What is deja vu from a scientific point of view ?

Andy Green

Transcript

00:00He had been here before, or so it felt.

00:03As the tram rolled down the cobbled street in Prague, a faint tremor passed through Elliot's spine.

00:09He leaned against the cold glass window, watching the raindrops trace chaotic paths,

00:13colliding like destinies or memories, fleeting, intersecting, vanishing.

00:17The buildings outside, ochre facades, iron balconies, a beggar with a violin,

00:22all conspired in their silence to whisper,

00:24You've seen this.

00:25He sat upright, heart accelerating, eyes wide with eerie familiarity.

00:31Not just the street.

00:32The tram.

00:33The smell of wet upholstery.

00:35Even the precise moment when a child dropped a red mitten and his mother shouted something in check,

00:39it had already happened.

00:41Not just similar.

00:42Identical.

00:43Déjà vu.

00:44A glitch in memory?

00:46A metaphysical message?

00:47A neurological hiccup?

00:49Elliot was no ordinary traveller.

00:51A professor of cognitive science and part-time poet,

00:54he was in Prague, not for sightseeing, but for silence.

00:58A sabbatical to write his next book on memory, perception,

01:01and the strange ghosts that wander between them.

01:04That red mitten haunted him all the way to his apartment in Malastrana.

01:08He dropped his coat, sat at his desk and opened a new document.

01:12The cursor blinked, impatiently.

01:14He typed,

01:15What is déjà vu from a scientific point of view?

01:18And then paused.

01:20Because if there was one thing Elliot knew, it was this.

01:23Science doesn't always begin with answers.

01:26Sometimes it begins with a red mitten on a rainy afternoon,

01:29and the peculiar feeling that reality is folding over itself.

01:34The first known mention of the phenomenon called déjà vu,

01:37literally already seen in French,

01:39came from Émile Boirac in the late 19th century.

01:42But the experience itself?

01:44As old as awareness.

01:46As old as dreams.

01:47Let us begin not with definitions, but with mysteries.

01:50The year was 1955.

01:52A young man named William, aged 23,

01:55was admitted to a psychiatric hospital in Wales.

01:58He was bright, articulate, and deeply disturbed.

02:01His complaint?

02:02He believed every moment of his life was a repetition.

02:06Every sound, every sight, every encounter had happened before,

02:09exactly as it was happening now.

02:11Unlike typical déjà vu, which lasts mere seconds,

02:14William's experience was chronic.

02:17The doctors called it persistent déjà vu,

02:19a condition so rare that most textbooks never mention it.

02:22Tests showed no brain lesions,

02:24no signs of temporal lobe epilepsy.

02:26And yet, William remained imprisoned in a living loop,

02:29endlessly repeating.

02:31Some dismissed it as a dissociative disorder.

02:34Others saw it as an extreme manifestation of a faulty memory circuit.

02:38But William insisted he wasn't ill.

02:40Reality was.

02:42So what happens in the brain during déjà vu?

02:45Modern neuroscience has a few suspects.

02:47The leading candidate is the medial temporal lobe,

02:50particularly the hippocampus and surrounding structures,

02:53the regions responsible for memory encoding and retrieval.

02:57The hippocampus is like a librarian filing away your experiences.

03:01But sometimes it misfires.

03:04It might tag a current event as already retrieved,

03:07even though it hasn't been stored.

03:09This creates the illusion of familiarity.

03:11Think of it like opening a brand new book,

03:14but feeling as if you've read it before.

03:16Not because you have,

03:17but because your brain has accidentally stamped it as familiar.

03:21This theory, called the dual processing hypothesis,

03:24suggests that there are two pathways in memory.

03:27One for processing a new experience,

03:29and one for recognizing familiar experiences.

03:32If the latter activates prematurely,

03:35or independently,

03:36you get déjà vu.

03:38But this elegant theory has a problem.

03:40It doesn't explain everything.

03:42Take this account from 2007.

03:44A woman named Claudia described an episode

03:46where she entered a bookstore she'd never visited.

03:49She walked to the second floor,

03:50turned left,

03:51and suddenly froze.

03:53I knew what book was on the third shelf,

03:54she said later.

03:56I even knew a passage from it.

03:57The book was there.

03:59The passage matched.

04:00So was this still déjà vu?

04:03Or precognition?

04:05No.

04:05Claudia had visited that same bookstore

04:07ten years prior in childhood.

04:10She didn't remember it consciously,

04:11but her brain had retained fragments.

04:14The layout.

04:15The color of the walls.

04:16The rhythm of the spiral staircase.

04:19This is called cryptomnesia,

04:20when forgotten memories re-emerge,

04:22but are mistaken for entirely new experiences.

