A recent study has revealed that the bad experiences a person has can make him strongly remember the negative content itself, but only weakly remember the surrounding context in the brain.
Researchers revealed that the study has important implications for understanding conditions such as post-traumatic stress disorder.
Lead author Dr. James Bisby said when they presented people with negative content alongside neutral content, the brain areas involved in storing the negative content were more active while those involved in storing the surrounding context were less active.
He added that when a person experiences a new event they not only store the contents of the event in memory, but they also form associations with the context in which the event took place. The hippocampus is a crucial brain region for forming these associations so that all aspects of the event can be retrieved together and placed in the appropriate context.
The experiment involved 20 volunteers who were placed in an MRI scanner and shown pairs of pictures to remember. Some of these pictures involved negative content such as a badly injured person. Participants' memory was then tested by showing them images and asking if they had seen that image before. If they had, they were asked whether they could remember the other picture that it had been presented with.
Senior author Professor Neil Burgess said that the imbalance between item memory and associative memory could lead to strong but fragmented memory for the traumatic content of an event, without the surrounding information that would put it in the appropriate context.
He added people, who have suffered a traumatic event can experience vivid and distressing intrusive images from it, as in post-traumatic stress disorder. These intrusive images might occur due to strengthened memory for the negative aspects of the trauma that are not bound to the context it occurred in. This may be the mechanism behind flashbacks, where traumatic memories are involuntarily re-experienced as if they are happening in the present.
The study appears in the journal Social Cognitive and Affective Neuroscience.