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Researchers at Universidad Politécnica de Madrid in Spain used propofol – the same surgical-grade sedative that Michael Jackson overdosed on, but at a low dose – to ‘reconsolidate’ traumatic memories in 50 volunteers. They found that the drug disrupted participants’ ability to remember the unpleasant film they’d been shown.
Propofol targets emotionally charged memories, but leave neutral ones intact, the new study reports. Trauma is exceptionally difficult to ‘treat,’ so the Spanish scientists hope that the already-approved drug might have promise to safely diffuse disruptive memories. Talk therapy has been the traditional treatment – and still is the predominant one – sometimes coupled with anti-anxiety drugs, but it isn’t always sufficient, and many therapists and scientists are exploring alternative treatments.
Among these is the sedative, ketamine, but scientists believe propofol, too, might work to diffuse traumatic memories. To test this theory, the Spanish team recruited 50 volunteers that were going to receive propofol to put them under anesthesia during gastrointestinal scope screening procedures any way.
They showed this group a narrated slide show of ‘aversive content’ – some sort of unpleasant images – before their procedures. The slide show had three phases, with the ’emotionally negative’ portion of the story falling in stage two.
Then, a week later, on the day of their procedures, they ‘reactivated’ these memories by showing the participants the first slides, and testing them to see if they could recall all three phases.
Triggering the memory this way is thought to sort of open it up for adjustment.
In other words, every time we recall a memory, it becomes a little less solid, and gets changed. After this reactivation, all of the patients were given propofol to ‘heavily sedate’ them for about 12 minutes for their procedures. Memory reconsolidation – the process by which memories get processed and encoded in the brain – is known to take about 24 hours, so the scientists tested one group’s recall immediately after they woke up from the propofol, and tested the other group 24 hours later.
The memories of people tested immediately after their propofol doses were intact.
The memories of people tested immediately after their propofol doses were intact.
But after 24 hours – when their memories had had a chance to reconsolidate – the other group couldn’t recall the emotional aspect of the slideshow they’d seen as well. Incredibly, they could still remember the emotionally neutral slides just as well, suggesting that propofol specifically targets emotional memory, not memory in general, at least at relatively low doses.
The scientists aren’t exactly sure why this is the case, but suspect it’s simply a happy accident of the way that propofol interacts with the brain.
The scientists aren’t exactly sure why this is the case, but suspect it’s simply a happy accident of the way that propofol interacts with the brain.
Prior research has shown that the drug has particularly significant effects on both the hippocampus and the amygdala.
The hippocampus is the key center for episodic memory in general, but it’s this regions interaction with the amygdala that creates emotionally-charged memories. The scientists were utterly surprised at the precision of propofol and suspect this will make it an even more exciting candidate for treating phobias and PTSD.
The hippocampus is the key center for episodic memory in general, but it’s this regions interaction with the amygdala that creates emotionally-charged memories. The scientists were utterly surprised at the precision of propofol and suspect this will make it an even more exciting candidate for treating phobias and PTSD.