WEDNESDAY, Jan. 18 (HealthDay News) -- Your emotional response to a disturbing image or traumatic event is weaker if you remain awake afterward, while sleep reinforces unpleasant emotional memories, according to new research.

The experiments involving 68 female and 38 male volunteers aged 18 to 30 also found that people who saw an unsettling image or traumatic event and then went to sleep are as upset as they originally were if they see the picture again or experience a flashback, but not those who stayed awake.

"We found that if you see something disturbing, let's say an accident scene, and then you have a flashback or you're asked to look at a picture of the same scene later, your emotional response is greatly reduced, that is, you'll find the scene far less upsetting, if you stayed awake after the original event than if you slept," Rebecca Spencer, a neuroscientist at the University of Massachusetts Amherst, said in a university news release.

"It's interesting to note that it is common to be sleep-deprived after witnessing a traumatic scene, almost as if your brain doesn't want to sleep on it," she added.

The study results may make sense from an evolutionary standpoint because this type of response would help our ancient ancestors survive by preserving negative emotions and memories of life-threatening situations, thus helping them avoid similar situations in the future, the researchers explained.

Spencer also said the "findings have significance for people with post-traumatic stress disorder, for example, or those asked to give eyewitness testimony in court cases."

The study appears in the current issue of the Journal of Neuroscience.

More information

The U.S. National Institute of Mental Health has more about post-traumatic stress disorder.