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Déjà vu is a French term that means "already seen". This term describes the feeling we have at a given time that We have seen or experienced something before, when we know that we have not.
There are some variations of the same term that are: déjà vécu "already experienced", déjà senti, "already thought" and déjà visited, "already visited". The French scientist Emile Boirac was one of the first to study this strange phenomenon and who gave it its name in 1876.
- 1 What is déjà vu?
- 2 memory systems
- 3 Theories to explain why déjà vu happens
What is déjà vu?
Many times the term déjà vu is used to define certain precognitive experiences, in which someone feels they know exactly what is going to happen next, and does. But an important feature of this phenomenon is that déjà vu is experienced while an event is happening, not before. Precognitive experiences, on the other hand, if they are real, show things that will happen in the future, not things that we have already experienced.
It is said that deja vu occurs occasionally in 60-80% of people. It is an experience that is almost always fleeting and brief, which occurs without warning and occurs randomly.
Most researchers claim that this phenomenon is a memory-based experience, so the brain's memory centers would actually be responsible for it.
The temporal lobes are the main ones involved in the retention of long-term memories, both of events and events. Certain regions of the medial temporal lobes are also very important in the detection of familiarity and recognition, as opposed to the detailed recall of specific events.
It is said that the detection of familiarity depends on the function of the entorhinal cortex, while the detailed memory is linked to the hippocampus.
Unfortunately, the randomness of the déjà vu experiences in healthy individuals makes it difficult to empirically study this phenomenon, since any research on the subject depends on the subjective information of the people involved. This means that to get to the root of the cause of déjà vu depends on the perceptions of each individual, which makes it very difficult to understand this strange and mysterious event.
But as with many phenomena that we still cannot understand, there are different theories surrounding the origin of déjà vu. Below we summarize the main ones.
Theories to explain why déjà vu happens
Some researchers propose that déjà vu is produced due to a discrepancy in memory systems that generates a detailed but incorrect memory of a new sensory experience. That is to say, déjà vu is evoked by a mismatch between sensory input and memory output. The information ignores our short-term memory and goes directly to our long-term memory, causing a mismatch between sensory input (hearing, vision, touch) and working memory. This causes a new experience to seem familiar, although this experience is not really strong enough to be true.
Another theory suggests that the activation of the neuroentorrinal system, involved in the detection of familiarity, arises without the activation of the memory system within the hippocampus. This leads us to have a sense of recognition, but without specific details.
It has also been proposed that deja vu is a reaction of brain memory systems to a family experience. This experience is known to be novel, but it has many recognizable elements, although in a slightly different environment. For example, find us in a bar or restaurant away from our place of residence, but that has the same design or very similar to the one we regularly go to in our city.
It has also been observed that a subset of Epilepsy patients constantly experience déjà vu at the start of a seizure, that is, when the seizures begin in the medial temporal lobe. This has given researchers some of the main clues to the empirical study of déjà vu.
Apparently epileptic seizures are caused by alterations in electrical activity in neurons within the focal regions of the brain. This dysfunctional neuronal activity can spread throughout the brain like shock waves generated by an earthquake. The brain regions in which this electrical activation may occur include the medial temporal lobes.
The electrical disturbance of this neural system generates an aura (a type of warning) in the form of deja vu before the epileptic event.
On the other hand, déjà vu experienced before an epileptic seizure can be quite lasting, and not a fleeting feeling as it happens in those people who do not have epileptic seizures.
There are many more theories about the cause of déjà vu. These range from the paranormal as saying that they come from memories of past lives, through precognitive dreams and even alien abductions.
Some justify this experience as the proof of the existence of a parallel universe. According to physicist Michio Kaku, quantum physics shows that there is a possibility that déjà vu is caused by the ability of the human brain to "walk among several universes." Michio explains these "parallel universes" by simulating the radio waves; We can't see them, but there are hundreds or even thousands that fill our space. However, as a result of the laws of gravity, the radio can only be tuned to one station at a time. Similarly, our mind is tuned into a single frequency of reality, and when we feel this reality as too familiar to be new, it could mean that we are "vibrating in unison" with a parallel universe.
Another theory within the paranormal states that déjà vu is generated by our spirit, not the memory of our brain. It would be like a hazy memory or a forgotten dream. Therefore, it is believed that this can only make sense if it originates from the spiritual ether. Apparently this experience is the way in which our spirit takes us root in the Now, and lets us know that it is in this place of time and space where we are destined to exist. It is like a little reminder of consciousness.