex
three surfaces:
lateral
medial (middle)
orbital (very front)
anatomy of prefrontal cortex
lateral surface
implicated in ‘cold’ controlled processes (cognitive aspects)
anatomy of prefrontal cortex
medial + orbital
implicated in ‘hot’ control (emotional/social regulation of behaviour)
executive functions in practice
1986: identified five general situations requiring executive functions
situations:
1. involving planning or decision making
2. involving erro correction or trouble shooting
3. where responses are not well-learned or contain novel sequences of actions
4. judged to be dangerous or technically difficult
5. that require the overcoming of a strong habitual response or resisting temptation
executive functions in practice
experiment
the towers of london
executive functions:
planning and decision making
brain areas
tower of london task
PFC, especially dorsolateral, activated in functional imaging during task (healthy participants) and damage to PFC results in poor performance
executive functions:
error correction, trouble shooting and task switching
wisconsin card sorting test
requires shofts in strategy following an unexpected rule change
executive functions:
error correction, trouble shooting and task switching
brain areas
Ventrolateral PFC related to rule change
patients with PFC damage fail to update the rule and exhibit perservation behaviour
–> keep responding using a previously correct response
therefore PFC is involved in error correction and trouble shooting
DLPFC responded during the feedback period regardless of whether it was +ve or -ve
VLPFC more strongly activated for negative feedback, suggesting the involvement of this region when there is a need to change the rule
executive functions:
overcoming habitual response
test
stroop test:
functional imaging and lesion studies suggest involvement of anterior cingulate cortext (ACC) and pre-SMA (supplementary Motor area)
2007
executive functions
role of anterior cingulate (ACC)
detection of errors and detection of response conflict (potential errors)
executive functions
role of anterior cingulate (ACC)
evidence
monkeys with lesions here dont trouble shoot after making an error
the error potential at scalp may originate here
fMRI shows activity greatest on error trial, but lateral PFC greatest on error+1 trial
suggests ACC detects but doesnt correct erors
what are the two models of executive functioning?
non-unitary
unitary
models of executive functioning
non-unitary
what
petrides’ 2000: Theory of working memory
considers there to be a difference between different types of processes within the PFC
models of executive functioning
non-unitary
assumptions
assumes division of PFC into at least two separate processes:
maintenance (retention)
manipulation (updating) - -ve feedback causing a change in behaviour
models of executive functioning
non-unitary
manipulation (where)
dorsal lateral PFC
(frontal)
models of executive functioning
non-unitary
maintenance (where)
ventral lateral PFC
(frontal)
petrides’ 2000: theory of working memory
task
a self-ordered pointing task
based on petrides and milner (1982)
Participants shown a set of images
They have to point at any random image
Then on trial 2 they have to choose an image that they haven’t already selected
Same on trial 3 (avoiding 2 things)
Images move around —> working memory
petrides’ 2000: theory of working memory
task
PFC damage
patients with PFC damage are impaired at self-ordered pointing task
petrides’ 2000: theory of working memory
task
PET study
short term maintenance of spatial information
= ventrolateral PFC,
but maintenance updating with new locations
= dorsolateral PFC
owen 1996
petrides’ 2000: theory of working memory
task
monkey study
monkey studies with task similar to self ordering pointing show that dorsolateral PFC is particularly important for updating (1995)
executive functioning
non-unitary
functional specialisation within PFC
frith (2000) - left DLPFC may be responsible for selecting a range of plausible responses
- “sculpting the response space” / task setting
Frith et al. (1991) - left DLPFC active in “free will”
- choosing which finger to move or which word to say vs. being told to do
TMS over left DLPFC distrupts random digit generation (jahanshaji et al. 1998)
- suggesting that it is functionally different to other areas in the PFC
executive functioning
non-unitary
functional specialisation within PFC:
Right Dorsolateral PFC test
N-back task (Is this the same image as ‘n’ before, N is how many images are before)
Right DLPFC activity increased for the 3-back and 2-back conditions compared with the 1-back and 0-back conditions
the conditions are thought to require more monitoring (but could also be updating)
executive functioning
non-unitary
functional specialisation within PFC:
Right Dorsolateral PFC
may be important in monitoring and sustaining attention
both for externally presented information (perception tasks) and internally generated information (memory tasks)
