Certain brain circuits make particular stimuli and actions feel worth pursuing. Collectively called the reward system, these pathways evaluate the value of outcomes, motivate approach behavior, and reinforce the actions that produced the outcomes.

Core elements include dopamine neurons of the ventral tegmental area and substantia nigra, their projections to the nucleus accumbens and prefrontal cortex, and interconnected structures such as the amygdala and orbitofrontal cortex. Phasic dopamine signals report reward prediction errors, updating expectations and guiding learning. Other transmitters and peptides contribute to the hedonic “liking” component and to the effort willing to be expended.

Drugs of abuse artificially activate these circuits, producing strong reinforcement that can override natural rewards. Natural rewards—food, social contact, novelty—engage the same pathways under physiological conditions. Dysfunction contributes to addiction, depression, and motivational deficits. Mapping and modulating the reward system remains a central enterprise in both basic and translational neuroscience.

• Circuits mediating pleasure and reinforcement
• Centered on mesolimbic dopamine projections
• Signals prediction errors and motivates action
• Hijacked by addictive drugs