Review Session
Thursday December 15th at 3:00pm
TH 173
Attention Deficit Hyperactivity
Disorder (ADHD)
Background
Attention Deficit Hyperactivity Disorder (ADHD)
-developmental disorder
-3-7% of childhood population
-2-5% of adult population
-heritability 80%
Hallmark Symptoms
- inattention, impulsivity & hyperactivity
ADHD previously known as:
- Hyperactive Child Syndrome
- Hyperkinetic Reaction of Childhood
- Minimal Brain Dysfunction
- Attention Deficit Disorder (with or without hyperactivity)
Symptoms
Inattention
Hyperactivity/Impulsivity
Fails to give close attention to details
Fidgets with hands or feet or squirms
Has difficulty sustaining attention
Can’t remain seated when required
Does not seem to listen
Runs about when inappropriate
Does not follow through
Has difficulty keeping quiet
Has difficulty organizing tasks
Is always on the go or “driven by a motor”
Avoids tasks requiring sustained effort
Talks excessively
Loses things
Blurts out answers
Is distracted by extraneous stimuli
Has difficulty waiting turn
Is forgetful
Interrupts or intrudes
Symptoms need to be persistent for over 6 months and be maladaptive or
inconsistent for developmental age
Quality of Life
ADHD associated with:
Low academic achievement
School suspensions
Poor peer-family relations
Anxiety and depression
Aggression
Conduct problems
Substance experimentation and abuse
Accidents (especially driving)
Difficulties in adult social relationships
Problems in marriage
Difficulty keeping employment
Subtypes
Predominantly Inattentive
The majority of symptoms are inattentive although
hyperactivity-impulsivity may still be present to some degree.
Predominantly Hyperactive-Impulsive
The majority of symptoms are hyperactive-impulsive although
inattention may still be present to some degree.
Combined Hyperactive-Impulsive and Inattentive
Symptoms of inattention and hyperactivity-impulsivity
Most prevalent subtype
Time
Mullins et al. 2005
Time reproduction task
-judge/replicate time intervals
-Controls, ADHD Inattentive, ADHD Combined (Children)
Time reproduction thought
to be a measure of
sustained attention
Controls preformed
significantly better than
both ADHD groups at
long intervals
No sub-type differences
in time reproduction
Motivation
Motivational and reinforcement deficits in ADHD
Stop Signal Task under conditions of low or high incentive
Normal Control Group, ADHD group, Clinical Control Group (Children)
Low incentive: ADHD group
less likely to inhibit reaction
and longer SSRT
High Incentive: ADHD group
preformed the task just as
well as the other groups
Inhibition deficits in ADHD
should be regarded in a way
that separates performance
from ability.
Slusarek et al. 2001
Interference
ADHD: deficits in interference inhibition
Anterior Cingulate Cortex (ACC)
-stimulus selection when faced with competing information
-response selection (facilitate correct; inhibit incorrect)
Bush et al. 1999
Counting Stroop Task
Un-medicated ADHD adults and Controls
Hypothesis: ACC dysfunction might
lead to inattention/impulsivity symptoms
observed in ADHD
Interference
Results:
-the ADHD group, unlike controls, failed to activate the ACC during interference trials
-ADHD group using alternate networks
Conclusion:
Possible dysfunction of the ACC in ADHD
Prefrontal Cortex (PFC)
Functions:
-sustaining attention, inhibiting distraction, dividing attention, behavioural inhibition
Lesions:
- cause distractibility, forgetfulness, impulsivity and hyperactivity
PFC is highly sensitive to its
neurochemical environment
Genetic alterations to NE and DA
pathways may contribute ADHD
pathophysiology
DA dysfunction particularly in
the striatum and PFC in ADHD
Pharmacological Treatments
Medications for ADHD enhance catecholamine (NE &/or/both DA) transmission
by enhancing the release or inhibiting the reuptake of NE and/or DA
Why NE & DA?
-NE enhances signals
-DA decreases “noise”
Examples:
Methylphenidate (Ritalin)
Amphetamine (Adderall)
Dextroamphetamine (Dexedrine)
Medications are an effective treatment for most
but their neural effects not fully characterized
Medication
Sustained Attention to Response Task (SART)
-presented a sequence of numbers and were not to respond to the number 3
-Tested before and after 6 weeks of treatment with MPH
-ADHD children and Controls
Commission Error: made an incorrect response
Omission Error: failed to make a correct response
Administration of MPH resulted in significantly less errors of commission but not of omission
(Johnson et al. 2008)
Medication
Rubia et al. 2011
Simon Task
-measures interference inhibition and selective attention
-wanted to investigate the effects of a single does of MPH
-ADHD boys and controls on MPH or placebo
-Compared incongruent to congruent trials
Incongruent Trial
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Press Left
Press Left
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Congruent Trial
Medication
Results:
Significantly reduced activation in ADHD vs Controls in the placebo condition
In MPH condition, difference between groups no longer observed in frontal-striatal
network
Conclusion: MPH significantly normalizes frontal-striatal underfunctioning in ADHD
The End
Happy Last Class Day!