Executive processes Properties of executive processes –Executive processes coordinate mental activity so that a particular goal is achieved –They do this

Executive processesExecutive 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


• 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)


• 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


• 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 functionsExecutive functions

http://images.google.com/imgres?imgurl=http://upload.wikimedia.org/wikipedia/commons/thumb/9/9f/Brainlobes.svg/313px-Brainlobes.svg.png&imgrefurl=http://herthought.com/w/List_of_regions_in_the_human_brain&usg=__OfrDJVV0rmRQLU3B8NzbsbrRk0k=&h=286&w=313&sz=26&hl=en&start=5&sig2=fc18_ugbxbSE2StcCqIzAw&tbnid=t8-3b9fNtr9g0M:&tbnh=107&tbnw=117&ei=0lNqSfCVI4HWMcXOgZ4H&prev=/images%3Fq%3Dfrontal%2Blobe%26gbv%3D2%26ndsp%3D20%26hl%3Den%26sa%3DN


• Frontal lobe:– Major subdivisions of

prefrontal cortex: lateral prefrontal cortex, ventromedial prefrontal cortex, and anterior cingulate


• 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 figureKolb & Whishaw frontal lobe figure

• Lateral area 6 premotor cortex

• Medial area 6 supplementary motor cortex

• Area 8 frontal eye field


• 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


• 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


• 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

Baddeley’s working memory model

Central Executive

Visuo-spatialsketchpad

Phonologicalloop


• 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


• 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


• 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


• Illustration of n-back task

• Note, the need to maintain information in memory and manipulate it


• D’Esposito et al. (1998)– Meta-analysis– D’Esposito 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


• 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)


• 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)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


• 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)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


Stroop test• This test assesses the ability to maintain a goal and

ignore/suppress habitual (prepotent) responses


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)Stroop (slide 1)

red yellow bluered

green red yellow green

blue green red yellow

red green red yellow





red yellow bluered

green red yellow green

blue green red yellow

red green red yellow



colours of the colour patches as rapidly as possible



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

Executive functionsExecutive functionsAge 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)

Troyer, Leach, Strauss (2006), 13, 20-35

Dot time = name dot color; color word time = name word colorDT = Name color of dot; CWT = Name color of word designating color


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


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)


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”



• 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


• 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 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


• 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

•


• 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


• 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





• 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)


• 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


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


• 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


• 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


• 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


• 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)


• 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

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


• 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


• 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


• 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


• 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 cards with n objects depicted on it

– The same objects are present on each card but their order is scrambled from card to card


• 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


• 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


• 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”)


• 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.)


• 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


• 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


• 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


• 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


• 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)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 & 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


• 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


• 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


• 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”)

0

200

400

600

800

1000

1200

1400

3 4 5 6 7

Item

Order

Sternberg, (1966,1967)


• 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


• 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


• 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)


• 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)


• 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


• 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 functionsExecutive 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 functionsExecutive 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)Buckner et al. (2001)

• Typical pattern of activation during recall of studied material – blue, dorsolateral (BA 44/6); green anterior frontal-polar (BA 10)


• 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


Memory retrieval successEvidence 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 itemsResults 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


• Panel a. paradigm• Exp’t in which

activation of old versus new items is compared


• Panel b.• fMRI imaging show

differential activation of brain regions associated with retrieval of success; note left parietal cortex activation (green arrow)


• 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)


• 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)

ACoAACoA

• 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


• Spontaneous confabulations– Gilboa et al. (2006) investigated spontaneous

confabulations – Participants were ACoA individuals who

confabulate, ACoA individuals who do not confabulate, and controls

Executive functionsExecutive functionsSpontaneous 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 functionsExecutive 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 performanceSemantic narrative performance

• Top: mean details produced• Bottom: proportion errors –

T = total errors; D = distortions; E = external details (other stories); I = idiosyncratic errors


– Further analyses– Only px with ventromedial prefrontal and

orbitofrontal cortical damage were spontaneous confabulators


– 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


– 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



– 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)

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

Documents

Executive processes Properties of executive processes –Executive processes coordinate mental activity so that a particular goal is achieved –They do this