New research from a team of American scientists indicates that doctors may one day be able to “turn off” or “turn down” memories that make future drug use much more likely to occur in addicted drug users.
Researchers and addiction specialists know that drug addiction is partially reinforced by strong urges, called cravings, which steeply increase the likelihood of additional drug use in the near or immediate future. Memories of previous drug use help drive the establishment of cravings. In a study published in March 2015 in The Journal of Neuroscience, researchers from four U.S. universities used laboratory experiments on rats to explore the possibility of sharply diminishing the strength of memories linked to prior drug use.
Drug Use, Addiction and Memory
Virtually all drugs of abuse produce much of their mind-altering effects by triggering a powerful sensation called euphoria in a brain area commonly known as the pleasure center. Underlying the onset of euphoria is a steep increase in the levels of a brain chemical called dopamine. When any person repeatedly consumes a drug of abuse, he or she can inadvertently alter the pleasure center’s long-term output of dopamine, and thereby set the stage for a physical dependence on the drug in question. In many cases, physical dependence directly leads to the uncontrolled and clearly life-destabilizing substance intake that characterizes full-blown drug addiction.
In addition to relying on dopamine for pleasure production, the brain partially relies on the same chemical for the complicated and interconnected processes of learning, memory formation and memory recall. When dopamine levels repeatedly rise inside the brain, an individual can unconsciously learn to expect the rewarding feelings associated with drug use. In turn, learned expectation for the pleasurable rewards of drug consumption can lead to the formation of memories tied to specific instances of drug intake, as well as to the formation of memories tied to the more general habit of drug intake.
Researchers and addiction specialists have long known that people dependent on drug use commonly develop strong cravings for additional use between active sessions of drug intake. These cravings essentially “tell” the brain that it’s time to consume more of the substance in question. In this manner, they sharply reinforce physical dependence/addiction and vastly increase the likelihood that excessive, damaging substance use will continue in the future. In 2013, the American Psychiatric Association officially designated the presence of cravings as a diagnosable symptom of substance use disorder, a mental health condition that encompasses both drug and alcohol addiction and non-addicted drug and alcohol abuse.
In a very real sense, drug cravings are the end product of the process of learned drug reward and the formation of drug-using memories. A dependent or addicted drug consumer tends to feel much stronger cravings when he or she is in an environment or situation linked to previous instances of drug intake. During drug treatment, the combined impact of learned drug reward, drug-related memories and drug cravings can easily lead to the onset of a relapse.
Turning Off Drug-Related Memories
In the study published in The Journal of Neuroscience, researchers from Oregon Health and Science University, the University of Wyoming and two branches of Washington State University sought to determine if it’s possible to “turn off” or “turn down” drug use-related memories, and thereby help reduce the urge to take more drugs in the present or in the future. During the project, the researchers repeatedly gave cocaine to a group of rats in a single setting in order to encourage the formation of specific drug-using memories. With every incidence of cocaine intake in the same setting, the memories associated with that setting grew stronger.
Next, the researchers separated the rats into two subgroups. In one of the subgroups, they surgically removed small structures in the brain that scientists believe play a critical role in the strength of the memories associated with any given situation or activity. When reintroduced into the previously established cocaine-using setting, the rats with the surgically altered memory structures displayed much less interest in returning to the scene of prior drug intake than their counterparts with fully intact memory structures.
The study’s authors don’t believe that the surgically altered rats forgot about their drug-using past. Instead, they believe that the rats no longer formed such intense memory associations with previous drug use. The authors feel that their findings lay the groundwork for the eventual development of new treatments that produce their benefits by selectively blunting the drug-related memories of people affected by addiction.