COGNITIVE NEUROSCIENCE OF ATTENTION-DEFICIT HYPERACTIVITY DISORDER AND HYPERKINETIC DISORDER

Currently, diagnoses of attention deficit hyperactivity disorder (ADHD ) and hyperkinetic disorder (HKD) are made on the basis of phenomenolo gy, but information is accumulating from the neurosciences about the b iological bases of these disorders. Recent studies addressing the neur opsychology, neuroanatomy, neurochemistry, and molecular biology of AD HD/HKD document abnormalities in well-defined neuroanatomical networks and neurochemical pathways. Magnetic resonance imaging (MRI) studies have shown that some regions of the frontal lobes (anterior superior a nd inferior) and basal ganglia (caudate nucleus and globus pallidus) a re about 10% smatter in ADHD groups than in control groups of children , and molecular genetic studies have shown that diagnosis of ADHD is a ssociated with polymorphisms in some dopamine genes (the dopamine D4 r eceptor gene and the dopamine transporter gene).