Déjà vu - How and why it occurs

Introduction

Have you ever felt as if you have lived through a particular moment, but it is actually your first time experiencing it? You may be experiencing déjà vu. The Britannica Dictionary defines “déjà vu” as the feeling that you have already experienced something that is happening for the first time. The word “déjà vu” originates from a French word that translates to “already seen” in English, referring to the illusory memory experience. [1] This word was first coined in 1876 by French philosopher and psychical researcher Émile Boirac. [4] The brain creates a sensation of recognition as if you have lived in a certain situation before but are unable to retrieve the actual memory or situation. [2]

How it works

“Déjà vu is an anomaly of memory caused by dysfunctional connections between the parts of your brain that play a role in memory recollection and familiarity,” Neurologist Dr. Khoury explains. The main part of the brain involved in memory recollection is primarily associated with the activity in the hippocampus and posterior parahippocampal located in the temporal lobe on both hemispheres of the brain. Specifically, the parahippocampal cortex supports recollection by encoding and retrieving contextual information. Familiarity, on the other hand, has been associated with activity in the perirhinal cortex, which supports familiarity by encoding and retrieving information on specific items. [1]

During déjà vu, the hippocampus and the surrounding brain tissue are activated. These seizures could be temporal lobe epilepsy -- a seizure disorder that starts in the temporal lobe, disrupting recognition memory systems, hence a sense of false familiarity. [2] 

There are four different theories of the cause of déjà vu [4]:

• Split perception theory is when an individual sees something at two different times. The first time is considered a brief distraction, and the second is when the person looks at it. Since the first time did not involve full attention, the second time is perceived as a different event, but it is, in reality, the same continued perception. 

• Minor brain circuit glitches: This is the disruption of electrical signals due to a seizure.

• Memory recall : This occurs when the brain cannot access a certain memory but feels a sense of familiarity with the situation that may not have happened before.

• Psychic experience: This is a theory where the déjà vu experience may have occurred in a previous life or dream. 

Types of Déjà vu

Déjà vu is categorised into two sub-divisions: pathological and non-pathological. Non-pathological déjà vu is considered relatively safe; over ⅔ of the population experience this. Non-pathological déjà vu can be easily influenced by the factors discussed below, while pathological déjà vu may be caused by an underlying disease associated with memory recall of the brain. Some scientists believe that all cases of déjà vu currently discovered fall under the category of pathological déjà vu as all cases of this experience are highly associated with the disturbance of electrical discharge via neurons. [4]

There are also different déjà vu types listed below:

Are déjà vu experiences common?

Déjà vu is most common in people who are 15 to 25 years old. [2] Déjà vu has also been shown to decrease with age. [4] Researchers also believe, though not fully proven, that déjà vu is more common when people have:

• A higher level of education

• Travel more

• Remember their dreams

• Hold liberal beliefs

• Are tired, stressed, or busy [3]

Concerns

Déjà vu may be a sign of underlying health concerns such as frontotemporal lobe dementia when experiences are persistent and tend to try to rationalise the illusion. [2] However, occasional déjà vu experiences are quite common.

Conclusion

Déjà vu is a strange phenomenon; however, many theories may attempt to explain déjà vu. Déjà vu usually disappears as we age and is more common in younger people due to their dreams and exposure to different experiences. Déjà vu is still not fully supported by research, and many may have superstitions about it; however, there is evidence showing that déjà vu most likely stems from brain dysfunction, in particular, the retrieval of memory.

Citations

1. Aitken, C. B. A., Jentzsch, I., & O’Connor, A. R. (December 2023). Towards a conflict account of déjà vu: The role of memory errors and memory expectation conflict in the experience of déjà vu. Neuroscience & Biobehavioral Reviews, 155, 105467. 

Retrieved November 23, 2023, from

https://www.sciencedirect.com/science/article/pii/S0149763423004360#sec0005

1. Deja Vu: What It Is and Why It Happens. (October 24, 2022). Cleveland Clinic, healthessentials.

Retrieved December 1, 2023, from

https://health.clevelandclinic.org/deja-vu-what-it-is-and-when-it-may-be-cause-for-concern

1. Feel Like You’ve Been Here Before? It Might Be Déjà Vu. (July 02, 2019). PennMedicine. Retrieved December 3, from

https://www.pennmedicine.org/updates/blogs/health-and-wellness/2019/july/deja-vu#:~:text=The%20eerie%20feeling%20that%20you,brain%20is%20telling%20you%20otherwise.

1. The deja vu types. (October 8, 2022). Tahira Rubab. 

Retrieved December 4, from 

https://tahirarubabhafeez.com/blog/deja-vu-types