TThe way we live the present is largely influenced by our memories of the past. Some memories help us navigate the world around us, while others can make life more difficult and uncomfortable. Intrusive pathological memories contribute to anxiety disorders such as post-traumatic stress disorder, a disease triggered by trauma that affects nearly 8 million Americans. On Wednesday, researchers from Progress of science describes a unique new way of bypassing the underlying process.
Scientists have long believed that memories are fixed and this hypothesis has been an obstacle to the development of treatments for traumatic memories. However, the new study shows that reactivating an old memory can place it in an unstable state – and once in that state, it can be manipulated.
This manipulation took the form of propofol anesthetic. The team responsible for the study found that people who receive a dose of propofol after reactivation of a negative memory have difficulty recovering this memory 24 hours later. Although this study is an early exploration of this process, the results suggest that memory reactivation, combined with a routine anesthesia procedure, could provide an effective and non-invasive approach to mitigating traumatic memories.
The study included 50 healthy participants recruited from Clínico San Carlos Hospital in Madrid, each of whom participated in this study before undergoing an endoscopy planned in advance. Instead of exposing healthy participants to an anesthesia they did not need, the team decided to conduct the study on who had to take propofol anyway .
They used propofol because previous studies had shown that it was blocking the coding and recovery of emotional memory. Electroconvulsive therapy (ECT), a medical treatment used in patients with severe major depression, also uses anesthetic while the patient undergoes brief electrical stimulation of the brain.
The authors of the new study questioned whether the role played by anesthetic in electroshock was greater than previously suspected. ECT is known to disrupt the reconsolidation of emotional memory, a process in which memory becomes malleable for 24 hours after memory. It is possible, however, that the reconsolidation has been linked to the anesthetic.
To test this idea, the participant followed a process of "emotional memory coding". They watched slideshows of two stories in three parts evoking negative emotions. The first and third parts of the story were emotionally neutral, while the second was negative. The idea was that the second part would ignite the memories they wanted to get rid of.
One week after the coding session, all participants watched the first slide of both stories and reported what they remembered from the other slides. Immediately after the memory reactivation, they received a dose of propofol and underwent the planned endoscopy procedure. Because sedation was dependent on weight, age, and the patient's clinical condition, the prescribed doses of propofol were individualized for each participant.
A group was asked about his memories of the slide show at once after they left the recovery room, while the other group was interviewed 24 hours later. Scientists have found that those tested can immediately remember every part of the stories told. However, people tested 24 hours later had great difficulty in remembering the negative emotional media of slide shows – even though they could still remember neutral beginnings and ends.
Scientists say this suggests that propofol causes the resonance loss of the emotional aspects of memory during the process of memory reconsolidation. They speculate that the amygdala 's activity is' very sensitive to the inhibitory effects of anesthesia' and that the effects on the patients may be the result of an inhibition of the 'amygdala'. amygdala and hippocampus by propofol, as well as the connection between these two regions of the brain.
Additional tests are needed to know if these memories come back after 24 hours. One may also wonder whether the emotional memories encoded in truly stressful life experiences are rooted in the brain in the same way as the memories of this study. What is shown here is a proof of concept, however, which deserves to be deepened.
Adaptation of maladaptive thoughts and behaviors associated with emotional memories is essential to the treatment of psychiatric disorders. Recent research, mainly on laboratory animals, indicates that memories may become temporarily susceptible to modification after reactivation, before undergoing reconsolidation. A method of selectively preventing the reconsolidation of specific emotional or traumatic memories in humans could result in an effective treatment against conditions such as post-traumatic stress disorder. We tested whether deep sedation could alter the reconsolidation of emotional memory in 50 human participants. The administration of propofol by intravenous anesthetic after reactivation of the memory disrupted the memory for the reactivated slide show, but not for this one. Propofol altered the memory of the reactivated history 24 hours later, but not immediately after the recovery of propofol. Critically, memory disorders have appeared selectively for the emotionally negative phase of reactivated history. A dose of propofol subsequent to memory reactivation selectively altered the recovery of subsequent episodic emotional memory in a time-dependent manner consistent with an alteration of reconsolidation.