why do we get deja vu moments

Have you ever experienced a sudden feeling of familiarity while in a completely new place? Or the feeling youve had the exact same conversation with someone before? This feeling of familiarity is, of course, known as dj vu (a French term meaning already seen) and its
to occur on an occasional basis in 60-80% of people. Its an experience thats almost always fleeting and it occurs at random. So what is responsible for these feelings of familiarity? Despite, experiences of dj vu are poorly understood in scientific terms. Dj vu occurs briefly, without warning and has no physical manifestations other than the announcement: I just had dj vu! Many researchers propose that the phenomenon is a and assume the memory centres of the brain are responsible for it. The are vital for the retention of long-term memories of events and facts. Certain regions of the medial temporal lobes are important in the detection of familiarity, or recognition, as opposed to the detailed recollection of specific events. It has been that familiarity detection depends on function, whereas detailed recollection is linked to the. The randomness of dj vu experiences in healthy individuals makes it difficult to study in an empirical manner. Any such research is reliant on self-reporting from the people involved. A subset of patients consistently experience dj vu at the onset of a seizure that is, when seizures begin in the medial temporal lobe. This has given researchers a more experimentally controlled way of studying dj vu. Epileptic seizures are evoked by alterations in electrical activity in neurons within focal regions of the brain. This dysfunctional neuronal activity can spread across the whole brain like the shock waves generated from an earthquake. The brain regions in which this electrical activation can occur include the medial temporal lobes.

Electrical disturbance of this neural system generates an (a warning of sorts) of dj vu prior to the epileptic event. By measuring neuronal discharges in the brains of these patients, scientists have been able to identify the regions of the brain where dj vu signals begin. It has been found that dj vu is more readily induced in epilepsy patients through as opposed to the hippocampus. These observations led to the speculation that dj vu is caused by a dysfunctional electrical discharge in the brain. These neuronal discharges can occur in a non-pathological manner in people without epilepsy. An example of this is a, the involuntary twitch that can occur just as you are falling asleep. It has been proposed that dj vu could be triggered by a similar, resulting in a strange sense of familiarity. that the type of dj vu experienced by temporal lobe epilepsy patients is different from typical dj vu. The dj vu experienced prior to an epileptic seizure may be enduring, rather than a fleeting feeling in those who dont have epileptic seizures. In people without epilepsy the vivid recognition combined with the knowledge that the environment is truly novel intrinsically underpins the experience of dj vu. Dj vu in healthy participants is reported as a memory error which may expose the nature of the memory system. that dj vu occurs due to a discrepancy in memory systems leading to the inappropriate generation of a detailed memory from a new sensory experience. That is, information bypasses and instead reaches. This implies dj vu is evoked by a mismatch between the sensory input and memory-recalling output. This explains why a new experience can feel familiar, but not as tangible as a fully recalled memory. Other theories suggest, involved in the detection of familiarity, occurs without activation of the recollection system within the hippocampus.

This leads to the feeling of recognition without specific details. Related to this theory, it was proposed that dj vu is a reaction of the brains memory systems to a familiar experience. This experience is known to be novel, but has many recognisable elements, albeit in a slightly different setting. An example? Being in a bar or restaurant in a foreign country that has the same layout as one you go to regularly at home. Even more theories exist regarding the cause of dj vu. These span from the paranormal -, and to memories formed from experiences that are not first-hand (such as scenes in movies). So far there is no simple explanation as to why dj vu occurs, but advances in neuroimaging techniques may aid our understanding of memory and the tricks our minds seem to play on us. You know that feeling you get when you step inside a new house or walk around a foreign cityplaces you know youve never been beforeand you cant help but think, Ive done this already? It's dj vu, and if you've never had it before, take it from us: Its kind of creepy. Dj vu is French for already seen, and about two out of three people at one time or another, according to a 2003 review in the journal Psychological Bulletin. Despite being fairly common, its not a widely studied subject, says Alice Medalia, PhD, a professor of medical psychology at Columbia University Medical Center. And because dj vu is a subjective experiencein other words, its difficult to induce in research subjectstesting the theories behind it can be tricky. That said, researchers have a few guesses about why we experience dj vu (and no, it's probably You ve been somewhere similar before Some researchers believe dj vu is triggered when you enter an environment similar to one you've experienced in the past. For example, you could experience it when you enter a hotel lobby where the furniture is configured the same way as your childhood home's living room. RELATED: Researchers tested that theory in a 2009 study published in the journal Psychonomic Bulletin People who travel and people who can recall their dreams are more likely to experience dj vu than those who stay at home or dont remember their dreams, according to the 2003 review. These people can draw on a wider range of sources (either from, say, their adventures Europe, or just their own imagination), so it makes sense that they should think other environments feel familiar, too.

Something s up with your brain Some people who have temporal lobe epilepsy (a type of epilepsy that occurs in the part of your brain that handles short-term memory) experience dj vu right before they have a seizureanother sign that the phenomenon may be connected with the way memories are activated. Plus, its why some experts think dj vu is triggered by a kind of disruption in the firing of neurons in the brain, says Dr. Medalia. It could also be the result of your brain struggling to process multiple pieces of information, but for some reason, cant align them correctly, she says. That lack of synchrony, in med-speak, might be responsible for that dj vu feeling. RELATED: The bottom line? Regardless of whats happening (or whats causing it), for the vast majority of people, dj vu is pretty harmless. Unless youre experiencing an epileptic seizureand in that case, there are plenty of other signs to watch out forits a relatively normal experience. And you never knowmaybe that castle in London looks so familiar because, in your past life, you were Kate Middletons great-great-great-great grandmother-in-law. Hey, we can dream, right?

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