How Your Memory Works

Summary

This script explores the intricacies of human memory, comparing it to Sherlock Holmes' attic analogy and debunking the myth of a single memory storage location. It delves into the role of the hippocampus, the process of memory consolidation, and the various ways we forget—naturally, through interference, or intentionally. The script also touches on the rare condition of hyperthymesia and the importance of forgetting for mental health and learning, concluding with a nudge towards improving logical thinking skills with Brilliant's courses.

Takeaways

• 🧠 Sherlock Holmes' attic theory suggests that the brain can only store a limited amount of information, implying that filling it with trivial facts can crowd out important memories.
• 🌍 The brain does not have a single 'memory bank'; memories are distributed across various regions and are formed by the collaborative action of many brain cells.
• 🔄 Memory is not a physical object but an action, similar to how 'the wave' at a baseball game is created by the collective movement of fans.
• 🐴 The hippocampus, shaped like a seahorse, is crucial for forming new memories but is not the storage location for them.
• 🧐 Case study of patient H.M. revealed the importance of the hippocampus in memory formation, showing that damage to it can prevent new memories from forming while preserving old ones.
• 🗺️ Memory consolidation involves the strengthening of neural connections through repeated activation, similar to a mouse retracing its path in a maze.
• 🌀 Memory recall can be triggered by various sensory cues, such as a smell, which can evoke associated memories, much like the scent of cinnamon might remind one of grandma's apple pie.
• 🔍 The brain's memory creation process is not infallible; mental replay of imagined events can feel as real as actual experiences, potentially leading to false memories.
• 🕊️ Forgetting is a natural and essential process that helps us move past trauma, clear out unnecessary information, and update our understanding of the world.
• 💤 There are three types of forgetting: passive oblivescence, targeted forgetting during sleep, and motivated forgetting, where we intentionally suppress unpleasant memories.
• 🧚‍♀️ Hyperthymesia, or the ability to never forget, is extremely rare and can be burdensome, as exemplified by Jill Price, who is haunted by her vivid and unrelenting memories.

Q & A

What is Sherlock Holmes' theory about the brain and memory storage?

Sherlock Holmes theorized that the brain is like an attic with a limited capacity for storing memories, suggesting that filling it with trivial information could crowd out important details.

What is the concept of 'the wave' used to illustrate in the context of memory?

The 'wave' analogy is used to explain that a memory is not a physical object but an action, involving many connected neurons firing in a specific pattern, similar to how no single fan is the wave but the collective action of fans creates it.

Why is the hippocampus significant in the process of memory?

The hippocampus is crucial for the formation of new memories. It was demonstrated through the case of patient H.M., who, after having most of his hippocampus removed, could not form new memories but retained pre-existing ones.

How does the process of memory consolidation work in the brain?

Memory consolidation involves the replaying of neural patterns associated with an experience, strengthening the connections between brain cells. This process is how new memories are committed to long-term storage.

What is the phenomenon where imagined experiences can feel as real as actual ones?

This phenomenon occurs when mental replay of imagined scenarios activates similar brain networks as real experiences, making the imagined events feel vivid and real, which can lead to the formation of false memories.

What are the three types of forgetting mentioned in the script?

The three types of forgetting are passive oblivescence, where memories fade over time; targeted forgetting, which occurs during sleep to clear out useless information; and motivated forgetting, where one intentionally suppresses unpleasant memories.

Why is forgetting considered an important cognitive function?

Forgetting is important because it allows us to move past traumatic events, clear out irrelevant information, and update our mental models with new, accurate information.

What is hyperthymesia, and how does it affect those who have it?

Hyperthymesia is a rare medical condition where individuals have an extraordinary ability to remember almost every detail of their lives. It can be burdensome, as they may be haunted by upsetting memories and regrets.

How does the script relate the concept of forgetting to the idea of learning and understanding new concepts?

The script suggests that while memorization can be a starting point, true understanding comes from seeing connections between concepts, exploring different interpretations, and integrating new information.

What is the role of sleep in the process of forgetting?

Sleep plays a role in targeted forgetting by allowing the brain to clear out random, useless information and erase outdated memories, helping to maintain an efficient memory system.

What is the script's stance on the possibility of having a perfect memory and the implications of never forgetting?

The script implies that having a perfect memory and never forgetting is not only unlikely without significant brain injury but also potentially burdensome, as it could lead to being haunted by negative memories and regrets.

