Déjà vu Is a Neurological Phenomenon Scientists Claim

Scientists in the UK have even identified four cases of "chronic déjà vu."

Have you ever experienced déjà vu? If so, you are among the 60-70% of the population who has. The majority of those who report déjà vu are between the ages 15 and 25. I’m a complete rationalist who believes that every phenomenon, no matter how strange or supernatural it appears, has a scientific reason behind it. Even so, I’ve met several people and walked into a few situations where, though I had never been there before or met the person before, I suddenly felt awash in a bizarre familiarity. This transcendental sensation can shake beliefs such as mine right to their very core.


But I wasn’t ready to denounce science yet. And I’m glad. Because it turns out, there is a rational explanation. Though some radical notions have in the past been connected to this strange feeling, such as déjà vu being a momentarily aligning with a past life or another you in a parallel universe, or as my editor suggests—a glitch in the matrix, scientists now believe it has a neurological basis.

Unfortunately, the feeling is here one minute and gone the next, making it difficult to study. Even so, there are quite a few theories on what causes it. One traditional hypothesis, posited by psychiatrists, is mismatched brain signals. For a second it feels as though we are transported to a moment in the past and we mistake it for the present. This may be why it’s been associated with the idea of reincarnation.  

Another theory is that déjà vu is our brain trying to piece together a situation on limited information. A third states that it is a misfiring in the parts of the brain that recall memory and decipher sensory input. Sensory information, rather than taking the proper channels, leaks out of the short-term memory and into the long-term one. In this way, current experiences seem to be connected to the past. Some studies even suggest that familiar geometric shapes give us a sense of knowing something about a place that is, in reality, totally unfamiliar to us.

Instead of a glitch in the matrix, déjà vu may just be a glitch in our memory.  

Since we are completely aware of everything that’s going on when we experience déjà vu, this suggests that every part of the brain need not participate for the sensation to take place. Psychologist Anne M. Cleary at Colorado State University, in a study in 2008, found that déjà vu followed patterns we associate with memory, specifically recognition memory. This is the kind that gets us to understand that we are confronting something that we’ve seen or experienced before. If you’ve ever recognized a landmark, a friend from across the room, or a song on the stereo, you’ve experienced recognition memory.

Familiarity-based recognition is associated with it. Here, we have that feeling of familiarity, but we can’t quite place where we’ve seen this person, place, or thing. For instance, you recognize someone across the street, but can’t remember their name or where you know them from. Prof. Cleary conducted several studies which found that déjà vu is a form of familiarity-based recognition. Her work suggests that our memory stores items in fragments. When there is a certain overlap between old and new experiences, we have strong feelings about the connection, which we interpret as déjà vu.   

Recent studies looking at epileptic patients made impressive breakthroughs in our understanding of the phenomenon. Epileptics with certain intractable conditions require electrodes to be placed inside their brains in order to locate the source of their seizures. During this procedure, some neurologists have had patients experience déjà vu. They soon discovered that the phenomenon takes place in the medial temporal lobe, which is responsible for memory. The electrodes are usually placed within the rhinal cortex—the most important piece of which is the hippocampus, the structure responsible for long-term memory formation. French scientists have found that firing current into this cortex can trigger an episode of déjà vu.

Location of the amygdala and the hippocampus. By OpenStax College [CC BY 3.0], Wikimedia Commons.

The French study, published in the journal Clinical Neurophysiology, measured EEG wave patterns from patients with epilepsy who experienced déjà vu through electrical stimulation. The areas of the brain they examined included the amygdala, which is responsible for emotion and the hippocampus. Researchers found that electrical patterns, emanating from rhinal cortices and the amygdala or the hippocampus, caused déjà vu to occur. These neuroscientists believe that some sort of electrical phenomenon in the medial temporal lobe activates the memory in such a way that it causes déjà vu to occur.

Stranger still, scientists in the UK have actually found patients who experience “chronic déjà vu.” In this case, experts identified four senior citizens who encounter the feeling on a consistent basis. What is the impact of such a phenomenon? It made them feel as if they were clairvoyant. All four refused to go to the doctor, believing they already knew what the physician would say, and avoided watching the news, thinking they already knew the outcome. That’s because each time they took part in either activity that was the result they came to.

Each individual experienced some type of problem with the temporal lobe of their brain. The circuits in that area were in a sense stuck in the “on” position. It just goes to show that when we don’t know the reason for a phenomenon or sensation, our mind assigns a meaning to it. But that isn’t necessarily the correct one. And even though knowing the neurological basis of déjà vu may evaporate the supernatural awe surrounding it, understanding the phenomenon better puts a scientific mind, like mine, at ease.

--

​There are two kinds of failure – but only one is honorable

Malcolm Gladwell teaches "Get over yourself and get to work" for Big Think Edge.

Big Think Edge
  • Learn to recognize failure and know the big difference between panicking and choking.
  • At Big Think Edge, Malcolm Gladwell teaches how to check your inner critic and get clear on what failure is.
  • Subscribe to Big Think Edge before we launch on March 30 to get 20% off monthly and annual memberships.
Keep reading Show less

Why are so many objects in space shaped like discs?

It's one of the most consistent patterns in the unviverse. What causes it?

Videos
  • Spinning discs are everywhere – just look at our solar system, the rings of Saturn, and all the spiral galaxies in the universe.
  • Spinning discs are the result of two things: The force of gravity and a phenomenon in physics called the conservation of angular momentum.
  • Gravity brings matter together; the closer the matter gets, the more it accelerates – much like an ice skater who spins faster and faster the closer their arms get to their body. Then, this spinning cloud collapses due to up and down and diagonal collisions that cancel each other out until the only motion they have in common is the spin – and voila: A flat disc.

Scientists study tattooed corpses, find pigment in lymph nodes

It turns out, that tattoo ink can travel throughout your body and settle in lymph nodes.

17th August 1973: An American tattoo artist working on a client's shoulder. (Photo by F. Roy Kemp/BIPs/Getty Images)
popular

In the slightly macabre experiment to find out where tattoo ink travels to in the body, French and German researchers recently used synchrotron X-ray fluorescence in four "inked" human cadavers — as well as one without. The results of their 2017 study? Some of the tattoo ink apparently settled in lymph nodes.


Image from the study.

As the authors explain in the study — they hail from Ludwig Maximilian University of Munich, the European Synchrotron Radiation Facility, and the German Federal Institute for Risk Assessment — it would have been unethical to test this on live animals since those creatures would not be able to give permission to be tattooed.

Because of the prevalence of tattoos these days, the researchers wanted to find out if the ink could be harmful in some way.

"The increasing prevalence of tattoos provoked safety concerns with respect to particle distribution and effects inside the human body," they write.

It works like this: Since lymph nodes filter lymph, which is the fluid that carries white blood cells throughout the body in an effort to fight infections that are encountered, that is where some of the ink particles collect.

Image by authors of the study.

Titanium dioxide appears to be the thing that travels. It's a white tattoo ink pigment that's mixed with other colors all the time to control shades.

The study's authors will keep working on this in the meantime.

“In future experiments we will also look into the pigment and heavy metal burden of other, more distant internal organs and tissues in order to track any possible bio-distribution of tattoo ink ingredients throughout the body. The outcome of these investigations not only will be helpful in the assessment of the health risks associated with tattooing but also in the judgment of other exposures such as, e.g., the entrance of TiO2 nanoparticles present in cosmetics at the site of damaged skin."

Photo by Alina Grubnyak on Unsplash
Mind & Brain

Do human beings have a magnetic sense? Biologists know other animals do. They think it helps creatures including bees, turtles and birds navigate through the world.

Keep reading Show less