That horror movie that you streamed in low quality last night might have looked more vivid to you than it would to others if you have a certain common genetic variation.

Participants in a recent study actually looked at arousing images of 1980s erotica and disturbing pictures of blood and gore for science. The study, published in the Journal of Neuroscience, found that people who had a common variation in the gene ADRA2b literally see more clearly images that invoke emotional reactions.

This gene variation was present in more than half of the 39 Canadians who participated in the experiment, which was inspired by previous work that showed people with the variation pay more attention to emotionally relevant things.

"We thought, if they pay more attention to emotionally relevant things and remember them better, maybe they do experience this emotionally enhanced vividness and maybe this is supported by different patterns of brain activity - and that's what we found," lead author Rebecca Todd of the University of British Columbia and her colleagues said in an interview. 

To compare how people with and without the variation saw emotionally relevant images, the researchers showed participants images that were positive, such as erotica; negative, such as snakes or gore; and neutral.

"We put visual noise on the image, like snow on an old television set," says Todd.

As the participants looked at the images, they rated how vivid they appeared while researchers monitored the activity in the brains using functional magnetic resonance imaging (fMRI).

"The emotionally enhanced vividness (EEV) effect is that people think that there's less snow on top of the image when it's emotionally relevant - the emotionally relevant thing is clearer underneath the static," says Todd. "And then what we found is that this effect is way stronger if you have this variant."

The gene ADRA2b affects a person's levels of the neurotransmitter norepinephrine, which is the brain's version of epinephrine, better known as adrenaline.

"It's really important in ramping up attention and arousal when something is emotionally relevant," Todd says. "It says, 'this is important, brain!' "

People with the variation analyzed in the study produce more norepinephrine than people without the genetic variation, and this difference likely accounts for the differences in the ways these people perceive emotional information. Better understanding differences like this one could improve treatments for PTSD and other forms of emotional trauma, according to Todd. 

"This is one piece of a body of evidence that suggests that there are huge individual differences in how people respond to emotionally relevant or stressful things," she says. "Knowing something about how these individual differences related to genes work, we can be more more effective at targeting treatment for a particular type of individual."

Todd notes, however, that the EEV variant appears to be more prevalent in some populations than others. A study that looked at the variant in a population of Swiss people, for example, found it in only about 30 percent of participants. Their work continues as they wrap up another study examining this concept in combat veterans with and without PTSD.

The Journal of Neuroscience article can be found here.

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