Review Session Thursday December 15th at 3:00pm

TH 173

Attention Deficit Hyperactivity Disorder (ADHD)

Background

Hallmark Symptoms- inattention, impulsivity & hyperactivity

Attention Deficit Hyperactivity Disorder (ADHD)-developmental disorder -3-7% of childhood population-2-5% of adult population-heritability 80%

ADHD previously known as:- Hyperactive Child Syndrome- Hyperkinetic Reaction of Childhood- Minimal Brain Dysfunction- Attention Deficit Disorder (with or without hyperactivity)

SymptomsInattention Hyperactivity/ImpulsivityFails 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 orinconsistent for developmental age

Quality of Life

ADHD associated with:

Low academic achievementSchool suspensionsPoor peer-family relationsAnxiety and depressionAggressionConduct problemsSubstance experimentation and abuseAccidents (especially driving)Difficulties in adult social relationshipsProblems in marriageDifficulty keeping employment

SubtypesPredominantly Inattentive

Predominantly Hyperactive-Impulsive

Combined Hyperactive-Impulsive and Inattentive

The majority of symptoms are inattentive although hyperactivity-impulsivity may still be present to some degree.

The majority of symptoms are hyperactive-impulsive althoughinattention may still be present to some degree.

Symptoms of inattention and hyperactivity-impulsivityMost prevalent subtype

TimeMullins et al. 2005 Time reproduction task-judge/replicate time intervals-Controls, ADHD Inattentive, ADHD Combined (Children)

Controls preformed significantly better thanboth ADHD groups at long intervals

No sub-type differencesin time reproduction

Time reproduction thought to be a measure of sustained attention

Motivation

Stop Signal Task under conditions of low or high incentiveNormal Control Group, ADHD group, Clinical Control Group (Children)

Slusarek et al. 2001

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 ADHDshould be regarded in a way that separates performancefrom ability.

Motivational and reinforcement deficits in ADHD

Interference

Anterior Cingulate Cortex (ACC)-stimulus selection when faced with competing information-response selection (facilitate correct; inhibit incorrect)

Bush et al. 1999Counting Stroop TaskUn-medicated ADHD adults and Controls

Hypothesis: ACC dysfunction might lead to inattention/impulsivity symptomsobserved in ADHD

ADHD: deficits in interference inhibition

InterferenceResults:

-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 DApathways may contribute ADHDpathophysiology

DA dysfunction particularly inthe striatum and PFC in ADHD

Pharmacological Treatments

Medications for ADHD enhance catecholamine (NE &/or/both DA) transmissionby 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 mostbut their neural effects not fully characterized

MedicationSustained 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

Administration of MPH resulted in significantly less errors of commission but not of omission

Commission Error: made an incorrect responseOmission Error: failed to make a correct response

(Johnson et al. 2008)

MedicationRubia 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

Congruent Trial Incongruent Trial

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Press Left Press Left

MedicationResults:

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!