PSYC 170 - Summer 2013 - Professor Claffey

Notes: Executive Function

"forming and maintaining a task plan" (Duncan et al)
"regulate, control, and manage other cognitive processes" (Elliott 2003)

Concepts

Working memory
Conflict resolution & error detection
Impulse control & delayed reward
Rules
Prediction
Information manipulation

Prefrontal Cortex (PFC) Anatomy

PFC reaches largest relative size in _________________
Comprises ____ of the surface area of the human cortex

Key areas for this lecture
    Dorsolateral prefrontal cortex (DLPFC)
    Dorsomedial prefrontal cotex and anterior cingulate cortex (ACC)
    Ventrolateral prefrontal cortex, specifically the right inferior frontal gyrus (rIFG)

Lesions to PFC

Phineas Gage

Railroad worker in 1848
metal rod passed through PFC
became impulsive, rude, unreliable

Source: boeatau.wordpress.com

Patient A

39 year old stock broker: restrained, modest

had large bilateral frontal lobe resection to remove a tumor

became boastful, lacked restraint, inappropriate in conversation, unable to plan for future, supported by family

could: learn complex procedures, play expert checkers, communicate, recognize his own deficits

(Source: Brickner, as cited in Neuroscience (1999), ed. by Purves, P474)

Experimental Evidence

Do you agree that the described concept (e.g. working memory, conflict) that is being tested by the task?

Experiment: Delayed Response

Concept: ______________________________

Task

Cue - Subject is shown a choice to remember (for monkeys, the location of food)
Delay - Subject is shown nothing, has to remember location/choice
Response - Subject allowed to make choice

Results

Monkeys - electrodes in area *like* DLPFC are active throughout delay and at response
Humans - fMRI shows increased blood flow in DLPFC throughout delay and at response

Summary

Prefrontal areas are active during working memory maintenance

Experiment: Delayed Non-match to Sample

Concept: ______________________________

Task: Recognition (above right in diagram)

First, select any of 3 objects, move it aside, retrieve food from underneath
Second, choose between 2 objects, select the one that you DID pick last time
Requires: picking the object that you recognize, that feels familiar

Task: Monitoring (above left in diagram)

(same) First, select any of 3 objects, move it aside, retrieve food from underneath
Second, choose between 2 objects, select the one that you DIDN't pick last time
Requires: both objects are familiar, so remember which you picked and ______________________________

Results

DLPFC lesions affect/don't affect recognition, affect/don't affect monitoring

Summary

DLPFC is not necessarily saving information, but managing what is _________________/important (monitoring)

Experiment: N-back task

Concept: __working memory__
Online task

n back task

Task:

Letters are presented in sequence (can be auditory or visual)
In the 0-back condition, subject has to react when the letter matches a target (here, when the letter is "X")
In the 1-back condition, subject has to react when any letter matches the previous letter (1 back)
In the 2-back condition, subject has to react when any letter matches the letter 2 back
Requires rotating letters in memory and constant monitoring

Results

With increasing n (the number of letters to be remembered), there was increasing blood flow in the DLPFC

Summary

A complex working memory task not only activated the DLPFC,
but a more _________________ task produced _________________ activations

Experiment: Stroop Task

Concept: _________________

Source: http://scienceblogs.com/cognitivedaily/2007/07/05/the-stroop-effect-not-as-autom-2/

Task: _________________ version (easy)

Read aloud the words on the left

Task: _________________ version (hard)

Read aloud the words on the right (the words, not the ink color)

Results

People are slower to read the incongruent version
Incongruent version has greater activation in the _______________________

Summary

ACC may be involved in detecting conflicts

______________________________

Have subjects repeat many trials, they sometimes make errors
Average all the error trials together
Within fractions of a second of making an error, there is a signal
Signal is strongest over _________________ cortex

Summary

Dorsomedial PFC not only detects external _______________,
but internal conflicts like _________________

Theory

This is a hypothesis but isn't confirmed by data
ACC detects conflict, DLPFC boasts activity in brain areas responsible for the task to resolve conflict
this is called _________________ control

Experiment: Stop Signal Task

Concept: ______________________________

Task

On most trials, press space bar as quickly as possible after GO signal
On a few random trials, a STOP signal appears a split-second after GO signal
Subject has to try to stop the button press action they have just started

Results

Patients with damage to right inferior frontal gyrus (rIFG) have deficits
Patients with damage to left inferior frontal gyrus do not have deficits

Summary

rIFG may issue the command to inhibit actions / thoughts