NOVA scienceNOW : 37 - Sleep

Summary

In this episode of NOVA scienceNOW, host Neil deGrasse Tyson explores the mysteries of sleep and its potential connection to memory. Scientists like Amita Sehgal and Matt Wilson study the sleep patterns of fruit flies and rats, respectively, to understand the brain's role in memory consolidation. They discover that sleep may be essential for reviewing and strengthening memories, suggesting that a good night's sleep could enhance learning and problem-solving abilities. The program also touches on the societal implications of sleep deprivation in our 24/7 culture.

Takeaways

• 🧠 Dreams and sleep are still largely mysterious phenomena; scientists are actively researching their purposes.
• 🐝 Dr. Amita Sehgal's research on fruit flies suggests that sleep deprivation can affect their behavior, similar to its effects on humans.
• 🧪 The 'Deprivator' experiment shows that sleep-deprived flies exhibit behaviors akin to catching up on lost sleep, indicating a universal need for rest.
• 🕷️ The mushroom body in fruit flies, associated with memory, also controls sleep, hinting at a link between sleep and memory consolidation.
• 🧐 Sleep researchers have debated the connection between sleep and memory, with some suggesting that sleep is essential for memory consolidation.
• 🎮 Dr. Robert Stickgold uses video games to study learning and memory, suggesting that sleep may help in reviewing and strengthening memories.
• 💤 Sleep is fundamental to all organisms, and its disruption can have profound effects on cognitive functions like memory and learning.
• 🐀 Matt Wilson's research on rats shows that their brains replay experiences during sleep, potentially aiding in memory consolidation and learning.
• 🧠 The hippocampus and neocortex are key brain regions involved in memory processing during sleep, suggesting a role in transferring short-term memories to long-term storage.
• 🌙 The idea of 'sleeping on a problem' may have a biological basis, as sleep could help process information and lead to insights or solutions.
• 🚫 Despite the intriguing theories, the exact function of sleep in relation to learning and memory remains speculative and requires further research.

Q & A

What is the purpose of the 'Deprivator' mentioned in the script?

The 'Deprivator' is a piece of equipment used to deprive fruit flies of sleep by jostling them all night long, which helps researchers study the effects of sleep deprivation on the flies.

Why are fruit flies used in sleep research as mentioned in the script?

Fruit flies are used in sleep research because they have a sleep cycle similar to humans, and their brain structures can provide insights into the fundamental aspects of sleep.

What is the significance of the mushroom body in fruit flies as discussed in the script?

The mushroom body in fruit flies is significant because it is a part of the brain that is not only required for memory but also controls sleep, suggesting a possible link between sleep and memory.

How does the script suggest that sleep might be connected to memory?

The script suggests that sleep might be connected to memory through experiments showing that sleep can enhance memory consolidation, as evidenced by improved performance on tasks after sleep.

What role does the hippocampus play in memory and sleep according to the script?

The hippocampus, a part of the brain in rats and humans, plays a crucial role in memory, including spatial memory. The script suggests that the hippocampus is active during sleep, replaying memories and possibly strengthening them.

How does the script describe the process of memory consolidation during sleep?

The script describes memory consolidation during sleep as a process where the brain reviews and strengthens new memories, possibly identifying goals and insights, which is supported by the replay of experiences in the brain during sleep.

What is the significance of the rat maze experiment mentioned in the script?

The rat maze experiment is significant because it demonstrates that rats replay their experiences in the maze while they sleep, suggesting that sleep is involved in the processing and consolidation of memories.

What does the script imply about the potential benefits of 'sleeping on a problem'?

The script implies that 'sleeping on a problem' might not just be a saying but could represent a biological process where the brain processes and organizes information, potentially leading to insights upon waking.

How does the script address the cultural implications of sleep deprivation?

The script addresses the cultural implications of sleep deprivation by suggesting that a 24/7 culture might be affecting our cognitive abilities and our ability to gain deep understanding and wisdom from our experiences.

What is the script's stance on the necessity of sleep?

The script presents sleep as a biological necessity, not a luxury, and suggests that disrupting sleep could have profound effects on our ability to learn and remember.

What does the script suggest about the relationship between sleep and wisdom?

