Neurophysiology of Drug Reward

Electrophysiological recordings conducted in animals during drug self-administration sessions show that individual neurons in the nucleus accumbens (NAcc), and interconnected regions exhibit phasic firing patterns in association with drug-directed behavior and drug-predictive cues. These firing patterns are similar to firing patterns previously documented to occur in relation to natural reward-directed behavior. However, the research has also led to the discovery of novel, sustained changes in neuron firing that occur during behavior directed toward natural and drug rewards. The firing patterns contribute to natural reward-behavior. In addition, the firing patterns, which are more prevalent during drug self-administration, can also reflect acute pharmacological drug actions. Finally, the studies have identified a number of lasting changes in NAcc firing that occur across repeated exposure to drug self-administration and which are not observed in animals with similar histories of self-administering natural rewards. The findings are relevant to understanding natural reward-directed behavior, drug-directed behavior, and drug addiction.