Why Do Bad Memories Haunt Our Minds?

The norepinephrine receptor mutation

Having an excellent memory can be a blessing, but it can also be a curse. It's good to retain useful information, but it would be great if you could erase the memory of certain moments... The emotional memories helped us during our evolution: you had to remember where the lions haunted in the African savanna, but when a traumatic event appears to be too strong for you, it can ruin your life, by inducing the post-traumatic stress disorder.

A new research has found that people vulnerable to traumatic memories carry a mutation in a gene encoding for a neurotransmitter receptor. This increases their ability to recall emotionally charged events. This is the first gene found to be involved in emotional memory and the finding could have applications against anxiety and other psychiatric disorders.

For over 10 years, researchers have known that our brains' emotional memory circuits are controlled by the neurotransmitter norepinephrine. Higher amounts of it, discharged during the fight-or-flight response, can rise a person's ability to recall emotional events.

But as the clarity of emotional memories differs significantly from person to person, an European-African team checked if a common mutation in a specific norepinephrine receptor gene named ADRA2B could induce this.

The study was made on a pool of about 450 Swiss volunteers and 200 refugees of the Rwandan civil war. The Swiss volunteers were presented images varying from cuddly puppies to accident scenes. They had to rate the images as emotionally positive, negative, or neutral and mark the emotional strength. Ten minutes later, the volunteers were asked to describe the images.

The two groups had similar results for describing neutral photos, but for emotionally charged photos, those carrying the mutation were 34 % more "successful" than the common gene carriers.

The Rwandan subjects had similar results. The mutation's carriers were 50% more likely to recall with details traumatic events of their country's civil war and genocide than the noncarriers did. "The findings make sense. ADRA2B shuts off norepinephrine release when levels of the hormone rise, so people with a mutated, impaired gene would be expected to have higher norepinephrine levels and thus better recall of emotional events," said Dennis Charney, a psychiatrist at Mount Sinai Medical Center in New York City.

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