Why and how do we experience déjà-vu? I am sure you must have asked yourself this question at least once in your life. Unless you’re among the 20-40% of people who are unaware of the phenomenon.
Déjà-vu is a French term which basically means “already-seen”. It is used to describe the very brief experience where you feel like you have already lived a moment before in spite of never actually having gone through it in the past — you are hit by a wave of familiarity for a fraction of a second or for a few seconds, and then, poof, the feeling goes away. Maybe, déjà-vu is about reliving true dreams we’ve dreamed before. Or, maybe, it has a more scientific explanation?
Since more than 50% of people have ‘felt’ déjà-vu, you would expect science to have proved its cause, or at least, to have some idea about it. The truth is, it is still not understood by researchers. This is so because “no clear, identifiable stimulus” is associated with triggering the feeling, says Michelle Hook, assistant professor in the department of neuroscience and experimental therapeutics at the Texas A&M Health Science Center College of Medicine. According to Hook, déjà-vu cannot easily be tested in laboratory. But, she does add that it might have to do with memory storage.
This is so because recognising familiarity is linked with specific regions of the temporal lobe which is where long-term memories are made and stored. This was concluded from studies involving epilepsy which are said to contain clues for déjà-vu and its cause. Some patients of temporal lobe epilepsy claim to experience déjà-vu before a seizure, almost as if that were a warning before the event happens, explains Hook.
As for healthy people, a glitch in the brain would account for déjà-vu. What this means is that the brain misunderstands the present to be the past as neurones linked with recognition and familiarity are at work. What further seems to support this idea is the fact that healthy people can also have the abnormal electrical impulses characterising epilepsy; for instance, the involuntary muscle spasm that many healthy people experience when falling asleep is a perfect example of this type of impulse.
Hook says that more research is needed to understand the phenomenon. According to her, this experience might not even have a simple answer. But, she is positive that a conclusive proof might be found in the future.