The study was published in the journal Neurobiology of Learning and Memory; it describes how, in a context of fear, our brain differently encodes contextual memory of a negative event (the place, what we saw…) and the emotional response associated.
The study measures electrodermal activity of eighty-six individuals in a fearful context generated in the laboratory and in a neutral context in which they have to learn a list of words. One week and two weeks after the experiment they were tested to see which words they remembered.
“In both contexts —explains Pau Packard, author of the study—, forgetting curve was normal. Over time, they forgot all the words, the explicit trace. Moreover, in the fearful context the electrodermal activity —the emotional implicit response— was exactly the same, much higher than in the neutral context”.
In traumatic events, it seems that, over time, there is a portion of memory that is erased or inaccesible; we forget the details but still maintaining the emotional reaction. The imprint is divided into two separate paths. According to Packard, “the brain dissociates the explicit memory of a negative event from the emotional response”.
This may help to understand why in pathological situations of post-traumatic stress disorders, the uncontrolled emotional response linked to the negative event is generated without knowing what causes it.
Lluís Fuentemilla, project coordinator, emphasises that “the study helps to explain how the processing of fearful memories can lead to post-traumatic stress disorder”. Furthermore, it opens the door to the investigation of new therapeutic strategies for these disorders because “the implicit memory trace in a fearful context does not loose over time and can be detected through electrodermal measures”.
Packard, P. A., Rodríguez Fornells, A., Stein, L. M., Nicolás, B., Fuentemilla, Ll. “Tracking explicit and implicit long-lasting traces of fearful memories in humans”. Neurobiology of Learning an Memory, September 2014. DOI: 10.1016/j.nlm.2014.09.004