04:25It's the ghost of memory dressed as a stranger.

04:27So perhaps déjà vu is not about time-folding.

04:31It's about memory failing,

04:33beautifully, subtly, momentarily.

04:35But what if memory isn't failing?

04:38What if it's remembering something

04:39we were never meant to access?

04:41It was a Thursday evening

04:42when Elliot wandered into the archive

04:44of Charles University.

04:46The librarian,

04:47an elderly man with bushy eyebrows

04:48and the calmness of someone

04:50who has seen many storms come and go,

04:52handed him a folder.

04:53Early work on temporal anomalies,

04:56the man said in Czech-accented English.

04:59Inside were yellowed pages

05:00from forgotten scientists,

05:02including a neurologist

05:03named Dr. Zina Hertzfeld.

05:06In a 1962 paper,

05:07never published but meticulously documented,

05:10Hertzfeld described a curious case,

05:12a patient who experienced déjà vu

05:14during near-death trauma.

05:16While drowning,

05:17the patient reported a cascade

05:18of replayed memories,

05:19but not from her own life.

05:21They weren't mine, she had said.

05:23They were from someone else,

05:24a woman.

05:25I saw her wedding,

05:26her children,

05:27her regrets,

05:28all of it in seconds.

05:31Hertzfeld speculated,

05:32without hard data

05:33but with poetic boldness,

05:35that déjà vu might not be

05:36a memory at all.

05:37Perhaps it was

05:38a momentary resonance

05:39with another consciousness

05:40somewhere in the architecture

05:42of space-time.

05:44Elliot raised an eyebrow.

05:45This wasn't science,

05:46it was metaphysics

05:47dressed as neurology.

05:49And yet,

05:50something tugged at him.

05:51There is a lesser-known theory

05:53in neuroscience

05:53called the hologram hypothesis.

05:56The idea is simple,

05:58profound,

05:58and unsettling.

06:00Memory in the brain

06:00might be stored

06:01not like a library of books,

06:03but like a hologram

06:04distributed across a network.

06:06Carl Prebram,

06:07one of its early proponents,

06:08suggested that each memory

06:09is not stored in a single place,

06:11but spread across regions.

06:13Damage one area,

06:15and you may still recall fragments.

06:16This is similar

06:18to how a holographic plate

06:19can be broken,

06:20yet each piece

06:21still contains the whole image,

06:23blurred,

06:23partial,

06:24but present.

06:25But here's the twist.

06:26If memories are holographic,

06:28then familiarity

06:29can be triggered

06:30by partial matches.

06:32A smell,

06:32a sound,

06:33a curve of a stranger's face

06:35might light up a fragment,

06:36just enough to simulate

06:37a full experience.

06:39Déjà vu, then,

06:40could be the brain

06:41trying to complete a puzzle

06:42it never saw,

06:43using pieces

06:44that almost fit.

06:46This theory explains

06:47the eerie rightness

06:48of Déjà vu,

06:50the way it feels

06:50not just familiar,

06:51but destined.

06:53The brain is trying

06:53to resolve a pattern,

06:55and in doing so,

06:56creates a temporary

06:57illusion of certainty.

06:59But Elliot knew

07:00that even this theory

07:00had gaps.

07:01What about the timing?

07:03The split-second feeling

07:04that fades just as fast.

07:07Why do some people

07:08experience Déjà vu frequently,

07:10while others never do?

07:11Why did he experience it

07:13that day in Prague?

07:15Now we must pause.

07:16Because there is a question

07:17that haunts every scientist,

07:19every philosopher,

07:20every soul

07:21who has stared

07:21into the strange corridor

07:22of Déjà vu.

07:23What if the experience

07:24isn't an error?

07:26What if it's a signal,

07:27a marker,

07:28a breadcrumb?

07:29Elliot's thoughts

07:29turn to quantum theories,

07:31not because he believed

07:32them all,

07:33but because they offered

07:34metaphors for the unknowable.

07:36In quantum mechanics,

07:37there is a phenomenon

07:38called superposition,

07:40where a particle exists

07:41in multiple states

07:42until observed.

07:44Could consciousness, too,

07:46operate in a probabilistic space

07:47where possibilities overlap?

07:50Some fringe physicists

07:51and a few brave psychologists

07:53have speculated

07:54that Déjà vu

07:55might be the mind

07:56brushing against

07:57a neighboring version

07:58of reality,

07:59a parallel track

08:00in the multiverse.

08:02Nonsense?

08:03Perhaps.

08:04But what if Déjà vu

08:05is not just the brain

08:06echoing its own memories,

08:08but synchronizing

08:09for a heartbeat

08:09with the echo

08:10of another life

08:11you might have lived?

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