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).
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.Įven more theories exist regarding the cause of déjà vu. This experience is known to be novel, but has many recognisable elements, albeit in a slightly different setting. Related to this theory, it was proposed that déjà vu is a reaction of the brain’s memory systems to a familiar experience. This leads to the feeling of recognition without specific details. 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 explains why a new experience can feel familiar, but not as tangible as a fully recalled memory. This implies déjà vu is evoked by a mismatch between the sensory input and memory-recalling output. That is, information bypasses short-term memory and instead reaches long-term memory. 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. Mismatches and short circuitsĭéjà vu in healthy participants is reported as a memory error which may expose the nature of the memory system. In people without epilepsy the vivid recognition combined with the knowledge that the environment is truly novel intrinsically underpins the experience of déjà vu. 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. Some researchers argue that the type of déjà vu experienced by temporal lobe epilepsy patients is different from typical déjà vu. It has been proposed that déjà vu could be triggered by a similar neurological discharge, resulting in a strange sense of familiarity. An example of this is a hyponogogic jerk, the involuntary twitch that can occur just as you are falling asleep.
These neuronal discharges can occur in a non-pathological manner in people without epilepsy. These observations led to the speculation that déjà vu is caused by a dysfunctional electrical discharge in the brain. 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.
The brain regions in which this electrical activation can occur include the medial temporal lobes.Įlectrical disturbance of this neural system generates an aura (a warning of sorts) of déjà vu prior to the epileptic event.īy 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. This dysfunctional neuronal activity can spread across the whole brain like the shock waves generated from an earthquake. This has given researchers a more experimentally controlled way of studying déjà vu.Įpileptic seizures are evoked by alterations in electrical activity in neurons within focal regions of the brain. 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.
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