The script suggests that sleep may be crucial for gaining wisdom, as it allows the brain to process and understand past experiences, which could be compromised by sleep disruption.

Outlines

00:00

💤 The Mystery of Sleep and Dreams

In this segment, Neil deGrasse Tyson introduces the topic of sleep and dreams, highlighting the enigma surrounding why we sleep and dream. He presents the work of Amita Sehgal, who uses fruit flies to study sleep patterns, employing a device called 'The Deprivator' to disrupt their sleep. Sehgal's findings suggest that sleep deprivation leads to compensatory sleep behavior, even at times when the flies are usually active. Tyson also discusses the broader implications of sleep for all organisms, including humans, and the potential connection between sleep and memory, which is a subject of ongoing scientific debate.

05:01

🧠 Sleep and Memory Consolidation

This section delves into the role of sleep in memory consolidation. Robert Stickgold suggests that sleep is crucial for reviewing and strengthening memories, leading to improved cognitive function. Studies are cited that show improved performance in visual pattern recognition and math puzzle-solving after sleep. Matthew Walker's research indicates that sleep enhances memory, as demonstrated by improved typing performance after a night's rest. The segment also explores the possibility that sleep helps in the processing and organization of important information, which is supported by the observation of rats' brain activity during sleep, showing replay of迷宫 running experiences.

10:03

🕵️‍♂️ The Role of Sleep in Learning and Problem-Solving

The final paragraph discusses the hypothesis that sleep is essential for learning from past experiences and solving problems. Matt Wilson's research with rats shows that the brain replays experiences during sleep, potentially aiding in memory processing. The hippocampus is highlighted as a key structure in this process, as it communicates with the neocortex to reinforce memories. The segment concludes with a discussion on the broader implications of sleep disruption in modern society, suggesting that lack of sleep may hinder our ability to gain wisdom from our experiences.

Keywords

💡Sleep

Sleep is a biological process that remains largely mysterious, but is essential for survival in all organisms, as noted by multiple experts in the video. It is portrayed as fundamental to maintaining life and enhancing brain function. In the video, researchers explore how sleep may be connected to memory processing and learning, especially through studies on humans, fruit flies, and rats.

💡Memory

Memory is highlighted as a critical function that may be influenced by sleep. Researchers like Amita Sehgal and Matt Wilson connect sleep to memory by showing how it helps consolidate and organize experiences. The hippocampus in humans and the mushroom body in fruit flies, which are responsible for memory, activate during sleep, suggesting the brain is processing memories while we rest.

💡Mushroom body

The mushroom body is a part of the insect brain, particularly fruit flies, involved in both memory and sleep regulation. In the video, Amita Sehgal's research reveals that this structure, originally thought to only control memory, also plays a crucial role in sleep, drawing a direct link between sleep and memory in simpler organisms like insects.

💡Hippocampus

The hippocampus is a critical brain structure involved in memory formation and spatial navigation, especially in mammals like rats and humans. In the video, it is shown to replay daily experiences during sleep, which strengthens memory. Matt Wilson’s experiments with rats reveal that the hippocampus is reactivated during sleep, highlighting its role in processing and consolidating memories.

💡Deprivator

The Deprivator is a piece of equipment used by Amita Sehgal to keep fruit flies awake by jostling them throughout the night. This device illustrates the connection between sleep deprivation and the body's need to recover lost sleep, as the flies that were deprived of sleep exhibited sleep-recovery behavior when allowed to rest.

💡REM sleep

Although not explicitly mentioned in the transcript, REM (Rapid Eye Movement) sleep can be inferred as part of the context in which memory and learning are enhanced during sleep. Researchers observe that sleep, possibly including REM phases, helps consolidate memories and improve learning outcomes, such as faster typing or recognizing visual patterns after rest.

💡Learning

Learning is closely connected to sleep in the video, where experts suggest that sleep helps the brain process and strengthen newly acquired information. For example, Neil deGrasse Tyson demonstrates how a night’s sleep improved his ability to type a five-digit sequence faster and more accurately. Sleep allows the brain to enhance and refine skills learned during the day.

💡Dreams

Dreams are depicted as a possible byproduct of the brain replaying and processing memories during sleep. Researchers like Matt Wilson observe that rats 'replay' maze-running experiences in their dreams, suggesting that dreams may help reinforce learning and memory. Similarly, Robert Stickgold suggests that dreams might help humans process new information, as illustrated by the common experience of dreaming about Tetris shapes after playing the game.

