Memory replay does not occur at a constant speed, but the changes were flexibly during recall, revealed study which is published in Nature Human Behaviour.
They quickly skip episodic blocks of information when recalling events in summary - for example, telling a friend about the plot of a movie they have seen, but can also delve into greater levels of detail at a slower speed when asked about a particular movie scene.
Experts at the Universities of Birmingham and Kent worked with a group of volunteers, who were asked to associate word-cues with a series of short videos, as the researchers investigated the flexible dynamics of episodic memory replay.
"On the other hand, if a friend asks you what the movie is about you would mentally skip between key scenes - omitting less important information - as you quickly summarise the action." "We may be able to design therapies that speed up the replay process to recall these memories in a less disturbing way."
Researchers studied a group of 24 participants in the video study, supplemented by 23 volunteers who took part in a further study enhanced by real-time, non-invasive brain scanning (magnetencephalography or MEG).
The tests used six-second video clips featuring three separate but coherent sequences of a single theme, such as a ship sailing followed by a diver jumping into water followed by an octopus floating in the water. Researchers found that participants in the study were able to flexibly skip between 'sub-events' during memory replay, demonstrating different levels of information compression.
The study links to earlier research carried out by Dr Hanslmayr and colleagues, which suggests that heavily traumatized people, such as refugees fleeing war, torture and natural catastrophes may not necessarily develop PTSD.
Dr Hanslmayr worked with a group of refugees - half suffering from PTSD, the others not - and asked them to suppress neutral memories. Results showed that participants who struggled to control these thoughts were more likely to show symptoms of PTSD.
This research raised the question of whether the ability to control memories protects against developing PTSD or if the condition causes an impairment in an individual's ability to control their memories.