Stimulating different parts of the brain can make up or down the emotional mass of a specific memory, shows the study – ScienceDaily

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What if scientists could manipulate your brain so that a traumatic memory would lose its emotional power on your psyche? Steve Ramirez, a neuroscientist at the University of Boston fascinated by memory, believes that a small structure in the brain could contain the keys to future therapeutic techniques for the treatment of depression, anxiety and PTSD, someday permitting doctors to improve positive memories or suppress negative ones.

Inside our brain, a cashew-shaped structure called the hippocampus stores the sensory and emotional information that make up memories, be they positive or negative. No two memories are exactly alike, and likewise, every memory we have is stored in a unique combination of brain cells that contain all the environmental and emotional information associated with that memory. The hippocampus itself, although small, includes many different sub-regions that work in tandem to recall the elements of a specific memory.

Now, in a new document in Current biology, Ramirez and a group of collaborators have shown how flexible the memory is if we know the regions of the hippocampus to be stimulated, which could one day allow a personalized treatment to people obsessed by particularly worrying memories.

"Many psychiatric disorders, particularly PTSD, are based on the idea that after a truly traumatic experience, the person is unable to go on because he remembers their fear over and over again," says Briana Chen. first author of the paper, who is currently a graduate researcher studying depression at Columbia University.

In their study, Chen and Ramirez, the senior author of the paper, show how traumatic memories – such as those at the root of ailments such as PTSD – can become so emotionally charged. By artificially activating the memory cells in the lower part of the hippocampus of the brain, negative memories can become even more debilitating. On the contrary, by stimulating memory cells in the upper part of the hippocampus it is possible to remove bad memories of their emotional energy, making them less traumatic to remember.

Well, at least if you're a mouse.

Using a technique called optogenetics, Chen and Ramirez mapped which cells of the hippocampus were activated when male mice made new memories of positive, neutral and negative experiences. A positive experience, for example, could be the exposure to a female mouse. On the contrary, a negative experience could receive an amazing electric zapping on the feet. Thus, by identifying which cells were part of the memory creation process (which they did with the help of a bright green protein designed to literally light up when the cells are activated), they were able to artificially activate those specific memories more later, using the laser light to activate the memory cells.

Their studies reveal how different the roles of the upper and lower parts of the hippocampus are. The activation of the upper part of the hippocampus seems to work as an effective exposure therapy, attenuating the trauma of reliving the bad memories. But the activation of the lower part of the hippocampus can impart a lasting fear and behavioral changes related to anxiety, suggesting that this part of the brain could be overactive when memories become so emotionally charged as to be debilitating.

That distinction, says Ramirez, is critical. He says he suggests suppressing hyperactivity in the lower part of the hippocampus could potentially be used to treat PTSD and anxiety disorders. It could also be the key to improving cognitive abilities, "like Limitless," he says, referring to the 2011 Bradley Cooper movie in which the main character takes special pills that dramatically improve his memory and brain function.

"The field of memory manipulation is still young … It sounds sci-fi, but this study is a preview of what will come in terms of our ability to artificially improve or suppress memories," says Ramirez, a BU College Arts & Sciences assistant professor of psychosis and brain 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 document that will be released by the new group of laboratories that Ramirez founded at BU in 2017.

"We are very far from being able to do it in humans, but the proof of the concept is here," says Chen. "Like Steve likes to say," never say never. & # 39; Nothing is impossible. "

"This is the first step to tease what these (brain) regions do to these truly emotional memories … The first step towards translating these people, which is the Holy Grail," says memory researcher Sheena Josselyn, a University of Toronto Neuroscientist who was not involved in this study. "(Steve's group) is really unique in trying to see how the brain stores memories with the goal of helping people … they're not just playing, but they are doing it for a purpose."

Although the brains of mice and the human brain are very different, Ramirez, who is also a member of the BU Center for Systems Neuroscience and the Center for Memory and the Brain, says that learning these basic principles in mice is helping his team drawing a project map of how 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 which side effects occur with different areas of the brain that are overstimulated.

"We use what we are learning in mice to make predictions about how memory works in humans," he says. "If we can create a two-way street to compare how memory works in mice and humans, then we can ask specific questions (in mice) about how and why memories can have positive or negative effects on psychological health."

This work was supported by an award for independence from the National Institutes of Health independence, by a young Grant investigator from the Brain and Behavior Research Foundation, a Ludwig Family Foundation Grant and the McKnight Foundation Memory and Cognitive Disorders.

. (tagsToTranslate) Nervous system; Psychological research; Brain tumor; Mental health research; Memory; Intelligence; Neuroscience; Brain damage

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