"Déja vu" phenomenon explanation
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Who has never felt, at least once, the feeling of having already seen a hitherto unknown place, already met a person whom one does not know yet, or even experienced a completely new event? space-medical, the tracks to better understand this strange phenomenon, the illusion of "déjà-vu".
"It's strange, I have the feeling that I have already experienced this situation." Many of us have experienced this illusion of déjà vu at least once.
What is the origin of this curious phenomenon? Zoom in on this strange impression, with brain and memory specialists.
"déjà vu", a feeling widely shared
The feeling of déjà vu is manifested when one has the feeling of having already met a person who is however unknown, or when one has the impression of having already experienced a situation which is however unprecedented. According to an American study 2, this strange feeling is very common, since almost 6 in 10 people have experienced at least one such episode in their lifetime.
According to this same study, the impression of déjà vu decreases with age and is favored by stress and fatigue. Moreover, it would seem that this phenomenon is more frequent among people with a high socio-cultural level, as well as among those who have traveled a lot.
A phenomenon difficult to explain
For two centuries, the impression of déjà vu has fascinated. It has moreover been the subject of no less than thirty explanations 1. Those which have been proposed range from the most eccentric, like paranormal phenomena, to the most serious, resulting from neuropsychology. "It's a very difficult phenomenon to explain", confirms Francis Eustache, Director of the Cognitive Neuropsychology and Functional Neuroanatomy of Human Memory Research Unit (Inserm, University of Caen) in France.
According to this specialist in the neuropsychology of memory, we can nevertheless suggest certain hypotheses. In the case of the déjà vu illusion, "the path that leads to a memory is wrong". It would therefore be our memory that would play a trick on us. The lived situation would provoke a stimulus, which would activate in our memory, knowledge related to the event. This will then induce an exacerbated feeling of familiarity, as if we were recalling a memory that does not exist.
"We can thus classify the impression of déjà vu in the category of false memories", explains Francis Eustache. According to him, it is a bit "the price to pay for the complex functioning of our memory". Indeed, it is constantly in reconstruction, in order to select or not the relevant information and memories. "This phenomenon, although complex, is quite normal. On the other hand, it should not be confused with certain symptoms of neurological diseases", specifies the researcher.
Epilepsy and a feeling of déjà vu
The feeling of déjà vu can, in fact, be a symptom of certain forms of epilepsy. This neurological condition manifests as a series of electrical discharges in the brain. There are multiple types of epilepsy and as many associated symptoms depending on the areas of the brain affected.
"The feeling of deja vu that we observe in some epileptic patients manifests itself in the same way as in" healthy "subjects. On the other hand, the frequency is much higher, so we can count up to several episodes per week in certain epilepsies ", explains Patrick Chauvel, Professor of neurophysiology and neurologist at the Hôpital de la Timone in Marseille (AP-HM, Inserm) in France.
Thanks to measurements carried out by the neurologist and his team 3, it seems that the impression of déjà vu arises in the internal regions of the temporal lobe. "One of the hypotheses that we are proposing would be an abnormal synchronization of our perception of the present and our memory of memories", specifies Professor Chauvel. The synchronization of these two information flows would thus lead the brain to interpret the present as being in the past. "But this feeling of déjà vu could also find another origin, such as the abnormal stimulation of our familiarity detection system, during an event which is completely new", adds the neurologist.
The strange feeling of déjà vu, therefore, would find its origin in the complex mechanisms of our brain. If the processes in play are still today the subject of different hypotheses, we can nevertheless affirm that the explanation is hidden in the functioning of our neural systems. Exit therefore paranormal phenomena and other mystical interpretations.
Here's an instructive video that may explain this phenomenon:
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Sources:
1 - The déjà-vu Illusion, Alan S. Brown, Current directions in Psychological Science 2004 , Vol 13, No 6.
2 - A Review of the déjà-vu Experience, Alan S. Brown, Psychological Bulletin 2003, Vol. 129, No. 3, 394-413.
3
- The dreamy state : hallucinations of autobiographic memory evoked by
temporal lobe stimulations and seizures. Vignal JP, Maillard L,
McGonigal A, Chauvel P. Brain. 2007 Jan;130(Pt 1):88-99.
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