During a lecture at St Petersburg University, neurobiologist Vladimir Alipov explains whether memories can be altered and whether this will help doctors in the fight against post-traumatic stress disorder

Speaking about what memory is, Vladimir Alipov gave the following example. If mice did not remember during their life that cats are dangerous, they would have died out long ago. It is memory that helps mice save their lives. Memory is the ability to save and reproduce information obtained from experience or learning. 

There are different types of memory, but scientists are especially interested in declarative, explicit memory, i.e. the memories that we can retell: knowledge about the world, birthdays of relatives, funny stories from life and, of course, everything that we learn throughout our life.

The lecture brought together over 150 students from St Petersburg University, the Kirov Military Medical Academy, North-Western State Medical University named after I.I. Mechnikov, Herzen University, St Petersburg State University of Economics, Higher School of Economics, Saint Petersburg State Chemical and Pharmaceutical University, ITMO University, St Petersburg Electrotechnical University "LETI", Pavlov First Saint Petersburg State Medical University, Almazov National Medical Research Centre, and Moscow Institute of Psychoanalysis.

There are two types of this memory: short-term and long-term. Hermann Ebbinghaus, a German psychologist, proved their existence, said Vladimir Alipov. For the experiment, he wrote meaningless syllables on cards. Immediately after he memorised them, the researcher could remember and reproduce almost all of them. But over time, the number of cards that he could remember began to fall. The scientist forgot 75% of the syllables, but he remembered a quarter and even after several months he still kept them in his head.

Today, we know that there is a very precise memory, but it is short-term. There is also a smaller memory, which has fewer details, but it stays with us throughout our lives.

Neurobiologist Vladimir Alipov

For most of the last century, scientists believed that short-term memory was labile and could be easily damaged, while long-term memory can extend for a lifetime. Yet, as it turned out, memories could easily be faked. For example, scientists conducted an experiment in which people were "implanted" with false memories. Children were told that they had got lost in a shopping centre on the eve of Christmas, adding many details to the story and repeating the legend over and over again. About 40% of the children were sure that they had really got lost. 

According to the modern model of scientific understanding of memory, every time we remember something that is stored in long-term memory, this moment becomes labile, mobile, and can be influenced. This is called memory reconsolidation. In other words, a person remembers, modifies something in the memory, adds something, and then "puts" it back again. 

Doctors are studying how to influence memory and how to make a person forget something using pharmacological drugs. In search of an answer, researchers conducted an experiment on mice and saw that if you shock a mouse with electricity at the same time as a sound signal, it will understand that one follows from the other, remember it and the next time it hears the sound, it will freeze. Analysing possible ways to solve the problem, doctors came to the conclusion: if you shock a mouse and at the same time inject it with a protein synthesis blocker, this will block the protooncogene gene, responsible for learning, and it will therefore experience a memory block. The mouse forgot about the danger and the next time did not perceive the sound signal as something scary.

Patients with post-traumatic stress disorder (PTSD) feel something similar. PTSD occurs after stress or severe traumatic situations. At first, a person feels fine, but after a few weeks, when memories become long-term memory, they begin to have nightmares, insomnia, severe anxiety, and cannot function normally or communicate with people. PTSD attacks are often caused by situations that seem to be in no way related to what happened, such as bright flashes of light or loud sounds. So far, as Vladimir Alipov said, there is no good way to treat PTSD. 

However, researchers are looking for a pharmacological way to solve this problem. The method that worked in the mouse study is not suitable for humans, since the use of a protein synthesis blocker has been associated with deaths.

It is too early to talk about the widespread use of pharmacology to treat PTSD. Yet, we have accumulated much information about how to "erase" memories. Doctors are constantly looking for drugs that are safe for people that can make life easier for patients with PTSD.

Today, scientists conduct many studies on animals, with a few of them being conducted on people. Neurobiologists have already found out that although pharmacological methods cannot make a person forget what happened, they can change the emotional perception of the time of the event.