Outlines

00:00

🔍 Sherlock Holmes' Brain Attic Theory and Memory Mechanisms

This paragraph explores the concept of memory limits, drawing from Sherlock Holmes' analogy of the brain as an attic with limited storage space for memories. It delves into the idea that cluttering the brain with trivial information could impede the storage of important details. The script then challenges this notion by explaining that memories are not stored in a single location but are distributed across the brain, involving various regions and neurons. The hippocampus is highlighted as crucial for memory formation, but not storage, with the memory consolidation process described through the example of a mouse navigating a maze. The paragraph also touches on the fallibility of memory and the potential for false memories to be formed through leading questions or vivid imagination.

05:03

💤 The Science of Forgetting and Its Importance

The second paragraph discusses the different types of forgetting: passive oblivescence, where memories fade over time due to weakened neural connections or lack of retrieval cues; interference, where new memories disrupt old ones; and targeted forgetting, which occurs during sleep to clear outdated or irrelevant information. Motivated forgetting is also introduced as a deliberate act to suppress unpleasant memories for emotional regulation. The benefits of forgetting are emphasized, such as moving past trauma and updating outdated beliefs. The paragraph introduces hyperthymesia, a rare condition where individuals have near-perfect memory, using Jill Price as an example to illustrate the potential downsides of never forgetting. It concludes by questioning the value of memorization versus true understanding and learning, suggesting that the latter is more beneficial for deep knowledge acquisition.

Keywords

💡Memory

Memory is the cognitive process of encoding, storing, and retrieving information. In the video, it is compared to an attic with limited space, emphasizing the idea that we can only hold a finite amount of information. The script also delves into the complexity of memory, discussing how it is not a physical object but an action involving the activation of multiple neurons in a specific pattern.

💡Hippocampus

The hippocampus is a region in the brain that plays a critical role in the consolidation of information from short-term memory to long-term memory. The script mentions the hippocampus in the context of a famous patient, H.M., whose surgical removal of this area resulted in severe amnesia, illustrating the hippocampus's importance in forming new memories.

💡Consolidation

Consolidation refers to the process by which memories are stabilized and transformed into long-term memories. The script uses the analogy of a mouse in a maze to explain how the brain cells fire in patterns that replay the experience, reinforcing the connections between cells and committing the new memories to long-term storage.

💡Forgetting

Forgetting is the loss of memory, and the script discusses it as a natural and necessary process. It outlines different types of forgetting, such as passive oblivescence, where memories fade over time, and targeted forgetting, which occurs during sleep to clear out unneeded information. The script also touches on motivated forgetting, where individuals intentionally suppress unpleasant memories.

💡Hyperthymesia

Hyperthymesia, also known as highly superior autobiographical memory, is a rare condition where individuals have an extraordinary ability to remember the majority of their life experiences in detail. The script introduces Jill Price as an example of someone with hyperthymesia, who can recall specific events and details from her past with remarkable clarity.

💡Neuroplasticity

Neuroplasticity, or brain plasticity, is the ability of the brain to change and adapt as a result of experience. The script implies this concept when discussing how the same group of neurons can encode multiple memories by firing in different patterns, thus increasing the brain's memory storage capacity.

💡Amnesia

Amnesia is a condition characterized by the inability to form new memories or retrieve existing ones. The script references a patient known as H.M., who experienced severe amnesia after his hippocampus was damaged, highlighting the critical role of the hippocampus in memory formation.

💡Interference

In the context of memory, interference occurs when the storage or retrieval of one memory is disrupted by another. The script suggests that memories could theoretically last forever, but interference from using the same neurons in other memories can disrupt the original memory, leading to forgetting.

💡Retrieval

Retrieval is the process of accessing and bringing memories back into conscious awareness. The script explains that memories are not stored in a single location but are reconstructed when the relevant neural patterns are activated, such as when a smell might trigger the recall of a memory.

💡Leading Questions

Leading questions are those that suggest a particular answer or interpretation. The script warns that a detective asking leading questions can inadvertently plant false memories in a witness by activating similar brain networks as if the imagined event had actually occurred.

💡Mental Models

Mental models are internal representations of external reality, used to understand and predict events. The script mentions that forgetting allows us to replace outdated or false information with better, updated knowledge, which is essential for maintaining accurate mental models of the world.

Highlights

Sherlock Holmes' theory that the brain is like an attic with limited memory storage capacity.

