The article discusses the mechanisms of action of addictive stimuli, focusing on the "incentive-sensitization" theory of addiction. This theory suggests that addictive drugs alter brain organization, particularly in systems involved in incentive motivation and reward. These changes make brain reward systems hypersensitive to drugs and drug-associated stimuli, leading to compulsive drug-seeking and drug-taking behaviors. The theory posits that these hypersensitive systems mediate "incentive salience" or "wanting," not the pleasurable or euphoric effects of drugs ("liking"). The theory is supported by evidence showing that repeated exposure to drugs of abuse can produce psychomotor sensitization, which is a complex and persistent phenomenon. This sensitization is influenced by environmental factors and associative learning. The expression of sensitization can be modulated by context, and neural sensitization can persist long after drug use has ceased, increasing the risk of relapse. Studies on drug reward indicate that the neural substrate involved in sensitization is also involved in mediating drug reward. This is supported by evidence showing that prior exposure to drugs enhances their rewarding effects and that sensitization-related neuroadaptations are associated with dopamine and accumbens-related circuitry. These neuroadaptations are thought to play a critical role in the development of addiction. The article also discusses the distinction between "wanting" and "liking" in the context of drug reward. It posits that the neural processes underlying "wanting" are different from those underlying "liking." Incentive salience attribution is the process that transforms stimuli into especially salient ones, leading to compulsive drug-seeking behavior. This process is mediated by different neural systems than those responsible for hedonic effects. The article concludes that the incentive-sensitization theory provides a framework for understanding the neural mechanisms underlying addiction. It suggests that the neural systems involved in incentive salience are the ones that become sensitized by addictive drugs, leading to compulsive drug-seeking and drug-taking behaviors. The theory also posits that individual differences in susceptibility to sensitization contribute to individual differences in susceptibility to addiction. Further research is needed to test the theory in humans, particularly in understanding the neural basis of sensitization in non-human animals and how it relates to addiction in humans.The article discusses the mechanisms of action of addictive stimuli, focusing on the "incentive-sensitization" theory of addiction. This theory suggests that addictive drugs alter brain organization, particularly in systems involved in incentive motivation and reward. These changes make brain reward systems hypersensitive to drugs and drug-associated stimuli, leading to compulsive drug-seeking and drug-taking behaviors. The theory posits that these hypersensitive systems mediate "incentive salience" or "wanting," not the pleasurable or euphoric effects of drugs ("liking"). The theory is supported by evidence showing that repeated exposure to drugs of abuse can produce psychomotor sensitization, which is a complex and persistent phenomenon. This sensitization is influenced by environmental factors and associative learning. The expression of sensitization can be modulated by context, and neural sensitization can persist long after drug use has ceased, increasing the risk of relapse. Studies on drug reward indicate that the neural substrate involved in sensitization is also involved in mediating drug reward. This is supported by evidence showing that prior exposure to drugs enhances their rewarding effects and that sensitization-related neuroadaptations are associated with dopamine and accumbens-related circuitry. These neuroadaptations are thought to play a critical role in the development of addiction. The article also discusses the distinction between "wanting" and "liking" in the context of drug reward. It posits that the neural processes underlying "wanting" are different from those underlying "liking." Incentive salience attribution is the process that transforms stimuli into especially salient ones, leading to compulsive drug-seeking behavior. This process is mediated by different neural systems than those responsible for hedonic effects. The article concludes that the incentive-sensitization theory provides a framework for understanding the neural mechanisms underlying addiction. It suggests that the neural systems involved in incentive salience are the ones that become sensitized by addictive drugs, leading to compulsive drug-seeking and drug-taking behaviors. The theory also posits that individual differences in susceptibility to sensitization contribute to individual differences in susceptibility to addiction. Further research is needed to test the theory in humans, particularly in understanding the neural basis of sensitization in non-human animals and how it relates to addiction in humans.