Scientists reveal how psychostimulant drugs work to control hyperactivityPublished on February 8, 2012This article describes a 2012 study which has shed light on why stimulant medication paradoxically reduces motor activity. Stimulant medications work by increasing levels of dopamine in the brain. The researchers found that stimulating dopamine D4 receptors in the basal ganglia and thalamus (structures deep in the brain) decrease motor activity, explaining how the stimulant can have a calming effect.