Is it possible to induce Deja Vu?

Déjà-vu

A déjà vu experience is the eerie impression for some people that they have already experienced something in exactly the same way, although cues from the current situation are likely to unconsciously trigger memories of a previous situation. Déjà vu is a phenomenon that seems inaccessible and crazy to people who have never experienced it. Therefore, for a long time in science it was only considered mentally ill to be susceptible to this experience.

As déjà-vu (French: “already seen”), déjà-vu-experience or déjà-vu-phenomenon, memory deception, illusion of familiarity or fausse reconnaissance (French: “false recognition”), also as a déjà-entendu-phenomenon or déjà -écouté phenomenon (French: "already heard") or déjà-vécu-experience (French: "already experienced") is the term used to describe the psychological phenomenon that expresses itself in the feeling of having already experienced, seen or seen a new situation to have dreamed. The human brain is constantly in the process of processing everything and creates countless connections with feelings, impressions, colors and smells. Even a well-known fragrance such as that of a flower or a familiar perfume can evoke emotions and impressions that were once connected to it and therefore make a current experience appear to have already been experienced. It is probably due to similarities in the experience compared to previous experiences Associations in the brain that evoke feelings that one has had before, even if only a small part of the resemblance to those feelings may be decisive. Some people like to perceive déjà-vus as something supernatural or as an esoteric phenomenon, but these are only perceptions and appearances that cannot be immediately understood due to a lack of information.

A déjà-vu is therefore a form of memory or experience in which one seems to experience a loop within time. You have a memory that you have already experienced exactly the event that you are currently experiencing and / or that you have foreseen the current event earlier. Up to 97 percent of all people have already had a déjà vu experience. Such experiences occur particularly frequently in people with epileptic seizures, the cause of which lies in the so-called temporal lobe of the brain (see below). This suggests that the feeling of familiarity probably originates in this lateral region of the brain. The brain may have stumbled upon an incorrectly stored memory, similar to a file system error that caused an inconsistency in the database. The data set itself can no longer be found and is therefore approximated as closely as possible by the current memory, which means that the apparently old memory is very similar to the current event. One explanation would therefore be that recognizing something consists of three steps: people experience something, in parallel their brain calls up memories from the past and compares the new impressions with the old memories, and if there are matches, the signal comes: “Know Me, yes". In the case of epileptics, déjà-vu can now be explained in such a way that the third step occasionally takes on a life of its own, i.e. the brain fires the message "I already know" without there being a specific reason for it. It is well known that an epileptic seizure causes a kind of short circuit in the brain, whereby the same areas of the brain are involved as those that are responsible for evaluating memory contents.

So a dejavu is probably a false or Error correction function of the brain. However, the assumption of some scientists that déjà-vus arises from the fact that what is seen with both eyes does not arrive in the brain at the same time, but slightly offset, is rather questionable. According to this view, information processing in the brain is desynchronized, because information from the sensors reaches the appropriate destination in the brain in different ways and is only then combined to form a uniform impression. It is conceivable that the image information of one eye takes a little longer than that of the other eye due to a synaptic breakdown, even if it only takes a microsecond. Instead of assembling the data into an overall impression, the brain could perceive it as experiencing the same experience twice. Although this could theoretically give the impression that what was seen has already been registered before, it does, however, report blind people of such experiences.

It kicks in healthy people sporadically spontaneously, in a state of exhaustion or in the event of poisoning (especially with neurotoxins such as alcohol or hallucinogenic drugs). As a side effect of neuroses, psychoses or organic brain diseases, especially of the temporal lobe, déjà vu experiences can also occur more frequently. How often déjà-vu occurs is obviously also due to age, because young people in particular report déjà-vu experiences, while these decrease over the course of life. It is also assumed that there is a connection between educational status, because the more educated a person is, the more likely they are to experience déjà-vus. Studies show that young, educated people and those who travel a lot are more likely to report déjà vu experiences. Stress and fatigue can also trigger this phenomenon. However, gender has no influence.

Anne M. Cleary et al. (2009) suspect on the basis of experiments that déjà-vu can occur because the brain switches back and forth between two types of memory: the Recognition memory (recognition memory) and the Familiarity memory (familiarity memory). The recognition memory recognizes, for example, those people in the shop who had already sat on the bus, while the familiarity memory is responsible for making a situation feel familiar. As a rule, these two memory systems work together, but in the case of déjà-vu, the familiarity memory may be particularly active and dominate the memory process. In their study, the participants were given names of famous people, and then some of them were shown in pictures. Although some of the stars whose names they had seen looked familiar to the test subjects, they could no longer reconstruct it because they had retained a fuzzy piece of memory that they could no longer put together. Obviously, events that one experiences are stored in the memory as individual elements or snippets, and a déjà-vu occurs when specific aspects of a current situation fit together with certain aspects of a previously experienced situation, whereby several sensory impressions coincide.

