Stephen Kintz
Feb 20, 2012

Altering memory: A new treatment for chronic pain, PTSD and phobias

Would you erase your memory? Would you erase an embarrassing moment, or take a cue from the movie “Eternal Sunshine of the Spotless Mind” and forever forget that tragic love? Perhaps, these moments seem too trivial for memory removal. Would you leave your memory intact, or would a life shattering, horrifying event convince you of the benefits of forgetting? Luckily, you do not have to answer now. Memories cannot be erased. However, researchers are experimenting with disrupting memories in the hopes of one day offering a better treatment to patients with chronic pain, post-traumatic stress disorder (PTSD), and chronic phobias.

In December, researchers at McGill University, led by Terence Coderre, published a paper in “Molecular Pain” that builds upon the knowledge that the protein kinase C, zeta (PRKCZ) is used by the central nervous system to store long-term memories. The researchers wanted to test whether the enzyme, PRKCZ, responsible for forming long-term memories within the hippocampus, might also be used by the central nervous system to form memory traces of pain – or chronic pain.

Chronic pain is usually defined as an injury that is continually processed by the central nervous system as pain even after the injury is healed. Fibromyalgia and phantom limb syndrome are two extreme examples of chronic pain. In Fibromyalgia, people feel chronic pain, but there is no known cause or injury. In phantom limb syndrome, people continue to feel the pain in a limb after it has been amputated. In both instances, the body has formed a memory of the pain, and any sensation (or the lack of sensation) can cause the central nervous system to register pain.

The researchers at McGill found that memory traces of pain are formed by the same enzyme that forms other long-term memories. So you can thank the same mechanism for causing you to feel knee pain twenty years after the car accident as allowing you to remember your sweetheart from high school. More importantly, the researchers also discovered that inhibiting the enzyme provided relief to rats. This is the first time that researchers have been able to do two things: (1) demonstrate the mechanisms that are important for maintaining memory traces of pain and (2) providing evidence that inhibiting these mechanisms after an injury occurred provides some pain relief. The researchers are hopeful that this line of research will provide non-narcotic relief to chronic pain sufferers.

You might be thinking that disrupting memory-traces of pain is not like erasing long-term memories. This is a fair assessment; however, if the traditional idea of memory functions somewhat like memory traces of pain, then researchers might be able to disrupt those memories with other techniques. In fact, scientists have been disrupting long-term memories for several years now.

Of course, the research at McGill University was done on rats, and researchers are not ready to disrupt the enzymes responsible for memory in people. Researchers are still not entirely sure how memories are formed; they simply have good evidence that they know some of the compounds involved.

For people, researchers typically focus on the stress hormone, cortisol, which has been implicated in helping/hurting memory. Researchers are unsure of the role that stress plays in memory, but research has shown that high levels of stress -- indicating a high level of cortisol -- seems to help cement negative memories into long-term memories.

With this knowledge, researchers conducted several studies that  blocked cortisol production with the use of beta-blockers or metyrapone. During a period of blocked cortisol production in the body, the researchers expected that any recalled negative memories will be altered or changed by the lack of cortisol -- hopefully, making the memories less negative and scary. The process that allows old memories to be altered once recalled is called reconsolidation.

Reconsolidation refers to the phenomenon that every time a person recalls a memory, the memory is brought into short-term memory and has to be re-stored into long-term memory. Therefore, every time someone remembers anything, he or she will have to re-store the memory into long-term memory -- just like when the memory was first made. Reconsolidation is a scary process to people because it suggests that every time a memory is recalled, it has the possibility of being altered by the re-storage process.

In fact, this is what researchers have found. After researchers reduced cortisol levels through the use of beta-blockers or metyrapone, the researchers asked participants to recall negative events in their life. Since the negative events were recalled by participants, the memories have to be re-stored, or reconsolidated, into long-term memory without the aid of cortisol to cement the negative aspects of those memories into long-term memory.

When the researchers asked participants to recall the same negative events four days later, participants remembered less negative details about the recalled events while maintaining the same amount of detail on neutral aspects of the events. This suggests that recalling stressful events in a less stressful environment, or perhaps on cortisol blockers, could disrupt the negative aspect of the memory from being re-stored into long-term memory.

No, this is not memory erasing research. Scientists cannot as of yet simply erase your bad memories. Yet it does suggest that one day patients of PTSD or intense phobias might have a more consistent, timely, and easier treatment for disorders than are currently offered by traditional therapy. More positively,  this research does suggests that recalling traumatic experiences in traditional therapy can lead to a better perception of an event if the experience is recalled in a controlled and peaceful environment.

Of course, the implications of this research are not all positive. Research into memory reconsolidation has given advertisers new insight into altering memories and could become a how-to guide for people with dubious intentions.