Busting the Most Common Misbelief About Memory Storage 🧠

Exploring the Distributed Nature of Memory in the Human Brain (8min read)

TL;DR Summary:

• Memory isn't stored in a single place in the brain but is a complex process involving multiple regions.

• The hippocampus quickly absorbs and sorts new information, while the neocortex stores long-term memories.

• The process of memory consolidation, mainly during sleep, transfers information from the hippocampus to the neocortex.

• Emotionally charged experiences create stronger memory imprints, making them easier to recall.

• Once memories are consolidated, they can be accessed directly from the neocortex, without the hippocampus's involvement.

Welcome Back!

Today we are diving deep into Neuroscience literature to bust the myth that memory is stored in 1 specific place in your brain.

This is a central, and often misunderstood, aspect of the brain. Memory is our ability to recall past events, experiences, and knowledge.

While popular culture often depicts memory as being stored in a specific vault, much like a library with books neatly arranged on shelves, the reality is far more intricate.

Let’s dive in.

The Dual Functionality of the Brain

To understand memory, you’ve got to understand how the brain takes in and digests information.

To make it very simple, you can think about the front half of your brain as the, “What should I do?” section.

This includes areas like the prefrontal cortex to give you some context.

The back half of the brain asks "What is happening?" in our environment and is made up of areas like the auditory cortex, the primary visual cortex, and much more!

Both halves of the brain converge in our working memory, which is the type of memory that creates our conscious experience of the world.

This is also where we decide what to do with the information we are taking in.

Bringing it all together, the back half of your brain tells your working memory what’s happening, so that it can then direct the front half on what to do about it!

In this interplay, working memory plays a critical role as it involves the manipulation of memories and the conscious awareness of them.

However, just because we're conscious of something doesn't necessarily mean it becomes a long-term memory.

The Grand Symphony of Memory: A Deeper Dive

Let's start with a simple example. You're at a party, and across the room, you spot an old acquaintance.

You remember their face, the sound of their laughter, and the conversation you once had about a book you both loved.

This simple act of recognition is a symphony composed of different sections of your brain, each playing its part in harmony.

It starts with the visual cortex in the back of your brain processing the sight of the acquaintance.

Then the auditory cortex chimes in, replaying the echo of their laughter.

The hippocampus and the neocortex come together in a waltz to retrieve the conversation you had about the book.

It's not a single, localized process, but a ballet of neural activity dancing across your brain, demonstrating the distributed nature of memory.

Hopefully, you’re starting to see the issue with the myth that memories are stored in 1 single location!

The Neuroscience of Memory Storage

There are 3 important stages of memory! Encoding/storage, consolidation, & retrieval.

The encoding portion involves what we just covered, but what we didn’t hit on, is how this gets stored in longer-term memory!

As the “what’s happening” portion of your brain is updating your working memory, it is also sending a message to a structure called the Hippocampus.

Memory Encoding/Storage in the Hippocampus & Neocortex

The hippocampus, located deep within the brain, is like the brain's notepad.

It's where new experiences and information are first recorded.

The neocortex, on the other hand, is like the brain's filing cabinet. It's where long-term memories are stored.

When we learn something new, our neocortex stores the new information in the hippocampus.

Simply put, the parts of your brain that are observing, listening to, and feeling various aspects of what you're learning take a "snapshot" of the experience and pass it on to the hippocampus.

The hippocampus is very plastic, and a rapid learner - capable of absorbing new information in one shot.

This “snapshot” is a specific mapping of the fire patterns of the specific neurons, in the specific regions of your brain that are firing while you’re learning.

These “snapshots” are called engram cell ensembles and it’s these engrams that get passed onto your hippocampus.

Engram Cell Firing Patterns

This means that your hippocampus now has a copy of this memory that includes the firing patterns from what you saw, what you heard, what you felt, and much more.

It’s in the hippocampus that these disparate pieces of information get integrated into 1 unified copy of all of the information taken in.

This is a bit like a group of musicians in an orchestra, each playing their part to create a symphony of memory.

This is the process of memory storage and encoding.

The Emotional Impact on Memory

Before we go on, as someone who researches and works with people struggling with trauma, I have to briefly mention the role emotions play in memory formation.

Think of emotions like an extra dose of ink, searing in more neural connections right away so we remember them easier.

This is why traumatic memories can be stored long-term after 1 experience.

It’s not just trauma though, any emotional event will be remembered better.

For example, you probably remember your wedding day, but I doubt you remember what you learned on the 4th day of 8th grade.

One was highly emotional, one wasn’t! Alright, on to memory retrieval.

Memory Retrieval

Alright, so let’s pretend it’s been day since the party where you saw your friend.

