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ATTENTION DEFICIT
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Theories of ADHD Deficits not in information processing or in Perceiving information. Observed Deficits: –Motor Inhibition –Control –Anticipating Events
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Current Theoretical Focus Central Deficit of Disorder: –Failures of Inhibition The capacity to inhibit learned responses Creating or maintaining a delay in responding to an event. The capacity to fluidly interrupt ongoing responses due to performance feedback. The ability to delay or refrain from responding due to environmental cues.
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Secondary Effects? Impaired motivational or reward systems. (particularly evident in ADHD inattentive subtype) –Exhibition of a shorter and steeper delay of reinforcement gradient. –Preference of small, immediate reward vs. delayed gratification. –Greater frustration on a partial reinforcement schedule. –(Treatment: low dose stimulants)
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Proposed Etiology Reduced DA release in Nucleus Accumbens Decreased Cortical AcH function –Increase in Smoking in ADHD Increased Cortical Noradrenergic Function –Increase in symptomatology under conditions of stress. Alternative: Changes in Ach at level of brainstem may be altering DA and NE.
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Supporting Evidence Neuroimaging – anatomical changes in globus pallidus and frontal cortex Reduced striatal activity during performance of inhibition tasks. Reduced Noradrenergic activity, altered DA reuptake, changes in the D4 receptor. Genes: DAT1 and DRD4 – higher rates of the 7 repeat allele in DRD4.
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Questions: What is happening to NE regulation? Is ACH system dysfunctional? What is happening to ACH and NE receptors?
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