ABSTRACT
Introduction One of the most insidious characteristics of cocaine addiction is its chronic relapsing nature [1]. It is believed that various types of cues (paraphernalia, drug-associated odors and sounds, availability of cocaine, drug-use partners, etc) present
during cocaine self-administration become learned and increase the probability that relapse will occur when an abstinent user is confronted with these cues [1], [2]. However, the behavioral mechanism that underlies cue-induced relapse is poorly understood. Recent theories of the neural basis of addiction posit that habit formation is a necessary contributor [2]–[6]. Habits have been dened as automatic behaviors that are insensitive to manipulations of their consequences [7]. Given that cocaine addiction is associated with a high risk of relapse despite negative consequences of returning to drug use such as sickness, depression, or loss of employment [1], it is reasonable to hypothesize that cue-elicited relapse is a habitual behavior. An alternate hypothesis [8] suggests that cues elicit an expectation of drug which drives drug-seeking (a goal-directed action). Distinguishing between goal-directed and habitual responding can be accomplished by manipulation of the response outcome [7], cocaine. In animal research, either of two methods, satiation of the reward or pairing the reward with an unpleasant outcome such as sickness, reduce the reward’s “value” to the animal [7]. If either of these methods reduces the number of responses emitted in order to earn the reward in the devalued relative to the normal valued reward group, then the behavior is interpreted as a goal-directed action. In contrast, if there is no dierence between devalued and valued groups, the behavior is deemed a stimulus-bound habit.
