Reward system

The reward system is a set of interacting brain circuits that process motivation, reinforcement, and reward, shaping learning and goal-directed behavior.

Mesolimbic pathway: A dopamine pathway from the ventral tegmental area to limbic regions, especially the nucleus accumbens. It carries signals central to incentive motivation and reward learning.
Incentive salience: The motivational pull that makes a cue or object attractive and capable of prompting approach. It explains why reward cues can provoke pursuit beyond the pleasure they provide.
Addiction: A disorder marked by compulsive engagement with a substance or behavior despite harmful consequences. Repeated drug exposure can alter reward learning and strengthen cue-driven pursuit.
Hedonic hotspot: A brain region where activating particular opioid-sensitive circuits can intensify pleasure responses. It identifies localized mechanisms for pleasure rather than reward processing as a whole.
Dopamine hypothesis of reward: The proposal that dopamine contributes to reward, motivation, or learning, with its precise role debated. Evidence challenges the simple claim that dopamine directly encodes pleasure.
Nucleus accumbens: A forebrain structure involved in motivation, reinforcement, and integrating signals that guide behavior. It combines reward-related inputs to influence whether actions are pursued.
Hedonic tone: The pleasant or unpleasant quality of an experience. Pleasure is one component of reward, but it is not identical to motivation.
Drug reinforcement: The process by which a drug's effects increase the likelihood of behavior that obtains it. Many addictive drugs directly or indirectly engage circuits that reinforce drug-taking.
Opponent-process theory: A theory that emotional responses are followed by opposing processes that restore balance. It accounts for changing affect after rewards, unlike models focused on prediction learning.
Effort-based decision-making: The selection of actions by weighing expected outcomes against the effort required to obtain them. Reward signals must be integrated with effort, an unresolved part of motivated choice.

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