Executive Control and the Prefrontal Cortex Notes

Contact Information

• Email: matt.roser@plymouth.ac.uk
• Office: PSQ B207
• Office Appointment Hours:
  • Tuesday: 10-11am
  • Thursday: 10-11am
• Check-in Code: XX-XX-XX
• Instructor: Dr. Matt Roser

Lecture 3: Part 2 - Executive Control and the Prefrontal Cortex

• Chapter 9 of Baars & Gage, "Fundamentals of Cognitive Neuroscience: A Beginner's Guide"
• Supplements:
  • Banich and Compton (2012). Cognitive Neuroscience (3rd ed.). Chapter 12.
  • Gazzaniga, Ivry, and Mangun (2009). Cognitive Neuroscience (3rd ed.). Chapter 13.

Learning Objectives

By the end of this lecture, you should be able to:

• Describe several executive control functions.
• Specify some subregions of the prefrontal cortex and their functions.
• Describe neuropsychological tests and task designs used to measure executive control.

Lecture Structure

• The prefrontal cortex (PFC)
• PFC and working memory
• Executive control and goal-directed behavior
• Emotions and decisions
• Paradigms for testing:
  • Working memory and set-shifting
  • Sensory attentional filtering
  • Impulse/response control and goal-directed behavior
  • Conflict resolution
  • Decision-making

Executive Functions

• Executive functions provide organization and order to our actions and behavior.
• Govern cognitive, linguistic, and motor domains.
• Involve prefrontal and subcortical loops.
• Include:
  • Representing and maintaining goals
  • Planning for the future
  • Inhibiting or delaying responding
  • Initiating behavior
  • Shifting between activities flexibly

The Prefrontal Cortex (PFC) Subregions

• Dorsolateral PFC (DL)
• Ventrolateral PFC (VL)
• Anterior pole (Ant)
• Ventromedial PFC (VM)

Brain Areas Related to PFC

• Lateral prefrontal cortex
• Ventromedial prefrontal cortex
• Premotor areas
• Primary motor area
• Posterior cingulate gyrus
• Anterior cingulate gyrus

Characteristics of PFC Neuroanatomy

• Late phylogenesis (evolutionary history)
• Late ontogenesis (developmental history)
• Highly interconnected with virtually all other brain areas (bilaterally)

PFC Damage

• Dorsolateral lesions lead to frontal executive syndrome
  • Problems in planning
  • Difficulty flexibly adapting to new situations
  • Withdrawal from social situations
• Ventromedial damage can lead to problems with emotional control
• Phineas Gage (1823-1861): Historic patient with ventral PFC damage

PFC and Working Memory

• Dorsolateral PFC lesions lead to stimulus-driven behavior.
• Disrupts working memory.
• Delayed-alternation task in humans and monkeys.
• Perseveration – repetition of response
• Environmental dependence syndrome exhibited by patients with frontal lobe damage.

Wisconsin Card Sorting Task

• Sorting rule changed during task.
• Learning rule requires WM.
• Lateral PFC patients perseverate with old rule (cognitive set).
• Sustained DLPFC activation over delay period in fMRI.
• Greater activity with greater WM demand.

Goal-Oriented Behavior

• Patients with frontal brain damage have problems with everyday life.
• Planning involves creating a hierarchy of goals and subgoals.
• Patients fixate on certain aspects and fail to consider others.
• Shifting focus – Task switching

Task Switching

• Intra- and extra-dimensional shifts
  • Individuals first taught to respond to one of two black shapes and to ignore the white shapes.
  • Intradimensional shift - discriminate between two new black shapes
  • Extradimensional shift - discriminate between the two white shapes
  • Greater deficit apparent in extradimensional shift (group x condition interaction)
  • Working memory allows information to be selected, maintained, and manipulated to support coherent goal-directed behaviour

Staying on Track

• How are interactions between frontally-mediated WM systems and posterior processing areas governed?
• As task difficulty increases, the Anterior Cingulate (AC) gyrus becomes increasingly active.

Anterior Cingulate (AC)

• The AC is involved in monitoring the environment, one‘s behaviour, and the relationship between the two.
• This keeps behaviour on track (goal-directed).
• Environment/Behaviour relationships may be encoded as ‘schemata’ and the AC may provide a top-down influence on the schema that is applied to a situation.
• The Error-Related Negativity (ERN)

Error Detection and Avoidance

• Detecting errors – the Error-Related Negativity
  • A negative component thought to be generated in AC
  • Occurs following error decisions
  • May aid learning
• Avoiding errors – AC activation is greater when people do tasks that elicit errors, such as the hard condition of the Stroop task, or with incompatible flankers
• Inhibiting habitual responses

Impulse Control

• Phineas Gage had problems with impulsive decisions.
• He also had problems with inappropriate emotions.
• These two aspects of mental life may be related and dependent on overlapping neural substrates.
• Damasio‘s somatic marker hypothesis
  • Bodily sensations may act as a heuristic guide to making decisions.
  • Emotions involve bodily sensations.
  • VM cortex is involved in emotions (provides inhibitory input into the amygdala).

vmPFC Damage

Lesions to vmPFC often result in:

• Reduced inhibition of affect – rude and hostile
• Deficits in reversal learning, (reverse learned response)
• Myopia for the future (impulsivity) - respond according to their momentary hedonic tendencies
• Impaired reward expectation/prediction – impaired long-term planning
• Impaired at maintaining a job and healthy social relationships despite their spared intellectual and mnemonic functions.

vmPFC and Decision Making

• VM patients lack skin-conductance response to emotive stimuli.
• Fail to learn aversion to a risky decision – Iowa Gambling task

Gradient of Control

• Posterior to anterior gradient of control Contextual Level (Koechlin & Summerfield, 2007)
  • Selection of processing alternatives based on sensory information, then the context in which that sensory information occurs, then the current episode or event, finally the context of prior episodes or events.
• Organisation of the frontal lobes for executive function
• Abstraction Level (Badre, 2008)
  • Posterior regions of prefrontal cortex implement control on the basis of more concrete dimensions, and that the representations used for selection become more abstract as one moves in an anterior direction
• Organisation of the frontal lobes for executive function

Summary: Executive Functions Involve

• Inhibition
• Planning
• Working memory
• Self-monitoring
• Response selection
• Motor control
• Regulation of emotion
• Motivation

Final Summary

• We reviewed a variety of paradigms where executive control is assessed (response inhibition, set-shifting, working memory) with patient studies, EEG/ERP, fMRI.
• The functions involve prefrontal cortex with some subregional variation (inhibition more ventral and maintenance/manipulation more lateral) and other brain structures.
• Taken together these functions allow for thinking, planning, reasoning, problem-solving, and goal-directed behavior.