You happen to be on your phone and see a picture of your friend on social media, which then reminds you of the conversation you had, the sound of their voice, etc.

What’s happening in the brain when this happens?

In simple terms, when you remember a part of a memory stored in your hippocampus, like your friend's face, it triggers all other related details of that memory too.

This triggers your Hippocampus to send signals back to the portions of your brain that the “snapshots” came from and reactivates them.

This reactivation then sparks the memories in your neocortex, which then get sent back to your working memory, and voila, you remember all the other aspects of your friend.

This is the memory retrieval process.

An easy way to think about this is that the encoding and storage process flows from the neocortex to the hippocampus.

The retrieval process goes from the hippocampus to the neocortex to the working memory!

Memory Consolidation… How We Remember Things.

This is where sleep comes in.

During sleep, particularly during the deep stages of sleep known as slow-wave sleep, the hippocampus, and the neocortex communicate with each other.

Think of the hippocampus as a dedicated printer of the brain, etching information into the cortex.

At nighttime, the hippocampus transitions into a teacher role, educating the cortex on what it learned during the day.

This process of transferring new information to long-term memory storage is known as consolidation.

A single memory from the hippocampus can be replayed hundreds of times as we sleep, and this replay reactivates the regions of the neocortex that represent the memory, fortifying the connections.

Over time, the hippocampus' memory imprints get erased as more data gets encoded into the cortex.

The hippocampus, although a quick learner, forgets quickly too.

Therefore, it must "teach" the cortex before it forgets.

Contrary to the hippocampus, the cortex learns slowly, but it also forgets slowly.

This is why you can remember things from years ago once you’ve learned them well enough to store them in your neocortex.

New vs. Old Memory Retrieval

We talked about retrieval earlier, but that was before consolidation.

After memories have been consolidated or etched into the neocortex, we don’t need the hippocampus to remember the information anymore!

Meaning, our working memory can call directly on this information now.

For example, I’m sure you don’t think twice about looking both ways before crossing the road anymore.

Why is that? It’s because this memory is stored in your neocortex, you have instant, subconscious access to it!

Explained This To Me Like I’m a Child…

This is all very advanced Neuroscience, so let’s simplify this down.

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.

And just like in the Memory Factory, this process helps to make sure that your memories are stored safely away, ready for you to recall them whenever you need.

The Case Study of H.M.

You might be wondering how do we know all of this stuff? One example comes from the 1950s in the case study of an anonymous patient named H.M.

He underwent surgery to treat severe epilepsy, which involved the removal of large parts of his hippocampus.

The aftermath was startling.

H.M. lost the ability to form new memories, yet he retained his intelligence and much of his previously acquired knowledge, including language skills and social manners.

This was a watershed moment in neuroscience.

It suggested that while the hippocampus plays a pivotal role in forming new memories, it is not the sole storage space.

Other areas, like we just learned about such as the neocortex, were still holding onto the wealth of information that made up H.M.'s personality and knowledge.

Fast forward to the 21st century, where neuroimaging techniques like fMRI and PET scans allow us to peer into the living brain like never before.

We can now see that when you're remembering the smell of your grandmother's kitchen or recalling the lyrics of your favorite song, different areas of your brain light up like a city at night.

It's a highly interconnected network, with various regions collaborating to create a symphony of memory.

So, Where Does That Leave Us?

In the end, the human brain isn't a vault for memory, but an orchestra.

Each neuron is an instrument, each region is a section, and each memory is a symphony.

It's not about storing in a single place, but about weaving intricate melodies that flow through the network, resonating throughout the vast concert hall of our minds.

Remember this the next time you recall a treasured memory or recognize a familiar face in a crowd.

It's not just a simple retrieval of information from a specific part of your brain, but a breathtaking ballet of neural activity, a symphony that plays the music of your life.

Hope you enjoy it.

Until next time… Live Heroically 🧠

Supporting Research:

• "Associative memory of structured knowledge" (2022). Springer Nature. DOI: 10.1038/s41598-022-25708-y. Available at: http://dx.doi.org/10.1038/s41598-022-25708-y

• "Brain-wide mapping reveals that engrams for a single memory are distributed across multiple brain regions" (2022). Springer Nature. DOI: 10.1038/s41467-022-29384-4. Available at: http://dx.doi.org/10.1038/s41467-022-29384-4

• "Coordinated hippocampal-thalamic-cortical communication crucial for engram dynamics underneath systems consolidation" (2022). Springer Nature. DOI: 10.1038/s41467-022-28339-z. Available at: http://dx.doi.org/10.1038/s41467-022-28339-z

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