Treating PTSD and Drug Addiction by Modifying Memories
Can we modify human memories in order to treat mental illness? Researchers from Ruhr-University Bochum have published a paper which states that a process called memory reconsolidation may serve as an effective treatment for illnesses in which memory plays a significant role, such as post-traumatic stress disorder (PTSD) and addiction.
The researchers stated, "In the novel Remembrance of Things Past, Marcel Proust makes a compelling case that our identities and decisions are shaped in profound and ongoing ways by our memories. This truth is powerfully reflected in mental illnesses." One of the main symptoms of PTSD is flashbacks: intrusive, debilitatingly vivid memories of a traumatic experience. This often causes other symptoms of PTSD, such as avoidance of triggers and extreme distress. Similarly, memories of drug use often compel sufferers of drug addiction to continue or resume use of narcotics. The research team postulates that, if the modification of human memories were perfected, then interfering with these memories could contribute to treatment of these disorders.
This interference occurs through a process called reconsolidation; it involves conjuring a stored, inactive memory in order to make it vulnerable to modification. Until recently, most reconsolidation research has been conducted with animals, and has shown to be successful with many different non-human species. For example, researchers were recently able to erase and then restore fear memories in rats using Pavlovian conditioning and a protein synthesis. Reconsolidation has proven effective in humans for fear memories and procedural memories (memories necessary for actions, like tying shoes or reading), but reconsolidation of episodic memory (memories that recreate past experiences), which would be necessary for the proposed psychotherapy treatments, has proven more difficult. Chief among the problems is the fact that many of the agents used to reconsolidate memories or block reconsolidation in animals, such as the protein synthesis used in rats, are not safe for human use.
However, evidence has been accumulating that reconsolidation of episodic memory is possible in humans. In a recent study, researchers from Lehigh University were able to demonstrate the ability to intentionally impair memories through cognitive behavioral strategies alone. They showed participants a set of objects (Set 1), and then after 48 hours showed them another set of objects (Set 2). One group was reminded of Set 1 immediately prior to exposure to Set 2, and while both groups identified the same number of objects on average, the reminded group was significantly more likely to recall objects from Set 2 when attempting to recall Set 1. There were essentially "additions" to their memories, and the researchers concluded that this occurred because making the memory active made it more vulnerable to modification.
Another recent study showed that neuroimaging seems to confirm the veracity of reconsolidation, while also suggesting a potential method that would work on humans. Researchers from McGill University visualized the brains of patients under the influence of propanolol using fMRI technology, and found that the combination of propanolol and memory reactivation was the only effective method of reducing subsequent memory retrieval. Using propanolol by itself had no effect, which shows that memory reactivation is crucial to the reconsolidation process.