A new type of therapy that helps “delete” distressing and fear-based memories may have tremendous potential for treating long-time sufferers of post-traumatic stress disorder (PTSD), a group of patients for whom curative and palliative care has traditionally been very limited, Massachusetts Institute of Technology (MIT) researchers said on Thursday.
Dr. Li-Huei Tsai, MIT principal investigator and senior author of the study published in Cell, said in a press release that the findings stand to dramatically improve exposure-based psychotherapy, the current mainstay of PTSD care. Essentially, the new treatment makes the brain more receptive to the type of “memory cleansing” that psychotherapy is designed to induce. It works by suppressing a gene called HDAC2.
"By inhibiting HDAC2 activity, we can drive dramatic structural changes in the brain,” Tsai explained. “What happens is the brain becomes more plastic, more capable of forming very strong new memories that will override the old fearful memories."
In case you didn’t do graduate work in neuroscience or psychology: A more “plastic” brain doesn’t really have anything to do with texture or material but rather its ability to grow and form new neuronal connections. Scientists refer to this quality as “neuroplasticity.” In psychotherapy, where a therapist tries to help the PTSD victim by triggering the traumatic memory in a safe environment, the degree of plasticity is closely related to efficacy of the treatment, as it more or less determines the brain’s malleability.
Sometimes, a patient’s mental malleability is on point, and the traumatic memory can be subdued with the help of a therapist. But with combat veterans, abused children, and other patients for whom the traumatic memory is older and more remote, it is not always that simple, as the fear may have become a fundamental part of the psyche itself. What the current findings show is that these deeply rooted fears can be “loosened” with the help of HDAC2 inhibitors.
Learning and Unlearning
For the study, Tsai and her colleagues conditioned a group of lab mice to fear a certain chamber by administering a mild foot shock whenever they entered it. Soon enough, none of the mice wanted anything to do with the chamber. The team then tried to remove this fear through exposure-based psychotherapy — which, in this case, meant placing the mice in the chamber without administering the shock.
This low-brow simulation of PTSD therapy worked fine when the mice’s memories had been formed within 24 hours of the intervention. After a while, the traumatic memory was “deleted,” and the mice were able to go about their business as usual. But when the team attempted to do the same with mice who had formed the memory 30 days earlier, the trauma appeared to persist in each subject’s brain.
Here’s where the new HDAC2 inhibitors come in. By administering these drugs throughout the therapy session, the team was able to extinguish month-old memories as easy as day-old trauma. "If you do something within this window of time, then you have the possibility of modifying the memory or forming a new trace of memory that actually instructs the animal that this is not such a dangerous place," Tsai explained. "However, the older the memory is, the harder it is to really change that memory."
For people living PTSD, this is great news. But does it mean that we’re entering an era in which physicians, psychologists, and researchers will be able to cherry-pick our minds and erase all unwanted memories? Will it be like that movie where Jim Carrey swears off women and scraps the memory of Kate Winslet, only to run into her on a train and start the whole thing all over again?
In an email to Medical Daily, Tsai explained that the new therapy is not really a way to delete past experiences altogether. Memories, it seems, are often far too complex to be pulled out by the root. Instead, it’s more accurate to imagine the therapy as something that strips the memory of its phobic “edge.” Essentially, “a condition initially associates with fear, is no longer associated with fear following the treatment,” she wrote.
In the end, the memory stays with you but in a form that doesn’t evoke fear or anxiety. Perhaps it is better that way.
Source: Graff J, Joseph NF, Horn ME, Tsai L. “Epigenetic Priming of Memory Updating during Reconsolidation to Attenuate Remote Fear Memories.” Cell. 2014.