Some researchers have hypothesized that the risk for post-traumatic stress disorder (PTSD) depends on the capacity a person has to form strong memories, especially emotional memories. Now a team of Swiss scientists has found that a variant of the gene PRKCA, that encodes an enzyme involved in the formation of emotional memories, correlates with PTSD in Rwandan refugees. The scientists tested 700 healthy volunteers by showing them photos with highly charged emotional content and quizzing them about details of the photos. Volunteers with two copies of the A allele of PRKCA remembered the most detail, those with two copies of the G variant the least amount of detail, and heterozygotes, with one copy of the A variant and one of the G variant, fell somewhere in the middle. The researchers also studied the distribution of the A allele in a group of 347 survivors of the 1994 Rwandan genocide; 134 of them had been diagnosed with PTSD, although all 347 refugees had experienced traumatic events. Carriers of the A allele had a 2-fold increase in risk for PTSD. The A allele is more frequent in Europeans than in African people. Larger studies will be needed to determine which other genes and variants are involved in PTSD; however, this finding is in itself very interesting because it confirms the hypothesis that increased emotional arousal can lead to the formation of stronger memories and to increased PTSD risk.
Dominique de Quervain of the University of Basel in Switzerland and his colleagues recruited around 700 healthy young volunteers, obtaining DNA samples from them to analyse the sequence of their PRKCA gene. This gene is one of many known to be involved in the formation of emotional memories, and encodes an enzyme called protein kinase C-α. The researchers then showed the participants a series of emotionally affecting photographs and shortly afterwards asked them to write down short descriptions of the images.
Participants carrying two copies of one variant within the PRKCA gene, dubbed the A allele, remembered the most details about the pictures. Those carrying two copies of the other variant — the G allele — remembered the least, with the performance of those carrying one copy of each variant lying somewhere in the middle.
The researchers then asked 394 additional participants to perform the same task while undergoing brain imaging. This confirmed that variations in PKRCA are linked to the capacity for emotional memory, and further revealed that they were also associated with differences in brain activity during memory encoding.
The task activated a large network of brain regions, including the hippocampus and amygdala, two structures in the medial temporal lobe that are known to be involved in memory formation and emotion, respectively. The brain scans also showed that the A allele was associated with increased activity in the lateral and medial prefrontal cortex, regions that belong to a network involved in the encoding of emotional memories.
Again, the increased activity in these areas was associated with the number of copies of the A allele carried by individuals — people with two copies showed a larger increase in activity than those with just one.
Read the rest here.
So if you're a "cold" bastard you can forget the trauma?
Let's rephrase this as: if you are not that good at saving in your memory the details of emotionally charged scenes, you may avoid PTSD more easily than if you're really good at storing the details. The relationship between the AA genotype and PTSD is not that everyone with AA get PTSD and the rest avoid it, but that if you are have the A allele, your risk for developing PTSD if twice as high than if you don't. Biology: it's complicated.
It's interesting how the mind works. When we buried my mother, I could not for the life of me remember the number on the location of her tomb. I still can't. My sister, on the other hand, can. I tend to erase the details of negative events, I think.
A couple of months ago I read an article that said people with good memories are more susceptible to PTSD. I don't think it had anything to do with this study though. It might have had to do with sleep. If memories are locked in by a good nights sleep, would it be better to stay awake after a traumatic event?