Deja Vu

***Déjà vu*** (/ˌdeɪʒɑː ˈv(j)uː/ (listen) *DAY-zhah-VOO, -⁠VEW*, French: [deʒa vy] (listen); "already seen") is a French loanword for the phenomenon of feeling as though one has lived through the present situation before. It is an illusion of memory whereby — despite a strong sense of recollection — the time, place, and context of the "previous" experience are uncertain or impossible. Approximately two-thirds of surveyed populations report experiencing déjà vu at least one time in their lives. The phenomenon manifests occasionally as a symptom of pre-seizure auras, and some researchers have associated chronic/frequent "pathological" déjà vu with neurological or psychiatric illness. Experiencing déjà vu has been correlated with higher socioeconomic status, better educational attainment, and lower ages. People who travel often, frequently watch films, or frequently remember their dreams are also more likely to experience déjà vu than others.

## Etymology

The expression "sensation de déjà-vu" (sensation of déjà vu) was coined in 1876 by the French philosopher Émile Boirac (1851-1917). He used it in his book *L'Avenir des sciences psychiques*. It is now used internationally.

## Medical disorders[edit]

Déjà vu is associated with temporal lobe epilepsy. This experience is a neurological anomaly related to epileptic electrical discharge in the brain, creating a strong sensation that an event or experience currently being experienced has already been experienced in the past.

Migraines with aura are also associated with déjà vu.[*citation needed*]

Early researchers tried to establish a link between déjà vu and mental disorders such as anxiety, dissociative identity disorder and schizophrenia but failed to find correlations of any diagnostic value. No special association has been found between déjà vu and schizophrenia. A 2008 study found that déjà vu experiences are unlikely to be pathological dissociative experiences.[*medical citation needed*]

Some research has looked into genetics when considering déjà vu. Although there is not currently a gene associated with déjà vu, the LGI1 gene on chromosome 10 is being studied for a possible link. Certain forms of the gene are associated with a mild form of epilepsy, and, though by no means a certainty, déjà vu, along with *jamais vu*, occurs often enough during seizures (such as simple partial seizures) that researchers have reason to suspect a link.

## Pharmacology

Certain combinations of medical drugs have been reported to increase the chances of déjà vu occurring in the user. Taiminen and Jääskeläinen (2001) explored the case of an otherwise healthy person who started experiencing intense and recurrent sensations of déjà vu upon taking the drugs amantadine and phenylpropanolamine together to relieve flu symptoms. Because of the dopaminergic action of the drugs and previous findings from electrode stimulation of the brain (e.g. Bancaud, Brunet-Bourgin, Chauvel, & Halgren, 1994), Tamminen and Jääskeläinen speculated that déjà vu occurs as a result of hyperdopaminergic action in the medial temporal areas of the brain. A similar case study by Karla, Chancellor, & Zeman (2007) suggests a link between déjà vu and the serotonergic system, after an otherwise healthy woman began experiencing similar symptoms while taking a combination of 5-hydroxytryptophan and carbidopa.

## Explanations

### Split perception explanation

Déjà vu may happen if a person experienced the current sensory experience twice successively. The first input experience is brief, degraded, occluded, or distracted. Immediately following that, the second perception might be familiar because the person naturally related it to the first input. One possibility behind this mechanism is that the first input experience involves shallow processing, which means that only some superficial physical attributes are extracted from the stimulus.