Mapping EF to the prefrontal cortex

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EF is essentially the
conductor of an orchestra
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it is the analogy that they are individual musicians because
every part is extremely skilled, but need somebody to keep them working together in time & tune
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without the conductor (EF) we may
do things in disorganised, scattered and illogical manner
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what can be affected if EF isn't there?
planning and being organised
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What is the issue in EF
if it is single or multiple mechanisms
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should it be considered unitary or
non-unitary
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what is unitary?
single, general construct with multiple interrelated sub processes
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what is non unitary?
collection of dissociable or independent processes
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what deficits are there when there is damage to the frontal lobe?
thinking, reasoning, self-control & cognitive
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What did Duncan et al 1997 say was a controversial issue in the studies of EF?
to what extent can different functions often attributed to frontal lobes or CE be considered unitary?
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He also questions within this if
specific brain locations have same underlying mechanism or ability
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Brain and frontal lobes
....
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frontal lobe syndrome (Talos et al., 2003) - which patient?
Phineus Gage
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which part of the brain was injured?
prefrontal cortex
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what did this do to his personality?
changed it, he became irritable, confused, change of character
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which section of the brain is the EF in?
frontal 1/3 of frontal lobe
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what does the motor ***** do? (motor area)
initiates and controls motor control and function
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what about the pre motor area?
helps to plan and sequence per motor movement
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the prefrontal area is the most
anterior part of the frontal lobe
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what does it do?
plans, executes, guide behaviours for motor and behavioural movements
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Frontal lobe syndrome is commonly encountered
psychiatric patients
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what happens to those with frontal lobe syndrome?
disinhibition, stimulus bound behaviour, disorganisation, social inappropriateness
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what else is effected?
apathy, overactivity, perseveration
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what kind of dementia is involved in FLS?
sub-cortical dementia
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Luria 1969 did what?
popularised the term following pivot work where p's studied with lesions to frontal lobe of the brain
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what was the term?
frontal-temporal dementia: or pick's disease or frontal lobe dementia
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lobes of the brain
frontal, parietal, temporal, occipital
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in the frontal lobe, how many key areas for psychiatric function are there?
5
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what are they?
1. personality, 2. intellect, 3. EF, 4. WM, 5. speech
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what does the left frontal operculum contains what?
Broca's area
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what is it responsible for?
fluency of speech
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not to be confused with?
Wernicke's area
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what is wernicke's area for?
where words are generated
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the right frontal operculum does what?
adds emotion to speech
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what else does it add?
gesturing, prosody, and inflection
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planning is the command and
control centre of the brain
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planning is the cognitive process that connects learned
experiences with present actions
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in this place, we encode,
retrieve and act upon and manipulate information
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There are problems with staying
focused and being organised
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developmental problems can be seen in some children by seeing
delays in cognitive skills
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what do they exhibit?
similar symptoms as those with acquired brain injuries (ABI) (frontal)
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development is connected to language, for language acts as a
mediator
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wha are some of the consideration?
According to Shallice & Burgess (1991) some frontal lobe p's don't show any problems with frontal lobe tasks
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however some P's who have lesions outside the frontal lobes can demonstrate
severe impairments (Anderson et al., 1991)
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alternatively, clinical observations which indicate some dissociations in
performance among the executive tasks
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in this respect according to Godefroy et al., 1999 differences on
two EF type tests e.g. TOH vs WCST
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what does this suggest?
EF function isn't completely unitary
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Functional localisation is what type of approach?
neuroscientific
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if particular region of brain is associated with specific function then:
performing the function should activate this region, and lesions in this region should impair the function
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how many methodological challenges are there?
4
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1 - EF have not yet
been well defined, there is no agreement on how or if EF can be fractionated into individual functions
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2 - frontal lobe tasks are impure
measures of EF - poor performance is not specific to deficits in the EF of interest e.g. memory impairment may reduce fluency score
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what can be said about test results in relation to 2?
they can be interpreted in different ways e.g. impaired strategy formation or inhibitory ability
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3 - human brain lesions are
accidents of nature; it is difficult to find P's with damage in area of interest
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this means that impairments in task performance may not
reflect true function of region e.g. damage may extend to other areas - may be sparing of brain tissue in area of interest
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the brain may develop
compensatory changes over time
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4 - the prefrontal cortex is
well connected, many interconnections within prefrontal cortex, inputs from posterior and subcortical regions
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left dorsolateral prefrontal cortex: dorsolateral
prefrontal cortex
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location?
46, 9 and on lateral surfaces (sides)
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responsible for?
the response selection
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Perret in
1974
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investigated?
neural regions
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involved in?
suppressing inappropriate habitual responses
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P's were grouped according to
location of brain lesion
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how many tasks of response suppression?
