Eliminate Bad Memories for Good
by Sarah Edmunds
When in danger, humans instinctively feel afraid. Fear is a basic survival mechanism encoded into our brains, an emotion which triggers split-second changes in the body to escape danger. This "fight-or-flight" response is healthy, a reaction meant to keep humans from harm, but people who suffer from Post-Traumatic Stress Disorder (PTSD) have damaged fear-sensory triggers and may experience stress, tension, or fright in a perfectly harmless situation. Years after a traumatic encounter, war veterans, people who have survived physical or sexual assault, disaster victims, etc., may be easily startled or experience flashbacks and nightmares, all due to the cognitive dysfunction of the memory process. However, recent developments in memory erasure therapy might be able to permanently eliminate these fearful memories.
For people with PTSD, catalysts - for example, the sound of a gunshot - usually trigger flashbacks and nightmares. Memory erasure manipulates these triggers to remove fearful associations. A procedure known as extinction therapy weakens the stressful responses by exposing a patient to his or her anxiety trigger in a controlled environment. Theoretically, the patient will eventually disassociate the catalyst, and the anxiety will disappear.
This procedure is flawed, however, because tests have shown that extinction therapy only works up to a certain point. Neuroscientist Marie Monfils and her colleagues at the University of Texas at Austin conducted an extinction-therapy study on rats, teaching them to associate a musical tone with an electric shock. Playing the tone with no shock caused the rats to freeze in fear. After repeating the tone nineteen times, the rats' fear decreased. A month later, their fear of the tone returned at a level similar to that of their original anxiety. While extinction therapy temporarily reduces fear, it is not a particularly effective way to treat post-traumatic stress.
However, neurologists have potentially discovered a way to eliminate triggered anxiety permanently. The idea is to manipulate the memory triggers at a point when the memory is least ingrained, known as the reconsolidation period. During consolidation, short-term memory converts into long-term memory. A memory increases in strength over time with repetition, and protein synthesis consolidates the memory at a molecular level. Reconsolidation is the process of recalling a consolidated memory and applying an emotional or sensory jolt, which weakens the memory for a few hours. If extinction therapy is administered during this time, the memory will be permanently erased - at least, in theory.
This theory proved to be successful on Monfils' study of rats. Her team of neuroscientists recalled the rats' memories of electrical shocks just once, and then waited an hour for reconsolidation to begin. The scientists then played the musical tone repeatedly, performing the same extinction procedure as before. This time, the rats no longer responded to the tone; their fearful association was permanently eliminated.
Timing makes all the difference. Extinction therapy creates two parallel memories, one good and one bad. Performing extinction therapy during the reconsolidation window, on the other hand, overwrites the bad memory completely. Human volunteers participated in similar shock-and-association method and confirmed the theory, but the treatment is still being developed and has not been tested on patients with Post-Traumatic Stress Disorder. After all, a slight electric shock on a volunteer has a weaker effect than the sound of a gunshot has on a war veteran. Still, reconsolidation-extinction therapy gives hope for the future of drug-free memory erasure. Researchers are optimistic that over time, painful memories will not be consolidated into the long-term, but instead will be eliminated into nothingness.
