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Revisiting Déjà Vu

We’ve all had that experience of feeling like we’ve been to new place sometime in the past, and so that experience is called “seeing before” or déjà vu. And for many years, scientists have been seeking to explain this phenomenon.

Originally, this brain occurrence was explained through a theory called optical pathway delay. This theoretical elucidation stipulates that images from one eye were delayed and arrived just microseconds after the images from the other eye, causing the sensation that they had been seen before.

University of Leeds

However, several new explanations have arisen. The University of Leeds is heralded as a world-leader in the study of déjà vu, with their findings having been printed widely in both scientific and news publications.

With their new findings now appear in the medical journal Brain and Cognition, researchers describe how mundane experiences provoking feelings of déjà vu (unbuttoning one’s jacket while listening to classical music on the radio, or sitting in the park while children sing a nursery song, etc.) can be caused by disruptions in a section of the brain that handles with familiar memories.

To validate their theory, the scientists are working with blind subjects to eliminate the visual aspect of memories and examine the experience from a purer perspective. For example, one experiment supplies words to be memorized. Then the subjects are hypnotized to make them forget. Finally, when the same words are reintroduced, they induce a déjà vu effect.  

MIT - Massachusetts Institute of Technology

Meanwhile, at MIT’s Picower Institute for Learning and Memory, researchers have discovered a specific memory pathway in the brains of mice that, they maintain, is the cause of déjà vu.

To begin, the basis of memory lies in the process of groups of brain cells being linked by very strong chemical connections (pathways). Recalling a memory requires locating and stimulating a specific group. For our survival, our brain is able to distinguish between rather similar experiences (specifying whether you ate a red berry or black berry could be a life-preserving memory). This specifying aspect of recognized differing details in memories is called pattern separation.

MIT scientists now have revealed a correlating system called pattern completion. This memory function makes it possible to recall memories related only on a single aspect (for example: did I meet you when I was in college?).  To prove their theory, the researchers bred mice missing this crucial gene (ability) and then put them through a series of rat-maze experiments testing their memory as compared with normal mice.

Judging their experiments a success, the scientists maintain déjà vu occurs when, once in a while, the pattern-separation circuit misfires and a new experience (though similar to a previous one) appears to be identical. And though your brain’s neocortex says you haven’t seen this circumstance before, while your hippocampus is signaling that you have.

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