Déjà Vu: What Happens When Memory Misfires?

You are busy having a conversation, when a sense of familiarity takes over - ‘Have I had this conversation with these people before?’, ‘Why do I feel like I’ve been in this exact position already?’. You're consciously aware that this event has not happened before, but your brain is telling you differently. That sensation, often leaving us confused or unsettled, is called Déjà vu. 

Translating to the French phrase “already seen”, this phenomenon is experienced by two-thirds of people at least once in their lifetime. But this isn’t a glitch in the matrix or a supernatural experience; rather, a real and common cognitive event, reflecting how our memory systems can misfire and the fascinating complexity of our brains. 

The Mystery of Déjà Vu 

Déjà vu is tricky to study due to its subjective and short-lived nature. The feeling cannot be summoned by purposely thinking about it, and it comes at random, unprepared times when we are least expecting it. However, there has been progress in understanding the neuroscience behind this sensation, particularly involving studies of individuals with temporal lobe epilepsy – where déjà vu is a common symptom. 

"Common déjà vu could result from neural ‘misfiring’ or even small seizures in the medial temporal lobe."

For decades, research has noticed that people with temporal lobe epilepsy experience déjà vu as an aura – a warning sign before a seizure is about to occur. This feeling is usually much more intense, frequent, and prolonged than the sensation reported in healthy populations (also known as non-clinical déjà vu). Studies suggest that déjà vu coincides with a brief electrical discharge in the temporal lobe and hippocampus, areas both crucial for memory. 

Out of Sync Memory Systems

Familiarity seems to be at the centre of experiencing déjà vu. Research suggests there are two main memory processes involved: familiarity and recollection. Familiarity appears automatic and fast at recognising a situation, whereas recollection is slower and takes time to retrieve details about the encounter. These processes occur in distinct brain regions – familiarity-based information occurs in the perirhinal cortex, compared to recollection involving the hippocampus and parahippocampal gyrus. In cases of déjà vu, cognitive models suggest there is a conflict between the two, and these systems become out of sync, resulting in familiarity arising when successful recollection is absent. The conflict manifests itself as a sensation that the feeling of familiarity is incorrect.

A proposed hypothesis suggests that common déjà vu could result from neural ‘misfiring’ or even small seizures in the medial temporal lobe. Studies found that electrical stimulation of the entorhinal and perirhinal cortices was more likely to elicit déjà vu than stimulation of the amygdala and hippocampus – all regions located in the medial temporal lobe. With familiarity-based information processing linked to the perirhinal cortex, perhaps stimulation can demonstrate the disruption that occurs during actual déjà vu, where familiarity of a memory is mistaken for an event that has not actually happened. 

Experimental Replications

To understand the process, researchers have begun to try and induce the feeling of déjà vu using experimental paradigms and neuroimaging. For example, work at the University of St. Andrews involved experimentally inducing déjà vu using a false memory procedure, with fMRI, to map areas active during the behavioural task. Frontal regions, particularly those responsible for memory conflict and checking, such as the anterior cingulate cortex, medial prefrontal cortex, and parietal cortex, were particularly active.

"Older adults may still experience déjà vu, but notice it less, as it has not been flagged as a memory conflict."

At the University of Melbourne, Howe et al. attempted to simulate the sensation using photographs, showing similar photos of the same person, but with slight differences. Participants were able to recognise that there was something different in each photo; however, they struggled to identify or even describe what the difference was. Howe suggested that our brains absorb far more detail than we consciously realise, and when we are presented with similar information later on, it can trigger a false sense of familiarity. 

Howe also showed word lists with words related to each other, e.g., door, glass, pane. When participants were later shown the word ‘window’, they reported that it felt familiar, even though it did not appear on the original list. It appears that their brains subconsciously registered the semantic relatability, and mistook the related word to the remembered words from the list. This mistake or ‘misfire’ may reflect what happens in the brain when experiencing déjà vu. 

What Can Affect Déjà Vu? 

Studies show that non-clinical déjà vu typically peaks in young adulthood – between 20 and 24 years old - and declines as age progresses. This may be due to stronger neural activity in the brain and ‘fact-checking’ ability during this period. As we age, neural activity weakens, and our ability to notice errors in memory decreases. Therefore, older adults may still experience déjà vu, but notice it less, as it has not been flagged as a memory conflict.

