Executive processes
• Properties of executive processes
– Executive processes coordinate mental activity
so that a particular goal is achieved
– They do this by modulating the operation of other
processes (modulate = to guide or modify);
however, executive processes do not actually
carry out these activities
Executive processes
•
•
Different types of executive processes
Several different types of executive processes have been identified. There is
currently controversy about whether there are several types of executive
processes or a single type (we are assuming several)
– 1. selective attention. (sometimes called executive attention (sustained attention) – this
type of attention is believed to act on the contents of working memory and directs
future mental activity in order to achieve a goal (e.g., driver focuses on traffic signs in
order to take correct exit)
– 2. switching attention – switching attention from one activity to another (e.g., having a
conversation and driving)
– Inhibiting information that has been perceived (e.g., ignoring music on radio when
traffic is heavy and one is driving)
– Scheduling a sequence of activities – planning the order in which a activities will be
carried out in order to achieve goal(s) (e.g., order in which you will pick up groceries,
dry cleaning, medications)
– Performance monitoring – review performance to ensure it is acceptable (e.g.,
checking speed limit while driving)
Executive processes
• It is generally agreed that the frontal lobes play an
important role when executive functions are carried
out
– The frontal executive hypothesis proposes that executive
processes are primarily mediated by the prefrontal cortex
(PFC)
– PFC – anterior to motor cortex (and for some authors the
premotor cortex)
– PFC includes dorsolateral PFC, anterior cingulate,
Broca’s area, and the medial and orbital regions of the
frontal lobes
Executive processes
• Frontal lobes:
– Prefrontal cortex: massive network that links the motor,
perceptual, and limbic (emotional network) regions
– Limbic system include amygdala, cingulate gyrus,
orbitofrontal cortex and parts of basal ganglia
Executive functions
Executive functions
• Frontal lobe:
– Major subdivisions of
prefrontal cortex: lateral
prefrontal cortex,
ventromedial prefrontal
cortex, and anterior
cingulate
Executive processes
• Frontal lobes:
– About third of cerebral cortex in humans; frontal lobes are
much larger in humans and are much larger than in other
mammals, especially its anterior aspect
– Frontal lobes separated from parietal lobes by central
sulcus and from temporal lobes by lateral sulcus
Kolb & Whishaw frontal lobe figure
• Lateral area 6
premotor cortex
• Medial area 6
supplementary
motor cortex
• Area 8 frontal eye
field
Executive processes
• Dorsolateral prefrontal cortex (areas 9 and 46)
• Medial frontal cortex (areas 25 and 32)
• Inferior (ventral) prefrontal cortex (areas 11, 12, 13,
and 14); also called orbitofrontal cortex
Executive processes
• Anatomical properties of PFC that are crucial for
executive processing
– Perceptual, motor, cortical, and subcortical brain
structures project to PFC
– This makes it possible to combine information from
diverse sources, thereby enabling complex behavior
– PFC has multiple projections to multiple brain structures
– This permits it to modulate (exert top-down guidance) on
other neural processes
Executive processes
• Working memory and lateral prefrontal cortex
– A previous lecture discuss working memory
– Baddeley’s model of working memory was presented
Baddeley’s working memory
model
Visuo-spatial
sketchpad
Phonological
loop
Central Executive
Executive processes
• Content-based model of working memory
– This is known as a content-based model of
working memory because it assumes that
different systems represent different content
– Phonological stores linguistic info and
visusospatial represents visual and spatial
information
– Model based on behavioral data reviewed in prior
lecture
Executive processes
• Process-based models of working memory
– It has been hypothesized that different regions of
the PFC are recruited to carry out different tasks
– In other words different processes are associated
with different brain regions
Executive processes
• Different types of working memory
– In some tasks a participant is presented a
stimulus, then is required to internally maintain a
