Title: Executive processes
1Executive 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
2Executive 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)
3Executive 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, Brocas area, and the medial and
orbital regions of the frontal lobes
4Executive 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
5Executive functions
6Executive functions
- Frontal lobe
- Major subdivisions of prefrontal cortex lateral
prefrontal cortex, ventromedial prefrontal
cortex, and anterior cingulate
7Executive 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
8Kolb Whishaw frontal lobe figure
- Lateral area 6 premotor cortex
- Medial area 6 supplementary motor cortex
- Area 8 frontal eye field
9Executive 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
10Executive 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
11Executive processes
- Working memory and lateral prefrontal cortex
- A previous lecture discuss working memory
- Baddeleys model of working memory was presented
12Baddeleys working memory model
Visuo-spatial sketchpad
Phonological loop
Central Executive
13Executive 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
14Executive 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
15Executive 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
16Executive functions
- Illustration of n-back task
- Note, the need to maintain information in memory
and manipulate it
17Executive processes
- DEsposito et al. (1998)
- Meta-analysis
- DEsposito and colleagues performed a
meta-analysis to investigate content-based and
process-based accounts of working memory - meta-analysis quantitative review of findings
from several studies
18Executive processes
- DEsposito 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 DEsposito
categorized studies based on their content
(spatial, nonspatial)
19Executive processes
- DEsposito et al. (1998)
- Results 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 - However, there was bilateral activation in many
studies - See top panel
20DEsposito et al. (1998)
- Top panel shows active foci for spatial and
nonspatial tasks (content) - Bottom panel shows active foci for maintenance
and maintenance tasks
21Executive processes
- DEsposito 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
22DEsposito et al. (1998)
- Top panel shows active foci for spatial and
nonspatial tasks (content) - Bottom panel shows active foci for maintenance
and maintenance tasks
23Executive functions
- Stroop test
- This test assesses the ability to maintain a goal
and ignore/suppress habitual (prepotent)
responses
24Executive functions
- Stroop effect demonstration
- in this next slide I want you to name the ink
colours of the words as rapidly as possible
25Stroop (slide 1)
- red yellow blue red
- green red yellow green
- blue green red yellow
- red green red yellow
26Executive functions
- Stroop effect demonstration
- in this next slide I want you to name the ink
colours of the words as rapidly as possible
27Stroop (slide 2)
- red yellow blue red
- green red yellow green
- blue green red yellow
- red green red yellow
28Executive functions
- Stroop effect demonstration
- in this next slide I want you to name the ink
colours of the colour patches as rapidly as
possible
29Stroop (slide 3)
30Executive 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
color-word interference effect (slide 1
time/slide 3 slide) - Note different versions of the Stroop assess
interference in slightly different ways
31Executive functions
Age Dot time (DT) M (SD) Color word time (CWT) M (SD) Interference CWT/DT Errors Color word 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)
Dot time name dot color color word time name
word color
DT Name color of dot CWT Name color of word
designating color
Troyer, Leach, Strauss (2006), 13, 20-35
32Executive 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
33Executive 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)
34Executive 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
35Executive functions
36Executive 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
37Executive 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
38Executive 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 Stroop-like effects
39Executive 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 -
40Executive 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
41Executive 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
42Executive functions
- Stroop effect demonstration
- in this next slide I want you to name the ink
colours of the words as rapidly as possible
43Executive 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)
44Executive 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 word-colour
condition, the conflict monitor increases
executive attention
45Executive 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
46Executive functions
- Neuroimaging evidence
- Jonides and colleagues (2002) performed a
meta-analysis 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
47Executive 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
48Executive 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
49Executive 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)
50Executive 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
51Milner recency discrimination experiment
- Top panel shows stimuli used in expt
- Bottom panel shows that PFC participants were
impaired relative to other 2 groups on recency
discrimination test but not on recognition test
52Executive 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
53Executive 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
54Executive 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
55Executive 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
56Executive processes
- Memory for temporal order Self-ordered pointing
- Task of participant is to point to the a
different object on each card (one that hasnt
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
57Executive 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
58Executive 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)
59Executive 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.)
60Executive 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
61Executive 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
62Executive 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 mans voice and half in a
womans voice
63Executive 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 womans voice and decided which
voice matched the studied sentence
64Executive 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
65Glisky (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
66Executive 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
67Executive 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
68Executive 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
69Executive 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
70Executive 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)
71Sternberg, (1966,1967)
72Executive 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
73Executive 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
74Executive 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)
75Executive 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)
76Executive 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
77Executive 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
78Executive 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 -
79Executive 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
80Buckner et al. (2001)
- Typical pattern of activation during recall of
studied material blue, dorsolateral (BA 44/6)
green anterior frontal-polar (BA 10)
81Buckner 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
82Executive 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
83Buckner et al. (2001)
- Panel a. paradigm
- Expt in which activation of old versus new items
is compared
84Buckner 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)
85Buckner 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)
86Executive functions
- Spontaneous confabulations
- Individuals, who spontaneously confabulate have
also been used to investigate role of the frontal
lobes and executive function in memory - Spontaeous 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)
87ACoA
- 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
88Executive functions
- Spontaneous confabulations
- Gilboa et al. (2006) investigated spontaneous
confabulations - Participants were ACoA individuals who
confabulate, ACoA individuals who do not
confabulate, and controls
89Executive 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
90Executive 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) -
91Semantic narrative performance
- Top mean details produced
- Bottom proportion errors T total errors D
distortions E external details (other
stories) I idiosyncratic errors
92Executive functions
- Spontaneous confabulations
- Further analyses
- Only px with ventromedial prefrontal and
orbitofrontal cortical damage were spontaneous
confabulators
93Executive 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
94Executive 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
95Executive 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
96Executive functions
97Executive 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