In a study conducted at Israel’s Weizmann Institute, researchers succeeded in shutting down a neuronal mechanism by which memories of fear are formed in the mouse brain. After the procedure, the mice resumed their earlier fearless behavior, “forgetting” they had previously been frightened.
“This research may one day help extinguish traumatic memories in humans – for example, in people with post-traumatic stress disorder (PTSD),” the researchers said in a statement.
According to lead researcher Dr. Ofer Yizhar, “the brain is good at creating new memories when these are associated with strong emotional experiences, such as intense pleasure or fear. That’s why it’s easier to remember things you care about, be they good or bad; but it’s also the reason that memories of traumatic experiences are often extremely long-lasting, predisposing people to PTSD.”
In the study, Yizhar’s team examined the communication between two brain regions: the amygdala and the prefrontal cortex. The amygdala plays a central role in controlling emotions, whereas the prefrontal cortex is mostly responsible for cognitive functions and storing long-term memories.
Previous studies suggested that the interactions between these two brain regions contribute to the formation and storage of averse memories, and that these interactions are compromised in PTSD; but the exact mechanisms behind these processes were unknown.
In the new study, the researchers first used a genetically-engineered virus to mark those amygdala neurons that communicate with the prefrontal cortex. Next, using another virus, they inserted a gene encoding a light-sensitive protein into these neurons. When they shone a light on the brain, only the neurons containing the light-sensitive proteins became activated.
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