The attribution of incentive salience to a stimulus that signals an intravenous injection of cocaine.

A central premise of a number of theories of addiction is that discrete environmental stimuli repeatedly paired with drugs of abuse acquire incentive salience as a result of Pavlovian learning. There is, however, no unequivocal evidence supporting this assumption. Thus, we employed a Pavlovian conditioning procedure known to imbue non-drug reinforcers with incentive salience and extended it to study the effects of intravenous cocaine. Specifically, we examined whether a cue paired with intravenous cocaine administration would come to elicit approach towards it (sign-tracking), even if no behavioral response were required to receive the cue or drug. We found that when a cue was paired with intravenous cocaine delivery (but not when it was unpaired) rats came to approach and investigate the cue, and did so with increasing rapidity. We conclude that Pavlovian learning can imbue drug-paired cues with incentive salience, making them attractive and "wanted" stimuli. Delineating the neurobiological mechanisms responsible for this process will be important for understanding and treating drug addiction.