How do you explain the feeling of deja vu?

The feeling of deja vu is observed more often in young people, in situations of fatigue or stress. Many theories exist to explain it, some falling under the paranormal : memory of a past life, premonition… Scientists have also tried to unravel this mystery to find more rational explanations.

Deja vu in people with epilepsy

Deja vu has been studied in particular in people with epilepsy because it is a symptom that is common during seizures. Indeed, during a epileptic crisis, the electrical activity of certain neurons is altered. This dysfunction spreads through the brain and the electrical activation affects the medial temporal lobes. This electrical disturbance generates a feeling of deja vu at the onset of the seizure.

The region responsible for this sensation in epileptics is the rhinal region, located under theseahorse. Thus, in a research published in 2012French researchers succeeded in stimulating the feeling of deja vu in epileptic patients by stimulating the cortex rhinal. But what about people who don’t have epilepsy? Either comparable electrical discharges take place in the lobe temporal in the absence ofepilepsyor deja-vu is a matter of other processes.

The role of the frontal areas of the brain

In 2016, researchers from St Andrews University (United Kingdom) described, during a memory conferencefrom scanners of people who experienced a feeling of deja vu. To create this sensation, the researchers presented them with a list of words that had a link between them (pillow, bed, night, dream…) without the keyword linking all these words (sleep). The researchers asked the participants if they had heard words beginning with “s” and they answered in the negative. When later they were asked if they had heard the word “sleep”, they remembered that they had not heard it but, at the same time, the word was familiar to them: they had a feeling of deja vu. .

The team made MRI of the brains of the 21 volunteers and showed that the areas involved in the memoryas’seahorse, did not come into play in the phenomenon. In contrast, the frontal areas of the brain, which play a role in decision-making, were activated. One hypothesis is that the frontal regions of the cortex check memories and send signals in case of error when there is a conflict between the lived experience and what we believe we have already lived. The feeling of deja vu would be a sign that the memory check system is working well.