Which brain chemical is most closely linked to the brain’s reward and motivation system?

Dopamine is a neurotransmitter that helps brain cells communicate and is especially important in reward processing, motivation, learning from feedback, and motor control. It is often called the brain’s “reward chemical,” though that is an oversimplification: dopamine is more about prediction, reinforcement, and wanting than simple pleasure. The loss of dopamine-producing neurons in the substantia nigra is a major feature of Parkinson’s disease, first described clinically by James Parkinson in 1817. Dopamine pathways also run through the mesolimbic and mesocortical circuits, which are heavily studied in addiction and decision-making. Because it affects both behavior and movement, dopamine is one of the most famous molecules in neuroscience.