💡Cognitive processing

Cognitive processing refers to the brain's ability to organize, analyze, and store information. The video explores how sleep may be a crucial time for cognitive processing, where the brain consolidates new information and enhances memory. This concept is reflected in the idea of 'sleeping on a problem,' where people often find solutions to complex issues after a night's rest.

💡24/7 culture

The term '24/7 culture' refers to the modern lifestyle that often prioritizes constant productivity over rest, leading to reduced sleep. In the video, experts suggest that this culture may harm our cognitive abilities and long-term memory, as sleep is essential for processing experiences and gaining wisdom. Matthew Walker emphasizes that sleep is not a luxury but a biological necessity, underscoring the risks of sleep deprivation in a fast-paced world.

Highlights

Dreams can be bizarre and their purpose remains unknown, just like the reason for sleep.

Amita Sehgal uses fruit flies to study sleep, affectionately referring to them despite subjecting them to 'The Deprivator'.

The Deprivator is a device that disrupts sleep, used to observe the effects of sleep deprivation on fruit flies.

Flies that are sleep-deprived exhibit behaviors similar to catching up on lost sleep, suggesting a need for sleep even in insects.

The connection between sleep and memory is a topic of debate among sleep researchers.

Sleep is considered fundamental to all organisms, yet its exact purpose remains a mystery.

Amita Sehgal's research indicates that the mushroom body in the fruit fly brain, known for memory, also controls sleep.

Bob Stickgold uses video games like Tetris to study how the brain learns and how sleep might influence memory.

Stickgold's research suggests that sleep strengthens memories, as evidenced by improved performance after sleep.

Matthew Walker's study shows that sleep can enhance memory, with people improving their typing speed and accuracy after sleep.

Matt Wilson at MIT uses tiny electric probes to read rats' minds, including their dreams, to study memory and learning.

Rats' dreams often replay their experiences, such as navigating a maze, suggesting sleep may be for memory consolidation.

The hippocampus in rats, similar to the mushroom body in fruit flies, plays a role in memory and is active during sleep.

The replay of experiences during sleep may serve to strengthen and organize memories for long-term retention.

Sleep may be a biological process that consolidates information, as evidenced by the 'sleeping on a problem' phenomenon.

Disruption of sleep could potentially rob us of wisdom by hindering our ability to gain deep understanding from past experiences.

The necessity of sleep is emphasized as it's not a luxury but a biological requirement for optimal brain function.

Transcripts

NEIL DEGRASSE TYSON: Hello.

I'm Neil deGrasse Tyson, your host for NOVA scienceNOW.

We all know that dreams can be, dreams can be a little weird, sometimes filled with bizarre

events that would never happen in real life.

Nobody really knows why we dream.

In fact, nobody really knows why we sleep.

Here are some folks who are trying to figure it out.

Amita Sehgal likes her flies, fruit flies, to be precise.

AMITA SEHGAL (University of Pennsylvania and Howard Hughes Medical Institute): I do have

a genuine affection for them.

NEIL DEGRASSE TYSON: But sometimes, she has a strange way of showing that affectionóespecially,

when she puts them into this thing.

AMITA SEHGAL: We use this piece of equipment we call "The Deprivator."

NEIL DEGRASSE TYSON: The Deprivator?

It's like riding a roller coaster during an earthquake.

What's interesting to Sehgal is what the flies do after spending a whole night in here.

The flies on the left were undisturbed last night, and they look fine.

But the flies on the right, they were jostled all night long in the Deprivator.

Now, some of them look dead, but they're not.

According to Sehgal, they're catching up on lost sleep.

AMITA SEHGAL: If we keep flies awake at night, they need to make up for the sleep they have

lost, and so will sleep in the morning, at a time when they're normally active.

NEIL DEGRASSE TYSON: But why would flies need to sleep?

Could it be for the same reason we need to sleep?

Maybe.

But if you ask an expert what exactly that reason is...

MATTHEW P. WALKER (Harvard Medical School): We actually know very little about what sleep

is doing for the brain.

AMITA SEHGAL: We spend a third of our lives sleeping.