representation of that stimulus, until a probe is
presented (maintenance condition)
– In an n-back task the participant is required to
keep in mind a stream of stimuli and respond
only if the stimulus was presented n-back
– Requires maintenance + manipulation
Executive functions
• Illustration of n-back
task
• Note, the need to
maintain information in
memory and
manipulate it
Executive processes
• D’Esposito et al. (1998)
– Meta-analysis
– D’Esposito and colleagues performed a metaanalysis to investigate content-based and
process-based accounts of working memory
– meta-analysis – quantitative review of findings
from several studies
Executive processes
• D’Esposito et al. (1998)
– One might expect based on the content account
of working memory that the phonological loop
might be left lateralized and the spatial sketchpad
should be right lateralized as it is for perception
– To investigate this possibility D’Esposito
categorized studies based on their content
(spatial, nonspatial)
Executive processes
• D’Esposito et al. (1998)
– Results partially support the hypothesis that
spatial tasks tend to be associated with activation
of the right prefrontal cortex, whereas nonspatial
tasks are associated with activation of the left
prefrontal cortex, but not
– However, there was bilateral activation in many
studies
– See top panel
D’Esposito et al. (1998)
• Top panel shows active
foci for spatial and
nonspatial tasks
(content)
• Bottom panel shows
active foci for
maintenance and
maintenance + tasks
Executive processes
• D’Esposito et al. (1998)
– to investigate the process-based account of
working memory, tasks were categorized as
requiring maintenance or maintenance plus
(maintenance + manipulation)
– Results showed that tasks requiring maintenance
plus had more dorsolateral activation
– See bottom panel
D’Esposito et al. (1998)
• Top panel shows active
foci for spatial and
nonspatial tasks
(content)
• Bottom panel shows
active foci for
maintenance and
maintenance + tasks
Executive functions
Stroop test
• This test assesses the ability to maintain a goal and
ignore/suppress habitual (prepotent) responses
Executive functions
Stroop effect demonstration
– in this next slide I want you to name the ink
colours of the words as rapidly as possible
Stroop (slide 1)
red
yellow
green
red
yellow
blue
green
red
yellow
red
green
red
yellow
blue
red
green
Executive functions
Stroop effect demonstration
– in this next slide I want you to name the ink
colours of the words as rapidly as possible
Stroop (slide 2)
red
yellow
green
red
yellow
blue
green
red
yellow
red
green
red
yellow
blue
red
green
Executive functions
Stroop effect demonstration
– in this next slide I want you to name the ink
colours of the colour patches as rapidly as
possible
Stroop (slide 3)
Executive functions
Stroop effect
• The increase in time it takes to name of color
when the word name does not match the color
versus naming color patches is called the colorword interference effect (slide 1 time/slide 3
slide)
• Note: different versions of the Stroop assess
interference in slightly different ways
Executive functions
Age
Dot time
(DT)
M (SD)
Color
Interference Errors
word time CWT/DT
Color word
(CWT)
M (SD)
M (SD)
18-39
11.0 (2.5)
22.1 (7.2) 2.0 (0.6)
0.8 (1.0)
75-74
13.3 (3.6)
32.6 (9.6) 2.6 (0.9)
0.6 (1.2)
timecolor
= name
color
word
time
= name color
word color
DT Dot
= Name
of dot; dot
CWTcolor;
= Name
color
of word
designating
Troyer, Leach, Strauss (2006), 13, 20-35
Executive functions
Stroop effect
• Age effects – age significantly increases the
magnitude of the interference effect
• Gender differences are not always present in the
interference score
• The higher the IQ score the lower the
interference effect
Executive functions
Stroop effect
• Standard interpretation of Stroop – participant
must selectively attend to the name of the ink
color and ignore the word name (of a color)
Executive functions
Wisconsin Card Sort
• Used to assess for frontal lobe damage
• 4 stimulus cards are arranged in front of a
participant; cards vary on 3 dimensions: shape,
color, number
• Participants are given a deck of cards and must
match each card with 1 of the stimulus cards, but
are not told on which dimension they are
matching
• Participants are told “right” or “wrong”
Executive functions
Executive functions
• Participants are given a deck of cards and must
