What is deja vu and why does it happen?
“Wait a minute. I’ve been here before …” Credit: Jonny/Flickr
Have you ever experienced a sudden feeling of familiarity while in a completely new place? Or the feeling you've had the exact same conversation with someone before?
This feeling of familiarity is, of course, known as déjà vu (a French term meaning "already seen") and it's reported to occur on an occasional basis in 60-80% of people. It's an experience that's almost always fleeting and it occurs at random.
So what is responsible for these feelings of familiarity?
Despite coverage in popular culture, experiences of déjà vu are poorly understood in scientific terms. Déjà vu occurs briefly, without warning and has no physical manifestations other than the announcement: "I just had déjà vu!"
Many researchers propose that the phenomenon is a memory-based experience and assume the memory centres of the brain are responsible for it.
The medial temporal lobes are vital for the retention of long-term memories of events and facts. Certain regions of the medial temporal lobes are important in the detection of familiarity, or recognition, as opposed to the detailed recollection of specific events.
The randomness of déjà vu experiences in healthy individuals makes it difficult to study in an empirical manner. Any such research is reliant on self-reporting from the people involved.
This video is not supported by your browser at this time.Glitches in the matrix
A subset of epilepsy patients consistently experience déjà vu at the onset of a seizure – that is, when seizures begin in the medial temporal lobe. This has given researchers a more experimentally controlled way of studying déjà vu.
Epileptic seizures are evoked by alterations in electrical activity in neurons within focal regions of the brain. This dysfunctional neuronal activity can spread across the whole brain like the shock waves generated from an earthquake. The brain regions in which this electrical activation can occur include the medial temporal lobes.
Electrical disturbance of this neural system generates an aura (a warning of sorts) of déjà vu prior to the epileptic event.
By measuring neuronal discharges in the brains of these patients, scientists have been able to identify the regions of the brain where déjà vu signals begin.
It has been found that déjà vu is more readily induced in epilepsy patients through electrical stimulation of the rhinal cortices as opposed to the hippocampus. These observations led to the speculation that déjà vu is caused by a dysfunctional electrical discharge in the brain.
These neuronal discharges can occur in a non-pathological manner in people without epilepsy. An example of this is a hyponogogic jerk, the involuntary twitch that can occur just as you are falling asleep.
This video is not supported by your browser at this time.It has been proposed that déjà vu could be triggered by a similar neurological discharge, resulting in a strange sense of familiarity.
The déjà vu experienced prior to an epileptic seizure may be enduring, rather than a fleeting feeling in those who don't have epileptic seizures. In people without epilepsy the vivid recognition combined with the knowledge that the environment is truly novel intrinsically underpins the experience of déjà vu.
Mismatches and short circuits
Déjà vu in healthy participants is reported as a memory error which may expose the nature of the memory system. Some researchers speculate that déjà vu occurs due to a discrepancy in memory systems leading to the inappropriate generation of a detailed memory from a new sensory experience.
This implies déjà vu is evoked by a mismatch between the sensory input and memory-recalling output. This explains why a new experience can feel familiar, but not as tangible as a fully recalled memory.
This video is not supported by your browser at this time.Other theories suggest activation of the rhinal neural system, involved in the detection of familiarity, occurs without activation of the recollection system within the hippocampus. This leads to the feeling of recognition without specific details.
Related to this theory, it was proposed that déjà vu is a reaction of the brain's memory systems to a familiar experience. This experience is known to be novel, but has many recognisable elements, albeit in a slightly different setting. An example? Being in a bar or restaurant in a foreign country that has the same layout as one you go to regularly at home.
Even more theories exist regarding the cause of déjà vu. These span from the paranormal – past lives, alien abduction and precognitive dreams – to memories formed from experiences that are not first-hand (such as scenes in movies).
So far there is no simple explanation as to why déjà vu occurs, but advances in neuroimaging techniques may aid our understanding of memory and the tricks our minds seem to play on us.
Source: The Conversation
This story is published courtesy of the The Conversation (under Creative Commons-Attribution/No derivatives).
