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 + + Press Left Press Left 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!