match each card to 1 of the 4 stimulus cards
• Participants guess at first, but since they are given
feedback, they learn the correct attribute
• After sorting about 10 cards correctly, the examiner
changes the attribute without warning
• Normal participants soon figure out correct attribute
for sorting
Executive functions
• Frontal lobe patients and normal participants
do not differ in learning first critical trial, but
they differ in the ability to switch attributes
• Normal participants switch after a few trials of
negative feedback; frontal lobe patients are
less able to switch
Executive functions
• Executive attention is needed whenever multiple
representations in working memory or multiple processes
are competing for control of behavior and thought
• In Stroop task there is competition, but this sort of
competition is a feature of a broad range of tasks
• E.g., it has been shown that naming the color of a picture of
a banana is slowed when it is not yellow (e.g., red)
• in general when there is an incompatibility between an
automatic response and a correct response you get Strooplike effects
Executive functions
• Stimulus response compatibility exists when the
response required is compatible with the way
people would naturally respond to that stimulus
• E.g., high pitch respond – “up”; low pitch respond –
“down”
• E.g., stimulus presented on left or right side of
display requires a response on same side as
stimulus was presented
•
Executive functions
• Stimulus response compatibility is strong and is observed
even when position of object is irrelevant to response
(Simon, 1990)
• E.g., suppose task is to make a right-handed response when
a circle is presented and a left-handed response to a
triangle; reaction time is faster when the circle or triangle is
presented on the side of the response
• Interpretation – when there is an automatic connection
between a stimulus and a response, little executive attention
is required;
• when 2 sources of information are incompatible, attention
must be paid in order to focus on the relevant information
and inhibit/ignore the irrelevant information
Executive functions
• Cohen and colleagues have developed a
neural network model of Stroop task
• It proposes that in addition to initial visual
perceptual processing of color (occipital
lobes) and visual words (temporal lobes), two
additional attentional processes are required
Executive functions
Stroop effect demonstration
– in this next slide I want you to name the ink
colours of the words as rapidly as possible
Executive functions
• 1. attention controller
– This process keeps track of the task goal – this is
necessary because during incompatible trials in the color
word condition, the name of the color font and the name
of the word, which designates a color are two competing
responses
– In the color-word condition it does this by activating more
strongly the processes associated with the task goal (in
this case the color of the word)
Executive functions
• 2. conflict monitor
– This process monitors the amount of conflict
between potential responses. When there is
more conflict as there would be in the wordcolour condition, the conflict monitor increases
executive attention
Executive functions
Stroop effect
• Other points – neuroimaging and lesion studies
are consistent with hypothesis that frontal lobes
are associated with Stroop
• Data also suggest that performance is mediated
by a more broadly based system
Executive functions
• Neuroimaging evidence
– Jonides and colleagues (2002) performed a metaanalysis of Stroop studies and related studies
– Results showed that the anterior cingulate and
dorsolateral PFC were activated; this is consistent with
theory because it is known from other research that the
anterior cingulate is activated mediates conflict and the
dorsolateral PFC is involved in executive attention
Executive processes
• Executive processes & effects on longer-term
memory
– Individuals with PFC damage may be impaired in
their ability to organize temporally events in
memory
– Milner (1995) performed a recency experiment in
which participants were required to discriminate
which of two events was presented more recently
Executive processes
• Memory for temporal order Milner (1995)
– Participants were presented pairs of stimuli (e.g.,
2 pictures of objects)
– Every so often a probe card is presented with ?
