déjà vu

   Also known as false memory. The term déjà vu is French for 'already seen'. As pointed out by the South African déjà vu expert Vernon M. Neppe, the term is used in a broad sense to denote "any subjectively inappropriate impression of familiarity of a present experience with an undefined past" (i.e. as a synonym of the generic term "déjà experience), and in a narrow sense to denote a " déjà experience occurring in the visual modality. As used in the latter sense, the term déjà vu is used in opposition to more than 20 related terms, such as déjà arrivé (already happened), déjà connu (already personally known), and déjà entendu (already heard). As used in the broad as well as the narrow sense, déjà vu is considered the obverse of "jamais vu. The origin of the term déjà vu is unclear, but it is sometimes attributed to the French philosopher and psychologist Emile Boirac (1851-1917), who reportedly mentioned it in 1876 in a letter to the French journal Revue Philosophique de la France et de l'Étranger.The concomitant concept, however, would seem to be much older. It has been suggested that the Church Father St. Augustine (354-430) referred to this phenomenon when he used the term falsae memoriae in his work De Trinitate. Although the term déjà vu may seem to suggest otherwise, this symptom is not conceptualized as a perceptual phenomenon but as a false, but compelling sense of familiarity or recognition (i.e. a mnestic event) that may accompany a regular perceptual experience or event. For example, one may walk into a restaurant, and observe the other guests sitting at their dinner tables, and have the feeling that one has witnessed that exact scene before. Pseudo-presentiments like these would seem to be fairly common in healthy individuals of all ages. They typically last for various seconds to minutes, without affecting the subjects' judgment of their present situation. The subject's feeling is rather characterized by the cognitive dissonance between the feeling of re-experiencing a given situation, and the simultaneous awareness of its impossibility. Epidemiological surveys indicate that the lifetime prevalence of déjà vu experiences in the non-institutionalized population lies between 30 and 96%. This broad range of prevalence figures is probably due to differences in the operational criteria of déjà vu, and to population biases. The literature also suggests that the incidence of déjà vu may be higher in young and imaginative individuals, and that its incidence tends to increase in the context of conditions such as fatigue and heightened perceptual sensitivity. Some studies also suggest that déjà vu may be more prevalent among individuals with a psychiatric disorder, such as anxiety disorder, dissociative identity disorder, mood disorder, personality disorder, or "schizophrenia. In addition, a heightened incidence of déjà vu is associated with the organic brain syndrome, temporal lobe epilepsy, Alzheimer's disease, and other types of dementia. When déjà vu is attributed to an organic cause, it is referred to as endogenous déjà vu. In the case of a specific association with epilepsy, the phenomenon is sometimes referred to as epileptic " aura or epileptic déjà vu. Epileptic déjà vu typically presents as a déjà vu phenomenon with a prolonged or recurrent course. It can be complicated by hallucinatory phenomena such as " abdominal aura and olfactory hallucinations, and by subjective phenomena such as derealization, depersonalization, and strong affective states. As to the pathophysi-ology of déjà vu, various competing models exist. Most of these revolve around the notion of a dissociated activation of the familiarity/remember-centres of the brain, as may occur in dysfunctional activation of the mesial temporal lobe. In the literature this dysfunctional activity is conceptualized as epileptic in origin or not. Alternatively, the dual pathway hypothesis suggests that perceptual information from the senses does not always converge on sensory cortical areas in a coordinated fashion, thereby luring the cortex into labelling a single percept as a duplicated (i.e. re-experienced) one. As the alleged delay in neurotransmission is thought to originate from the optic nerve, the concomitant model is referred to as the optical pathway delay hypothesis. A third hypothesis suggests that déjà vu may arise from an instance of unattended perception, followed by an instance of attended perception. In parapsychology, déjà vu and other déjà experiences are sometimes regarded as telepathic phenomena, or as veridical memories of an alleged past life.

   References

   Berrios, G.E. (1995). Déjà vu in France during the 19th century: A conceptual history. Comprehensive Psychiatry, 36, 123-129.

   Brown, A.S. (2003). A review of the déjà vu experience. Psychological Bulletin, 129, 394-413.

   Neppe, V.M. (1983). The psychology ofdéjà vu. Have I been here before? Johannesburg: Witwa-tersrand University Press.

   Sno, H.N., Linszen, D.H. (1990). The déjà vu experience: Remembrance of things past? American Journal of Psychiatry, 147, 1587-1595.