The Neuroscience of Déjà Vu 🧠

Diving into the Neuroscience Behind That 'I've Been Here Before' Feeling (6min Read)

TL;DR Summary:

• Déjà Vu: That eerie sensation where a new experience feels like a rerun, affecting 30% to 60% of people.

• Age Factor: More common in brains under 25-30 years old.

• The Culprit: The hippocampus, vital for memory, might cause déjà vu through misfiring, making new moments feel old.

• Memory Factory Analogy: Our brain, especially during sleep, sorts and stores memories, akin to a factory's processes.

• Storage and Deletion: Not all memories are stored; some are discarded to make room for important ones.

• Memory Mechanisms: Déjà vu might stem from novel experiences matching close enough to stored neural patterns, tricking our brain into feeling familiarity.

• Why It Matters: Understanding phenomena like déjà vu illuminates the complexities and wonders of our brain, enriching our human experience.

Welcome Back!

Have you ever experienced Déjà Vu?

Not everyone does, in fact, some estimates put it at just 30% of people who experience this in their lives.

Other estimates put it at around 50-60%, but it’s hard to test or measure because of how randomly it occurs!

In fact, I’d like to know what percent of our readers have, so I made a quick poll.

Brains under the age of 25-30ish tend to experience this more often than older brains, but what is it?!

That’s exactly what we’re going to talk about today!

As you know, I love the Neuroscience of things, so this was a fun one to write.

Let’s dive in!

What Does Déjà Vu Feel Like?

Déjà Vu is a French term that means “already seen.”

If you’ve never experienced it, let me try to explain it.

It’s kind of like finding yourself in a situation that feels like a rerun.

You're certain you've lived this moment before, even though logic tells you it's your first time there.

It’s a strange, often eerie sensation…

It's not just feeling that something is familiar though.

It's a profound conviction that you've lived through the exact situation in the past, complete with the sights, sounds, and emotions, despite knowing logically that it's your first time encountering it.

It's like your brain hits a glitch, replaying a scene you can't remember recording.

A lot of us have experienced it, but what's really going on upstairs?

The Brain Behind the Mystery

The hippocampus, that seahorse-shaped part of your brain tucked inside the temporal lobe, plays a starring role in this phenomenon.

This area is crucial for memory formation and retrieval.

Many neuroscientists believe Déjà vu arises when there's a slight misfire in this intricate system, causing a momentary hiccup in the flow of time perception and memory recall.

Imagine you're visiting a café for the first time, but it strikes you as oddly familiar.

That's your hippocampus sending mixed signals, mistakenly flagging the present as a memory, even if the timestamp doesn't match.

It's like your brain's version of mistaking someone for a friend because they wear the same hat.

To truly understand this, we need to go a couple layers deeper and understand a bit more about memory & the hippocampus!

Learning, Memory, & the Hippocampus

I will spare you the advanced Neuroscience lecture, and simplify this down into a story about a factory!

Imagine your brain as a busy factory, the Memory Factory, where memories are made.

The hippocampus is like the factory's receiving department. It's where new information comes in and is quickly sorted and labeled.

But the factory is busy, and there's not a lot of room to store these new memories for long.

That's where the neocortex comes in. It's like the factory's warehouse, a vast space with plenty of room to store memories for the long term.

But moving the memories from the receiving department to the warehouse is a big job, and the factory workers can't do it while they're busy with the day's work.

So, they wait until night, when the factory is quiet and the day's work is done.

This is when the factory workers, like little neurons, get to work moving the memories from the receiving department to the warehouse.

They carefully pack up each memory and transport it to the warehouse, where it's stored safely away.

This is a bit like what happens in your brain when you sleep.

Your hippocampus, the receiving department, sends the day's memories to the neocortex, the warehouse.

This process helps to make sure that your memories are stored safely away, ready for you to recall them whenever you need.

This is also why sleep is so important for learning!

Where Are My Memoires Located Though?

Okay, we’re getting there, this is the last concept we need to explore to truly get to the bottom of Déjà Vu!

That’s because where your memories are stored is a complex question, but inside the answer, we’ll find what happens in these bizarre moments of Déjà Vu!

Memories aren’t stored in one single location, and not all memories are even stored in our brain.

In fact, a lot of what your hippocampus is doing while you sleep is destroying memories you don’t need.

Remember, we only have so much storage in our Memory Factory warehouse!

So, we have to forget the unimportant things to make room for the most important bits of information.

For example, it’s good to remember 2 + 2 = 4, but it’s less important to remember whether this concept was written on a piece of paper or on a whiteboard when you learned it.

The concept is important, not the paper or whiteboard.

In this way, our brain and hippocampus constantly delete, distort, and generalize what we remember and perceive from moment to moment.

They have to, otherwise we would be overloaded with sensory information and unable to function!

So, What About the Memories We Do Keep?

The memories we keep are stored in a complex web of synapses, neural connections, and neuron-firing patterns!

A memory is essentially a pattern of neurons firing, just like a song is a sequence of notes or keys being played on a piano.

We know this because neuroscientists have done studies where they measure the exact firing pattern of a memory in a patient.

Then when the scientist electrically stimulates this exact firing pattern in the patient, the memory resurfaces.

Wild, right?!

When we sleep, our hippocampus is essentially doing the same thing.

For the important memories, it fires and wires the neurons that represent the memory thousands of times, forwards and backward to train up the network of neurons!

It’s these two mechanisms, how we generalize memories, and how the ones we remember are stored, that create the sensation of Déjà Vu, let me explain.

What Déjà Vu Is

Alright, it’s all come down to this moment, I can finally explain what Déjà Vu is, thank you for your patience!

When we experience Déjà Vu, what happens is that there is novel sensory information coming in that is a close enough match to a neural firing pattern that we’ve previously stored.

And because our brain generalizes our senses and memories, it causes us to instantly and subconsciously perceive this new information or situation as old information or a situation that we have experienced before!

So, let’s say that you’re visiting a completely new place, and the Déjà Vu sensation hits you… You’re certain you’ve been there before.

What’s really happening is that you have stored memories in your brain from other places you’ve been, or that you’ve read about, or seen in a movie.

And because these stored memories have a neural firing pattern that is a 70% match to the neural firing pattern that this new place is lighting up in your brain; your brain generalizes the new experience with these old experiences and tells you that you’ve been there before.

At which point you experience Déjà Vu.

70% is a random number, the point is that the firing pattern of what you’re experiencing presently is close enough to an old firing pattern already stored in your brain!

And that my friends, is the Neuroscience of Déjà Vu.

Who Cares?

So, why does all this matter to you?

I believe that understanding the quirks of our brain, like déjà vu, helps demystify the human experience, making us more aware of the marvels and mysteries within our own heads.

Neuroscience isn't just about dissecting brains; it's about connecting with the universe inside our heads.

So, the next time déjà vu strikes, take a moment to marvel at the complex network of neurons working overtime to make sense of the world around you.

And until next time… Live Heroically 🧠