2
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1?
verbal fluency
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and what did this entail?
2 trails
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trail number 1?
name as many words that start with 'S'
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trail 2?
name as many 4-letter words starting with 'B'
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what does trail 2 involve?
suppressing habit of using words according to their meaning
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suppression task 2
Stroop
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how many conditions?
3
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which were?
1. name the colour of the dots, 2. colour of ink - normal word e.g. 'when' in blue
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number 3?
name colour of ink e.g. 'red' in green, suppresses reading response
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results in the left hemisphere compared to right? (mean fluency scores)
frontal, temporal and posterior all lower number of words
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what was the worst performance for number of words? (mean fluency scores)
the frontal lobe, left hemisphere
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The mean results for trail 3 showed (time taken)
the worst performance was again in the frontal lobe, left hemisphere - by far
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Stroop results - conclusion; common factors across tasks is
suppression of using words according to their meaning
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which part of the brain is involved with suppression of habit?
left frontal lobe
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evaluation? unable to precisely
localise neural region (left frontal)
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and? do 2 taks have
other things in common? e.g. strategy formation? attention?
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Frith et al.,
1991
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PET study to measure
neural blood flow during two tasks
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each task P touched on either
index or middle finger
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Task A?
move finger that is touched each time
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Task B?
move either finger each time you're touched
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what does this show?
areas involved in response selection
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Willed action, Frith et al.,
1991
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what did he consider?
related willed acts
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he used?
techniques pioneered by Petersen et al 1988
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and designed?
tasks that differ in terms of wether performance is willed
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differences in rcBFs (regional cerebral blood flow) elicited by
tasks
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must therefore show?
location of brain activity associated with willed action
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action is willed when?
we consciously pay attention to its selection
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Results? bilateral activation in dorsolateral prefrontal cortex (DLPFC) for
selecting own response rather than following instruction
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Frith et al 1991 - left dorsolateral prefrontal cortex activation obtained in similar set of verbal tasks: Task A;
repeat word heard each time
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task B
say any word beginning with 'S' each time hear word next
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this showed that dorsolateral prefrontal cortex involved with:
highlighting available responses, than inhibiting inappropriate responses - so appropriate is made
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evaluation? left dorsolateral activation in verbal task but
bilateral activation in motor taks
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so is left hemisphere only specific for
non-motor response selection?
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response selection involves many components such as
generating response options such as remembering previous responses, inhibiting unwanted responses
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there is various ways the results can and have been
interpreted
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Jahanshahin et al
1998
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task?
random number generation task
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P's asked to say
numbers 1-9 in random sequence
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how many trials?
for 100 e.g. 3, 7, 4, 9, 1
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normally people avoid
producing habitual number sequences that don't feel random e.g. 3, 4, 5... 2, 4, 6
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how often such sequences produced therefore provides
measure of P's ability to suppress responses
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repetitive TMS used to
disrupt brain activity in area of prefrontal cortex during tasks
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how many conditions?
4
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condition 1?
no TMS
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2?
TMS to medial frontal cortex
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3?
TMS to right dorsolateral prefrontal cortex (DLPFC)
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4?
TMS to left dorsolateral prefrontal cortex (DLPFC)
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what did this measure?
number of consecutive pairs of numbers produced e.g. 2, 3 ... 5, 6
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greater number of consecutive pairs indicates
lower ability to suppress inappropriate responses
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summary... Perret 1974:
P's with lesions to left frontal cortex impaired at Stroop and verbal fluency - both involve response inhibition
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summary... Frith et al 1991:
activity in DLPFC associated with selecting own response; therefore inhibiting other responses
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summary... Jahanshahi et al 1998:
disrupting left DLPFC impairs ability to generate random sequence - by disrupting ability to inhibit responses
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summary... LEFT DLPFC involved in
selecting responses by inhibiting inappropriate responses
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other function-region associations? right dorsolateral prefrontal cortex:
monitoring info that is held in mind and relating it to current ask - WM
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other function-region associations? ventrolateral prefrontal cortex:
activating info in memory to facilitate current DM
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other function-region associations? anterior prefrontal cortex:
multi-tasking working towards more than one goal at a time
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Summary - functional localisation refers to idea that
individual cog functions carried out by particular, specialised regions of the brain (Bunge 2004)
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Summary - converging evidence that some EF can be
localised to specific regions of the prefrontal cortex
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Summary - practical and theoretical issues related to
neuroscientific study of EF may limit precision and robustness of these conclusions
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Card 2

Front

it is the analogy that they are individual musicians because

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every part is extremely skilled, but need somebody to keep them working together in time & tune

Card 3

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without the conductor (EF) we may

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Preview of the front of card 3

Card 4

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what can be affected if EF isn't there?

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Preview of the front of card 4

Card 5

Front

What is the issue in EF

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