The feeling of "déjà vu"

I often exclaim: However, I've already experienced this scene!. I'm sure you, too, have already experienced this strange feeling of having already lived a certain moment.

According to Wikipedia,

*Déjà vu* […] from French, literally "already seen", is the phenomenon of having the feeling that the situation currently being experienced has already been experienced in the past.Déjà vu is a feeling of familiarity, and déjà vécu (the feeling of having "already lived through" something) is a feeling of recollection. Scientific approaches reject the explanation of déjà vu as "precognition" or "prophecy", but rather explain it as an anomaly of memory, which creates a distinct impression that an experience is "being recalled".

When I was younger, I thought I had divinatory, premonitory or even paranormal talents, but in reality, there was something going on in my brain.

This sensation happens to me all the time... It is from here that I choose my pseudonym: Mrs Nobody... from the film Mr Nobody (below, a list of films of choice on this theme).

To learn more, here is an excellent video :

Unfortunately, at the present time, science is still unable to explain this deja vu phenomenon... Because, as you know, the brain is still very mysterious for our dedicated scientists and probably lacks the most advanced tools for their research. And above all, since they cannot go to the brain to study this phenomenon, they are obliged to base themselves on what patients say... And there, a dose of subjectivity arrives (and for science, subjectivity is complicated). Finally, it is difficult to reproduce the conditions of the already seen since this impression is always linked to a sense of startle and astonishment, almost impossible to reproduce in an experience!

Dozens of theories have seen the day over the years but no satisfactory answer has yet been found. However, the philosopher Saint Augustine, in the year 300, was already wondering about this subject!

The introduction of the term "déjà vu" was proposed by Frenchman Michel Boirac in 1876.

Let's discover here the rational theories (I won't talk about irrational and paranormal theories that make us believe there is a "bug in the Matrix").

Various (scientific) theories to explain this sensation

As we have seen, since the year 300, people have been wondering about the subject and yet no answer has been found (part of the answers, yes, but not a commonly accepted answer).

Indeed, how can we study such a phenomenon that is impossible to feel on order? But scientists, nothing stops them.

In fact, this sensation is usually observed in people experiencing severe fatigue or stress.

In the theories we find, there is that of divided attention, of the hologram, of double treatment for example. But I'm only going to talk about two that have been analyzed scientifically.

Epilepsy and déjà vu: neural short circuit

Scientists first noticed that in people with epilepsy, this type of sensation often occurs just before the seizure. In other words, when there is an important electrical activity in the brain that prevents me from functioning normally of the neurons... And it is this electrical disturbance that generates a sensation of déjà vu at the beginning of the seizure.

"The cerebral region often affected is that of the hippocampus and its structures adjacent to the temporal lobe", says the Swiss neurologist Serge Vulliémoz.

I had already told you several times about the hippocampus which is, to recall a place where memories are encoded in order to be stored in memory (long-term). However, it is not easy to observe it because it is buried in the brain. He's hiding like he said he would!

So it's important to understand where all this is happening in an attempt to deconstruct and understand what's going on. This feeling of "déjà vu" would therefore be linked to the memorization process.

Thus, according to neurologist Serge Vulliémoz, for epileptics, the seizure would be a kind of short-circuit that unintentionally releases information stored in the hippocampus and creates this feeling of déjà vu.

A search that finally gives a plausible explanation

A recent study led by Akira O' Connor, neuropsychologist and her team of researchers at St. Andrew's University in Scotland recently observed 21 brains from 21 volunteers at the exact moment they were experiencing this sensation with a IRM that enabled them to visualize the brain activity of the subjects.

The idea of the research:"simulate the impression of déjà vu using a standard technique of creating false memories". And so, to create an experimental déjà vu.

The search went like this:

Reading a series of words related to the same theme that is never said:"Pillow","bed","night","blanket","dream"... without ever pronouncing the word "sleep"[...] The rest of the protocol is treacherous: at first, volunteers are asked if they heard a word beginning with the letter "S". The answer is no. But it gets more complicated when they are then asked if they have heard the word "sleep". There, the participants know that this word could not be uttered, since it begins with an "S", and yet... they have the vivid impression of hearing it.

Thanks to this study, the researchers found that the déjà vu would be due to "an error of the brain that inscribes a perception directly present in the long-term memory".

Because the seahorse, which has been mentioned many times in my previous articles, has not activated. He remained in standby for the duration of the experiment.

So this would be a kind of brain check process. In other words:

It is a"conflict between a subjective feeling of familiarity and an objective feeling that this familiarity cannot be correct".

Good news: the déjà vu would not be a dysfunction of our brain but on the contrary, this sensation would be the perfect tool to verify that the present situation is indeed different from what we have already experienced. So it would be a sort of filter against false memories! So, this feeling would be positive because it shows that our brain checks its memories and therefore is well!

Warning: this theory is one of many. It still needs to be checked. You can't rely on one theory alone.

Movies that talk about this feeling (and which I recommend)

• One day without end
• Fight Club
• Mr Nobody

• Minority Report
• Edge of Tomorrow

Finally, is it déjà vu or already lived ?

Personally, I had feelings of already seen (déjà vu) /lived with smells, noises, tastes... I wouldn't say anything to the scientists because if they had to add all this to the visual, they would be looking for them for years to come!

it seems that as we age, these sensations become rarer. I'll confirm it for you! And that 30% of the population would never have experienced this sensation!

Sources:

• https://en.wikipedia.org/wiki/D%C3%A9j%C3%A0_vu

• http://www.nytimes.com/2006/07/02/magazine/02dejavu.html?pagewanted=2&_r=0

• https://www.letemps.ch/sciences/2017/12/18/dejavu-defie-methodes-scientifiques

• http://www.atlantico.fr/decryptage/quand-science-comprend-mieux-deja-vu-cette-sensation-avoir-deja-vecu-instant-present-493199.html

• https://www.futura-sciences.com/sante/questions-reponses/cerveau-expliquer-sensation-deja-vu-6835/

• https://www.sciencesetavenir.fr/sante/cerveau-et-psy/cerveau-d-ou-vient-cette-etrange-sensation-de-deja-vu_104463