Addiction: making the connection between behavioral changes and neuronal plasticity in specific pathways.

146 T here is an emerging consensus that drug addiction is a form of maladaptive learning. Drugs of abuse usurp the neuronal circuitry involved in motivation and reward, leading to aberrant engagement of learning processes. As a result, drug-associated cues can trigger craving and compulsive drug-seeking behavior, and voluntary control over drug use is lost. Abused drugs can also modulate long-term potentiation (LTP) and long-term depression (LTD) in neuronal circuits associated with the addiction process, suggesting a way for the behavioral consequences of drug-taking to become reinforced by learning mechanisms. This review will assess progress in correlating these effects on LTP and LTD with behavioral changes in animal models of addiction, particularly behavioral sensitization. The image evokes the alluring yet sinister nature of cocaine. By usurping neuronal pathways normally involved in motivated behavior, cocaine promotes "learning" of compulsive behavioral responses that underlie drug craving and addiction.