Scientists Selectively Erase Unwanted Memories in Rats and Mice

Memory can call up a range of emotions, facts and associations. Yet for recovering addicts and individuals suffering from post-traumatic stress disorders (PTSD), these memories may be unwanted and devastating. Now, scientists have discovered a way to selectively erase dangerous drug-associated memories without impacting more benign memories.

Former meth addicts report strong cravings that are triggered by associations with cigarettes, money or even gum. These associations can push a former addict back toward the drug that they so desperately want to stop taking. Yet this latest study could potentially help with this particular issue.

In order to learn how best to target and erase specific memories, the researchers worked with mice and rats. First, though, they had to learn exactly how a memory was produced. The structure of nerve cells alters via changes in the dendritic spines, which are small bulb-like structures that receive electrochemical signals from other neurons. Normally, these changes occur via actin, the protein that makes up the infrastructure of all cells.

In this study, the researchers inhibited actin polymerization, which is the creation of large chainlike molecules, by blocking a molecular motor called myosin II in the brains of mice and rats during the maintenance phase of methamphetamine-related memory function. The scientists then tested the animals and discovered that they persistently lost memories associated with methamphetamine with no other memories affected.

"Our memories make us who we are, but some of these memories can make life very difficult," said Courtney Miller, one of the researchers, in a news release. "Not unlike in the movie 'Eternal Sunshine of the Spotless Mind,' we're looking for strategies to selectively eliminate evidence of past experiences related to drug abuse or a traumatic event. Our study shows we can do just that in mice--wipe out deeply engrained drug-related memories without harming other memories."

Currently, researchers aren't quite sure why powerful methamphetamine-related memories are so fragile. Yet they believe that the findings could be related to the role of dopamine, a neurotransmitter involved in reward and pleasure centers in the brain. Dopamine has been known to modify dendritic spines and is released during both learning and drug withdrawal.

"We are focused on understanding what makes these memories different," said Miller in a news release. "The hope is that our strategies may be applicable to other harmful memories, such as those that perpetuate smoking or PTSD."

The findings are published in the journal Biological Psychiatry.