Executive
Function
Ref: Banich pp.366-376 (skim “Cognitive estimation”), pp. 380-382
Behaviour Involves "Control"
• Taking initiative
• Focusing a single task, ignoring distractions
• “Multi-tasking” (switching between tasks)
• Planning, organising behaviour towards goals
• Thinking and acting flexibly
• Reasoning, drawing inferences
These skills often referred to as “executive functions”
Prefrontal Cortex (PFC)
•
= frontal lobes excluding primary and secondary motor areas:
Prefrontal Cortex
Secondary Motor
Primary Motor
Cortex
Cortex
• Rich interconnections with other cortical/subcortical regions
Three Major Subdivisions
Dorsolateral
Prefrontal Cortex
Orbitomedial
Prefrontal Cortex
Anterior Cingulate
Three Major Subdivisions
1. Dorsolateral - key role in executive functions (today)
2. Anterior cingulate - evaluating one’s behaviour (Weds.)
3. Orbitomedial - emotional aspects of control (Thurs.)
Dorsolateral Prefrontal Cortex
Some functions discussed earlier:
•
Working memory
•
Memory for temporal order
•
Source memory
Working Memory
• Cells in dorsolateral PFC can sustain activity over short delays
• Different regions specialised for different types of information
e.g. verbal span - region anterior to Broca's area in left
hemisphere
Working memory may underlie many “executive functions”:
• goal-oriented behaviour involves keeping the goal in mind
• reasoning involves manipulating information “on line”
Other PFC Functions
However, other PFC functions may go beyond working memory:
1. Initiating new plans, activities (and knowing when to stop!)
2. Attending to one activity, filtering out others (“dynamic filtering”)
3. Task switching
4. Flexibility - suppressing habitual responses when inappropriate
1. Initiation, Cessation of Action
• P's with damage to dorsolateral PFC may exhibit
Psychological inertia:
Dr. P was a successful surgeon, who while undergoing a simple operation,
suffered a brief hypoxia. After the surgery, standard IQ tests revealed Dr. P's
intelligence to be, for the most part, in the superior range. Yet, he could not
handle many simple day-to-day activities... For example, his sister-in-law had to
tell him to change his clothes... He did not initiate any activities or ask questions
about his existence, being content to spend his free time watching television.
A waitress explaining why she had lost her job after frontal lobe surgery said,
"You have to have a "push" to wait on several tables at once, and I just didn't
have it any more"
1. Initiation, Cessation of Action
• Another common
feature of damage
to this region is
Perseveration:
Other PFC Functions
However, other PFC functions may go beyond working memory:
1. Initiating new plans, activities (and knowing when to stop!)
2. Attending to one activity, filtering out others (“dynamic filtering”)
3. Task switching
4. Flexibility - suppressing habitual responses when inappropriate
2. Dynamic Filtering
e.g. Stroop task:
• Give the name of the colour this word is written in:
Red
• Failed by P’s with dorsolateral PF lesions
2. Dynamic Filtering
Wisconsin Card Sorting Task:
Cards can be sorted on three dimensions:
i. colour
ii. shape
ii. number
P must sort on one dimension, ignore others
Other PFC Functions
However, other PFC functions may go beyond working memory:
1. Initiating new plans, activities (and knowing when to stop!)
2. Attending to one activity, filtering out others (“dynamic filtering”)
3. Task switching
4. Flexibility - suppressing habitual responses when inappropriate
3. Task Switching
Trail-Making Test:
A
End
D
4
2
Begin
B
1
C
3
Must switch between two types of sequencing
3. Task Switching
Wisconsin Card Sorting Task:
Following initial sort, P must change his/her sorting rule
Other PFC Functions
However, other PFC functions may go beyond working memory:
1. Initiating new plans, activities (and knowing when to stop!)
2. Attending to one activity, filtering out others (“dynamic filtering”)
3. Task switching
4. Flexibility - suppressing habitual responses when inappropriate
4. Flexibility/Inhibitory Control
• P’s with dorsolateral PFC damage may exhibit
Environmental dependency syndrome:
a) Utilisation behaviour
b) Imitative behaviour
a) Utilisation behaviour:
Professor Lhermitte would place a hammer, nail and
picture on a table in the entryway to his office. On
seeing this array of objects, the frontal lobe patient
might pick up the hammer and nail and hang the
picture on the wall.
4. Flexibility/Inhibitory Control
b) Imitative behaviour:
Lhermitte sat opposite a patient and, without
explanation, produced gestures. Some were innocuous:
folding paper, combing his hair, or tapping his leg.
Others were socially inappropriate: thumbing his
nose, chewing paper or kneeling in prayer. The
patients with frontal lobe lesions mimicked these
actions.
4. Flexibility/Inhibitory Control
P’s may also have problems with Cognitive Flexibility
Alternate uses test:
"Think of as many uses as you can for these objects"
e.g. brick, pencil, paper, clip, toothpick
Verbal Fluency:
“Say as many words as you can that start with ‘f’”
Executive Control: Issues
• Many "Frontal" tasks can be described in >1 way:
e.g. Wisconsin Card Sorting Task: dynamic filtering,
task switching or cognitive flexibility?
• Problem of circularity
• How can we describe what the frontal lobes do in a
way that is directly testable?
• Thursday - more on this issue