Our memories make up so much of who we are, and the experiences we remember can craft our worldview in ways we hardly realize. Just as positive memories can help us grow and thrive, unpleasant memories can be part of a learning curve and have equally as profound effects. However, in some cases, these unpleasant memories can be truly traumatic and recalling them can lead to severe emotional distress and lifelong consequences. For years, scientists have explored the complications that riddle memory formation, and the study of traumatic memories in particular has attracted considerable attention and curiosity.
When traumatic memories linger and resurface, it is called intrusive reexperiencing of trauma, which is a core attribute of post-traumatic stress disorder (PTSD). Those who suffer from the disorder may unexpectedly recall a traumatic memory or feel as if they are revisiting the environment that produced the trauma. This effect can cause unbearable distress and lead to volatile and self-destructive behaviours, such as aggression and self-harm, as coping mechanisms.
Due to this, many scientists have started examining various methods for weakening negative memories. One such study published in 2014 by Harvard Medical School and McLean Hospital researchers examined a memory phenomenon known as reconsolidation, a process by which memories temporarily become susceptible to modification every time they are recalled. The researchers were particularly interested in the memory manipulation ability of Xenon gas. This gas is known to hinder receptors involved in memory formation and can affect the adaptive ability of synapses (links that allow neurons to “communicate”) in the amygdala and hippocampus – two areas of the brain associated with emotion and memory, respectively, which contribute to fear conditioning in PTSD. Due to the fact that these receptors are also involved in fear memory reconsolidation, the study examined whether Xenon administered after memory recall could affect subsequent fear-induced behaviour in rats, such as freezing when exposed to triggers. The study ultimately found that researchers could prevent the reconsolidation of negative memories in the brains of mice by administering Xenon gas after the memory was recalled. The broad principles learned from these studies eventually helped inform further scientific research into finding treatments for memory disorders in humans.
More recently, a team of scientists from five research institutions – Universidad Politécnica de Madrid, Universidad Complutense de Madrid, Reina Sofia–CIEN Foundation, New York University, and the Radboud University Medical Centre – took on the challenge of trying to weaken distressing memories in humans and reduce their psychological impact. Their research builds on existing evidence that recalling an established memory can allow it to become vulnerable to external manipulation within a short time window. Using this technique, they decided to work with a group of human participants and test an interference method involving an anesthetic known as propofol.
In the study, the scientists recruited 50 healthy participants, in whom they instilled unwanted memories by presenting two narrated slideshows featuring negative emotional content. To reactivate these negative memories, the researchers invited the participants back one week later and displayed the first slide from only one of the two presentations, asking them targeted questions about its content. Once the participants started recalling the unwanted memories associated with one of the presentations, the researchers anesthetized them with propofol to assess its potential in memory manipulation.
Twenty-four hours after the propofol injection, the participants took a test evaluating their recollection of the content of each of the two slideshows – both the one which they were prompted to remember before sedation and the one which they were not urged to recall. The team found that twenty-four hours after its administration, propofol had effectively weakened the emotional response associated with the fear memory they had recalled earlier that day.
While participants were still able to remember the negative content associated with the slideshow they were not asked to recall before the sedation, they could not properly recollect the unpleasant memory they had been asked to recall. The researchers speculate this reaction is due to the fact that activity in the amygdala may be extremely sensitive to the inhibitory properties of anesthesia. This is relevant to any further research on the application of propofol for the management of PTSD, as functional neuroimaging studies suggest that the amygdala is usually hyper-reactive in PTSD; this abnormality explains the hyperattention to threat, impaired emotion regulation, and persistence of fear memories that characterize this disorder.
Ultimately, the results of this study led the research team to conclude that sedation can, in some cases, help prevent the reconsolidation of traumatic memories in humans if delivered after reactivating these memories. The research suggests that after an individual learns to associate a certain trigger with a painful emotional reaction, the interference of anesthesia can break that association, effectively reducing the fear response and removing the emotional trauma associated with it. The team believes that they have found a successful method of weakening traumatic memories and reducing the psychological impact of the recurrent nightmares, distressing thoughts, and vivid flashbacks that often haunt those who suffer from PTSD.
Following the success of this study, researchers are now using its findings to inform further research about interfering with memory formation and recall. These studies can help with not only finding innovative treatments for PTSD, phobias, and other mental disorders, but they may also reveal new information about memory-related brain functions.
Moving forward with these scientific advancements, however, it important to understand that this future technology should not be applied to everyday bad experiences, and that these discoveries must be followed by a detailed discussion about the ethics of memory manipulation. Their use should only be considered in severe cases where the patient is suffering unbearable pain that interferes with their daily activities and has exhausted all other treatment options. According to Sheena Josselyn, a University of Toronto professor of physiology and psychology, the goal is not to sanitize life or keep people in a constant state of bliss, but rather to “make everyone a functional person, capable of moments of joy.”
By Raagavi Ramenthiran
Please note that opinions expressed are the author’s own. They do not necessarily reflect the views and values of The Blank Page.
