Proof that it is possible to improve or delete memories

And if scientists could manipulate your brain in such a way that a traumatic memory loses its emotional power over your psyche? Steve Ramirez, a neuroscientist at Boston University fascinated by memory, believes that a small structure in the brain could be the key to future therapeutic techniques for treating depression, anxiety, and PTSD, thus allowing clinicians improve positive memories or remove negative ones.

In our brain, a cashew-like structure called the hippocampus stores the sensory and emotional information that makes up the memories, whether positive or negative. There are not two identical memories, and every memory we have is stored in a unique combination of brain cells containing all the environmental and emotional information associated with that memory. The hippocampus itself, although small, includes many different subregions all working in tandem to recall the elements of a specific memory.

Now, in a new paper in Current biologyRamirez and a team of collaborators have shown how flexible memory is if you know which regions of the hippocampus to stimulate – which might one day allow personalized treatment for people haunted by particularly troubling memories.

"Many psychiatric disorders, especially PTSD, are based on the idea that after a traumatic experience, the person can not change their life because they remember their fear again and again," says Briana Chen, first author of the newspaper. , currently a graduate researcher in depression at Columbia University.

In their study, Chen and Ramirez, the newspaper's lead author, show how traumatic memories, such as those that cause disorders such as PTSD, can become so emotionally charged. By artificially activating memory cells in the lower part of the hippocampus of the brain, negative memories can become even more debilitating. In contrast, stimulation of memory cells in the upper part of the hippocampus can erase the bad memories of their emotional courage, thus making them less traumatic to remember.

At least if you are a mouse.

Using a technique called optogenetics, Chen and Ramirez determined which hippocampal cells were activated when male mice created new memories of positive, neutral, and negative experiences. A positive experience, for example, could be exposure to a female mouse. On the other hand, a negative experience could give rise to a slight electric shock to the feet. Then, by identifying the cells that were part of the memory creation process (using a glowing green protein designed to literally illuminate when the cells are activated), they were then able to trigger artificially these specific memories later, laser. light to activate memory cells.

Their studies reveal how different the roles of the upper and lower parts of the hippocampus are. Activating the top of the hippocampus seems to work as an effective exposure therapy, alleviating the trauma of reliving bad memories. However, activation of the lower part of the hippocampus can result in lasting behavioral changes related to fear and anxiety, suggesting that this part of the brain might be too active when memories become so emotionally charged that they are debilitating.

According to Ramirez, this distinction is essential. He says it suggests that suppressing overactivity in the lower part of the hippocampus could potentially be used to treat post-traumatic stress disorder and anxiety. This could also be the key to improving cognitive skills, "like that of Limitless," he said, referring to the 2011 film starring Bradley Cooper, in which the main character takes special pills that dramatically improve his memory and his brain functions.

"The field of memory manipulation is still young … It sounds like science fiction, but this study is a foretaste of what we can artificially improve or remove memories," says Ramirez , professor at BU College of Assistant Professor of Arts and Sciences in Psychological and Cerebral Sciences. Although the study began while Chen and Ramirez were both doing research at the Massachusetts Institute of Technology, his data was the backbone of the first article published by Ramirez's new laboratory group at the BU in New York. 2017.

"We are far from being able to do it in man, but the proof of concept is there," said Chen. "As Steve likes to say," never say never, "nothing is impossible."

"This is the first step to tease those two [brain] the regions are dealing with these very emotional memories (…) The first step to translate that into people, which is the Holy Grail, "says researcher in memory, Sheena Josselyn, a neuroscientist at the University of Toronto who did not not participate in this study. "[Steve’s] The group is really unique in trying to see how the brain stores memories in order to help people … they do not just play, but they do it for a purpose. "

Although the brains of mice and human brains are very different, Ramirez, who is also a member of the Center for Systems Neuroscience and the Center for Memory and Brain (BU), explains that learning how these fundamentals manifest in the mouse helps his team to model the memory works in people. Being able to activate specific memories on demand, as well as areas of the brain involved in memory, allows researchers to see exactly what side effects occur when different areas of the brain are overexcited.

"Let's use what we learn in mice to predict how memory works in humans," he says. "If we can create a two-way street to compare how memory functions in the mouse and in humans, then we can ask specific questions [in mice] how and why memories can have positive or negative effects on psychological health. "