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Tai Asks Why – Season 2

Episode 2: What is Deja Vu?

TAI: You guys know that feeling when you’re in the middle of your day, doing whatever, doing your normal thing, or your unnormal thing, doing whatever really, and then just all of a sudden you just get this weird like epiphany feeling where you’re like wooah I’ve done this before. And you know you haven't but you feel like you have.

Deja vu right? Which I learned from my papa that it comes from the french and it means already seen… so like you feel like you’ve been in the situation before.. .you feel like, that’s the important thing but you haven’t because it’s happening right now?

If you guys like it that’s great but I think it’s like a really weird sensation.

FINN: deja vu is like, I know exactly what's coming next. This is really weird.

ZOE: Well sometimes I just get this weird feeling.

KADEN: There’s sort of nothing else like it.

ZOE: like it happened to me this morning actually but sometimes it’s stronger than other times

But why!?

My friends had some theories

ZOE: maybe you just dreamed about it. I don’t really know. I have that feeling sometimes.

KADEN: but people think that it has something to do with like a parallel universe where pretty much you have memories from like another parallel universe where like, you've already experienced that before, you're experiencing it simultaneously so you feel like you've already experienced it.

PIPER: Sometimes I feel like when I have deja vu it's like Oh well then this is actually meant to happen or something like that.

ZOE: Maybe it's because your brain is really good at figuring out patterns. If you notice something is really similar maybe that's your brain saying wait a second

My friends had some good ideas but, you know, which one is it? Is it a past life. Is it a part of a dream. What's happening in your brain when you experience deja vu? Is it a good thing? Is it a bad thing? Why do we even have it in the first place?

[Hit theme]

SHOW OPEN - I'm Tai and this is my podcast, Tai Asks Why. There are so many good questions out there that you just really want to get answered: How does a song get stuck in your head? When the dinosaurs died, how did some other animals survive? What are animals saying to each other? What is the science of bullying? Why is space so dark?

And what is deja vu?

[Theme out]

MOULIN: I think deja vu is a memory problem.

This is Chris Moulin he’s a neuropsychologist at the University Grenoble Alps in France. And he’s an expert on memory and deja vu

So Chris what exactly is deja vu?

MOULIN: I think deja vu is caused by like a little glitch in the memory system where you have two feelings at the same time. You have the feeling that you find something familiar. And at the same time is that you also know that that familiarity is false. In fact it couldn't possibly be true.

TAI: For some reason you get the experience of remembering it while it's being stored your memory for the first time you get a feeling like, I've been here before. If you're like on the moon.

MOULIN: Yeah exactly so. You would have like the feeling that you're having a memory but without actually having the memory. And the example of being on the moon is a great example because we know that deja vu in fact happens more likely in a novel environment. So if you go to a place for the first time it's then that you're likely to get deja vu. So I went to New York for the first time in my life and it was a really big deal. And when I was there I turned the corner and I had a massive sense of déjà vu. I had this big feeling of familiarity but I knew it was the first time I've been in New York so it wasn't possible that I'd been there before so it wasn't possible that it was a memory. It was a very strange experience.

TAI: Yeah because you’re like hold on. Like I swear I saw it before but like I guess I didn't. Is it still deja vu if you like, if you feel the sense of familiarity but you're not sure that you've been there before you're like Oh wait hold on. I've been to New York before. Is that still deja vu.

MOULIN: that is such an excellent question. So one of the conundrums in deja vu research is why old people get less deja vu. I think just like you've kind of suggested they get less déjà vu because they say well they've just done so much that it is it is quite possible they're confused because they did already do something very very similar and I don't think that is deja vu because I think deja vu is only that time when you're really saying it hasn't happened before and there's not that sort of confusion.

Yeah that that does make sense. So according to Chris deja vu starts around the time you’re 10 and it just kinda dies out after your 30s. So I'm in the height of my years I gotta get out there and take advantage of this sweet spot before the world gets too familiar. And you know what I'm actually going to New York with my family for the first time next week. Who knows maybe I'll get it deja vu.

[Street sounds]

TAI: OK. So I'm here in New York. Manhattan specifically man. This place is massive. It's really big. The buildings and the skyline. I really like how it's so organized and everything is just so big. But unfortunately I'm not getting any deja vu yet. You know everything's completely new.

