Déjà vu: Was I here before or is my mind playing tricks on me?
What is Déjà vu?
Endless descriptions exist for the experience we call déjà vu. The French term meaning “already seen”, is a strange phenomenon that occurs when one feels the sense of having experienced an event, even though they have never experienced it before. The déjà vu phenomenon is well studied in patients suffering from psychiatric disorders and epilepsy. In epileptic patients, déjà vu often precedes a seizure (Carey, 2004). Psychiatrist Vernon Neppe defines déjà vu as “any subjectively inappropriate impression of a familiarity of a present experience with an undefined past” (Wild, 2005). It is this inability to pinpoint a past at which this event occurred combined with the familiarity of the scene, which composes the strange feeling of déjà vu.
Essentially this feeling is the opposite of what happens when someone cannot remember a place or location, despite having actually been there before, such is the case in neurodegenerative diseases. Unlocking the theory behind déjà vu could elucidate the mechanism of memory loss in patients with neurodegenerative diseases.
How déjà vu occurs?
Paranormal theorists propose the déjà vu experience is evidence for reincarnation, citing that experiencing something for the second time around indicates your soul experienced this event in a previous life (Wild, 2005). This interpretation of the déjà vu experience would make sense if there were evidence supporting Descartes view that the soul and body are separate entities. However, this explanation is less biological and does not explain what might happen at the molecular level. Early thinkers believed in a “double consciousness” and suggested déjà vu was the result of two halves working asynchronously such that “only one brain has been used in the immediate preceding part of the scene—the other brain asleep, or in an analogous state nearly approaching it (Berrios, 1995). For example, when a person sees something in quick succession they see it first time, superficially and a second time with full awareness (Foer, 2005). Therefore, the déjà vu sensation may occur as a result of not remembering the first glance. So, when the second glance occurs, you feel as if you have seen it before, creating the sensation of déjà vu (Foer, 2005).
Others suggest déjà vu occurs as a result of a piece of a scene, an object, triggering the feeling of familiarity of a scene. Alternatively, the “tape recorder hypothesis” suggests as present events are recorded, memory recall is reproducing the memory, thus déjà vu occurs as a result of these two actions working simultaneously (Wild, 2005).
Déjà vu also occurs when a dream scene becomes a real life scene. This creates the sensation that one has experienced this event at a previous time, which is true, however the previous experience occurred in a dream state not a real state, thus in all actuality one has not been there before. So if one has not actually been there before, how was the mind able to create the scene at a previous point in time? There is also the instance that the original time and place this event occured cannot be pinpointed and rather one just feels they have previously experienced this event.
The most interesting consideration to ponder about déjà vu is that we become aware that this scene happened before. Just because our conscious mind does not believe it has happened before, does this mean it hasn’t? This argument raises concerns about the validity of the reality we perceive, whether we are in a reality, a lucid dream, or something of the like, which is outside the scope of this paper but should be acknowledged.
Why is déjà vu such a shock?
Why is it such a shock when our conscious mind experiences déjà vu and does not believe this event could have happened before? When déjà vu is experienced, we are aware that déjà vu has occurred. Our I-function, the conscious mind, kicks in to tell us that this is a strange thing. Our conscious mind knows from experiences that events do not happen twice in the exact same way. In addition to the acknowledgement of the eerie feeling, the I-function then decides which event is the real experience which is the non-real experience because our mind only wants one story at a time. It cannot and does not want to experience two stories at the same time and accept that both are true. If déjà vu is simply an illusion, how can our mind (I-function) distinguish between this illusion and the story it is creating? Is it that the story it is creating is intercepted because it doesn’t have to work as hard if the memory is already there? Is this when we realize we are experiencing an episode of déjà vu?
A Biological Basis for Déjà vu
While all these notions of the origination of déjà vu exist, little is known about the biological basis of déjà vu. What is happening to the neuronal connectivity that allows for the construction of a story of an event prior to it happening? Also, what triggers the recall of this story as being a prior story to give the sensation of déjà vu? Josef Spatt suggests déjà vu is the result of the mind playing tricks on you. Spatt hypothesizes a perceived scene is given characteristics of familiarity that normally accompany conscious recollection (Spatt, 2002). This suggests a flaw in the connections between memory and perception.
In terms of anatomical structures related to déjà vu experiences, the hippocampus is responsible for memory recall. The parahippocampal cortex is responsible for the feeling of familiarity or unfamiliarity. Furthermore, the frontal networks are well characterized for the ability to determine the specific time (Spatt, 2002). Spatt suggests false activations of connections among these areas initiate the déjà vu sensation (Spatt, 2002). Alternatively Biologist Susumu Tonegawa suggest déjà vu is simply a “malfunction in the brains ability to sort through new information” (Steenhuysen, 2007).
The lack of biological evidence supporting a cause for déjà vu results from the difficulty of reproducing déjà vu experiences in the laboratory. In most instances, déjà vu occurs infrequently and one could imagine the difficulty in trying to observe a déjà vu experience. Furthermore, most research on déjà vu experiences is limited to a subject’s self report that déjà vu has occurred (Wild, 2005).
Research on the déjà vu experience raises interesting questions about the intersection between memory, dreams and reality. If déjà vu is the result of a premonition like experience, where a dream happens and then the event happens in real life, is the brain indeed ‘wider than the sky’ encompassing more than we could ever imagine? Is the brain able to anticipate events before they occur, thus acting as a survival mechanism?
While these interesting hypotheses about déjà vu are proposed, a definitive description of the déjà vu experience has yet to be investigated. Other interesting questions which arise from attempting to understand déjà vu include asking what scenes become déjà vu and whether these instances are meant to foreworn us of mistakes or tell us of good fortune? Alternatively, if déjà vu is a malfunction of memory recall, understanding the mechanism of déjà vu may elucidate the mechanism of normal memory recall and what happens when this process malfunctions. So whether our mind is playing tricks on us or actually recalling a previously viewed event, understanding the neurobiology of this phenomenon will advance current understandings on the biological basis of memory recall.
(1)Berrios, G. (1995). Deja Vu in France During the 19th Century: A Conceptual History. Comprehensive Psychiatry , 123-129. http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6WCV-4CR8YHC-5&_user=423519&_coverDate=04/30/1995&_rdoc=1&_fmt=high&_orig=search&_sort=d&_docanchor=&view=c&_acct=C000020258&_version=1&_urlVersion=0&_userid=423519&md5=d8b04d6eda217b0eae541272e5bd2bcb
(2)Carey, B. (2004, September 14). Deja Vu: If It All Seems Familiar, There may be a reason. New York Times http://www.nytimes.com/2004/09/14/science/14deja.html
(3)Foer, J. (2005, September). The Psychology of Deja Vu. Discover Magazine . http://discovermagazine.com/2005/sep/psychology-of-deja-vu
(4)Spatt, J. (2002). Deja Vu: Possible Parahipocampal Mechanisms. J Neuropsychiatry Clin Neurosci , 14 6-10. http://neuro.psychiatryonline.org/cgi/content/full/14/1/6
(5)Steenhuysen, J. (2007, June 8). Brain mechanism explains sense of deja vu. Reuters . http://www.reuters.com/article/idUSN0728049020070608
(6) Wild, E. (2005). Deja Vu in Neurology. Journal of Neurology , 252, 1-7. http://www.springerlink.com/content/h7f0r295lyk7ul3x/