Scientists replace bad memories in mice
In a study using light therapy, scientists at M.I.T. have been able to rewire the brains of mice and change bad, scary memories into happy ones. Experts say this development offers promise for how PTSD and depression in humans could be treated.
In the study, researchers looked at neurons in the parts of the brain called the hippocampus, which is where memories get their context, such as time and place, and the amygdala, where memories get their emotional imprint, such as fear. As the genetically engineered mice experienced fearful or pleasant memories, a light-sensitive protein was stimulated in the neurons that encoded the new memories. That enabled the researchers to tag those neurons, and later use light to reactivate the memory those brain cells held.
When the researchers activated the neurons in the hippocampus, it evoked the "where" part of the memory, while new events the mouse was experiencing rewrote the emotional part of the memory in the amygdala. This led to a new memory of a place but with a different, happier emotional association.
The researchers were able to confirm that the memories were actually changed after manipulating them by looking at the cells under a microscope. This confirmed that the connection between the two brain regions is able to be manipulated or changed.
By identifying the circuit through which memories are formed and then changing the emotional impact of those memories, the research opens up the possibility of one day using drugs to have the same effect in humans.