New Insights into the Pathogenesis and Pharmacogenomics of Attention Deficit Hyperactivity Disorder

performance of cognitive tasks. Reductions in volume have been observed in the total cerebral volume, the prefrontal cortex, the basal ganglia (striatum), the dorsal anterior cingulate cortex, the corpus callosum and the cerebellum. Hypoactivation of the dorsal anterior cingulate cortex, the frontal cortex and the basal ganglia have also been reported. Caudate volume is reduced in association with externalizing disorders of childhood/adolescence. Working memory deficits appear in familial high-risk offspring and those with externalizing disorders of childhood. There are specific white matter abnormalities in patients with ADHD. Different ADHD subtypes may have some overlapping microstructural damage, but they may also have unique microstructural abnormalities. ADHD-I is related to abnormalities in the temporo-occipital areas, while the combined subtype (ADHD-C) is related to abnormalities in the frontal-subcortical circuit, the frontolimbic pathway, and the temporo-occipital areas. An abnormality in the motor circuit may represent the main difference between the ADHD-I and ADHD-C subtypes [7].