We’ve all felt it at some point in our lives. That feeling of already having experienced what you’re currently experiencing. We call it Déjà Vu which is french for “already seen” and we are so sure to have seen that thing or heard that other thing before that we most often attribute it to possibly having dreamt of that same exact scenario. This phenomenon comes randomly, doesn’t last more than a few seconds and has no physical manifestation therefore it is very difficult to research. But that doesn’t mean that experts and researchers aren’t looking into it and putting forward viable theories that may explain it.
One of principal theories that surround this phenomenon is one that links it directly to our memory compound in the brain. In this case, the main culprit would be the rhinal cortex located in the medial temporal lobes. This area is closely related to our ability to familiarize and recognize our environment as opposed to the hippocampus which helps us with detailed recollection of what surrounds us. The theory goes that déjà vu happens when the rhinal cortex takes action instead of the hippocampus when the brain is actually trying to form a detailed recollection of an event and that causes us to feel like we’ve already been there.
In previous research on epileptic patients, researchers have found that epileptic seizures are often preceded by an experience of déjà vu. This allowed the scientists to narrow down the area where the phenomenon starts. They found that déjà vu is part of an electrical discharge that happens in the brain as part of an aura warning of an upcoming epileptic event. But since the event also occurs with non epileptic healthy brains, the researchers were able to conclude that déjà vu is simply due to a mismatched neuronal discharge that also happens regularly in healthy people without pathological consequences. Another instance of this symptom is called Hypnagogic jerk and it is that feeling of falling that happens just as you are about to fall asleep.