[street sounds fade out]

Turns out I can’t really force myself to get a deja vu.

MARTIN: When it happens it's really fleeting it's hard to put your finger on it it's almost over before you even recognize that it's even happened. It's also hard to predict when it will happen. So it makes it really challenging to study in the laboratory.

This is another Chris. Chris Martin not Moulin. He’s a postdoctoral fellow working in the Psychology Department at the University of Toronto. And just like other Chris he’s spent a lot of time studying deja vu. And he explains that even though it’s really hard to know when it’s gonna happen there are actually ways that we can study it

MARTIN: What we can do though is look at populations that have it in the context of temporal lobe epilepsy which is a particular type of epilepsy, a little more than half of those patients experience deja vu with their seizures.

So Chris explained that the way they figure this stuff out is that when people are having seizures whatever they experience helps give us clues about where in the brain the seizures are. So if you start seeing weird dots and colours and shapes when you have a seizure then they're able to figure out that it's probably happening around the part of your brain that deals with vision, and when people have deja vu with their seizures it's probably because it's happening in the part of the brain that deals with memory.

TAI: But is the deja vu that they get with their seizures the same as the deja vu that I get?

MARTIN: They're not radically different than what you or I would describe it might last longer. So sometimes they could last up to a full minute versus what we might experience being two three four or five seconds something like that.

TAI: It's a nifty feeling but I guess if it happens for longer periods of time it could be like really scary like what's going on everything has happened before.

MARTIN: Yeah So one neat anecdote I can share with you this patient I'm thinking in particular said something to the effect of you know I'm looking around to find something that isn't familiar but everything seems to be familiar. Even though I know it shouldn't be

Ok so to learn more about what’s happening in the brain when these dejas are vuing Chris Moulin brings epileptic patients to his lab to check out their brain activity. So I got him to take ME to his lab to check out what deja vu looks like in the brain.

MARTIN: Ok so we are in Sydney Smith Hall at University of Toronto, the Psychology Department and most of our labs are downstairs which is where the lab that I work in is. We're heading down there.

So this is where he takes patients that are part of their experiments. Its really cool!

TAI: How are you able to understand what goes on with deja vu. How are you able to capture what's going on in the brain?

MARTIN: So one way to do this is implant electrodes that would go deep into the brain and have multiple recording sites on the electrodes so they can really localize with a high degree of precision where in the brain the seizures are starting. And what's really interesting about these depth electrodes is that you can also use them to stimulate the brain.

WOW that’s gnarly. So Chris can apply these electrical impulses to the brain through these sites and see what sort of experience the patient has. And what they’ve seen is that the seizures are starting in these specific parts of the brain called the perirhinal and entorhinal cortex. Rhinal means nose so perirhinal means near your nose and entorhinal means in your nose so you can try and picture this weird deja vu area inside your head where your nose ends and your brain begins.

MARTIN: And what's most compelling is if you stimulate those regions the participants have these sort of fleeting experiences of familiarity. They wouldn't know that you've just stimulated they just spontaneously say I'm experiencing deja vu right now.

TAI: So you guys do have ways to induce deja vu.

MARTIN: There are ways in clinical settings to induce deja vu. You can connect the dots and say well if we stimulate here we see deja vu. If we stimulate elsewhere we don't see that response.

TAI: So you say that you have you have pictures. What do those look like?

MARTIN: Oh yeah. They look like brains. So I just thought I'd give you a sense of where in the brain we're talking about.

TAI: Best part of the job kids.

MARTIN:So these are in fact pictures from inside your brain not your brain but inside of a brain inside someone skull

TAI: OK. It looks like I have no interpretation because it has nothing that I could relate it to.

MARTIN: Yeah it looks a little bit like cauliflower.This is looking at it from the front as if you're coming in through someone the face or the back of the head and just scroll through any one of these and you can go through the entire brain.

TAI: Wow.

CHRIS: So it's this purple part of the brain that that if you stimulate you you may experience deja vu

TAI: I can see deja vu!

[brain music out]

OK guys. It really does look like a weird complex slightly moldy cauliflower with all the grooves and the branches. It's really cool that Chris can just pinpoint these exact locations where deja vu occurs.

