The study by a team of researchers at the University of Montreal contradicts the theory that memories cannot be modified once they have been stored in the brain.
“Metyrapone is a drug that significantly decreases the levels of cortisol, a stress hormone that is involved in memory recall,” explains Marie-France Marin, leader of the study. Manipulating the levels of cortisol when new memories are formed in the brain may reduce the negative emotions associated with that memory.
“The results show that when we decrease stress hormone levels at the time of recall of a negative event, we can impair the memory for this negative event with a long-lasting effect,” said Dr. Sonia Lupien, a researcher who directed the study.
33 men took part in the study. They were told a story composed of neutral and negative events. Three days later, volunteers were divided into three groups: participants from the first group received a dose of metyrapone, those in the second group received a double dose, and the third were given placebo. They were then asked to recall the story they were told in the first day. The memory was tested 4 days later, once the drug was out of their bodies.
“We found that the men in the group who received two doses of metyrapone were impaired when retrieving the negative events of the story, while they showed no impairment recalling the neutral parts of the story. We were surprised that the decreased memory of negative information was still present once cortisol levels had returned to normal,” Marin explained.
The results of this research could offer hope to those who suffer from conditions such as posttraumatic stress disorder.
“Our findings may help people deal with traumatic events by offering them the opportunity to ‘write-over’ the emotional part of their memories during therapy,” Marin said.
One obstacle could be that metyrapone is no longer commercially produced. “Other drugs also decrease cortisol levels, and further studies with these compounds will enable us to gain a better understanding of the brain mechanisms involved in the modulation of negative memories,” the doctor concluded.