- 2003
activity greatest in conditions of uncertainty
- tip-of-tounges states, confidence judgments in memory (low confidence = greater activity)
executive functioning
non-unitary
summary of possible roles of PFC:
ventro-lateral PFC
left hemisphere:
retrieval and maintenance of semantic and/or linguistic information
right hemisphere:
retrieval and maintenance of visual and/or spatial information
executive functioning
non-unitary
summary of possible roles of PFC:
dorso-lateral PFC
left hemisphere:
selecting a possible range of responses and suppressing inappropriate ones; manipulating the contents of working memory
right hemisphere:
monitoring and checking of information held in mind, particularly in conditions of uncertainty; vigilance and sustained attention
executive functioning
non-unitary
summary of possible roles of PFC:
anterior PFC
left + right hemispheres
multi-tasking; maintaining future intentions / goals while currently performing other tasks or sub-goals
executive functioning
non-unitary
summary of possible roles of PFC:
anterior cingulate cortex (dorsal)
monitoring in situations of response conflict and error detection
executive functions:
unitary accounts
what
unitary accounts argue that there are no ‘executive functions’ just one general underlying function
- one function
executive functions:
unitary accounts
evidence to support
patients’ performance on many tests of executive function are correlated with each other and with fluid intelligence (2010)
- if good at one good at all
- Perhaps this is the underlying concept that supports these sorts of separate functions
executive functions:
unitary accounts
evidence from monkeys
single-cell recordings of PFC neurons in monkeys show that they change their responsiveness flexibilty according to task demands (2002)
so any part of PFC may be able to do any ‘executive function’ given the right circumstances
- So not separate
Sometimes neurons for one executive function,, sometimes for another
Depending on task
* Brain selects whichever parts of PFC most useful to solve task in front of you
executive functions:
unitary accounts
the multiple-demand network
duncan and owen (2000)
Did a review of where the focal activity was across a wide range of functional neuroimaging studies that involved difficult tasks. Essentially finding where the most activity is (the overlaps)
evidence for a single set of fronto-parietal regions called the multiple demand network that is active during all tasks that we consider to involve executive functions
- Network of brain regions across the frontal lobe and parietal which is always active across tasks we consider to require executive functions
2017: multiple demand network divides complex tasks into a sequence of “attentional episodes”
ie. the ability to break down a complex task into smaller less complex segments (tower of london tasks)
executive functions:
unitary accounts
the multiple-demand network as the seat of complex thought
woolgar 2018
80 patients with focal, adult-onset brain lesions
patients with more of their lesions with in the MD system showed a greater deficit in fluid intelligence (reasoning)
this relationship didnt exist for lesions within th elanguage network
thereofre, MD is needed for complex thought
- also language is not necessary for complex thought
executive functions:
unitary accounts
the multiple-demand network as the seat of complex thought
woolgar 2018 what did they do
woolgar 2018
For each patient worked out how much of their brain injury overlapped with the multiple demand network
Did they same thing with the language network
* These are on the x axis
Postmorbid change in fluid intelligence
This I show much their scores on Intelligence tests have changed between before and after their injury
* Y axis
executive functions:
unitary accounts
the multiple-demand network as the seat of complex thought
woolgar 2018: challenges
Challenge in neuropsychology in not having baseline measures
* Guess work
Calculate the likely change
Intelligence tests are challenging
Possible to get better at intelligence tests
So not relevant to underlying ability
Bias across race ect.
How do we define intelligence
executive functions:
unitary accounts
the multiple-demand network as the seat of complex thought
damage to language
Damage to language doesn’t seem to effect performance
* Language not necessary for complex thoughts
executive functions are those functions that….
…allow you to complete a complex task
do you control executive functions?
yes
or maybe they are you (the voice in your head)
what are executive functions supported by…
.. prefrontal cortex
are their different types of executive functions?
possible that there are not different types of executive function,
but just one underlying high level ability of healthy humans:
to break down a complex task into manageable parts and perform each in order
–> possibly the same as fluid intelligence
