Traumatic memories stem from a past fear and can recur over and over, leaving a person emotionally-loaded and wary, such as those who suffer from PTSD or similar psychological disorders.

Briana Chen, a graduate researcher studying depression at Columbia University, US, has explained that psychiatric disorders rooted in a really traumatic experience will prevent someone from moving on because of theall-consuming fear.

A new therapy may change psychological treatments by allowing medical experts to suppress negative memories and enhance positive ones instead. Steve Ramirez, a neuroscientist from Boston University’s(BU) Division of Psychological and Brain Sciences, US, has demonstrated the pliability of memory through stimulating select regions of the hippocampus – which could someday enable personalised treatment for people haunted their troubled past.

The highlight of the study was cashew-shaped hippocampus where sensory and emotional information of a memory is stored –each memory is distinct and many subregions are involved in the process. Optogenetics allowed the scientists to map out cells in the hippocampus as they were activated when male mice made new memories of positive, neutral, and negative experiences. A positive experience could be exposure to a female mouse, while a negative experience could be a startling but mild electrical zap to the feet. After identifying which cells were part of the memory-making process with a glowing protein, the scientists were able to artificially trigger those specific memories again with laser lights.

Artificially activating memory cells at the base of the hippocampus was observed to ruck up negative memories. In contrast, stimulating memory cells in the upper region of the hippocampus stripped bad memories of their emotional depth, making them less traumatic to remember.The top of the hippocampus seemed to function like exposure therapy, deadening the trauma of bad memories. But the bottom part of the hippocampus caused lasting fear and anxiety-related behavioural changes, so this part of the brain could be overactive when memories are emotionally-charged.

Even though human and mouse brains are significantly different, Ramirez has noted that understanding of on-demand memory activation will guide targeted brain stimulation and therapy – suppressing over activity in the bottom part of the hippocampus could be used to treat PTSD and anxiety disorders in people. It could also sharpen cognitive skills and brain function. This seemingly sci-fi idea was introduced in a 2011 film where its protagonist used brain-enhancing drugs.

Memory manipulation is still in its early development, but will change greatly if according to Ramirez: “We can address specific questions via a two-way path about how and why memories have positive/negative effects on psychological health.”