The reward system refers to a tract of dopamine-containing neurons that are centrally involved in the experience of desire. The object of desire is not important. This is an all-purpose motivation machine that is active in drug craving (cocaine, methamphetamine, alcohol, and cigarettes) and in gambling, eating, and sex. It may be active as well in many other activities that elicit strong motivation and desire. The reward system is composed of the mesolimbic dopaminergic tracts, which reach from the ventral tegmental area in the midbrain to the nucleus accumbens in the forebrain.