{"id":27512,"date":"2023-05-26T16:00:00","date_gmt":"2023-05-26T14:00:00","guid":{"rendered":"https:\/\/www.sciencefocus.com\/?p=74582"},"modified":"2023-05-26T16:37:11","modified_gmt":"2023-05-26T14:37:11","slug":"what-causes-deja-vu-the-quirky-neuroscience-behind-the-memory-illusion","status":"publish","type":"rss_feed","link":"https:\/\/c01.purpledshub.com\/bbcsciencefocus\/rss_feed\/what-causes-deja-vu-the-quirky-neuroscience-behind-the-memory-illusion\/","title":{"rendered":"What causes d\u00e9j\u00e0 vu? The quirky neuroscience behind the memory illusion"},"content":{"rendered":"

Why d\u00e9j\u00e0 vu is far from a memory fault \u2013 and how some people experience it constantly. <\/p>

By Thomas Ling\n \t\t<\/p>

Published: Friday, 26 May 2023 at 12:00 am<\/p>

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Sorry if you think we\u2019ve already asked, but do you know exactly what d\u00e9j\u00e0 vu is? If you\u2019re like most sensible people, you\u2019ll likely say it\u2019s the bizarre feeling that you\u2019ve experienced something that\u2019s happened before.<\/p>\n

However, many neuroscientists would say this answer lacks a little je ne sais quoi. According to experts like Dr Akira O\u2019Connor<\/a>, senior psychology lecturer at the University of St Andrews, d\u00e9j\u00e0 vu \u2013 the French for \u2018already seen\u2019 \u2013 is not only a feeling of familiarity, but also the metacognitive recognition that these feelings are misplaced.<\/p>\n

\u201cD\u00e9j\u00e0 vu is basically a conflict between the sensation of familiarity and the awareness that the familiarity is incorrect. And it\u2019s the awareness that you\u2019re being tricked that makes d\u00e9j\u00e0 vu so unique compared to other memory events,\u201d he explains.<\/p>\n

\u201cMost healthy people don\u2019t tend to believe the sensation of familiarity and change their behaviour \u2013 like Neo in The Matrix<\/em>, they logically know something isn\u2019t right.\u201d<\/p>\n

So what happens in the brain<\/a> during d\u00e9j\u00e0 vu? And why do some people experience this phenomenon more than others? In case you\u2019ve drawn a blank, you can familiarise yourself with our full guide below.<\/p>\n

What is d\u00e9j\u00e0 vu, according to neuroscience?<\/strong><\/h2>\n

Unfortunately, as far as we know, the 60 per cent of people who report feeling d\u00e9j\u00e0 vu in their lives<\/a> haven\u2019t just experienced a glitch in the Matrix.<\/p>\n

However, neuroscientists have determined that this memory illusion isn\u2019t a sign of an unhealthy brain \u2013 it\u2019s by no means a memory error. In fact, almost the opposite. As O\u2019Connor argues, d\u00e9j\u00e0 vu occurs when the frontal regions of the brain attempt to correct an inaccurate memory.<\/p>\n

\u201cFor the vast majority of people, experiencing d\u00e9j\u00e0 vu is probably a good thing. It\u2019s a sign that the fact-checking brain regions are working well, preventing you from misremembering events.<\/p>\n

\u201cIn a healthy person, such misremembering is going to happen every day. This is to be expected because your memory involves millions and billions of neurones. It\u2019s very messy,\u201d he says.<\/p>\n

Unfortunately, there is no single agreed model that explains exactly what happens in the brain during d\u00e9j\u00e0 vu. However, most of the main competing theories share the same idea: d\u00e9j\u00e0 vu occurs when areas of the brain (such as the temporal lobe) feed the mind\u2019s frontal regions signals that a past experience is repeating itself.<\/p>\n

\u201cAfter this, the frontal decision-making areas of the brain effectively checks to see whether or not this signal is consistent with what is possible. It will ask \u2018have I been here before?\u2019<\/p>\n

