The psychomotor stimulant effects of cocaine and other drugs of abuse are related to increases in dopamine levels in the corpus striatum.20-22 Ventral domains of the striatum, particularly the shell region of the nucleus acumbens and the olfactory turbercle, play an important role in the rewarding effects of cocaine in rodents upon initial exposure to the drug.23,24 The core region of the nucleus accumbens appears to be important for the satiating effects of cocaine,25,26 and may also regulate the enhancement of drug seeking that is observed in the presence of response-contingent pavlovian cues.27,28 By contrast, the dorsal striatum does not appear to play a role in the motivational properties of cocaine or other addictive drugs, although cocaine and other drugs increase extracellular dopamine levels in this brain region.23,29 Instead, it seems that the dorsal striatum is ”recruited“ by repeated drug intake and contributes to the enhancement of drug-seeking induced response-contingent pavlovian cues after overtraining.30 Similarly, the dorsal striatum regulates habitual31 and punishmentresistant32 drug-seeking behaviors that emerge after extensive exposure to the drug. This suggests that ventral portions of the striatum