MARTIN: The other thing you can do in the context of epilepsy is look at long term consequences of these repeated seizures. So what we find is that we see reduced volume in patients who have deja vu as compared to those who don't in these very specific regions.

Woah, so the epilepsy patients who have deja vu, have these regions in their brains that are smaller than those who don't. It's really weird and I don't have epilepsy or anything but I do get deja vu. So is it perfectly fine and part of a healthy brain, or is it shrinking my brain sponge?

TAI: Is it bad, like is it not good or is it just kind of just like a byproduct. Kind of just what happens because we see that it links to the reduction in size but we don't necessarily know that that's the cause of the reduction. So is it necessarily bad?

MARTIN: So anytime you have a seizure that's bad, but I don't think that deja vu is necessarily bad. In fact, I think it's evidence of a healthy working good working memory system because it's an indication that everything is going right and that you can detect that conflict.

I asked Chris Moulin about this too. You remember him from earlier?

MOULIN: I think deja vu is caused by a little glitch in the memory system

Two Chris’s its kinda like deja vu right? Anyway Chris Moulin agrees with Chris Martin that deja vu isn’t bad for us. Two Chris’s, two different last names, one result.

So if they both say that it's not bad for me then I'm going to assume that the Chris’s aren't lying and deja vu isn't shrinking my brain sponge.

MOULIN: No I don't think déjà vu is a bad thing at all. I think is a sign that something's going on that's healthy. It's like a check saying hey hang on a minute. No no no.

Oh so my friend Zoe was right!

ZOE: Maybe its your brain saying wait a second

MOULIN: So it's something that checks the familiarity system doesn't run away with itself that things don't get too familiar or that you have strange sensations of familiarity when you shouldn't.

MOULIN: I think it's something that's uniquely human in that sense that is this higher order consciousness we can have about our thought processes.

TAI: Yeah. If your brain's going to slip up every once in a while it's best that you are able to recognize when it's messing up.

MOULIN: Absolutely. And more than that most people describe it as quite a pleasant experience so I don't know if you like it when you've had it.

TAI: It's a good thing at a bad thing because for the first five minutes you're like woah it's like really weird you're kind of like creeped out. But for the five minutes after that you're going like WOAH more like woah like you know like woah that was that was cool cause it's like creepy but not like makes you unnerved.

MOULIN: Its like weird but it doesn't really scare you. Its like ohhh

TAI: And then for the next couple of days you're just like woah that was that was cool.

MOULIN: Yes. It makes you sit up and think Hey what's what's going on how does my mind do this to me.

(woahs)

TAI: Woooah that was that was cool.

MOULIN: So I don't think it's a bad thing. I think some people get it at times of stress and some people can have like a kind of pathological forms of it but I don't think it's a bad thing when we when we experience it.

Ok for those of you who don’t know pathological means something related to a disease pretty much. So like the people with epilepsy getting deja vu that counts as a pathological kind of deja vu. But Chris says he’s seen some other weird bad kinds too.

MOULIN: Just after completing my Ph.D. when I worked in a memory clinic there was a guy who came in and his complaint was unusual and he complained that he had already been tested before in the memory clinic and his wife said that that was his problem instead of being forgetful he complained that everything was a repeat of something he had already done.

So whats that like? What happens if you get like really frequent deja vu.

MOULIN: It's a sad thing really because the people I've worked with who do have very constant forms of déjà vu like this patient I was talking about the first guy I started working with. They become withdrawn and depressed because just as you say they can't find anything new. And if you think about your life what motivates you. And a lot of the good stuff is the new stuff. You don't want to watch the last episode of your favorite show. You want to watch the new episode. So we see that the people like that they do kind of get a bit difficult to motivate and to find interesting things just because they they feel that everything's everything's repeating

MOULIN: You begin to understand when you work with rare disorders like that how the memory system is constantly active like you are constantly looking at everything in your environment to see whether it's familiar or not whether it's something you already encountered or not. And thankfully it all goes on automatically without you ever really thinking about it until you have something like a deja vu. But the deja vu that shows you just how that automatic process is always going on.

