They have developed a technique that uses light to switch neurons inside the brain on and off.
Since the research is at the moment only conducted on mice, it is hard to confirm if the research can be replicated in humans. Yet experts confirm that the research will help draft effective therapies for people suffering from psychological disorders, like depression, anxiety and post-traumatic stress disorder.
"Imagine you can go in and find a particular traumatic memory and turn it off or change it somehow. That's still science fiction, but with this we're getting a lot closer to it," said David Moorman, Assistant Professor of Psychological and Brain Sciences at the University of Massachusetts.
MIT scientists started off by labeling neurons inside the brains of the mice being tested using a light sensitive protein.
Next, they used a technique called optogenetics, where they used light to switch the cells on and off. A pattern of neurons were then identified that turned on after a negative memory and a good memory.
Negative memories were created by giving the mice mild electric shocks on their feet, while positive memories were formed when the male mice spent time with the females.
Hence, the mice were first subjected to a negative memory via an electric shock and later left in the company of female mice, as the scientists used light to activate the memory of the shock. This led to the negative memory becoming milder.
Similarly some mice were first left in the company of female mice and later, while being subjected to electric shocks, the positive memory was slowly reduced using the same neuron activation method.
The scientists concluded that overall the mice froze more and sniffed less, which are usually behavior patterns associated with feeling fearful.
The Human Factor
The study's senior author and a professor of Biology and Neuroscience at MIT, Susumu Tonegawa, says the research provides a neurological basis for the psychotherapy, where patients are encouraged to replace good memories with negative memories, and hence, "reduce the feelings of a bad memory they have or stress they have had."
Joshua Johansen, a neuroscientist at Japan's Riken Institute, said the findings, "provide clues as to how we go about tackling things like anxiety disorder. If we can figure out how to associate bad experiences with neutral or pleasurable experiences, it could guide development of drugs, gene therapy or other treatments for mental illness."
The research study was published in the Nature journal on Wednesday (27 August) and be accessed here: Bidirectional switch of the valence associated with a hippocampal contextual memory engram