PSYC 301 Final - Dysfunction Associated with Psychiatric Disorders 4

ADHD and Executive Dysfunction

Describe the Tripartite Model of Executive Function

Proposes that executive function is composed of three interconnected + distinct components:

• working memory (updating)

• cognitive flexibility (shifting)

• inhibition control

What are the three core executive functions?

1. Working Memory

   • Holding and mental working with information “in mind” 

2. Inhibitory Control

   • Resting temptations

   • Not acting impulsively/prematurely

   • Overriding automatic behaviour 

3. Cognitive Control

   • Fluidly changing perspectives/approaches to solving a problem 

   • Adjusting to new demands

   • Switching between priorities or tasks

How can we test inhibitory control?

• Stroop Test

  • incongruent colour/visual info (ex. meaning and colour of text misaligned)

• Flanker Task

  • Correspond to middle stimuli with incongruent distractors surrounding

How can we test cognitive flexibility?

• Wisconsin Card Sort

  • look to see how quickly person can adapt changing rules + suppress old rules

• Trail Making w/alteration

  • switch between 2 different lists

What is involved in higher order executive function?

• Planning

• Organizing

• Multi-tasking

• Self-awareness

• Regulating emotions

• Inhibiting inappropriate behaviour

• Motivation

• Concentrating

What is the prefrontal cortex?

Non-motor parts of the frontal lobe

What are the symptoms of severe frontal lobe damage?

• Abulia: Lack of drive (motivation problem, not motor problem) 

  • Passive state (don’t eat/use bathroom/socialize)

• Return of primitive reflexes (“frontal release signs”) 

  • Ex. close palm when something placed on it 

• Utilization Behaviour 

  • Cant stop themselves from using objects (ex. If presented with a glasses, will wear even if the person has glasses on) 

  • Inability to inhibit behaviours even if they are inappropriate 

  • Severe, impacts life

What is orbitofrontal circuit dysfunction + where is it located?

Located at the bottom left + right sides of the prefrontal cortex

• Pattern of disinhibition (reduced ability to control impulses + actions)

• Socially inappropriate 

• Poor safety judgement 

• Difficulty evaluating anticipated rewards + punishments 

• Don't learn from mistakes due to diminished guilt and regret 

What is dorsolateral circuit dysfunction + where is it located?

From a lateral view, front middle of the prefrontal cortex

• Distractible 

• Disorganized

• Perseverative (repetitive nature on thoughts, “stuck” on topic. common in those with autism)

• Difficulty multitasking 

• Poor time management + prioritization

What are the major symptoms of ADHD + what are some diagnostic statistics?

Extreme inattention, hyperactivity, impulsivity 

• ~5-7% of children, ~2-3% of adults 

  • Younger children within a classroom = more likely to be diagnosed

  • Rapid rise in adult diagnosis 

  • Underdiagnosis of hyperactivity in girls

What is the neurobiology of ADHD?

• Reduced activity + volume of PFC

• Slower maturation of PFC 

  • Normal cortical thinning is slower

  • Correlated with hyperactivity/impulsivity

What is the dual-pathway model of ADHD?

• Executive circuit (dysfunction: inattention) 

  • dlPFC

• Reward circuit (dysfunction: lack of motivation) 

  • OFC , ACC, nucleus accumbens

Evidence of a hypoactive dopamine system!

What is the major treatment for ADHD?

Medications that act upon dopamine + norepinephrine systems in PFC and subcortical structures