Erasing the worst and most traumatic memories of our life is something that until recently seemed to belong exclusively to the field of science fiction. However, more and more studies suggest that this possibility could one day become a reality. The latest research is signed by scientists from the Weizmann Institute of Sciences, in Israel, who have managed to erase memories linked to fear in mice .
According to this study, published recently in the journal Nature Neuroscience , the researchers were able to neutralize the neural mechanism by which fear-related memories are formed in the brains of the mice in their experiment. Once the procedure was completed, the rodents had forgotten the feeling of fear they had experienced and acted normally, with no signs of fear.
The objective of this study is to make findings that in the future can help human beings eradicate memories that have been traumatic for them – we can think, for example, in cases such as those of a person who has suffered some type of violence or a traffic accident -, and thus be able to alleviate the symptoms of fear and anxiety disorders.
“The brain is good at creating new memories when they are related to strong emotional experiences, such as intense pleasure or fear. For that reason, it is easier to remember things that matter to you, whether they are good or bad . But it is also the reason that memories of traumatic experiences are often very long-lasting and predispose individuals to PTSD (post-traumatic stress disorder), “explains Dr. Ofer Yizhar, lead author of the study.
In their research, this scientist and his colleagues examined in depth the communication that occurs between two brain regions : the amygdala – which plays an important role in controlling basic emotions, such as fear and anger – and the prefrontal cortex – primarily responsible for complex cognitive functions and long-term memory storage. In previous research, it had been suggested that the interactions between these two areas contribute to the acquisition and storage of bad memories, and that, therefore, these interactions would be related to post-traumatic stress disorder. However, how exactly these processes occurred was unknown.
Optogenetics, key
The researchers in this new study used a genetically modified virus to mark those neurons in the amygdala that communicate with the prefrontal cortex. Then, using another virus, a gene encoding a light-sensitive protein was inserted into these neurons. When a light shone in the brain, only the neurons that contained the light-sensitive proteins were activated. This type of manipulation, linked to the field of optogenetics –born from optics and genomics–, allowed Yizhar’s team to activate only those neurons in the amygdala that interact with the cortex and then develop a map of the cortical neurons that receive the stimulation of these light-sensitive neurons.
When they re-observed the behavior of the mice, they found that when they were exposed to stimuli that induced the appearance of fear, a powerful line of communication between the amygdala and the cortex was activated; and rodents that showed more this type of reaction were more likely to retain a memory of fear and were fearful when they heard again the sound that had previously accompanied the stimuli that induced fear.
Finally, to clarify how this line of communication contributes to the formation and permanence of memories, the researchers developed an innovative optogenetic technique to weaken the connection between the amygdala and the cortex, using a series of light pulses. And, once that connection was weakened, they found that the mice no longer showed fear when hearing the sound that they previously linked to the stimulus that had scared them .