There are other factors that can increase the likelihood of déjà vu, including fatigue and stress. When the brain is tired, its ability to regulate neuronal systems worsens, leading to a higher chance of neural misfiring – perhaps inducing déjà vu. Dopamine can also play a role due to its association with signalling familiarity: when the brain signals for this, neurons produce a strong dopaminergic action. Recreational and medicinal drugs that affect dopamine levels have been found to induce instances of déjà vu.

The Future of Déjà Vu

Studying déjà vu remains a challenge due to its spontaneity and subjective nature, but technologies to capture it have been increasing. The use of virtual reality enables participants to be placed within a scene, where researchers have manipulated environments to have the same spatial layout, but distinct in other aspects. Findings have demonstrated that déjà vu was more likely to happen when individuals were in a scene with the same spatial layout of an earlier scene they viewed but did not recall.

"These systems become out of sync, resulting in familiarity arising when successful recollection is absent."

Imaging studies have revealed activation not only in memory-related areas, but also in regions linked to cognitive control and error detection, such as the anterior cingulate cortex or medial prefrontal cortex. This highlights how déjà vu causes our brain to pause and check for errors and familiarity before it can proceed with identifying the memory as a mistake. 

Future research should further consider how the role of age, emotion, neurobiological mechanisms and memory conflict interact to produce the sensation, and utilise computational models that can capture the exact moment of déjà vu occurring and help us better understand its representation within the brain. 

Déjà vu is not us experiencing a time loop, or parallel universes – it is an experience that exposes the complexity of the human brain, demonstrating how quickly information can be processed, yet can ultimately, be mistaken. Our brains can be genius, but they are a testament to being human, in that they too, can make mistakes. 

References

A.H. Chapman et al. (1951). Déjà vu experience and conscious fantasy in adults. Psychiatric Quarterly Supplement. 

Aitken, C. B. A., Jentzsch, I., & O'Connor, A. R. (2023). Towards a conflict account of déjà vu: The role of memory errors and memory expectation conflict in the experience of déjà vu. Neuroscience and biobehavioral reviews, 155, 105467. https://doi.org/10.1016/j.neubiorev.2023.105467

Cassady, M., & Baslet, G. (2023). Dissociation in patients with epilepsy and functional seizures: A narrative review of the literature. Seizure, 110, 220–230. https://doi.org/10.1016/j.seizure.2023.06.020

Cleary A.M., Neisser J., McMahan T., Parsons T.D., Alwaki A., Okada N., Vosoughi A., Kheder A., Drane D.L., Pedersen N.P. (2021). Subjective distinguishability of seizure and non-seizure Déjà Vu: A case report, brief literature review, and research prospects. Epilepsy & Behavior, 108373.

Cleary, A.M., & Brown, A.S. (2021). The Déjà Vu Experience (2nd ed.). Routledge. https://doi.org/10.4324/9780429296116

Jackson G.D., Briellmann R.S., Kuzniecky R.I. (2005). Temporal Lobe Epilepsy. Magnetic Resonance in Epilepsy, 99-176. 

O’Connor, A. R., Lever, C., & Moulin, C. J. A. (2009). Novel insights into false recollection: A model of déjà vécu. Cognitive Neuropsychiatry, 15(1–3), 118–144. https://doi.org/10.1080/13546800903113071

Stanton, K. (2025). Do You Get Déjà Vu? Memory Glitches Make Time Feel Repeated. Neuroscience News. deja-vu-memory-neuroscience-29771

Wells, C., O'Connor, A., & Moulin, C. J. A. (2018). Déjà vu experiences in anxiety. Memory.https://doi.org/10.1080/09658211.2018.1538418

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This article was written by Lily Wilson and edited by Julia Dabrowska, with graphics produced by Lilly Green. If you enjoyed this article, be the first to be notified about new posts by signing up to become a WiNUK member (top right of this page)! Interested in writing for WiNUK yourself? Contact us through the blog page and the editors will be in touch.