Cocaine addicts have trouble making judgments about rewarding and punishing behaviors, researchers at the University of Maryland School of Medicine found.
“There?s a misconception that addiction is just a problem with your personality or character or you just need to suck it up,” said Dr. Geoffrey Schoenbaum, assistant professor of anatomy and neurobiology and lead researcher on the study. “It?s clear to us now that in people who are addicted, the brain has really been altered in fundamental ways.”
As many as 1.5 million Americans have a cocaine problem, and 2.5 percent of American youth have used cocaine, according to National Institute on Drug Abuse, which funded this study. The drug, sold as a fine white powder or a smokeable granule, is highly addictive, requiring the user to take more and more to get high.
Schoenbaum?s study found rats addicted to cocaine that had been “clean” for several weeks had difficulty in testsof their ability to learn new cues about rewards and punishments.
The rats were given two different “odor cues,” one of which led to a reward of sucrose, while the other just got the rodent a dose of quinine ? the flavoring ingredient of tonic water.
Then they switched the cues.
“Normal rats switch their behavior pretty rapidly,” Schoenbaum said. But the addicted rats “are impaired at using information about regular consequences to adapt or modify their behavior.”
Studies have shown similar reaction in humans, he said, and are thought to reflect the poor decision-making that is characteristic of addiction.
The animal study, published online in the July journal Nature Neuroscience, strips moral and character values from the equation, Schoenbaum said.
The drug apparently damages signal pathways in the basolateral amygdala, deep within the temporal lobe, that is responsible for processing new information about the rat?s environment, according to the study.
Acting on their research, Shoenbaum?s team intentionally damaged this region and found the rats lost their confusion about which smell led to a reward.
“It?s clear that exposing rats to cocaine can cause fundamental deficits in adaptive decision-making,” Schoenbaum said. “These results are important in understanding how addictive drugs change the brain and also provide information that may lead to potential therapeutics agents for the treatment of addiction.”