– Task: to choose picture with more recently
presented object
Executive processes
• Milner (1995) Memory for temporal order
– Experimental condition– both objects had been
presented previously
– Control condition – one picture presented
previously one picture new (Recognition test)
Executive processes
• Memory for temporal order Milner (1995)
– 3 groups of participants were tested
– Controls
– Unilateral damage to dorsolateral PFC px
– Unilateral damage to temporal px
– Px underwent surgery for relief from focal
epilepsy
Milner recency discrimination
experiment
• Top panel shows
stimuli used in exp’t
• Bottom panel shows
that PFC participants
were impaired relative
to other 2 groups on
recency discrimination
test but not on
recognition test
Executive processes
• Memory for temporal order Milner (1995)
– Other findings – this experiment was also
performed with word stimuli
– Results showed that the effect was lateralized –
– Patients with LHD were more impaired on
recency discrimination when words were used,
whereas px with RHD were more impaired with
pictures
Executive functions
• Memory for temporal order
– Milner et al. (1991) performed an experiment in which
frontal and parietal patients were shown pairs of items
– Occasionally the pairs had a question mark between
them
– Participants task was to decide which item had been
presented more recently
– When only 1 item had been actually presented the test
was an item recognition test
– When both items had been presented, the test requires
order (and item) information
Executive functions
• Memory for temporal order
– Patients with frontal lobe damage were impaired
in their memory for order but not item information
– Patients with parietal lobe damage were impaired
in their memory for item but not order information
Executive processes
• Memory for temporal order Self-ordered
pointing
– Keeping track of previous experienced events
(memory for temporal order) has been examined
using a self-ordered pointing task
– In this task participant is presented n card with n
objects depicted on it
– The same objects are present on each card but
their order is scrambled from card to card
Executive processes
• Memory for temporal order Self-ordered
pointing
– Task of participant is to point to the a different
object on each card (one that hasn’t yet been
pointed to)
– Results
– Frontal lobe patients made more errors than
controls; discrepency between 2 groups
increased with n, the number of objects and
cards
Executive processes
• Source memory
– Source memory refers to when we learned a fact
or the context in which a fact was learned –e.g.,
who told you fact or in what context you viewed a
face
– Source memory appears to require frontal lobe
function
Executive processes
• Source memory
– Janowsky, Shimamura, & Squire (1999)
– In this experiment participants were taught new
facts (e.g., “The name of the dog on the cracker
box is Bingo”)
Executive processes
• Source memory
– Janowsky, Shimamura, & Squire (1999)
– 6-8 days later participants were asked to answer
questions about these newly learned facts and
other facts that might have been acquired outside
of the experiment; if they recalled the fact they
were asked questions about when they learned
the fact (during the previous session or reading,
school etc.)
Executive processes
• Source memory
– Janowsky, Shimamura, & Squire (1999)
– Results
– Controls and frontal lobe patients did not differ in
recall of facts
– Frontal lobe participants were impaired in recall
of source of facts
Executive processes
• Source memory
– Glisky et al. (1995)
– Investigated role of memory and executive
function on item and source memory
– Neuropsychological tests assessed memory
(temporal) and executive (frontal) function
– Performance on these two types of tests was
weakly correlated
Executive processes
• Source memory
– Glisky et al. (1995)
– Study: participants heard sentences describing
events (e.g., The boy went to the store to buy
apples and oranges)
– Half were read aloud in man’s voice and half in a
woman’s voice
Executive processes
• Source memory
– Glisky et al. (1995)
– Memory test
– Item memory: recognition test in which pairs of
studied and unstudied sentences were presented
together
– Source memory: participant heard sentence read
aloud in a man or woman’s voice and decided
which voice matched the studied sentence
Executive processes
• Source memory
– Glisky et al. (1995)
– Results
– Controls and frontal lobe patients did not differ in
recall of facts
– Frontal lobe participants were impaired in recall
of source of facts
Glisky (1995)
• Source memory
relatively more
impaired than item
memory by low frontal
function
• Item memory relatively
more impaired than
source memory by low
temporal function
Executive processes
• Executive processes & effects on longer-term
memory
– Individuals with PFC damage may be impaired in
their ability to organize temporally events in
memory
– Milner (1995) performed a recency experiment in
which participants were required to discriminate
which of two events was presented more recently
Executive functions
• Sequencing
– Many activities of everyday living require people
to plan and then carry out a sequence of
activities, which must satisfy certain requirements
in order to achieve a goal
– Studies have shown that patients with PFC
damage are impaired on certain sequencing
activities, but not all sequencing activities
Executive functions
• Sequencing – how is temporal order coded?
