Group of neural structures responsible for motivation and desire

The **reward system** (the mesocorticolimbic circuit) is a group of neural
structures responsible for  incentive salience  (i.e., "wanting"; desire or craving for a reward and
motivation),  associative learning  (primarily  positive reinforcement  and  classical conditioning
 ), and  positively-
valenced  "Valence \(psychology\)")  emotions
 , particularly ones involving  pleasure
 as a core component (e.g.,  joy  ,  euphoria  and  ecstasy
 "Ecstasy \(emotion\)") ).  [1]  [2]  Reward is the
attractive and motivational property of a stimulus that induces appetitive
behavior, also known as approach behavior, and consummatory behavior.  [1]  A
rewarding stimulus has been described as "any stimulus, object, event,
activity, or situation that has the potential to make us approach and consume
it is by definition a reward".  [1]  In  operant conditioning
 , rewarding stimuli
function as  positive reinforcers  ;  [3]  however, the converse statement also holds true: positive
reinforcers are rewarding.  [3]  [4]

Examples of primary rewards.  [3]  Clockwise from top left: water, food,
parental care, and sex.

Addiction and dependence glossary  [5]  [6]  [7]
---

* ** addiction  ** – a  biopsychosocial  disorder characterized by persistent use of drugs (including alcohol) despite substantial harm and adverse consequences
* ** addictive drug  ** – psychoactive substances that with repeated use are associated with significantly higher rates of substance use disorders, due in large part to the drug's effect on brain  reward systems
* ** dependence  ** – an adaptive state associated with a withdrawal syndrome upon cessation of repeated exposure to a stimulus (e.g., drug intake)
* ** drug sensitization  ** or **reverse tolerance** – the escalating effect of a drug resulting from repeated administration at a given dose
* ** drug withdrawal  ** – symptoms that occur upon cessation of repeated drug use
* ** physical dependence  ** – dependence that involves persistent physical–  somatic  withdrawal symptoms (e.g., fatigue and  delirium tremens  )
* ** psychological dependence  ** – dependence socially seen as being extremely mild compared to physical dependence (e.g., with enough willpower it could be overcome)
* ** reinforcing  stimuli ** – stimuli that increase the probability of repeating behaviors paired with them
* ** rewarding  stimuli ** – stimuli that the brain interprets as intrinsically positive and desirable or as something to approach
* ** sensitization  ** – an amplified response to a stimulus resulting from repeated exposure to it
* ** substance use disorder  ** – a condition in which the use of substances leads to clinically and functionally significant impairment or distress
* ** tolerance  ** – the diminishing effect of a drug resulting from repeated administration at a given dose

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The reward system motivates animals to approach stimuli or engage in behaviour
that increases fitness (sex, energy-dense foods, etc.). Survival for most
animal species depends upon maximizing contact with beneficial stimuli and
minimizing contact with harmful stimuli. Reward cognition serves to increase