What if you could forget painful memories without damaging positive ones? Scientists at the The Scripps Research Institute in Florida have figured out how to selectively erase the memories of rodents–science which they hope can one day help drug addicts overcome their dependency and free soldiers from post-traumatic stress disorder.
“We stumbled across idea that very powerful memories–with drugs or trauma–may have their own unique storage mechanisms,” said Dr. Courtney Miller. “Once we understood what that storage mechanism was, we went in and inhibited process.”
First scientists had to create new memories in mice. They put the creatures in a lab setting that was unlike any other the mice had experienced: multi-colored, multi-scented (with vanilla and peppermint), and tactilely complex. Then the mice were give meth. Yes, meth. They were even given access to a lever that let them receive the drug at will.
After the mice got nice and high they were put in a neutral setting with a lever that did not dispense meth. Soon the mice learned that pressing the lever left them stone cold sober. But when they were put back in the high-sensory environment, (excuse the pun) they immediately ran to the lever. “It’s because they remembered the smell, feel, and look of the room to where they got meth,” says Miller.
The science behind dismantling a memory is obviously complicated, but here’s the brief version. We store our memories where neurons connect in the brain, specifically in structures called dendritic spines. These spines are made out of Lego-like building blocks calls actin. Memories are created when pieces of actin stack up, or polymerize, to create chains that enlarge the spines. When normal memories are stored, individual actins are thought to come off the top of the spine slowly and reattach at the bottom. This happens over and over in a self-renewing pattern, maintaining the memory.
The creation of powerful memories, like drug addiction, happens in the same way, only the storage is a bit different. The actins seem to come off and reattach much faster. The Scripps scientists administered a drug directly into the rodents’ brains, which had the effect of collecting the quickly moving actins and preventing them from reattaching at the bottom. This resulted in the breakdown of dendritic spines because they couldn’t be added to the bottom. Because the storage mechanism was disrupted, the memory was lost.
Obviously, doing meth is bad for you, but the memory of being high is often great. So how do scientists distinguish between positive and negative memories? Miller says that addiction memory is defined by its power, not qualitative emotions. “Most people don’t have memories that are as strong as an addict’s or PTSD, so my prediction is that you could give a drug like this to the average person and it wouldn’t do anything at all,” she says.
But she does acknowledge that if a person who was in the infatuation stage of a romantic relationship happened to take the memory blocking drug, they might lose interest in the object of their desire. On the flip side, such a drug could do wonders for the broken-hearted. At the moment, however, the Scripps team has a lot more research to do, including finding a way to administer the memory-blocking drug that doesn’t require a needle directly to the brain. Talk about a painful memory.