A new study, appearing in this week's issue of Nature Neuroscience, reports that those who carry a common variant of a gene called ADRA2B may have better recall of emotionally charged moments than those who lack the gene.
"This was a first proof of principle that we are able to identify genes [specifically] related to emotional memory," says the new paper's lead author Dominique de Quervain, a professor in the University of Zurich's Division of Psychiatry Research. "[This work] may have consequences for anxiety disorders where emotional memory plays a critical role."
From laboratory studies, this specific mutation of ADRA2B is known to cause the deletion of three amino acids in the protein that it encodes. This deletion disrupts the behavior of a receptor for the neurotransmitter noradrenaline, which is known to be involved in emotional memory.
According to the study's results, this receptor modification actually improves the recall of emotional memories.
After genotyping 435 young Swiss adults, de Quervain's team presented their subjects with 30 pictures in random order for four seconds each. Each scene fell into one of three emotional arousal categories: neutral (such as a secretary on the phone); positive (a grandfather playing with his grandchildren); or negative (a car accident involving a head wound). After viewing all the pictures, subjects had to write short descriptions of each scene.
Subjects with the gene variant—which is believed to be in 30 percent of the U.S. Caucasian population and 12 percent of African-Americans—could recall up to 80 percent of the emotionally arousing scenes. (Participants without the gene could only remember 40 percent of them.)
"If that deletion variant enhances emotional memories," in the context of an experiment, de Quervain says, "we thought maybe it also enhances very [real] emotional memories". The team then tested 202 refugees from the 1994 Rwandan civil war—133 who had been diagnosed with post-traumatic stress disorder (PTSD). Among this population, subjects with the gene variant reported (and reexperienced) more distressing wartime memories than those without the variant—regardless of PTSD status.
"Traumatic memory is one of the core features of PTSD," explains de Quervain. "The variant just predisposed to traumatic memory, but not to PTSD."
Going forward, de Quervain said that neuroimaging studies are necessary to determine where exactly the effect on the noradrenaline is taking place in the brain. (Odds are that the amygdala, which is the seat of emotional response to memory, has some involvement.) In addition, the team will continue to look for other genes that may be related to emotional memory. Once more novel genes are discovered, de Quervain says, researchers can begin to test for relevance to anxiety disorders like PTSD.