- Researchers explore secret origin of deja vu Aug 12, 2012 | not rated yet | 0
- Scientists uncover deja vu mystery May 28, 2012 | not rated yet | 0
- Probing Question: What causes deja vu? Feb 12, 2010 | not rated yet | 0
- Spatial configuration can spark deja vu, psychology study reveals May 24, 2012 | not rated yet | 0
- Deep brain stimulation may improve memory Jan 30, 2008 | not rated yet | 0
- Motion perception revisited: High Phi effect challenges established motion perception assumptions Apr 23, 2013 | 3 / 5 (2) | 2
- Anything you can do I can do better: Neuromolecular foundations of the superiority illusion (Update) Apr 02, 2013 | 4.5 / 5 (11) | 5
- The visual system as economist: Neural resource allocation in visual adaptation Mar 30, 2013 | 5 / 5 (2) | 9
- Separate lives: Neuronal and organismal lifespans decoupled Mar 27, 2013 | 4.9 / 5 (8) | 0
- Sizing things up: The evolutionary neurobiology of scale invariance Feb 28, 2013 | 4.8 / 5 (10) | 14
How can there be a term called "intestinal metaplasia" of stomach
5 hours ago Hello everyone, Ok Stomach's normal epithelium is simple columnar, now in intestinal type of adenocarcinoma of stomach it undergoes "intestinal...
Pressure-volume curve: Elastic Recoil Pressure don't make sense
May 18, 2013 From pressure-volume curve of the lung and chest wall (attached photo), I don't understand why would the elastic recoil pressure of the lung is...
If you became brain-dead, would you want them to pull the plug?
May 17, 2013 I'd want the rest of me to stay alive. Sure it's a lousy way to live but it beats being all-the-way dead. Maybe if I make it 20 years they'll...
MRI bill question
May 15, 2013 Dear PFers, The hospital gave us a $12k bill for one MRI (head with contrast). The people I talked to at the hospital tell me that they do not...
Ratio of Hydrogen of Oxygen in Dessicated Animal Protein
May 13, 2013 As an experiment, for the past few months I've been consuming at least one portion of Jell-O or unflavored Knox gelatin per day. I'm 64, in very...
Alcohol and acetaminophen
May 13, 2013 Edit: sorry for the typo in the title , can't edit I looked around on google quite a bit and it's very hard to find precise information on the...
- More from Physics Forums - Medical Sciences
More news stories
Johns Hopkins researchers say they have discovered specific chemical alterations in two genes that, when present during pregnancy, reliably predict whether a woman will develop postpartum depression.
Psychology & Psychiatry 7 hours ago | not rated yet | 0 |
A Mediterranean diet with added extra virgin olive oil or mixed nuts seems to improve the brain power of older people better than advising them to follow a low-fat diet, indicates research published online in the Journal of ...
Psychology & Psychiatry 17 hours ago | 2 / 5 (1) | 2
More people are being diagnosed with eating disorders every year and the most common type is not either of the two most well known—bulimia or anorexia—but eating disorders not otherwise specified (eating disorders that ...
Psychology & Psychiatry 17 hours ago | not rated yet | 0
Turns out, that old "practice makes perfect" adage may be overblown. New research led by Michigan State University's Zach Hambrick finds that a copious amount of practice is not enough to explain why people ...
Psychology & Psychiatry 18 hours ago | 3.3 / 5 (12) | 0 |
(Medical Xpress)—Individuals who learn two languages at an early age seem to switch back and forth between separate "sound systems" for each language, according to new research conducted at the University of Arizona.
Psychology & Psychiatry 19 hours ago | 5 / 5 (4) | 1 |
(Medical Xpress)—Native peoples in regions where cameras are uncommon sometimes react with caution when their picture is taken. The fear that something must have been stolen from them to create the photo ...
44 minutes ago | not rated yet | 0 |
Australian scientists have charted the path of insulin action in cells in precise detail like never before. This provides a comprehensive blueprint for understanding what goes wrong in diabetes.
30 minutes ago | 4 / 5 (1) | 0 |
The level of immunity to the recently circulating H7N9 influenza virus in an urban and rural population in Vietnam is very low, according to the first population level study to examine human immunity to the virus, which was ...
9 minutes ago | not rated yet | 0 |
Researchers at Emory University have identified a protein that stimulates a pair of "orphan receptors" found in the brain, solving a long-standing biological puzzle and possibly leading to future treatments for neurological ...
6 minutes ago | not rated yet | 0 |
In a striking, unexpected discovery, researchers at Albert Einstein College of Medicine of Yeshiva University have determined that vitamin C kills drug-resistant tuberculosis (TB) bacteria in laboratory culture. The finding ...
21 minutes ago | not rated yet | 0 |
Prostaglandin analogues (PGAs), drugs which lower intraocular pressure, are often the first line of treatment for people with glaucoma, but their use is not without risks. PGAs have long been associated with blurred vision, ...
8 minutes ago | not rated yet | 0