How the brain reacts to fear

Even if people forget the details of a traumatic event or what is called explicit memory, the emotions associated with that event also known as implicit memory may remain ingrained in the brain for a long time, says a new study.

In the context of fear, our brain differently encodes contextual memory of a negative event, such as the place, what we saw and the emotional response associated, the results found.

"The study helps explain how the processing of fearful memories can lead to post-traumatic stress disorder," said project coordinator LluAs Fuentemilla from the Bellvitge Biomedical Research Institute (IDIBELL) in Spain.

For the study, the researchers tracked the traces of implicit and explicit memories of fear in humans.

They measured electro-dermal activity of 86 individuals when a fear inducing situation was generated in the laboratory and in a neutral context in which they had to learn a list of words.

"In both contexts, the forgetting curve was normal. Over time they forgot all the words, the explicit trace," said Pau Packard, author of the study.

But in the context of fear, the electro-dermal activity in the emotional implicit response was exactly the same and much higher than in the neutral context," Packard added.

"Over time there is a portion of memory that is erased or we do not have access to, we forget the details but still maintain the emotional reaction. The imprint is divided into two separate paths", Packard said.

The study was published in the journal Neurobiology of Learning and Memory.