In the 2004 film “Eternal Sunshine of the Spotless Mind,” Joel (played by Jim Carrey) is in anguish over his breakup with Clementine (played by Kate Winslet) and vows to forget her. A group of doctors map neural patterns in his brain while he’s awake — the doctors then descend upon him as he sleeps. At Joel’s request, they erase memory after memory until his mind contains no trace of his lost lover.
Could this be our future?
According to a recent publication in Nature, it just might be. Scientists from the French National Center for Scientific Research (CNRS) and ESPCI ParisTech have succeeded at manipulating mice’s memories while they slept.
To achieve this science fiction-esque feat, researchers first placed one electrode in the mice’s hippocampus, a brain region associated with memory formation and spatial awareness, and another electrode in the mice’s reward center. One by one, the mice were placed in a new environment, a common experimental technique known as an open field test and permitted to explore as they pleased. While they perused the environment, the electrode in the hippocampus picked up activity in so-called “place cells.”
Place cells are specialized neurons that respond to where an animal is in the environment – for instance, one place cell might fire if an animal is exploring a specific bush and another might fire after the animal passes by a certain boulder. Scientists believe that place cells provide the brain with a map of the outside world and give humans and animals their sense of navigation. Based on where and when the place cells fired during the open field test, scientists were able to decode that map and determine which place cells were associated with which areas in the environment.
While the mice slept, the researchers used their knowledge of this map to their advantage. Prior studies have observed that during sleep, the hippocampus appears to “replay” newly acquired memories, spatial or otherwise, in a specific oscillatory pattern known as sharp wave ripples. Scientists theorize that the hippocampus converts short-term memories into long-term memories by reviewing each memory from the day before, a process known as consolidation. While the mice slept, various place cells within the hippocampus reactivated. Scientists artificially paired one of these place cells with the reward center so that every time the hippocampus replayed that specific memory during sleep, the reward center was also activated. This created for the mouse a strong connection between the spatial memory and a reward, such as food or sugar.
When the mice returned to the open field environment, they immediately moved to that area and looked for the promised reward.
Who could benefit?
This scientific team managed to successfully change a neutral memory into a positive one. Does this mean that memory alteration could be a future technology, not just for mice but for people? Can this technique eventually help people with post-traumatic stress disorder? It’s a tantalizing possibility, but scientists have a long way to go.
The researchers were able to identify specific memory traces in this study only because the memories were very recent – no one knows where humans store long-term memories. Changing a neutral memory into a positive one is also distinct from making a negative memory neutral or positive – would trying to “fix” the negative memory be akin to spraying a skunk with perfume? Lastly, implanting electrodes into the human brain is a risky procedure – it would be ideal if this technique could be performed without surgery.
Even though scientists have a lot to do before memory manipulation can become a therapeutic option, determining how the brain processes memories in the first place is essential. A greater understanding of how memories form, fade and shift could pave the way toward mitigating the harmful memories associated with post-traumatic stress disorder. Studies like this one bring us one step closer to treating diseases that severely impact the human brain.
Sovereign Health Group follows the development of cutting-edge techniques while using current, proven therapies to treat patients. Sovereign Health treats mental illnesses and drug addiction, and is also at the forefront of dual-diagnosis treatment. For further information, please contact 866-524-5504.
Written by Courtney Lopresti, Sovereign Health Group writer