EXECUTIVE FUNCTIONS

Mental abilities that involve planning, controlling, and regulating the flow of information

processing. Essential for successful completion of goal-directed behavior and decision-

making.

PFC: the CEO, conductor, air-traffic controller metaphors.

Anatomy of Cognitive Control

1. Lateral PFC: selective attention, short-term memory, planning, action selection,

response inhibition

2. Ventromedial PFC (vmPFC) /orbitofrontal cortex (OFC): emotion and reward

processing, decision making.

3. Medial frontal cortex /Anterior cingulate cortex (ACC): error detection, resolving conflict, rational cognitive

functions.

Goal Oriented Behavior

Some of our actions are goal-oriented (working towards a goal) and require cognitive control.

Successful goal directed behavior involves:

• The creation and maintenance of a goal or plan

• Sequencing

• Maintaining relevant information in working memory

• Switching or shifting

• Selection of relevant information/Inhibition of irrelevant information

• Self-monitoring and evaluating

Planning

• Complex goals need to be translated into plans and strategies for action to be taken.

• To achieve a goal, planning needs to happen at multiple levels.

• Dorsolateral PFC is involved in goal planning. PFC damage is associated with Psychological Inertia,

characterized by difficulties in starting an action or behavior, and, once engaged in action, difficulties stopping it

(remember patient W.R., who consulted a neurologist because he “lost his ego.”)

Sequencing

• To choose the order in which actions are taken to best achieve the goal.

• Demonstrated by the Tower of London task.

• Dorsolateral PFC is also involved in sequencing.

Goal maintenance

• To maintain the current goal, and to resist distractions/interference. Involves selecting task relevant information

and/or filtering out the task-irrelevant information.

• Involves PFC. Patient with PFC damage wander off task.

Switching

• Ability to shift from one subgoal to another in an appropriate manner to achieve the overall goal; also involved in

multi-tasking, when attention is quickly shifting among multiple tasks.

• Trail-making task

• Wisconsin Card Sorting Task: subjects sort cards according to arbitrary rules, and rules change

frequently.

o Frontal lobe patients show perseveration—difficulty in adjusting responses when the rules

have changed and the original responses are no longer appropriate.

o Perseveration implies a lack of cognitive flexibility.

Selection of relevant information/Inhibition of irrelevant information

• Dorsolateral PFC regions may help in creating and maintaining an attentional set which identifies which

information is relevant to the task and filters-out task-irrelevant information

• Ventrolateral PFC regions: Inhibition

• Disruption in inhibitory control = inability to override inappropriate behaviors => can lead to perseveration

• Inhibition: Stroop task

• Go/No-Go task. Brain activity during successful 'no-go' trials is considered as an index of response

inhibition, and the proportion of errors on 'no-go' trials is considered a behavioral marker of

impulsivity.

• PFC regions are involved in inhibiting responses.

Goal Monitoring

Monitoring is necessary to ensure the success of goal directed behavior. Anterior cingulate cortex

(ACC) is critical for monitoring.

• Error detection hypothesis: ACC is involved in detecting errors, which serves to increase

cognitive control.

o The ERP component Error related potential (ERN) is generated by the ACC; it

shows up when people make an incorrect response.

o ERN amplitude is reduced in frontal lobe patients, but increased in patients with

obsessive-compulsive disorder.

• Response conflict hypothesis: ACC is involved in evaluating response conflict (encompassing

the higher-level attention and error detection functions).

o Supporting evidence: Stroop task. ACC activity is high for incongruent trials, even though people usually

do not make mistakes on these trials → ACC activity is modulated by monitoring demands.