Monday, January 21st, 2019

Simple science: Déjà vu debunked

Posted on January 27, 2015 in Perspectives
By USM Free Press

By: Donald Szlosek

You know those moments that felt like they already occurred? In fact, you are certain that they have, but you don’t know when or how it became too familiar?

Well this is known as déjà vu (which in French mean “already seen”) and was first studied in 1876 by the French scientist Emile Boirac. To this day, déjà vu is difficult to scientifically study because there is no reliable way to cause it to happen in a laboratory.

Well, what do we know?

Humans don’t seem to experience déjà vu until they are at least 8 or 9 years old. Déjà vu occurs most frequently occurs in our teens and twenties and then tapers off as we get older, so it might have to do with brain development.

So what causes déjà vu?

Currently there over a dozen theories as to how déjà vu occurs. Much like a stomach ache, déjà vu might be a symptom with many possible causes. One of the most prominent theories involves a disconnect that may be occurring between the deep structures of the brain that process our experiences unconsciously and the parts of our brain that are conscious about that they experience.  In order to get a better understanding of how Déjà vu might work, we have to understand a little neuroanatomy and physiology of the visual system.

As your eyes see images, they send this information to the back of the brain, this is where your occipital lobe is located and where the visual cortex processes images so that we are aware of what we are seeing. But visual cortex isn’t the first stop that information makes. Instead, we know that it stops in lots of other places. For instance, the amygdala, where it is processed at an involuntary emotional level, and the tectum, where it’s involved in preliminary visual processing and helps control eye movement.

It is those preliminary structures that are involved in the disconnect which cause déjà vu.

If I experience event A and then B, and then C, and the inner parts of my brain commit it to memory and generate an emotional response, but then, a fraction of later out of synch, my visual cortex finally gets around to telling me, the conscious aware part of my brain, what I am seeing. It will say “ok guys, we are looking for A and then B and then…” and then the brain says “whoah whoah whoah, wait and then C, right? That’s already happened I thought?” That might be deja vu.

What could cause these processes dealing with the same information to get temporarily out of sync like that? Well its probably a neurological abnormality, possibly an epileptic episode where neurons all fire in sync. We also know that patients who experience chronic and persistent deja vu tend to have brain damage in the temporal lobes of their brain. So the next time you are experience déjà vu and thinking you are a fortune teller, just remember that you are having a small neurological abnormality.


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