Déjà vu is a very peculiar, surprising feeling that a given situation has already taken place in our life. 'Déjà vu is associated with a kind of cognitive conflict: on the one hand, the situation seems familiar and we have a strong impression of +immersion in the past+, and on the other hand, we are certain that this event is happening for the first time', Dr. Barzykowski. The scientist delves into the secrets of how spontaneous cognitive processes work.

Dr. Barzykowski conducts research on déjà vu together with neuropsychologist Professor Chris Moulin from the University of Grenoble - as part of the European Marie Skłodowska-Curie grant.

'Although there are very esoteric explanations of what déjà vu is, we point out that the answer may be quite simple: in our opinion, the phenomenon of déjà vu is related to typical processes characteristic of autobiographical memory. This is because déjà vu always concerns our personal past. It is always the impression that it happened to me before', says Barzykowski. Déjà vu may therefore be a clue to how autobiographical memory works.

Video: Director Michel Gondry sensed that the phenomenon of déjà vu was related to autobiographical memory, as seen in a scene from the film Eternal Sunshine of the Spotless Mind, in which the protagonist undergoes a process of erasing memories of his partner. Such a procedure is currently fiction. However, thanks to the progress of neuroscience, inducing the process of déjà vu may be getting closer.

REMEMBER ABOUT YOURSELF!

'Autobiographical memory concerns episodes from our lives. This memory is particularly sensitive, for example, to brain pathologies related to ageing. Defects in this memory are particularly visible in Alzheimer's disease', says Dr. Barzykowski. According to the scientist, we can use autobiographical memory intentionally or unintentionally. For example, we consciously use it when we recall our first childhood friendship, remember when we last ate pizza or wonder what our favourite colour is.

Sometimes, however, the stimuli around us (a pattern on a material, the weather, a smell, music, someone's facial expression, a sentence we read) completely spontaneously bring out memories. And we are transported with our imagination to a situation from our past with all the richness of details - emotions, colours, mood.

MADALEINE? A RARE THING

'The father of the popularisation of interest in the phenomenon of involuntary memories is undoubtedly Marcel Proust and his In Search of Lost Time. In this novel, a madeleine dipped in tea brings the protagonist extremely vivid memories from childhood. We know from research that involuntary autobiographical memories of this type are rather rare. However, it is difficult to fight this popular association', Barzykowski continues.

Video: the final scene from the film Ratatouille, in which a food critic tries the title dish and its taste triggers a very vivid memory of the warmth of a family home. This is an example of an involuntary autobiographical memory.

MEMORY WITHOUT CONTENT

Dr. Barzykowski points out that déjà vu shows a surprising number of similarities to involuntary autobiographical memories. It is also triggered automatically, in an uncontrolled manner, in response to some stimuli or situations. Just as memories are usually pleasant and evoke a sense of familiarity with a given situation, déjà vu, although devoid of content, is built on a strong 'sense of immersion in a familiar past'.

In a paper in Behavioral and Brain Sciences, Barzykowski and Moulin present the idea that both involuntary autobiographical memories (IAMs) and déjà vu can be explained as natural phenomena resulting from typical processes involved in retrieving information from memory, i.e. remembering something. 'We hypothesise that both can be described as +involuntary+ or spontaneous cognitions (...) We explain the emergence of the déjà vu phenomenon by relating it to well-known mechanisms of autobiographical memory retrieval, concluding that IAMs and déjà vu lie on a continuum', the scientists write in their paper.

Dr. Barzykowski believes that retrieving autobiographical information from memory can take different forms and proceed in different ways. And as a result, it can lead to experiencing various impressions. While in the case of IAMs the associations are quite specific, in déjà vu the result is less precise.

'Something in our memory that refers to our personal past is triggered by the current situation, but this activation is so weak, non-specific, and diffuse that it does not extract any specific episode from the past. The only specific thing associated with this activation is the feeling of familiarity, that +after all, this has already happened somewhere, once, to me+. However, the content of this association remains inaccessible', the researcher says. In his opinion, this is a natural effect that sometimes occurs when the brain tries to spontaneously connect the present with the past.

FLASHBACK

Dr. Barzykowski draws attention to several other phenomena related to the functioning of autobiographical memory, which are worth examining in the context of déjà vu. One of them are flashbacks, which he distinguishes as a separate phenomenon from involuntary autobiographical memories. In a flashback, memories are replayed so intensively that one can even have the impression that one is experiencing a given event once again. It may even be a problem to distinguish reality from memory. However, flashbacks are rare phenomena. They are usually associated with extremely unpleasant and traumatic situations and are characteristic of people with PTSD (post-traumatic stress disorder).

TIP OF THE TONGUE

Another phenomenon that reveals a bit about how memory works - also the autobiographical one - is the so-called tip of the tongue phenomenon. This is, for example, a situation when you try to remember something and you have the impression that the answer is on the tip of your tongue - you 'almost' know. The answer balances somewhere on the threshold of awareness, recollection, the impression of familiarity, but without any specific content yet. When you remember the information - there will be relief that the content has been found.

FEEL AT HOME

Another such sensation that shows the process of recalling information from autobiographical memory is the sense of familiarity that appears in certain situations: although you are somewhere for the first time - you feel at home, or intuition tells you that you can feel safe. Sometimes this feeling is clear - you can point out elements of the environment that are responsible for this feeling. And sometimes this impression is more blurred - you cannot identify what exactly is the source of these associations. 'There are quite a few situations in services and business - e.g. in the hotel industry - in which the ability to evoke such a sense of familiarity on demand could contribute to higher revenues'.

Interestingly, in scientific literature, no one has drawn attention to the similarities between déjà vu and autobiographical memory until now. In order to develop this hypothesis, it still needs to be confirmed. That is why scientists want to invite people suffering from temporal lobe epilepsy to participate in their experiments. Some people with this condition experience déjà vu much more often than the rest of the population.

PAP - Science in Poland, Ludwika Tomala

The research conducted by Dr. Krystian Barzykowski and Professor Chris Moulin is funded by the EU under the Marie Skłodowska-Curie Postdoctoral Fellowship programme.

tr. RL