– An important component of sequencing is coding
temporal order of events
– Evidence suggests that there are several
different ways in which temporal order might be
coded and that the coding of temporal order often
involves separate processes from the coding of
item information
Executive functions
• Sequencing – how is temporal order coded?
– Sternberg, (1966, 1967) compared performance
on an item recognition (was letter presented?)
and an order task (what is the next letter?)
– Item recognition – memory set (BGRD); probe
(g); response (“yes”)
– Order task -- memory set (BGRD); probe (g);
response (“r”)
1400
1200
1000
800
Item
Order
600
400
200
0
3
4
Sternberg, (1966,1967)
5
6
7
Executive functions
• Sequencing – how is temporal order coded?
– Sternberg, (1966, 1967)
– note the large slope differences between the two tasks
– Results suggest that different processes are involved item
and order tasks; one difficulty with experiment is that one
task requires recognition while the other requires recall;
however, many studies are consistent with the idea that
item and order information are stored and processed
differently
Executive functions
• Sequencing – how is temporal order coded?
– For example, there is evidence to suggest that
memory for order information (information about
associations) depends critically upon the
hippocampus, but item information can be carried
out independently of the hippocampus
– There is also evidence indicating that sequential
information can be stored and processed in a
variety of ways
Executive functions
• Sequencing – how is temporal order coded?
– There are many ways to code temporal order and there is evidence
for each of these ways depending upon the task and other factors
– 1. Associative – e.g., X R C B L ; code as X precedes R; R precedes
C; C precedes L etc.
– 2. order tags – e.g., X R C B L; code as X is first; R is second; C is
third, etc.
– 3. familiarity – e.g., a form of representation in which strength or
familiarity of item is continuously represented, so more recent items
are stronger than earlier items, allowing participants to make a
judgement on that basis (e.g., B is stronger then C)
Executive functions
• Sequencing related items
– In many everyday situations, sequences of actions are
related to each other, and in many cases have been
performed several times in the past
– E.g., eating out typically involves being greeted, taken to
a table, ordering a meal, eating, getting a bill, paying, and
leaving (Schank & Abelson, 1977)
– It is also possible to generate a novel script (e.g., opening
a beauty salon)
Executive functions
• Sequencing related items
– Sirigu et al. (1985) performed an experiment in
which patients with PFC damage, damage to the
posterior cortex, and normal controls were tested
on familiar and novel scripts
– Participants were asked to generate familiar
(going to a restaurant) and novel (opening a
beauty salon) actions and then they were asked
to order the actions into correct sequences
Executive functions
• Sequencing related items
– No significance difference in the number or type of
actions generated
– Individuals with PFC damage made more errors than
other 2 groups when asked to order generated actions in
correct sequence and the pattern was amplified with
novel scripts
– Similar findings were obtained when the different groups
were given cards with actions for scripts written on them
Executive functions
• Brain imaging studies
– Buckner & Wheeler (2001) reviewed findings
from neuroimaging of remembering
– Several studies have shown consistently with a
variety of stimuli (words, faces, pictures) that
during memory recall the dorsolateral prefrontal
cortex and the anterior frontal-polar cortex are
activated
–
Executive functions
• Brain imaging studies
– e.g., Buckner et al. (1995)
– Participants studied a list of words (couple,
string)
– At test, during imaging, participants were shown
the beginning of the word and were intstructed to
recall the word (e.g., cou---, stri---- )
– Results on next slide illustrate the pattern of
activation
Buckner et al. (2001)
• Typical pattern of
activation during recall
of studied material –
blue, dorsolateral (BA
44/6); green anterior
frontal-polar (BA 10)
Buckner et al. (2001)
• 2 brain regions appear
to have distinct
functional properties
• Selectivity of anterior
suggests it may have a
specific memory
function; late onset
consistent strategic
retrieval/monitoring
Executive functions
Memory retrieval success
Evidence that MTL and PFC involved during memory
retrieval, but are there additional regions?
