Déjà Vu et Jamais Vu: Science or Fiction?

You’ve probably heard the term ‘déjà vu‘ a lot in your life. But have you ever heard of ‘jamais vu‘ before? Perhaps the first thing that comes to your mind when you hear jamais vu is BTS and that’s all fine. Many people are familiar with déjà vu but only a few have heard about the latter. So, what exactly is jamais vu? What do these terms mean? What’s the difference? And how is it related to science?

Déjà vu 

Déjà vu is the sensation of recognising that a situation feels familiar even though, logically speaking, you know it isn’t; the term is commonly translated as ‘already seen’. We have likely experienced déjà vu occasionally – approximately 60-80% of healthy respondents experience this phenomenon. Scientists and neurologists say it’s really just a trick of the brain. Nevertheless, heightened cases of déjà vu have also been observed in people with epilepsy at the onset of a seizure – we will talk about later. 

First, let’s talk about memory

Although memories aren’t stored in a single part of the brain, it has been shown that some episodic memories (including long-term memories and events) are stored in the hippocampus in the temporal lobe of the brain. This part of the brain is also responsible for recognising something. It’s important to bear this in mind as we continue down the road of understanding déjà vu. 

In addition to this, memories with an emotional significance (such as strong emotional responses) are stored in the amygdala (also in the temporal lobe). The neocortex is involved with higher functions such as motor commands and language. On the other hand, the prefrontal cortex of the brain is commonly responsible for short-term working memory.

Déjà vu and epilepsy

Although déjà vu is still a mystery to scientists, they have found that patients with epilepsy may experience an extreme feeling of déjà vu at the start of a seizure.

Epilepsy is a neurological disorder where excessive and abnormal brain activity leads to the formation of recurrent seizures. These seizures can be further divided into generalized and focal seizures. Generalised seizures take place simultaneously in both hemispheres of the brain while focal seizures originate from one area of the brain and then proceed to spread. 

Focal onset #seizures, sometimes referred to as partial seizures, begin in  one side of the #brain. In some cases… | Seizure disorder, Seizures,  Seizures in children

Focal seizures can be further subclassified into temporal lobe seizures and frontal lobe seizures. Remember the good ol’ temporal lobe where the hippocampus is located? Déjà vu happens due to excessive firing of a signal (an action potential) in the hippocampus in patients experiencing temporal lobe seizures. Thus, déjà vu takes place in epileptic patients as a warning sign (along with ‘epigastric rising’ which is a fancy scientific term referring to a weird sensation in the stomach that rises to the chest and throat like nausea or indigestion).

Then you might ask, is déjà vu dangerous? Generally, no. Déjà vu is very common and is nothing to worry about… unless you’re experiencing heightened and excessive periods of déjà vu or anxiety along with loss of consciousness or uncontrollable jerking – this might be a symptom of epilepsy. 

Jamais Vu

Have you ever said a word so many times that it doesn’t even sound like a word anymore? It feels unfamiliar? Or when you look at your face in the mirror for a long period of time, it begins to feel very strange? Have you ever thought about why this happens? 

This is commonly described by the French phrase ‘jamais vu’ meaning ‘never seen’. It is the phenomenon where a familiar situation is not recognized by the observer. Unlike déjà vu, which is common among the population, jamais vu is less common and is more prevalent in patients with neuropsychiatric conditions. Similar to déjà vu, jamais vu is also known to be a symptom of epilepsy and migraines. 

Remember what I said about repeating a word in your head so many times that it doesn’t sound familiar anymore? This is ‘semantic satiation‘. It is a psychological phenomenon where repetition causes a word or a phrase to lose its meaning momentarily. 

What causes this sensation? 

According to an article, Professor Leon James, a psychology professor, believed that jamais vu is a form of fatigue called ‘reactive inhibition‘. This is the tendency for a response to reduce with increased fatigue caused by repeated firing of signals. With each firing, the brain cells take up more energy than the previous attempt and therefore become fatigued. 

James also delved into semantic satiation in music where he studied pop charts. He found that the songs that entered the charts the fastest were also the songs that left the charts the fastest. Semantic satiation can also be found in your everyday music. Research has found that the use of repetitive words and choruses allows the listener to be more attentive to other layers of sounds in the song on their second or third or even fourth listen. Now, this makes sense if you think about. Have you ever heard a song several times but only on the fifteenth listen you suddenly noticed a different harmony or an underlying guitar riff? This is due to semantic satiation. 

Let’s have a look at the song Jamais Vu by BTS as an example. Their performance of this song during Bang Bang Con really fascinated me. Their set design was simplistic and was all black and white, and the members would repeatedly climb up and down stairs throughout their performance. By doing this, they created a feeling of jamais vu – that sensation of repeating a word so many times that it begins to sound strange to your brain. It’s all about repetition, and they captured this perfectly during their performance and through their music. 

Both déjà vu and jamais vu are interesting phenomena and scientists have yet to discover more about them. Now you have a general idea about the two terms and the science behind them. The next time a word suddenly feels foreign to your brain, you know why. 

Written by Nethmi Dimbulana