If you don't sleep, you die.

MATT WILSON: Sleep is an enigma.

What is its purpose?

That's something that we do not understand.

NEIL DEGRASSE TYSON: Looks like a waste of time.

But then why would so many creatures do it?

MATT WILSON: Sleep is something that, the more we look at it, the more we see that it

is fundamental.

It's fundamental to essentially all organisms.

NEIL DEGRASSE TYSON: Including, it seems, organisms like fruit flies.

When they're not being knocked around all night, Amita Sehgal's flies follow a pretty

familiar schedule.

AMITA SEHGAL: They're active during the day and they sleep at night, for the most part,

although there is an afternoon siesta as well, especially in males.

NEIL DEGRASSE TYSON: Trying to pinpoint the reason for a fly to snooze up to 12 hours

a night, Sehgal's lab studies the fruit fly's brain.

AMITA SEHGAL: What we were doing was trying to figure out which part of the fly brain

was important for sleep.

NEIL DEGRASSE TYSON: Sehgal's experiments pointed to the mushroom body, a part of the

brain found in creatures like insects and spiders, but not in humans.

Biologists have known about the mushroom body for years, but they associated it, not with

sleep, but with something else entirely, an insect's memory.

AMITA SEHGAL: There is, then, this structure in the fly brain, which we already knew was

required for memory, and we now find that it controls sleep.

NEIL DEGRASSE TYSON: The finding's intriguing because, for a long time now, sleep researchers

have been debating a possible connection between sleep and memory.

Bob Stickgold has been looking into this possibility, sometimes in unconventional ways.

For him, video games are research tools that can help reveal how our brains learn.

ROBERT STICKGOLD: Do you remember when you first started playing TetrisÆ...

NEIL DEGRASSE TYSON: Oh, yeah.

ROBERT STICKGOLD: ...that you went to bed at night, and you lay in bed, and you closed

your eyes, and you saw little Tetris pieces floating around in front of your eyes?

NEIL DEGRASSE TYSON: How did you know that?

How did you know that...

ROBERT STICKGOLD: Because...

NEIL DEGRASSE TYSON: ...I dreamed Tetris shapes?

ROBERT STICKGOLD: ...because everybody does.

NEIL DEGRASSE TYSON: After taking a few rides on a ski machine, Stickgold's research subjects

fall asleep, and then he promptly wakes them up.

ROBERT STICKGOLD: If we wake you up just two or three minutes after you fall asleep and

ask you, "Neil, what's going through your mind?"

You'll say, "Seeing those suckers somersaulting down when I crash."

NEIL DEGRASSE TYSON: And why would I dream of this embarrassing moment?

Stickgold is convinced that while you sleep, your brain is reviewing what you've learned

and strengthening your memories.

ROBERT STICKGOLD: The brain is being modified while we sleep, so that when we wake up in

the morning, in some way, we have a different brain.

And it's a brain that functions better.

NEIL DEGRASSE TYSON: At least it seems to function better on some kinds of memory tasks.

Recent studies show that after a single night's sleep, sometimes even after a nap, we can

do a better job recognizing visual patterns and even solving some math puzzles.

MATTHEW WALKER: What we're going to have you do is try and type out a short, five-digit

sequence.

NEIL DEGRASSE TYSON: I saw it first hand when I took a simple typing test, typing a string

of five numbers over and over again as fast as I could.

After a night's sleep, I could suddenly type the numbers faster and more accurately.

And research backs this up.

Most people improved their typing by about 20 percent after sleep.

MATTHEW WALKER: Practice doesn't make perfect.

It seems to be practice with a night of sleep that makes perfect.

Sleep is enhancing that memory so that when you come back the next day you're even better

than where you were the day before.

NEIL DEGRASSE TYSON: But exactly how could sleep enhance your memory?

We don't know.

But possible clues have been showing up, not just in the brains of flies, but in the dreams

of rats.

MIT researcher Matt Wilson says he can read rats' minds, including their dreams, with

tiny electric probes.

MATT WILSON: What it means is that we're able to, at any time, plug in our electronics,

and...

NEIL DEGRASSE TYSON: Figure out what they're thinking.

MATT WILSON: ...read their, read their mind.