\u201cIf you have actually been in that place before, you may try harder to retrieve more memories. If not, a d\u00e9j\u00e0 vu realisation can occur.\u201d<\/p>\n

What makes somebody more likely to experience d\u00e9j\u00e0 vu?<\/strong><\/h2>\n

Although O\u2019Connor estimates a healthy person will experience d\u00e9j\u00e0 vu once a month on average, several factors can raise your chance of feeling the sensation.<\/p>\n

Firstly: how tired and stressed you are. \u201cWhen your brain is fatigued like this, your internal neuronal systems haven\u2019t had the chance to kind of recuperate and really regulate themselves. And so your neuronal firing is more likely to be a bit off and result in d\u00e9j\u00e0 vu,\u201d he explains.<\/p>\n

Research has also highlighted a possible link between the neurotransmitter dopamine (a known mood-booster) and d\u00e9j\u00e0 vu<\/a>.<\/p>\n

\u201cDopamine is what\u2019s called an excitatory neurotransmitter. And when we talk about the brain regions that are signalling familiarity, there would be dopaminergic action in those neurones \u2013 this basically means dopamine is involved,\u201d O\u2019Connor explains.<\/p>\n

\u201cThis could be why dopaminergic drugs, recreational or otherwise, tend to often cause elevated reports of d\u00e9j\u00e0 vu.\u201d<\/p>\n

\u00a0<\/p>\n

\""Deja\"<\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/picture><\/div>
\u00a9 Getty<\/span><\/figcaption><\/div>\n

There\u2019s also another factor. Wondered why you don\u2019t experience d\u00e9j\u00e0 vu as much as you used to? This is because, according to rigorous scientific research, you\u2019re getting on a bit.<\/p>\n

\u201c<\/em>Unfortunately, like many memory issues, it\u2019s just a natural part of ageing. You become less able to notice errors,\u201d says O\u2019Connor.<\/p>\n

\u201cIt\u2019s really interesting that younger people get more d\u00e9j\u00e0 vu \u2013 older people are normally expected to have more memory quirks. However, this happens as younger people generally have a greater kind of excitatory activity in their brains \u2013 they\u2019re generally more active. And they have a real healthy fact-checking frontal part of the brain.<\/p>\n

\u201cWhen I first started researching d\u00e9j\u00e0 vu nearly 20 years ago I had it all the time, but a lot less so now!\u201d<\/p>\n

Can d\u00e9j\u00e0 vu ever be unhealthy?<\/strong><\/h2>\n

If memory serves you right, you\u2019ll now know d\u00e9j\u00e0 vu is a healthy mind mechanism \u2013 something far from dangerous. But what would happen if you felt d\u00e9j\u00e0 vu constantly? What if every new experience felt familiar?<\/p>\n

Strangely enough, this can happen to some people. \u201cThere\u2019s an extraordinary case of a man in Finland who took a mixture of flu medications which are known to be particularly excitatory to certain dopamine neurons. And this caused him to have persistent d\u00e9j\u00e0 vu,\u201d says O\u2019Connor.<\/p>\n

\u201cHe found it so interesting he kept on taking them for a while \u2013 it did stop eventually!\u201d<\/p>\n

Unfortunately, however, some people don\u2019t have the luxury of halting this mental Groundhog Day. People suffering from \u2018d\u00e9j\u00e0 v\u00e9cu\u2019 (French for \u2018already lived\u2019) have the constant sensation of having already experienced the present situation. In short, nothing feels new to them.<\/p>\n

\u201cOne of the things that makes people with d\u00e9j\u00e0 v\u00e9cu so interesting is that they tend to lose the ability to fact check these sensations. Often these people will simply stop watching TV as it feels like they\u2019ve seen every episode previously \u2013 everything will feel like a repeat,\u201d says O\u2019Connor.<\/p>\n

\u201cAlthough it sounds interesting and novel, it\u2019s heartbreaking to see as it can often happen in dementia patients, and it can be a sign of a worsening development.\u201d<\/p>\n

Read more about the science of memory:<\/strong><\/p>\n