The sudden feeling of vague familiarity about certain scenes or things of life is a common phenomenon we might all have experienced one time or the other. Many of them were dream-like experiences, while some were so vivid; we almost thought it was a replay of the past.
The term “déjà vu” is believed to have been used first in 1876 by French physician Émile Boirac. Each episode last a few seconds only and is much common for Younger people to have these dream-states more often than older adults, yet people of all ages experience déjà vu, especially when they are stressed. There is a reverse of déjà vu, called jamais vu. Here, a familiar person or place is rejected as having never seen before.Many mysteries cloud this curious play of brain chemistry and many of them give rise to beliefs in rebirth, telepathy and clairvoyance. But is this strange feeling of familiarity really a message traveling thru time and space, from the light cone of our past? Or is it just some unconsciously managed memory trace that is peeking up at a second stimulus thru the same neural pathway?
Science has been tracking this question for many years but the stumbling block in investigating the phenomenon is the problem of recreating it in labs.
The Freudian psychoanalysts call déjà vu a replay of suppressed memories. They call it paramnesia. The original event was somehow linked to distress and was being suppressed from conscious recognition, no longer accessible to memory, they say. Temporal lobe epilepsy patients have been thought as good candidates, but their memories lack the true quality of déjà vu – the subject’s disbelief in the memory!
Dr. Vernon M. Neppe , the Director of the Pacific Neuropsychiatry Institute in Seattle, empirically defined the term déjà vu as:
“any subjectively inappropriate impression of familiarity of a present experience with an undefined past.”
(His book titled The psychology of Déjà vu: Have I been here before? has detailed out a long list of déjà vu presentations long back in the 1980s.)
In déjà vu, the subjective feeling of “replay of past” is imminently followed by a feeling of disbelief and rejection of the memory trace, as is widely documented. The act of seeing or hearing also does evoke a feeling of familiarity. It doesn’t pertain just to the memory alone. These qualities are absent in epileptic patients’ recollections and in drug-induced hallucinations. In such cases, the patient or the subject strongly “believes” in these traces of replayed “memory”. A similar phenomenon is seen in schizophrenics too (‘false recognition’). Hence many scientists believe that there should be a “non-epileptic” theory for deja vu that will encompass al the attributes of the phenomenon.
New light on an old problem
Robert Efron, in 1963 suggested the delayed vision theory. He stated that it is possible that sometimes the blending of information into the temporal lobe might not synchronize well and this may result in the deja vu episodes. Words flashed too rapidly to subjects without giving time for the conscious brain to register them were later identified as familiar by the same subjects in the pioneering experiments of Dr. Larry Jacoby in 1989. Recent simulated studies on attention and priming for attention have brought out certain correlations between gaps in attention and feelings of familiarity as in déjà vu. There are also reliable correlations between déjà vu and stress/fatigue as well as mood swings. It seems that whereas déjà vu may be triggered during times of peak tension when one is overly alert, it may be even more likely when one becomes tired and attention starts to wane. Alan Brown of the Southern Methodist Univ and Elizabeth Marsh at Duke University, ran a few tests on a group of students; based on the idea that deja vu’s originate in subliminal suggestion. They support the the diverted attention theory.
According to the theory, people sometimes see things twice in quick succession: the first time superficially or peripherally; the second time with full awareness. You might glance at a building while talking on a cell phone, for instance, and not really register it, then give it a second look a little while later after you get off the phone. You might not remember the first glance, but your brain has registered it subliminally, so the second glance may seem oddly familiar (see Dr.Brown’s new book “The Déjà Vu Experience”)
Temporal lobe – seat of Deja vu
Open brain surgery stimulations of déjà vu in temporal lobe has been done from the time of Dr. Penfield the latest being that of Dr.Bancaud.These expositions are being investigated with greater fervor, ever since the Alison R. Preston and John D.E. Gabrieli paper on the role of hippocampus as a scrap book of the brain, has come out.
….the relational/familiarity distinction predicts that patients with focal hippocampal damage would be selectively or disproportionately impaired on associative recognition, but exhibit intact or less impaired performance on single-item recognition. However, patients with selective hippocampal damage were equally impaired on the single-item and associative recognition tasks….. results suggest that the hippocampal formation contributes similarly to declarative memory tasks that require relational or familiarity processing…. the para-hippocampal gyrus differentiates between familiar and unfamiliar stimuli – and does so without having to retrieve a concrete episode from our memories.
The excitement is inexplicable, as the research has opened new ways to understand how we create a world of our own around us rather than fit ourselves into the world around. And that’s were evolutionary psychology starts taking up the issue.