Frequently Asked Questions
1. What causes déjà vu?
Our view is that déjà vu is caused by disruptions to brain functioning in the temporal lobe, the area of the brain behind the ears. We know this area to be important for memory function, and our view is that déjà vu is just a brief memory error. The exciting thing about déjà vu is that it is the results of two opposing evaluations, the knowledge that something hasn't happened before, but the feeling that it has. We believe that one of the functions of the temporal lobe is to produce these feelings of memory. Sometimes, when this area is overactive, or 'tricked' into thinking something is familiar, we get a brief sensation of feeling something is old, but knowing it is new. Our view is largely based on the work we've done on people with chronic déjà vu (actually déjà vecu, or recollective confabulation), a rare memory disorder caused by cell loss in the brain which leads to almost constant déjà vu - especially for novel events.
2. Why déjà vu and déjà vecu?
Déjà vu translates as 'already seen' and déjà vecu as 'already lived'. Somewhat confusingly, déjà vu is a catch-all generic term, to describe all kinds of peculiar sensations. We use déjà vu, as others do to refer to a normal, healthy sensation, a fleeting experience of familiarity for something you know to be unfamiliar. We use déjà vecu to distinguish our patients, who have an ongoing sensation. Here déjà vecu captures the chronic nature of the problem. But also, déjà vecu emphasises that these patients don't have a fleeting sense of false familiarity, but quite strong feelings of false recollection. This usage may be somewhat contentious (see here) but we feel the advantages of this term outweigh the disadvantages.
3. What is the relationship between 'healthy' déjà vu and your patients with déjà vecu?
Of course, the patients' experience is very different from the fleeting sensation of déjà vu we get. These patients withdraw from activities because they feel they've done them before - we don't do that with 'health' déjà vu. But the idea is broadly the same - there are two separable elements to memory function: knowledge or memory content, and the subjective experience of that - a conscious state of remembering, or a feeling. See here for a description of deja vecu.
4. Why does déjà vu occur more in the young?
We're not sure why déjà vu - a memory error - should occur more in the young than the old - that doesn't seem like other forms of memory error. But my favourite explanation is that as you get older you are slightly, but definitely, more forgetful - so that you just forget the déjà vu experiences you may have had. But there are other explanations, some more based on common sense - like, as you're older you visit less novel places - and novelty, ironically, is somewhat critical for having déjà vu. Everything is likely to be more familiar for older people. Other explanations are more scientific and need more support from experiments: for instance, older adults have a lack of 'recollection', related to slight reductions in temporal lobe activity, so they have a lack of the conscious feeling associated to memory, and thus they are less likely to have disruptions to it.
5. What about déjà vu in temporal lobe epilepsy?
It has long been known that epilepsy in the temporal lobe is associated with frequent and strong sensations of déjà vu, and other more striking memory-related phenomena. Temporal lobe epilepsy helps us converge on how important the temporal lobes are in feelings of recollection and remembering, because it supports the view that déjà vu is a temporal lobe phenomena, related to over activity of this brain area, and an illusion based on the malfunction of normal memory processes.
6. What are your patients who experience chronic déjà vu (déjà vecu) actually like?
We are surprised by the common experience of these people: nearly all have withdrawn from watching the television, for instance, saying that they've seen each programme (even if it is new) before. They all seem to have difficulties for the most novel events in their life: if they go to a new place, they are likely to claim they've been there before. But despite the very similar patterns of everyday experience, and measures on formal memory tests, there are some differences. We've seen equal numbers of men and women, and a range of ages from the early 60s to the 90s. Broadly speaking, these people have some sort of memory disorder, they are usually forgetful and vague about memory, but a definite diagnosis isn't always possible.
7. Is this a new form of memory pathology? Is it a new disease?
We do view this as a pathology: but not a new diagnostic entity. It seems to be another way in which memory can be disrupted by the aging process, albeit very rare. It isn't necessarily indicative of any diagnosis, but where it does occur, it is certainly very disruptive for the carer and the patient, and leads to large changes in everyday life. Normal déjà vu, is, just that, entirely normal. It actually can be fairly pleasant, a mildly peculiar sensation which gives you a little window on how the mind works. But our patients don't have this awareness: that are not conscious of the fact that their mind is playing this awful trick on them.
8. What are the aims of your research?
Our aims are to elucidate this unsettling symptom, and to accurately gauge prevalence and prognosis. Our ultimate aim is to be able to understand this symptom to the extent that we can offer informed care and support, and hopefully treatment. Progress is somewhat slow because we have a lack of people with this condition, and we cannot keep researching the same people over and over, because of the nature of their difficulties, anyway. Of course, as well as helping sufferers and carers, this work throws up very interesting perspectives on the mind and how consciousness and memory works, and the knowledge that we gain in that area can be applied to all different situations and conditions. By publishing work on this condition we also hope to remove some of the stigma attached to this issue: we believe that symptoms like this associated to memory problems are actually more common than the few published studies suggests: but that people are reluctant to talk about this unsettling and bizarre condition to their doctor. It is much easier to talk about forgetfulness, which doesn't have nearly such a taboo attached to it. People who have this condition, and their carers are likely to be worried that they are going mad - which certainly isn't the case. Our research suggests that this is just a very unsettling peculiar memory problem.
9. How about other theories of déjà vu?
Because these people tend to have clear temporal lobe pathology, and quite clearly have a memory disorder, we are happy to suggest that déjà vu and déjà vecu are both produced by memory systems in the brain malfunctioning or misfiring, somewhat briefly or more chronically. Of course, this isn't necessarily incompatible with other explanations of déjà vu. One popular notion is that déjà vu is caused by the eyes working out of synchronisation (see here). However, since blind people experience déjà vu this seems an unlikely explanation. Because it is such a peculiar, and personal sensation, we believe that reactions to déjà vu can be quite profound, and as such, people generate striking interpretations and causes of their experience. We've also been exploring the sensations of deja vu by using hypnosis. Check out Akira O'Connor's work here. There may be as many interpretations and explanations of déjà vu as there are people: this is one of the interesting aspects of this memory glitch. If you'd like to record your view of what deja vu is, try our poll
10. What should I do if I am worried about having déjà vu?
We know that experiencing déjà vu is mostly very normal, and part of healthy experience. Just as some people claim never to have experienced it, some people have it much more frequently. We also know that you get it more when you're tired or stressed. But normally, déjà vu sensations shouldn't be distressing or difficult on a day-to-day basis. If they occur alongside more serious forgetfulness or other difficulties, it is worth talking to your family doctor about them. But, just like momentary forgetfulness, forgetting someone's name, having a nightmare or having the hiccups, it isn't necessary to worry about them normally, or contact the doctor when you experience one. In the Leeds Memory Group, we are interested to hear about your déjà vu experiences, although you will appreciate it may not be possible to respond to everyone who contacts us.