Habib and Lepage (1999) meta-analysis
compared activation of old and new items
Results showed that a network consisting of left parietal
cortex, left anterior frontal lobe (near frontal-polar
region) responded more to old items (i.e., retrieval
success)
This finding has been replicated in more recent studies
with a variety of materials
Buckner et al. (2001)
• Panel a. paradigm
• Exp’t in which
activation of old versus
new items is compared
Buckner et al. (2001)
• Panel b.
• fMRI imaging show
differential activation of
brain regions
associated with
retrieval of success;
note left parietal cortex
activation (green arrow)
Buckner et al. (2001)
• Panel c.
• Event-related potential
(ERP) shows a rapid
positive waveform that
develops over left
parietal sites during
remembered old items
(red) as compared to
new items (green)
Executive functions
• Spontaneous confabulations
– Individuals, who spontaneously confabulate have
also been used to investigate role of the frontal
lobes and executive function in memory
– Spontaneous confabulation – statements are
actions that reflect unintentional but obvious
distortions of memory
– “honest lying”
– Spontaeous confabulation is found sometimes
but not always after px who survive aneurysms of
the anterior communicating artery (ACoA)
ACoA
• Ventral view of arteries
in brain
• Damage to ACoA may
result in memory loss,
personality change and
amnesia
• Damage to ACoA often
results in PFC damage
Executive functions
• Spontaneous confabulations
– Gilboa et al. (2006) investigated spontaneous
confabulations
– Participants were ACoA individuals who
confabulate, ACoA individuals who do not
confabulate, and controls
Executive functions
Spontaneous confabulations
– Temporal context judgment experiment
– In this experiment participants were required to
make temporal context judgments about pictures
of objects (Was this object presented earlier in
this list; i.e., not a previous list?)
– Results
– Not all ACoA patients were impaired on the
temporal context confusion experiment, but those
with ventromedial prefrontal cortex damage were
impaired
Executive functions
• Spontaneous confabulations
– Familiar narratives experiment (fairy tales and
bible stories)
– In this experiment participants were asked to
recall familiar narratives
– Results: spontaneous confabulators did not differ
from ACoAs in terms of details recalled, but
differed in terms of the number and type of errors
(e.g., incorporation of details from other stories,
idiosyncratic details)
–
Semantic narrative performance
• Top: mean details produced
• Bottom: proportion errors –
T = total errors; D =
distortions; E = external
details (other stories); I =
idiosyncratic errors
Executive functions
• Spontaneous confabulations
– Further analyses
– Only px with ventromedial prefrontal and
orbitofrontal cortical damage were spontaneous
confabulators
Executive functions
• Spontaneous confabulations
– Conclusion: spontaneous confabulation does not
appear to be a result of confusing true memories
in time (evidence: spontaneous confabulator
errors such as semantic narrative external
details)
– instead it appears to be a difficulty of strategic
retrieval and difficulties of monitoring
– Strategic retrieval refers to a type of memory
retrieval in which the target memory is not
directly elicited by the retrieval cue (e.g., what did
you do on your birthday?), but appears to require
problem solving
Executive functions
• Spontaneous confabulations
– Evidence for strategic retrieval
– 1. Evidence from current study
– 2. Finding that spontaneous confabulation is
observed even for remote memories acquired
prior to brain damage (when encoding of
memories was intact); suggests stored memory
is relatively intact and problem is in retrieval
Executive functions
Executive functions
• Spontaneous confabulations
– Gilboa et al. proposed:
– Strategic retrieval helps frame the memory
problem and memory search
– Constrains memory search
– Once a memory is retrieved strategic retrieval
monitors recovered memory for plausibility
Executive functions (social,
personality and emotional functions)
Overview
•
•
•
Gage walked away from accident, could describe the accident
the next day, and within a month was deemed able to resume
work as a foreman
It became clear that Gage was “no longer Gage”
• Prior to injury Gage was a sober, responsible, intelligent,
home body, with no peculiar or bad habits; he was a
responsible, valued employee
• After injury he was erratic, given to grossest profanity,
impatient, unwilling to listen to advice, and unable to plan
effectively
Subsequent research has shown that damage to frontal lobes
can lead to dramatic changes in personality while keeping
perception, consciousness, and most cognitive functions
intact