The idea that drug addiction is a result of “learning gone wild” was bolstered by several reports at SfN revealing profound, drug-induced changes in the same neural circuitry the brain applies to learn useful behaviors.

One emerging view is that repeated drug use jacks up the brain’s plasticity, the trait that underlies our ability to learn and remember. This repeated use produces distinct and persistent chemical and structural adaptations in the brain that make it exceedingly difficult to “unlearn” the bad habit of taking drugs—and far too easy to relapse.

“Addiction usurps the brain circuitry that normally regulates learning behaviors aimed at obtaining biological rewards” such as food or mating, said Peter Kalivas, a psychologist at the Medical University of South Carolina. In a special lecture Oct. 18, Kalivas outlined the case for addiction as a form of overlearning, or, put another way, as “a disease of too much neuroplasticity.”

A cardinal feature of addiction—whether the drug of choice is nicotine, alcohol, cocaine, or methamphetamine—is the inability to stop taking the drug, even when taking it has disastrous consequences. Animal models have enabled researchers to unravel the brain pathways involved in this “compulsive relapse” phase of drug dependence to an unprecedented degree, yielding new insights about the underlying pathology. These drug-induced changes in neural circuits are now the focus of therapeutic development aimed at recalibrating the system and returning to the drug user the ability to “just say no.”

“If we can understand the neurobiology of drug relapse, we may be able to intelligently design effective treatments for addiction,” said Kalivas. “The goal of therapy would be to push the compulsive drug user back to occasional social use or to abstinence.”