Total recall: memories can be lost and found

New findings suggest that memories are not as vulnerable as we thought.

In recent years, scientists have thought that some memories, even extremely stable long-term memories, can be disrupted and even wiped out completely depending on what is happening at the time of remembering. This process, is known as reconsolidation and suggests that the very act of remembering and accessing a memory can lead to changes in the brain. Therefore memories must be continually maintained and rebuilt after recall so as not to be lost.

Patients who suffer from Post-Traumatic Stress Disorder (PTSD) and anxiety-related disorders have excessively strong memories of traumatic events. This means the memories are hard to ignore and are problematic to everyday life. Using the theory that memories can be disrupted and even wiped out during the reconsolidation phase, therapies have been developed to interfere with the reconsolidation phase. For example intrusive fearful memories can be treated through a combination of having the patient recall the memory whilst at the same time receiving a drug such as a beta-blocker that can interfere with the reconsolidation process.

Simon Trent July 2016However the case for reconsolidation is as yet just a theory and not been clearly proven experimentally. We recently found that memories thought lost, through reconsolidation interference, in animals can in fact be recovered (Trent, 2015).

In other words, under certain conditions, lost memories could be found. These figures show that reducing the molecule Arc in the hippocampus of rats, a critical brain structure for remembering contexts and environments,  reduces fear memory measured by the amount of time the rodents freeze in a certain environment. However, this deficit was only temporary and could be rescued under a gentle condition of reminding the rat of the original memory.

These animal models closely reflect what’s happening in humans and suggest that our autobiographical memories and our self-histories are clouded by new memories and not in fact lost.

Our research also sheds light on the biology of memory processes. Molecules found in the brain such as Arc were found to be important in forgetting and we argue that it is the reduction of Arc and other molecules in the brain that then open the floodgates and permit new learning, in the form of extinction of memory, to occur.

Altogether this type of work is important in helping us think about new treatments for memory disorders such as PTSD and psychiatric illnesses such as schizophrenia and psychosis. The findings raise fundamental questions about how we remember and if reconsolidation is a valuable treatment option for patients. We can now devise new drug or behavioural techniques that can strengthen new learning when we recall events. Furthermore, we can develop these therapeutic interventions in the knowledge that we won’t be overwriting our past experiences.

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