Science knows not so much about the origin of deja vu, although this phenomenon is not at all rare.
Remember how often you say, "I just had deja vu!"
Today, there are several theories regarding its origin.
1. Neural discharges
It turned out that patients with epilepsy at the very beginning of the attacks of the disease also quite often experience deja vu. This discovery made it possible to study this phenomenon in more detail. Epileptic seizures are caused by changes in the electrical activity of neurons in the focal region of the brain. Neural activity can travel like a shock wave during an earthquake throughout the brain, including the middle temporal lobe, which plays a key role in long-term memory storage. From this, just before the seizure of epilepsy, deja vu arises.
In order to determine the regions from which the signals of deja vu are coming, the researchers measured the neural activity of the brain of these patients. The olfactory cortex turned out to be such a department. As a result, it has been suggested that deja vu is the result of dysfunctional electrical discharges in the brain. Similar neuronal discharges can occur in people without epilepsy. An example is the involuntary shudders that sometimes occur when falling asleep.
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However, some researchers believe that déjà vu of epileptic patients and healthy people are different phenomena, and indicate that in the former it can last quite a long time, in the latter it is always fleeting.
2. Memory failure
Deja vu in healthy people can be the result of a malfunctioning memory, which is divided into short-term and long-term. Deja vu happens, according to some scientists, due to differences in memory systems that process new experiences. Information can somehow bypass short-term memory and go straight to the "daddy" in the brain, where the long-term is stored. This explains why a new event or phenomenon seems painfully familiar, but not as “material” as a real memory.
3. Reacting to familiar details
Another theory is that déjà vu may be a reaction of the brain's memory systems to familiar details of a completely new experience. For example, when you enter a restaurant in a foreign country with interior decoration details similar to those of a restaurant in your hometown.
So far, we have only theories, but science does not stand still and sooner or later this riddle, like many others that our gray matter is asking us, will be solved.