Déjà Vu: the strange sensation of living something already lived before

Have you ever experienced something that you think you have already experienced at another time? Have you been in a place that is familiar to you but without remembering why it is known to you?

If you have felt something similar, it is very likely that you have experienced a Deja vu.

What does Déjà Vu mean?

Deja vu is a French term coined by the psychic researcher Émile Boirac that means "already seen" and implies a sensation of living a situation identical to another experienced previously, of which, however, we are unable to remember when or why it is familiar to us. Its duration, normally, is a few seconds and is characterized by the feeling of living again a moment already lived, as if the same story were repeating itself.

Through data collection by Millon and his team, it has been observed that approximately 60% of people experience it and it turns out to be a more frequent phenomenon under stress and fatigue situations (Brown, 2003). It tends to appear between 8-9 years of age, because for a Dèjá Vu to occur, a certain level of brain development, but once we experience it, it becomes more common between 10-20 years (Ratliff, 2006).

When we talk about Dèjá Vu, we are not talking about a new term, since experiences of Dèjá vu have already been described in works by great writers such as Dickens, Tolstoy, Proust and Hardy (Sno, Linszen & Jonghe, 1992).

Why does a Déjà Vu occur?

This question is still uncertain to us. Numerous fields offer various explanations for this phenomenon, some of the best known theories are those that relate Dèjá Vu as a symptom of paranormal experiences (past lives, premonitions, etc.) and even, in the field of psychoanalysis, Freud (1936) postulated that this sensation was caused by the similarity of the present situation with a repressed fantasy of an unconscious dream, however, he declared the phenomenon as somewhat confusing of investigate.

What does neuroscience tell us about the Déjà Vu phenomenon?

Focusing on a neurocognitive analysis, Alan Brown (2004), psychologist at Southern Methodist University and author of "The Déjà vu Experience", shows us a classification of the various scientific explanations in relation to Déjà Vu through four theories:

1. Double processing

The central idea is the affirmation of Déjà Vu as result of two synchronized parallel cognitive processes momentarily out of sync.

This asynchrony may be due to the absence of one process when the other is activated or that the brain is encoding information and recovering it at the same time, that is, two related pathways are merging that are normally separated. The fact of observing an image and that at the same time it is being remembered gives us a feeling of having previously lived that situation.

2. Neurological

Déjà Vu is produced because of a brief dysfunction / disruption in a temporal lobe circuit, involved in the experience of remembering lived situations, this fact generates a “false memory” of the situation. This theory is justified with the study of patients with temporal lobe epilepsy, who frequently experience Déjà Vu just before suffering one of their seizures.

By measuring neuronal discharges in the brains of these patients, scientists have been able to identify the brain regions where Déjà Vu signals begin and how by stimulating those same regions it is possible to produce that sensation.

3. Mnesic

Define Déjà Vu as a experience generated by the similarities and overlaps between past and present experiences. The psychologist Anne M. Cleary (2008), researcher of the neural bases underlying Déjà Vu, postulates this phenomenon as a normal metacognitive mechanism that occurs when a past experience bears a resemblance to the present and, consequently, makes us believe that we have already been there.

Through various studies and research it has shown that the mind stores fragments of information, that is, it does not store the complete information and that, therefore, when we observe, for example, a street that looks like another or that has identical or similar elements, this sensation.

4. Double perception or attention

It is postulated that the phenomenon is produced as a consequence of a momentary distraction of the brain just after part of the scene has been captured (I recall not explicit) and, when this attention, is retaken (fractions of a second) and makes a capture complete, we attribute to that scene a strong sense of familiarity without being aware of its origin, giving a feeling of "false memory", since part of that scene had been recorded implicitly and unconsciously.

The fact that there are various theories shows that such a phenomenon is not due to a single cause. Likewise, it is true that not all Déjà Vu is the consequence of a normal mnesic process, since there seems to be a type of Déjà Vu related to a memory alteration observed in pathologies such as schizophrenia or, as mentioned above, in temporal lobe epilepsy in which the phenomenon can last a few minutes or even hours (Thompson, Moulin, Conway & Jones, 2004).

For the moment, there is no clear and definitive explanation that determines the anatomical and functional bases for this phenomenon to occur, but advances in neuroimaging techniques and current research may help to better understand the topic from a neurocognitive perspective.

Bibliographic references:

• Brown, A. (2003). A review of the déjà vu experience. Psychological bulletin, 129 (3), 394.

• Brown, A. (2004). The Dèjá vu experience. England: Psychology Press.

• Cleary, A. M. (2008). Recognition memory, familiarity, and déjà vu experiences. Current Directions in Psychological Science, 17 (5), 353-357.

• Freud, S. (1964). A disturbance of memory on the Acropolis. In The Standard Edition of the Complete Psychological Works of Sigmund Freud, Volume XXII (1932-1936): New Introductory Lectures on Psycho-Analysis and Other Works (pp. 237-248).

• Ratliff, E. (2006). Déjà vu, again and again. New York Times Magazine, 2, 38-43.

• Sno, H., Linszen, D., & Jonghe, F. (1992). Art imitates life: Deja vu experiences in prose and poetry. The British Journal of Psychiatry, 160 (4), 511-518.

• Thompson, R., Moulin, J., Conway, M. & Jones, R. (2004). Persistent Déjà vu: A disorder of memory. International journal of geriatric psychiatry, 19 (9), 906-907.