‘It’s as if I’ve lived this moment before’

Have you ever experienced the feeling of “I’ve lived this moment before”? Have you ever wondered what causes this feeling? What is déjà vu, how does it occur, and what does science say about it? You can find everything you’re curious about in this article. Enjoy your reading.

The term déjà vu, first used by French physicist Emile Boirac in 1876, was defined in the scientific literature in 1928 in Edward Titchener’s book “A Textbook of Psychology.” According to Dr. Titchener, the brain creates a partial perception before generating a precise perception of an experience, and this partial perception leads to the experience of déjà vu. So, what does science say now?

Before delving into the reasons and mechanisms behind déjà vu, let’s talk about how it can be observed. Déjà vu can manifest in two ways:

1. Déjà senti: Perceiving an event as if it has occurred before, experiencing a feeling that has not been felt before.
2. Déjà visité: Feeling as if a place you’ve never been before has been visited.

Déjà senti is the most common type of déjà vu.

Why and how does déjà vu occur?

Unscientific views on the cause of déjà vu suggest that it is triggered by events related to our lives in parallel universes. They propose scenarios involving reincarnation, where memories of our past lives are recalled. Some views suggest a connection between déjà vu and depression, stating that the brain relives memories it wants to forget but cannot. Another perspective claims that déjà vu involves glimpses into the future.

However, scientific research on déjà vu, which began in the 20th century and continues today, indicates that déjà vu is not a supernatural or metaphysical phenomenon. It is not related to reincarnation, as some might think; instead, it is a result of a memory-related anomaly.

Events in our daily lives, the emotions they evoke, and the places we visit briefly enter our short-term memory. Later, this information transitions from short-term to long-term memory. During this transition, information can be misrouted. The emergence of this path problem creates the feeling of déjà vu, as if the information is coming from long-term memory instead of short-term memory. The main cause is a temporal mismatch in the brain’s memory systems.

The human brain is not flawless; it frequently makes errors. These errors can distort, corrupt, or even erase existing information in memory. Sometimes, information in our memory is largely erased through encrypted amnesia, leaving only small fragments. In subsequent instances, when similar situations arise, an attempt is made to recall these erased memories, but they cannot be remembered accurately and vividly. In this situation, déjà vu occurs.

According to some scientists, déjà vu arises from a microsecond difference in the processing speed of data between the two brain hemispheres. When confronted with data, both the left and right brain hemispheres process it according to their own structures. This processing usually occurs at the same speed and time. However, at times, a disruption may occur in the neural networks of the corpus callosum, the bridge connecting the two hemispheres. In this case, the data from the two hemispheres may not overlap temporally. This mismatch lasts for an extremely short time, around 1 microsecond. Either the left brain perceives what the right brain has perceived with a slight delay or vice versa. This results in the person perceiving the same event, feeling, or place twice, with a 1 microsecond difference between them. Consequently, the person perceives the event not realizing that the first perception occurred a fraction of a second earlier. This is explained as déjà vu. Although this explanation makes sense in the scientific community, it has not been proven yet.

So, in which part of the brain does déjà vu occur? Recent studies indicate that the region responsible for déjà vu is the temporal lobe. The temporal lobe is crucial for storing new memories and recalling old ones. Patients with epilepsy originating from the temporal lobe report experiencing déjà vu just before having a seizure. This suggests that déjà vu is likely a sensation originating from our brain’s temporal lobe.

References:

noroblog.net/2018/12/21/bu-ani-sanki-daha-once-yasamistim-dejavu-nedir/

https://www.makaleler.com/dejavu-nedir-nasil-olur

https://www.artigercek.com/haberler/insan-nicin-dejavu-hissine-kapilir

‘The only way to achieve the impossible is to believe that it is possible’ – Lewis Carroll

ZEYNEP KARAKUŞ – 3rd Year Medical Student, SAKARYA UNIVERSITY FACULTY OF MEDICINE