The pathophysiology of attention deficit-hyperactivity disorder (ADHD) includes neurobiological deficits. Which of the following has been suggested as a pathologic basis for ADHD?

Decreased dopamine in the mesocortical pathway and increased dopamine in the mesolimbic pathway

Abnormalities of frontosubcortical pathways

Increased activity in the ventral tegmental area and the nucleus accumbens

Increased serotonin production in the raphe nucleus