Memory Erasure for PTSD Treatment
Memory erasure is the selective artificial removal of memories or associations from the mind.
There are many reasons that research is being done on the selective removal of memories. Potential patients for this research include patients suffering from psychiatric disorders such as Post-Traumatic Stress Disorder, or Substance use disorder, among others.
Several psychotherapies have been developed that change, weaken, or prevent the formation of traumatic memories. Pharmacological methods for erasing traumatic memories are currently the subject of active research. The ability to erase specific traumatic memories, even if possible, would create additional problems and so would not necessarily benefit the individual.
Memory erasure has been shown to be possible in some experimental conditions; some of the techniques currently being investigated are: drug-induced amnesia, selective memory suppression, destruction of neurons, interruption of memory, reconsolidation, and the disruption of specific molecular mechanisms.
There are several different types of possible patients that have the potential to draw great benefit from the selective memory erasure; these include people suffering from drug addiction, or Post-Traumatic Stress Disorder (PTSD). PTSD patients may include war veterans, people who witnessed horrific events, victims of violent crimes and many other possibly traumatic events. These potential patients have unwanted memories that can be absolutely devastating to their daily lives and cause them to not be able to function properly.
A type of memory of main concern for memory erasure are emotional memories. These memories often involve several different aspects of information in them that can come from a variety of the different categories of memories mentioned above. These emotional memories are very powerful memories and can have very strong physiological effects on a person. An example of an emotional memory can be found in patients suffering from PTSD, for these patients a traumatic event has left a lasting emotional memory that can have powerful effects on a person even without them consciously retrieving the memory.
Selective Memory Suppression is the idea that someone can consciously block an unwanted memory. There are many different therapeutic techniques or training that has been done to test this idea with some success. Many of these techniques focus on blocking the retrieval of a memory using different suppression techniques to slowly teach the brain to suppress the memory. Although some of these techniques have been useful for some people it has not been shown to be a clear cut solution to forgetting memories. Because these memories are not truly erased but merely suppressed the question of how permanent the solution is and what actually happens to the memories can be troubling for some.
Selective Memory Suppression is also something that can occur without a person being consciously aware of suppressing the creation and retrieval of unwanted memories. When this occurs without the person knowing it is usually referred to as memory inhibition; the memory itself is called a repressed memory.
Research reported in 2013 revealed that it is possible to artificially stimulate prior memories and artificially implant false memories in mice. Using optogenetics, a team of RIKEN-MIT scientists caused the mice to incorrectly associate a benign environment with a prior unpleasant experience from different surroundings. Some scientists believe that the study may have implications in studying false memory formation in humans, and in treating PTSD and schizophrenia.
The part of the brain that is critical in creating the feeling of emotion is the amygdala, which allows for stress hormones to strengthen neuron communication. The chemicals cortisone and adrenaline are released in the brain when the amygdala is activated by positive or negative excitement. The most effective way to activate the amygdala is fear, because fear is an instinctive, protective mechanism which comes on strong making it memorable. Sometimes the feeling can be overwhelming. This is when a memory can be hazy yet vivid, or haunting with perfect clarity. This discovery led to the development of a drug to help treat posttraumatic stress disorder (PTSD). When someone is in a heightened emotional state, the events causing it to become strong and ground in the memory, sometimes disrupting daily life for years.
An experiment done with rats helped create the drug for treating this issue. Dr. Kerry Ressler at Emory University, used tones and shocks to test an existing drug called cycloserine (an anti-tuberculosis drug). Rats would hear a tone and receive a mild shock, training them to fear the tone. Then the drug was given to one set of rats, and the tests were done again. The rats that did not receive the drug froze in fear. When the tone was heard, the rats given the drug ignored the tone and continued on. The drug can effectively allow for new receptor connections between neurons and relaxing of the amygdala when it comes to fear, allowing patients to have a chance of recovery from PTSD.
Dr. Barbara Rothbaum at Emory University conducts experimental treatments for PTSD using the knowledge that exactly the same neurons are active when remembering an event as when it was created. Her administration of the drug cycloserine is intended to help patients foster new connections between neurons, providing a window to lessen former traumatic connections. Rothbaum decided to use the drug in a therapy session that utilizes virtual reality to give PTSD suffers a second chance. Once the events that have caused the PTSD are identified, the process can begin. The surroundings of the events are recreated in a virtual reality helmet (for instance, in a combat vehicle in the desert). This would help to recall the target memories in a safe environment, and activate the neurons without activating the fear response from the amygdala. When the dicyclomine is in the patient's system and the same neurons are active that were active during the event, the patient can now have a chance to re-form neural connections, with less chemicals present from the amygdala. This does not erase the memory, but rather lessens the strength of it, giving some relief so that people suffering from PTSD can try to move on and live their lives.
Optogenetics uses light to control neurons which have been genetically sensitised to light. It is a neuromodulation technique employed in neuroscience that uses a combination of techniques from optics and genetics to control and monitor the activities of individual neurons in living tissue—even within freely-moving animals—and to precisely measure the effects of those manipulations in real-time. The key reagents used in optogenetics are light-sensitive proteins. Spatially-precise neuronal control is achieved using optogenetic actuators like channelrhodopsin, halorhodopsin, and archaerhodopsin, while temporally-precise recordings can be made with the help of optogenetic sensors for calcium (Aequorin, Cameleon, GCaMP), chloride (Clomeleon) or membrane voltage (Mermaid).
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