Holmes' view on forgetting trivial facts to make room for important memories.

The animated film 'Inside Out' analogy for how memories are stored in the brain.

The actual complexity of memory storage in the brain, involving multiple regions and cells.

Memory as an action involving connected neurons firing in a specific pattern, rather than a physical object.

The hippocampus' role in memory formation and its discovery through patient H.M.'s case.

The process of memory consolidation in animals, including humans, through neural replay.

The phenomenon of false memories created by leading questions or vivid imagination.

Three types of forgetting: passive oblivescence, targeted forgetting during sleep, and motivated forgetting.

The importance of forgetting in moving past traumatic events and clearing out irrelevant information.

Hyperthymesia, a rare condition where individuals have near-perfect autobiographical memory.

The challenges faced by individuals with hyperthymesia, such as being haunted by upsetting memories.

The limitations of current methods in selectively erasing unwanted memories in humans.

The necessity of both remembering and forgetting as part of the human learning and adaptation process.

The promotion of Brilliant's course on logic and deduction for enhancing learning and problem-solving skills.

A special offer for the first 200 people signing up for Brilliant's free trial and a discount on the annual Premium subscription.

Transcripts

Thank you to brilliant dot org for supporting PBS Digital Studios.

Sherlock Holmes, the legendary detective, had a theory that the brain is like an attic

where a person can only store a limited amount of memories.

Dr. Watson once told him that the Earth travels around the sun, duh, to which Holmes replied,

“Now that I do know it I shall do my best to forget it.”

Holmes figured, clutter your attic with random facts and trivia, and you won’t have room

for the things that matter, like identifying the tiny differences between lethal poisons.

Was Holmes right?

Is our memory limited, like the storage capacity of a computer?

Or is our memory unlimited?

And if we did have perfect memory, what would life be like if you never forgot anything?

[OPEN]

The animated film Inside Out depicted memories as glowing spheres stacked in the brain, like

books in a library.

But the reality is a little more complicated.

There is no one place in the brain that serves as our memory bank.

Instead, individual memories are scattered all over the brain.

Many brain cells, in several different regions, work together to make one memory.

For example, a memory of eating grandma’s apple pie might involve some brain cells to

help you remember what the pie looked like, others to remember the smell of the cinnamon,

and even cells to remember the delicious taste – just to name a few.

In reality, though, a memory isn’t a physical thing that we can find in any given brain

cell.

It’s an action, not an object.

Think of baseball fans doing “the wave”: no single fan IS the wave, the magic only

happens when all the fans are together, doing their thing in a specific order.

In the same way, a memory only happens when many connected neurons fire in a specific

pattern.

And because the same cells can fire in many unique patterns, one group of neurons can

encode multiple memories.

This increases the memory storage capacity of the brain.

Buried deep in the middle of the brain we find a group of cells shaped like a seahorse,

which is why 18th century scientists named this bit the ‘hippocampus.’

Without your seahorse, you might never remember.

We owe a lot of our understanding of memories to one famous patient, known for years only

by his initials, H.M.

In 1953, H.M. underwent a surgery for epilepsy which demolished most of his hippocampus,

and for the rest of his life, he exhibited a severe type of amnesia where he was unable

to form new memories of facts or events, but, he was still able to remember things he had

learned before the surgery.

This showed us that the hippocampus is a key to making memories, but that it isn’t where

memories are stored.

So how do experiences become memories?

If we look inside the brain of a mouse in a maze, we could

draw a kind of map, showing which brain cells are active as the mouse experiences something

[mouse in maze].

Later, we would see the mouse's brain cells firing in the same

patterns, replaying the experience in fast forward, over and over,

backwards and forwards, to make the connections between cells stronger.

This is called consolidation, and it’s how animals - including humans - commit new memories

to long-term storage.

Days or weeks later, a smell might trigger this same pattern of cells nerve firing in

the mouse brain, a recall of the maze memories - just like smelling cinnamon might trigger

memories of grandma for you.

But the brain’s way of creating memories isn’t foolproof.

Sometimes, our mental replay of something we only imagined can feel as vivid as a real

experience.

If you picture all the sights, smells, and sounds of a crime scene from someone’s description,

you activate similar brain networks as if you had really been there.

The more you replay the scene in your mind, the more it feels like a real memory.

That’s why a detective who asks leading questions can inadvertently plant a false

memory in a witness.

We’re able to remember a lot, but we forget even more.