So your memory is constantly accumulating all your experiences trying to see what has helpful info for the future and this process just keeps on going and keeps on going behind your nose in that brain area that Chris Martin showed me. And you know it's a good thing because if everything was super familiar all the time you'd be really sad cause you know movies would just suck. Nothing would be new and exciting it'd be really sad and the opposite can be kind of bad too. Like if nothing was familiar I wouldn't remember my route to school how to tie my shoes I wouldn't remember the answers for a test I was studying for so I'm glad I got this weird déjà vu gl-gl-gl-glitch checking in on me because it helps me make sure the world is just the right amount of familiar.

And it turns out theres other helpful glitches we get too

MOULIN: I mean have you had this sensation where you look at a word for a long long time and it starts to look strange like it might be spelt wrong or did you like sometimes go to write a word and then think hang on a minute is it spelt like that. No that looks completely weird. Did you ever have that?

TAI: Yes.

MOULIN: So that that is related to deja vu and that's that's you can think of that as the opposite of deja vu that's called Jamais vu.

In French of course. My papa who's great at French tells me that Jamais vu means never seen. So it's like the opposite of deja vu already seen it's just never seen. Mon francais, tres bon, oui oui oui. Merci Papa.

MOULIN: And again we can think of it as the same kind of a control mechanism but working in the other sense, so that you don't want things to get so familiar like imagine if you if you like just kept repeating stuff and repeated it stuff and you never had any check on on whether it was right or not.

TAI: Yeah I play piano so like every time you're doing a song and if it's like three or more pages every once in a while it'll just kind of be muscle memory. And then when you actually think about it you just like stumble over your hands and then your hands just like you're like What. Because the more you think about how you play. You just like completely fall apart.

MOULIN: Yeah Exactly. I had it once when I was driving and then all of a sudden I was like you this while those pedals for I don't remember which pedals which.

TAI: Yeah that is that's that's bad yeah. Okay so then what does deja vu tell us about memory itself. You know because it's like it's a little unnerving that our brain does have these glitches.

MOULIN: Yeah. I mean I think I think you're right. It makes me sometimes question how would I ever know if something I'm remembering is a real memory or not. And then in fact there's plenty of evidence not just for deja vu to make you think that, hang on memory isn't that reliable it has its biases and we tend to confuse very very similar events and similar people and similar objects. So one of the things that deja vu really rams home Is that kind of idea that memory is kind of constructive and you make up a memory but not only that, the thing that deja vu tells you is that what makes a memory is that it feels like a memory and sometimes you can have that feeling even when it's false. So if you didn't have deja vu and if you didn't have this fact checking mechanism then you'd be in real trouble because you'd never know whether what you were remembering was a real memory or not.

TAI: that was just my mind exploding that was really awesome.

MOULIN: and I must say you're pretty awesome too.

So I see what Chris is getting at. Memories are just assumptions, you assume that this happened and this happened at this time. And if my memories, these assumptions are subjective, then there's no real objective perception. Like myself my life it's all based on these assumptions of what are my memories? They're all just things I just thought was right.

But there is a real world out there. Maybe that's why we get deja vu in new places because the mind just kind of has to acknowledge that this is the big wide world. It's either I've been there or I haven't. And you know whether or not it's happened before is deja vu double checking these assumptions.

I wonder what my friends would think of my new deja vu insights.

TAI: So how do you guys take the idea that deja vu might just be your brain double checking your memories? If you’re like I’ve been here before your brain is just helping you snap out of it and realize your not

KADEN: Yeah that’s thats interesting but it also makes a lot of sense.

FINN: I sort of imagine the brain as a computer, wires can cross and its not predictable.

ZOE: Brains are weird.

[DEJA VU SONG]

Thank you so much for listening. I'm Tai Poole. This show was produced by Veronica Simmonds and Amanda Buckiewicz. Today my guests were Chris Moulin, Chris Martin and special thanks to Tina Verma, Sonya Buyting, and my friends Finn, Piper, Kaden and Zoe for talking to me about deja vu.

The theme music is by Johnny Spence. And another big thanks to Johnny for helping me write and record the Deja Vu Song.

[Next time on Tai Asks Why...]

Till next time I’m Tai keep asking why

TRANSCRIPT: Tai Asks Why - Season 2, Episode 2

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