Scientists have isolated and erased selective memories formed during drug intoxication in mice and rats, leading researchers to consider the possible implications for drug addiction and psychiatric conditions.

The findings, published in the September 9th issue of Biological Psychiatry, offered the first report of successfully removing specific memories, in this case those formed in rodents addicted to methamphetamine, or meth. The results may lead to advances in the potential treatment of drug addiction and other conditions.

“If there is a way of selectively intervening and disrupting memories that might be formed as a result of association with drugs of abuse, for instance, that’s a very practical intervention,” said Dr. Matthew Wilson, Professor of Neuroscience at the Massachusetts Institute of Technology who was not affiliated with the study.

In the study, researchers led by Dr. Courtney Miller at the Scripps Research Institute delivered meth to rodents and trained them to link various cues to the drug’s effects. In one setting, the rodents were directly injected with meth while exposed to stimuli such as color and peppermint oil, while in another, the rodents were taught to inject themselves with meth by pressing a lever.

After training, the meth-addicted rodents were divided into two groups. Rodents in the first group were given a chemical that disrupted the storage of the memory formed during intoxication. Rodents in the second group did not receive the chemical.

When the drug stimuli were reintroduced to the rodents in each context, the animals that did not get the chemical – whose memories were presumably intact – responded to the cues. For example, they continued to press the lever that formerly delivered a meth injection, whereas the animals in the group that received the memory-erasing chemical had no response.

Animals in all groups kept other memories, such as those associated with food rewards, indicating that removal of the memories linked to the drug did not impact other types of memories.

However, the findings raise questions as to why these drug-related memories are different from other types of memories.
“One hypothesis is that these memories are very strong and alter the storage mechanisms the brain is using,” said Miller. “You have your typical memory but then you have this ‘super memory,’ whether it’s one for a traumatic event or whether it’s one for a drug of abuse.”
When asked about the ethical implications of the research, the team said they are focused on understanding the results before they can determine how they need to be controlled.

“I think that people would be largely in agreement that if it was used for the right applications it would be a very useful thing,” said Dr. Miller. “That’s one reason we’re studying it in the form of addiction.”