A schematic showing how the NAc core and shell regulate aspects of impulsivity. Changes in the dopaminergic system that increase DA tone in the shell promote impulsive action. In contrast, changes in the dopaminergic system that decrease DA signaling in the core promote impulsive choice. DA, dopamine; D1 receptor, dopamine 1 receptor; D2 receptor, dopamine 2 receptor; DAT, dopamine transporter.