There is therefore basically two hypotheses to explain this phenomenon: one says that it is based on a real memory and not on a hallucination, but a familiar situation has actually already been experienced and perhaps unconsciously stored, and is now awakened by a sound, a smell or a sensation and on the current scene transfer. A second explanation assumes that déjà-vu is a short-term disturbance in the brain, i.e. a kind of illusion or hallucination that arises when the brain constructs an image of reality.

By the way: There are also numerous spiritual-esoteric explanations that refer to supernatural experiences, for example that in such cases one is dealing with memories from a previous life. Esoteric people therefore suspect memories of a past life in Déjà-vus, sometimes a form of telepathy or suppressed fantasies.

Experimentally generated déjà vu experiences

Earlier studies showed that déjà vu experiences are related to neurochemical processes in the temporal lobes of the brain, because electrical stimulation of the outer temporal lobes increased the probability of a déjà vu experience fourfold. Studies have also shown that déjà-vus often occurs after periods of great stress, when the stress subsides and the person relaxes again. Other studies have shown a relationship between a person's ability to imagine and the frequency of déjà-vus.

British researchers have even managed to artificially create déjà vu experiences in the laboratory and thus come closer to the secret of the strange feeling. One of two brain processes that also play a role in normal memory is responsible for déjà vu. When this process occurs on its own, it can evoke the typical feeling of having seen something completely unknown before.To recognize an object, two processes must take place in succession: First, the brain searches in memory to see whether the object or scene is already stored somewhere. Next, another part of the brain identifies the object as known, which comes with a sense of familiarity. Scientists working with Akira O’Connor now tried to separate these two processes in their experiment. To do this, they hypnotized their subjects and showed them words in a red or green frame. The participants were told that words in the red frame would feel like they knew them from somewhere. They had actually seen the words in the green frame before. If the test subjects were shown new words in red and green frames after the hypnosis, 10 of the 18 people examined so far reported a strange feeling of familiarity when they saw the words framed in red. Five test subjects even reported that they felt this feeling just like a déjà vu. The experiment shows that two separate processes actually play a role in recognition and that it is possible to run the second without the first, says O’Connor. The investigation therefore also contributes to a better understanding of human memory.

Neurologists at the University of St. Andrews in Great Britain working with Akira O'Connor read out words on the subject of sleep to test subjects at the beginning of an experiment, for example the words "bed", "pillow", "night", "dream", but not the word " sleep ”yourself. After a pause, the subjects were asked which words were read to them, with the majority also thinking that they had heard the word "sleep". But in order to create a real déjà vu experience, after the list of words was read out to them, the study participants were also asked whether they had heard a word that began with an "s". The participants said no, but when asked if they had heard the word "sleep" they answered in the affirmative. When they were told that they had previously stated that they had not heard a word beginning with the letter “s”, the participants were confused. During the experiment, the participants' brains were scanned with an MRI, which was expected to be the part of the brain responsible for memory, but instead the part of the brain responsible for decision-making was most active . Even if this is not a perfect correspondence to a déjà vu experience, there was a comparable memory conflict in this experiment, because the brain believes it has a certain memory but could not find it because it did not exist. In such a case, like in a déjà vu experience, the brain cannot decide which memory is the right one.

literature

Cleary, A.M., Ryals, A.J., & Nomi, J.N. (2009). Can déjà vu result from similarity to a prior experience? Support for the similarity hypothesis of déjà vu. Psychonomic Bulletin & Review, 16, 1082-1088.
Hupfer, A. (2006). How is a déjà vu experience created? Spectrum - The week of December 23rd.
Jersakova, R., Moulin, C. & O’Connor, A. R. (2016). Investigating the role of assessment method on reports of déjà vu and tip-of-the-tongue states during standard recognition tests. PLoS One. 11, 4, e0154334.
Mill, R. D., Cavin, I. & O’Connor, A. R. (2015). Differentiating the functional contributions of resting connectivity networks to memory decision-making: fMRI support for multi-stage control processes. Journal of Cognitive Neuroscience. 27, 8, p. 1617-1632.
Urquhart, J. & O'Connor, A. R. (2014). The awareness of novelty for strangely familiar words: a laboratory analogue of the déjà vu experience. PeerJ. 20 p., E666.
Wolfradt, U. (1989). Déjà vu experiences: theoretical assumptions and empirical findings. Journal of Clinical Psychology, Psychiatry, and Psychotherapy, 359–376.

Other sources i.a.
http://www.wiener-blutgasse.at/magie/de_ja_vu_erlebnis.html (10-01-03)
http://de.wikipedia.org/wiki/D%C3%A9j%C3%A0-vu (10-01-03)
http://at.galileo.tv/science/deja-vu-studie-liefert-neue-erklaerung-fuer-das-raetselhaft-phaenomen/ (16-08-18)


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