Some forgetting just happens, but our brains also forget on purpose.

We have at least three different ways of forgetting.

The first is what happens when a memory fades over time, so-called “passive oblivescence”

(a term you will probably forget).

This may happen because the connections between brain cells gradually weaken over time; or

perhaps the memory is still there, but you might lose the triggers–sights, sounds,

smells–you need to retrieve it.

Another idea says memories could theoretically last forever, but when the same neurons get

used in other memories, this “interference” disrupts the original memory.

This slow fade type of forgetting happens to all of us, eventually.

A second type of forgetting–targeted forgetting–happens at night while we sleep.

This is when we clear out random, useless tidbits of information we’ve learned during

the day and erase outdated memories.

For example, if yesterday, you thought Earth was, say, a flat disk supported by three elephants,

and today you learned that the Earth is round, your brain needs to purge one of these contradictory

ideas - hopefully, the one about the elephants.

In certain stages of sleep, we trim and prune connections between cells and erase unneeded

memory circuits.

The third type of forgetting is motivated forgetting, something we all wish we could

do for one thing or another.

This is when a person intentionally suppresses unpleasant memories.

Forgetting on purpose is a way to regulate our emotions and to focus on what needs to

be done in the present, instead of getting lost in negative memories of the past.

We may need motivated forgetting to maintain our self-image, to maintain confidence, to

stay optimistic about the future, or to be able to maintain relationships with people

who have hurt us.

We don’t know exactly how motivated forgetting happens, but part of our brain seems to step

in and block the troubling memory from being retrieved.

So that even though it’s still somewhere in our brain, eventually we can’t find it.

Our brains have so many ways to forget because forgetting is one of the most important things

we do.

Forgetting allows us to move past traumatic life events.

In fact, PTSD may be a problem where someone simply remembers too much.

Forgetting also allows us to clear out junk.

Imagine every sight, sound, smell, and piece of information your brain processes every

day!

If our brains didn’t sweep out the garbage every night, we would soon overflow our neural

networks with random useless trivia, just like Sherlock Holmes predicted.

We also wouldn’t be able to replace things that are no longer true with better information

and update our mental models of the world.

Deep in the scientific literature we find stories of a handful of people who NEVER forget

anything.

They are so rare that their unforgetfulness has a medical name: hyperthymesia.

The most famous case is Jill Price, an American woman now in her fifties.

Starting from age 14, Jill’s memory of her life is nearly perfect.

For any date in the past, she remembers what she wore and had for lunch that day, key historical

events that she paid attention to, and detailed incidents from her life.

She describes memories playing in her mind in vivid detail like a video reel that has

been enhanced with smells and emotions, whether the events occurred yesterday or decades ago.

This might sound like a blessing, especially if you’re in school, but Jill has described

being haunted by upsetting memories and by regrets, because unlike the rest of us, she

can clearly remember every choice she made and how it turned out.

There’s probably something you truly *want* to forget, like that extremely embarrassing

moment in high school that always seems to pop up at the worst times.

Can we erase those unwanted memories somehow?

In an episode of House, MD, Dr. House treated a patient suffering from painful memories

by performing something called electroconvulsive therapy: controlled electric shocks to the

brain.

People who undergo ECT do lose some memories – only not necessarily the ones they hope.

When it comes to erasing memories in humans, our best tool still works like a hammer, not

a scalpel.

It’s no accident that our ability to forget, like our ability to remember, is a complex

and finely-tuned mechanism.

If humans couldn’t remember and learn from important events, our species probably wouldn’t

have survived.

But it seems that being able to forget is just as critical, an elementary part of solving

this great mystery we call life.

Stay curious!

So you probably can’t teach yourself to have perfect memory, and never forget anything.

Not without a massive brain injury or something.

But is memorization really the best way to learn something?

Memorizing can definitely help you get started with a new concept.

However, truly understanding it requires much more - seeing how concepts are related to

each other, looking for different interpretations, dealing with new information.

These are the skills that will help you learn anything, and if you’d like to sharpen your

brain and develop these tools, then Brilliant could be the place to go for that.

Check out this Brilliant course on logic and deduction [screen recording]

It’s got fun and challenging riddles and mind-benders, broken up into bite size pieces,

and they’ll guide you through the problems until you’re a Sherlock Holmes-level logical

thinker…

To support It’s Okay To Be Smart and learn more about Brilliant, go to brilliant dot

org slash BESMART and sign up for free.

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