The psychology and neurobiology of addiction: an incentive-sensitization view Terry E. Robinson & Kent C. Berridge Department of Psychology (Biopsychology Program), The University of Michigan, Ann Arbor, MI, USA Abstract The question of addiction specifically concerns (1) the process by which drug-taking behavior, in certain individuals, evolves into compulsive patterns of drug-seeking and drug-taking behavior that take place at the expense of most other activities and (2) the inability to cease drug-taking; the problem of relapse. In this paper current biopsychological views of addiction are critically evaluated in light of the "incentive-sensitization theory of addiction", which we first proposed in 1993, and new developments in research are incorporated. We argue that traditional negative reinforcement, positive reinforcement, and hedonic accounts of addiction are neither necessary nor sufficient to account for compulsive patterns of drug-seeking and drug-taking behavior. Four major tenets of the incentive-sensitization view are discussed. These are: (1) Potentially addictive drugs share the ability to produce long-lasting adaptations in neural systems. (2) The brain systems that are changed include those normally involved in the process of incentive motivation and reward. (3) The critical neuroadaptations for addiction render these brain reward systems hypersensitive ("sensitized") to drugs and drug-associated stimuli. (4) The brain systems that are sensitized do not mediate the pleasurable or euphoric effects of drugs (drug "liking"), but instead they mediate a subcomponent of reward we have termed incentive salience (drug "wanting"). We also discuss the role that mesolimbic dopamine systems play in reward, evidence that neural sensitization happens in humans, and the implications of incentive-sensitization for the development of therapies in the treatment of addiction. Introduction In thinking about the problem of addiction, and the development of animal models of addiction, it is important to remember that at some time many people experiment with a variety of potentially addictive drugs, but most do not become addicted. In other words, mere self-administration of a drug, by a human or by a non-human animal, is not tantamount to addiction. Indeed, the factors responsible for experimental or casual drug use may or may not be directly relevant to the problem of addiction. Drug-seeking and drug-taking in the addict may involve factors that are qualitatively different from those that motivate drug-taking in the non-addict. The question of addiction specifically concerns (a) the process by which drug-taking behavior, in certain individuals, evolves into compulsive patterns of drug-seeking and drug-taking behavior that take place at the expense of most other activities, and (b) the inability to cease drug-taking, that is, the problem of relapse. The purpose of this paper is to explore one view of the psychological and neurobiological mechanisms responsible specifically for theThe psychology and neurobiology of addiction: an incentive-sensitization view Terry E. Robinson & Kent C. Berridge Department of Psychology (Biopsychology Program), The University of Michigan, Ann Arbor, MI, USA Abstract The question of addiction specifically concerns (1) the process by which drug-taking behavior, in certain individuals, evolves into compulsive patterns of drug-seeking and drug-taking behavior that take place at the expense of most other activities and (2) the inability to cease drug-taking; the problem of relapse. In this paper current biopsychological views of addiction are critically evaluated in light of the "incentive-sensitization theory of addiction", which we first proposed in 1993, and new developments in research are incorporated. We argue that traditional negative reinforcement, positive reinforcement, and hedonic accounts of addiction are neither necessary nor sufficient to account for compulsive patterns of drug-seeking and drug-taking behavior. Four major tenets of the incentive-sensitization view are discussed. These are: (1) Potentially addictive drugs share the ability to produce long-lasting adaptations in neural systems. (2) The brain systems that are changed include those normally involved in the process of incentive motivation and reward. (3) The critical neuroadaptations for addiction render these brain reward systems hypersensitive ("sensitized") to drugs and drug-associated stimuli. (4) The brain systems that are sensitized do not mediate the pleasurable or euphoric effects of drugs (drug "liking"), but instead they mediate a subcomponent of reward we have termed incentive salience (drug "wanting"). We also discuss the role that mesolimbic dopamine systems play in reward, evidence that neural sensitization happens in humans, and the implications of incentive-sensitization for the development of therapies in the treatment of addiction. Introduction In thinking about the problem of addiction, and the development of animal models of addiction, it is important to remember that at some time many people experiment with a variety of potentially addictive drugs, but most do not become addicted. In other words, mere self-administration of a drug, by a human or by a non-human animal, is not tantamount to addiction. Indeed, the factors responsible for experimental or casual drug use may or may not be directly relevant to the problem of addiction. Drug-seeking and drug-taking in the addict may involve factors that are qualitatively different from those that motivate drug-taking in the non-addict. The question of addiction specifically concerns (a) the process by which drug-taking behavior, in certain individuals, evolves into compulsive patterns of drug-seeking and drug-taking behavior that take place at the expense of most other activities, and (b) the inability to cease drug-taking, that is, the problem of relapse. The purpose of this paper is to explore one view of the psychological and neurobiological mechanisms responsible specifically for the