NEIL DEGRASSE TYSON: Wilson's mind-readers are actually thin wires, about a tenth of

the width of a human hair, that pick up the electrical signals among dozens of brain cells.

The wiresópainlessly implanted in the rat's brain, and held there by a kind of hatócarry

the signals right into Wilson's computers.

That information comes up back through these connectors into your computer, and you're

sitting there watching a map of the thoughts of this rat?

MATT WILSON: Exactly.

That's exactly right.

NEIL DEGRASSE TYSON: It's remarkable.

Wilson is most interested in mapping the rat's thoughts in a part of its brain called the

hippocampus.

Like the fruit fly's mushroom body, the hippocampus of a rat or a human plays an important role

in memory, including our sense of space and location.

Wilson uses a specially designed rat maze.

If the rat follows the right route, he's rewarded with some chocolate syrup.

And as he moves through each different spot in the maze in search of his goal, a unique

pattern of cells fires in his brain.

MATT WILSON: So we can tell where the animal is, simply based upon which cells in the hippocampus

are active.

That pattern will be unique for a given location in a given environment.

NEIL DEGRASSE TYSON: What's amazing is that the same patterns turn up again, even after

the rat drifts off to sleep.

That's right, Wilson eavesdrops on his rats' dreams.

And they aren't about cheese, they're about running the maze.

MATT WILSON: So when the animals would go to sleep, we would see these patterns of brain

activity that were expressed while the animals were running on the maze, being replayed,

in the same sequence, the same order in which they had been experienced.

NEIL DEGRASSE TYSON: But the replay wasn't exactly the same as when the rat ran the maze.

Sometimes it was like an extreme fast-forward; quick flashes of the experience.

MATT WILSON: Now, at the time, you never know what is going to be important and what is

not important.

So you may re-evaluate or edit those memories to identify the things that were important.

NEIL DEGRASSE TYSON: And this fragmented replay wasn't just happening in the hippocampus.

Wilson also detected it in the visual cortex, meaning the rats were likely seeing the maze

in their sleep.

What's more, the visual cortex is part of the larger neocortex, which, in humans, is

responsible for, among other things, long-term memory.

MATTHEW WALKER: The hippocampus is replaying the events of the day.

The hippocampus is almost, sort of, reactivating the memories at night and playing them out

to the neocortex.

It's almost as though the hippocampus is having a therapy session with the, with the neocortex.

And it's almost saying, "Okay, here's what we learned during the day."

MATT WILSON: What are rats and what are people doing during sleep?

They are processing memory.

They are replaying memory.

Now, we could ask, "Is this about learning?"

And I believe that's exactly what it is about, that animals are, and humans are trying to

learn from past experience.

NEIL DEGRASSE TYSON: So, the idea here is that the sleeping brain might be reviewing

and strengthening new memories it wants to hold on to for the long-term.

And it might identify certain goals we want to work towards.

Some believe the sleeping brain could lead us to real insights.

ROBERT STICKGOLD: We all know about "sleeping on a problem."

And sleeping on a problem is when you have a lot of new information and don't know what

to do with it, and you can't decide how to interpret it.

And so you say, "Let me sleep on it."

And, with remarkable success rates, you can wake up the next morning and have an answer

to a problem that you couldn't find the answer to the night before.

And that's all about processing information, processing memories in the brain.

NEIL DEGRASSE TYSON: So could it be that sleeping on it isn't just an old saying but a biological

process that consolidates and organizes important information?

MATT WILSON: These are pretty big concepts.

And they certainly are controversial.

The function of sleep, as it relates to learning and memory, that's something that, at this

point, remains speculation.

We're making a leap.

NEIL DEGRASSE TYSON: Not everybody is leaping into bed with this idea.

And researchers have a long way to go before they know what sleep is really doing for our

brains.

But if the speculation turns out to be true, then you'd have to wonder, "What is our 24/7

culture doing to our ability to think straight?"

MATTHEW WALKER: Sleep is not just something that we can choose to sort of dabble in every

now and again.

It's not a luxury; it's a biological necessity.

MATT WILSON: My sense is that disruption of sleep is much deeper than simply, you know,

robbing us of rest.

My guess would be that we lose the opportunity to gain understanding, a deep understanding

of our past experience, that what we sacrifice, in a sense, is wisdom.