Under the Hood

Memory Upgrade? Neuroscientists Successfully Turn Bad Memories Into Good Ones For Mice

Stimulating the brain's reward center may be key to forgetting bad, traumatic memories. jaeming/CC BY-NC-SA 2.0

Could humans soon be able to erase their bad memories? If the results of a recent mouse study from the French National Center for Scientific Research (CNRS) and ESPCI ParisTech are any indication, signs point to yes.

Memories become stable once they’re consolidated — and experts say memory consolidation takes place during sleep. In which case, neuroscientists monitored the brain activity of mice navigating a maze. When the mice were asleep later on, scientists placed electrodes on their hippocampus and reward center in order to manipulate the way mice consolidated maze information.

Specifically, scientists stimulated the reward center in order to create a positive association with certain areas of the maze. So they essentially took neutral information about the environment and associated it with something positive, such as food. Scientists knew they were successful when mice woke up and made a beeline for the now-positives areas of the maze.

"The learning we induced during sleep was just to change the emotional value of the different locations of the environments," Dr. Karim Benchenane, a neuroscientist at CNRS and one of the study's authors, told The Huffington Post. "Indeed, during waking hours, all the locations were neutral. What we made them learn during sleep is that a particular location is now associated to a reward."

The brain’s hippocampus forms, organizes, and stores memories, while the brain’s reward center controls responses to, well, awards, such as food, sex, and social interaction. When the center is activated, it indicates to an individual what they need to do in order to receive that reward again. Benchenane and her team find it interesting then it’s the reward center that changed the emotional value of memories, not necessarily the hippocampus. HuffPost reported this suggests the factual and emotional parts of memories are stored in different parts of the brain.

Obviously more research needs to be done, namely in humans, before scientists can say they can for sure turn neutral, even bad memories into positive ones. However, if they do, this will be especially major for individuals who’ve suffered a traumatic experience. Think of post-traumatic stress disorder.

"For humans, you would need a way to detect during sleep the periods during which the traumatic experiences are reactivated," Benchenane said. "It is likely that it will be soon possible to do so with fMRI."

It’s worth noting electrodes aren’t so easily placed in human brains, so “soon” doesn’t exactly translate to tomorrow. Nonetheless, Steve Ramirez, a neuroscientist at the Massachusetts Institute of Technology told HuffPo “the study gives us a fantastic and novel framework under which to work to achieve these kinds of treatment-related goals.”

Source: Benchenane K, et al. Explicit memory creation during sleep demonstrates a causal role of place cells in navigation. Nature Neuroscience. 2015.