How the Brain Responds to Traumatic Events that Later Become Flashbacks

How the brain responds to a traumatic event predicts whether that event becomes a flashback.

Post-traumatic stress disorder (PTSD) symptoms include flashbacks (the re-experiencing of the trauma in the form of intrusive, involuntary memories). Bourne and colleagues (2013) emphasize that flashbacks range from transient sensory impressions to full-blown flashback, and not all traumatic memories become flashbacks:

“… a soldier may regularly experience traumatic scenes, such as of dead bodies or firefights. But these memories, despite being highly distressing, may never involuntarily intrude.  However, the moment when he witnessed a comrade’s arm being blown-off may repeatedly flash back.” (p. 1521).

So which moments become flashbacks? A new brain study (with a fMRI-design) by Bourne and colleagues (2013) prospectively examined the neural basis of flashbacks in 22 healthy participants.

The authors wondered if there were any differences in the way the brain processes traumatic experiences that later become flashbacks and those that do not.

The participants watched a film depicting traumatic events such as actual or threatened death or serious injury. Afterwards, they were given a diary, in which they were told to record flashbacks of the film during the next seven days.

The authors ensured that the flashbacks were analogue of PTSD flashbacks in that the participants were told to note only the flashbacks that were involuntary and had vivid sensory properties.

All participants had flashbacks after watching the potentially traumatic film scenes, with a mean of 6.82 flashbacks over a week. The study shows, at the time of encoding a film scene that later becomes a flashback, the brain becomes activated in regions that are involved in emotional processing, higher-level visual processing, mental imagery and threat.

These findings are consistent with the fact that flashbacks are highly emotional, visual memories of threatening situations.The authors suggest that a hypersensitivity in these brain regions may be a risk factor for the development of PTSD.

At last, they note that it may be possible to hinder flashback memory consolidation in the immediate aftermath of a trauma by, somehow, targeting the associated neural networks.

Image: Krystian Majewski