Ever had that feeling where you are adamant that you have experienced something before when you know for a fact that you haven’t?
Around 70% of the population claim to have had this feeling of ‘Déjà vu’, a term coined by the French Philosopher Emile Boirac in 1876, which logically translates to ‘already seen’.
Occurring most commonly in younger members of the population, déjà vu has been linked with conditions such as epilepsy and dementia as well as being associated with anxiety and fatigue.
Sometimes the experience leaves you thinking whether or not you have actually been there before and then our mind wanders down the weird and wonderful path of alternate universes and past lives and whether déjà vu is actually a glitch where you get a split-second snapshot of something that you may have done, just not as you. Just me?
It turns out that this is a theory actually considered by Parapsychologists, who try to explain the workings of the brain by relating it to the paranormal, however whilst this idea may be quite appealing in a mystical sense, it is basically impossible to prove at present.
Epilepsy is a condition where patients experience seizures due to the abnormal firing of neurons of the brain with one theory stating déjà vu occurs due to this misfiring. This is supported by the fact that patients who suffer from Temporal Lobe Epilepsy (TLE) have been found to experience déjà vu both prior to the start of a seizure or in between convulsions. This disturbance of perception is a symptom of Epilepsy known as an ‘aura’ and can occur in other conditions such as migraines.
In TLE this neuronal discharge occurs in the temporal lobe of the brain, which is associated with functions such as sensory perception and memory association.
Interestingly another theory of déjà vu is related to memory and on a basic level, it may just be your brain sparking a false memory by interpreting a genuinely familiar sound/situation. Within the medial temporal lobe (the area affected in TLE patients) are structures called the perirhinal cortex (PC) and entorhinal cortex (EC), which play a role in explicit memory, which is the conscious recollection of an experience.
Research conducted in 2004 showed that direct electrical stimulation of the PC and EC in the brains of epilepsy patients produced a déjà vu-type response, with this being produced more upon stimulation of the EC in comparison to the stimulation of the amygdala and the hippocampus, which are other brain areas involved in memory and emotions. Whereas stimulation of the PC was found to be associated more with the reminiscence of a memory.
Patients with dementia, a form of memory loss seen with aging, also experience more frequent episodes of déjà vu, again suggesting a link with memory.
It is therefore possible that there is something physically changing in the brain in order for déjà vu to occur.
A curious case of déjà vu has also been linked to anxiety and depression and was discovered in a 23 year old man who experienced 8 years of a chronic form of déjà vu, meaning that performing tasks such as reading or watching TV felt pointless to him as he believed that he had ‘heard it all before’. Unlike the déjà vu experienced by dementia patients, this man was fully aware of the false nature of his déjà vu, making his condition all the more confusing. Whilst it can’t be concluded that there is a definite causal link between anxiety and déjà vu, it has opened a door to possible new areas of study.
The main problem with attempting to study this in the lab is that déjà vu tends to occur spontaneously and for a very short amount of time, making it almost impossible to recreate.
However a study conducted by the ‘Leeds Memory Group’ used hypnosis in an attempt to recreate this experience. The study was performed based on the theory that the brain goes through a two-step process in order to retrieve a memory, so when presented with a situation the brain first attempts to search for the memory to see if it is new and the second being another part of the brain that would ultimately identify the situation as being familiar or not. This is obviously a very simple way of looking at the mechanisms of the brain without stepping into the terrifying territory of molecular biology, but the general idea is that in déjà vu, the second step is somewhat dysfunctional, leading to the individual believing a completely novel experience to be something of the past.
Participants were asked to read 24 words before being hypnotized to believe that any words they later saw in a red frame would seem familiar to them, but they would not know why. Once removed from this hypnosis, participants were shown a number of words in both red and green frames, some of which were not from the original 24.
10/18 people studied claimed that they had a weird sensation similar to that of déjà vu, when they saw the words in the red frames.
However, this is a very small sample size and we are exposed to words everyday, making most a familiarity. It may therefore be too simple an idea to base the phenomenon on at present, but hypnosis may be an interesting tool to explore déjà vu further if used in combination with brain-imaging techniques such as functional magnetic resonance imaging (fMRI).
There are many people who believe that we shouldn’t be trying to understand déjà vu and just accept that our brains can’t always function perfectly, but where is the fun in that? Humans are extremely complex and it’s these complications that make us both bizarre and beautiful. We have a thirst for knowledge and in my opinion it would be a wasted opportunity not to quench it. Déjà vu is just one of the many glitches that our brains experience and who knows, on our journey of déjà vu discovery we might just find more clues as to how the elusive human brain works.