The Science website is reporting on a study that has found that people with a variant of the ADRA2B gene, which regulates the effect of key memory neurotransmitter norepinephrine, are more likely to have enhanced memory for emotional and traumatic events.
A strong emotional response at the time of an event is known to make the event more memorable, and the neurotransmitter norepinephrine, also known as noradrenaline, has been found to be a key player in this process.
The researchers, led by neuroscientist Prof Dominique de Quervain, wondered whether a version of the ADRA2B gene, that codes for the alpha-2b norepinephrine receptor, would influence emotional memory recall.
One of the defining features of post-traumatic stress disorder or PTSD is that distressing memories of the original trauma intrude into everyday life.
People differ in their tendency to remember emotional memories, so understanding the factors behind this difference might help us better understand why some people can survive trauma with little long-lasting disturbance, while others are seriously affected.
The team determined the genotype (gene version) of 435 young Swiss adults and 202 refugees from the Rwandan civil war.
The Swiss volunteers were shown a series of pictures from the International Affective Picture System, a series of photos that range from the pleasant (e.g. sunsets) to the disturbing (e.g. mutilated bodies) that have been rated for their emotional impact.
Participants with a common variant of the ADRA2B gene were more significantly more likely to recall the emotional, but not the neutral pictures.
The refugee participants were asked to recall memories from their time in Rwanda during the civil war.
Participants with the same gene variant that was linked to an increase in emotional picture recall in the Swiss participants, recalled significantly more traumatic incidents than others.
However, the rate of PTSD in the refugee sample did not depend on gene version.
This is possibly because a diagnosis of PTSD requires three things: intrusive traumatic memories, hyperarousal (a feeling of being ‘on edge’ all the time) and avoidance of the reminders of the trauma.
The gene variant was only linked to the likelihood of re-experiencing traumatic memories, and not the other symptoms, suggesting that the effect is specific to memory and not trauma in general.