Everything you wanted to know about Deja Vu

We’ve all heard the term deja vu before, right? Many of us know it from that scene in The Matrix (you know the one, with the cat). Okay, so we went off on a tangent. Apologies. The term deja vu is a term known outside of The Matrix as well. In fact, the French expression translates as “already seen” and perfectly summarizes exactly what deja vu means. It’s that feeling we get when we see or experience something incredibly familiar.

Often we will have had the same experience at a much earlier time and forgotten about it. Only our brain and subconscious recognizes that feeling, and understand that this is something familiar to us. Deja vu can signify feelings of unease and apprehension but is also useful for developing instinct and offers an opportunity for us to learn more about ourselves.

Occurrences of deja vu

Deja vu is one of those things that affects upto 70% of the population on a semi-regular basis. It’s something almost everyone has experienced at least once in their lives, but it is still very poorly understood in terms of what it actually is and what causes it. The main problem with deja vu is that it occurs almost entirely at random, and there are no warning signs in the build-up. The accepted theory is that deja vu is a memory-based experience and that the brain is responsible for causing it to occur.

Everything you wanted to know about Deja Vu

Memory systems

The brain is fascinating, particularly with regards to memory and the way memory works. The medial temporal lobes are the part of our brain that is responsible for storing and processing long-term memory of events and experiences. But some subsets of these brain regions are essential for detecting recognition and memory. Because many of these run deep, we aren’t always aware of the information and memory they’ve stored until something like deja vu happens. The rhinal cortex function is the one most associated with familiarity detection, and this is what feeds into the idea of deja vu.


Because epilepsy is a condition that affects the brain, curiously, many people who suffer from epilepsy often experience deja vu just prior to a seizure, when that seizure occurs in the medial temporal lobe. Epilepsy is caused by glitches and alteration in the way electrical activity works in the brain. The electrical disturbance, which can occur across the whole brain, leads to a feeling of deja vu just before the onset of a seizure. In fact, this has led to the discovery that scientists can identify where deja vu signals begin in the brain, by looking at the neuronal discharges of epilepsy patients.

Deja vu is a strange experience and brings with it many different feelings. For some people, deja vu is experienced because they have in fact lived through the exact same experience before. For others, they might have retained memories from a lucid dream, and be remembering those. Overall, it is difficult to assess and study deja vu because it’s random, and relies on feedback from those involved, and has to be self-managed. But, we are making breakthroughs every day, so it seems only a matter of time before we are able to study deja vu properly.

Everything you wanted to know about Deja Vu