Chapter 13: Executive Function
Executive function is about guiding and coordinating perception, action, attention, long-term
memory, language, decision-making, and emotion in service to our plans and goals.
- It is cognitive control, emotional control, executive control, and even self-control.
- Problem: what are we trying to achieve, and how should we go about achieving it?
- Importance: To free us from the tyranny of the present, and act with regard to the future.
- Challenge: What to focus on, and when to switch?
Wisconsin Card Sorting Task (WCST): Participants were asked to sort cards into 4 different decks
(based on colour, pattern, etc); figure out what the rule is based on feedback. After awhile the rule
changes without indication.
- Working memory maintenance: Which rules have I already tried? (DLPFC)
- Working memory updating: remember that I just tried colour (BASAL GANGLIA)
- Inhibition of prepotent actions: Don’t sort by a rule that I’m used to using (DLPFC)
- Shifting between rules, sets, and tasks: Try each rule in turn until finding one that works (DLPFC)
- Monitoring and adjusting performance: Detect when a rule is no longer working & respond (ACC)
Brain basis of executive function: Prefrontal cortex
- With lesions to the prefrontal cortex, patients exhibit:
Perseveration - repetition of a particular response; in the WCST: stick to a rule when it is no
longer working. Failure of monitoring, updating, shifting
Impulsiveness - Inability to stay focused on the current task set; in the
WCST: jumping between rules in a disorganized way. Failure of maintenance,
Occulomotor delayed response task: performed by monkeys; single-cell recordings on neurons in the
dorsolateral prefrontal cortex (DLPFC)
- Fixated on a central point; were given a visual cue in another location in the frame. When the visual
cue dissapeared, monkeys were supposed to move their eyes to where the visual cue had been.
- Dorsolateral prefrontal cortex neurons are involved in
working memory maintenance:
Have delay period activity
Are directionally tuned
Firing lasts for duration of delay
Activity (firing or not firing) predicts memory
Damage to specific neurons impairs short-term
memory for corresponding locations
- Strong evidence that DLPFC neurons support maintenance of short-term memories for spatial
locations as sustained firing in delayed response tasks.
Stroop Effect: When colour words and ink colours conflict, colour words are much harder to ignore
than the ink colours.
- Easy/fast: read colour word (RED or GREEN) or ready colour word (RED or GREEN)
- Pretty easy/medium fast: name ink colour (XXXX or XXXXX)
- Hard/slow: Name ink colour (RED or GREEN)
- Why does this occur? More practice with word reading than colour naming; overcome by
inhibition of prepotent responses DLPFC is involved in inhibition of prepotent responses: Goal representations maintained in the
dorsolateral prefrontal cortex provide top-down biasing of perceptual motor-mappings.
Working memory provides the signal & inhibition is the effect.
Eriksen Flanker Task: Respond to the central letter