Inside our brains, a cashew-shaped structure called the hippocampus stores the sensory and emotional information that makes up memories, both positive and negative. No two memories are exactly alike; each memory we have is stored inside a unique combination of brain cells that contain all the environmental and emotional information associated with that memory. The hippocampus itself, although small, comprises many different subregions working in tandem to recall the elements of a specific memory.<\/p>\n
In a new paper in Current Biology<\/i><\/a>, Ramirez, an assistant professor of psychological and brain sciences, and a team of collaborators have shown just how pliable memory is if you know which regions of the hippocampus to stimulate; their research could someday lead to personalized treatment for people haunted by particularly troubling memories.<\/p>\n \u201cMany psychiatric disorders, especially PTSD, are based on the idea that after there\u2019s a really traumatic experience, the person isn\u2019t able to move on because they recall their fear over and over again,\u201d says Briana Chen<\/a>, first author of the paper and a Columbia University graduate researcher studying depression.<\/p>\n In their study, Chen and Ramirez, the paper\u2019s corresponding author, show how traumatic memories\u2014such as those at the root of disorders like PTSD\u2014can become so emotionally loaded. By artificially activating memory cells in the bottom part of the brain\u2019s hippocampus, negative memories can become even more debilitating. In contrast, stimulating memory cells in the top part of the hippocampus can strip bad memories of their emotional oomph, making them less traumatic to remember.<\/p>\n Well, at least if you\u2019re a mouse.<\/p>\n Using a technique called optogenetics, Chen and Ramirez mapped out which cells in the hippocampus were being activated when male mice made new memories of positive, neutral, and negative experiences. A positive experience, for example, could be exposure to a female mouse. In contrast, a negative experience could be receiving a startling but mild electrical zap to the feet. Then, identifying which cells were part of the memory-making process (which they did with the help of a glowing green protein designed to light up when cells are activated), they were able to artificially trigger those specific memories again later, using laser light to activate the memory cells.<\/p>\n![\"This](\"\/cas\/files\/2019\/09\/ramirezembargo.jpg\")