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  • What I'd like to do today is talk about one

  • of my favorite subjects,

  • and that is the neuroscience of sleep.

  • Now, there is a sound --

  • (Alarm clock) --

  • aah, it worked --

  • a sound that is desperately, desperately familiar to most of us,

  • and of course it's the sound of the alarm clock.

  • And what that truly ghastly, awful sound does

  • is stop the single most important behavioral experience

  • that we have, and that's sleep.

  • If you're an average sort of person,

  • 36 percent of your life will be spent asleep,

  • which means that if you live to 90,

  • then 32 years will have been spent entirely asleep.

  • Now what that 32 years is telling us

  • is that sleep at some level is important.

  • And yet, for most of us, we don't give sleep a second thought.

  • We throw it away.

  • We really just don't think about sleep.

  • And so what I'd like to do today

  • is change your views,

  • change your ideas and your thoughts about sleep.

  • And the journey that I want to take you on,

  • we need to start by going back in time.

  • "Enjoy the honey-heavy dew of slumber."

  • Any ideas who said that?

  • Shakespeare's Julius Caesar.

  • Yes, let me give you a few more quotes.

  • "O sleep, O gentle sleep, nature's soft nurse,

  • how have I frighted thee?"

  • Shakespeare again, from -- I won't say it --

  • the Scottish play. [Correction: Henry IV, Part 2]

  • (Laughter)

  • From the same time:

  • "Sleep is the golden chain

  • that ties health and our bodies together."

  • Extremely prophetic, by Thomas Dekker,

  • another Elizabethan dramatist.

  • But if we jump forward 400 years,

  • the tone about sleep changes somewhat.

  • This is from Thomas Edison, from the beginning of the 20th century.

  • "Sleep is a criminal waste of time

  • and a heritage from our cave days." Bang.

  • (Laughter)

  • And if we also jump into the 1980s, some of you

  • may remember that Margaret Thatcher

  • was reported to have said, "Sleep is for wimps."

  • And of course the infamous -- what was his name? --

  • the infamous Gordon Gekko from "Wall Street" said,

  • "Money never sleeps."

  • What do we do in the 20th century about sleep?

  • Well, of course, we use Thomas Edison's light bulb

  • to invade the night, and we occupied the dark,

  • and in the process of this occupation,

  • we've treated sleep as an illness, almost.

  • We've treated it as an enemy.

  • At most now, I suppose, we tolerate the need for sleep,

  • and at worst perhaps many of us think of sleep

  • as an illness that needs some sort of a cure.

  • And our ignorance about sleep is really quite profound.

  • Why is it? Why do we abandon sleep in our thoughts?

  • Well, it's because you don't do anything much

  • while you're asleep, it seems.

  • You don't eat. You don't drink.

  • And you don't have sex.

  • Well, most of us anyway.

  • And so therefore it's --

  • Sorry. It's a complete waste of time, right? Wrong.

  • Actually, sleep is an incredibly important part of our biology,

  • and neuroscientists are beginning to explain why

  • it's so very important.

  • So let's move to the brain.

  • Now, here we have a brain.

  • This is donated by a social scientist,

  • and they said they didn't know what it was,

  • or indeed how to use it, so --

  • (Laughter)

  • Sorry.

  • So I borrowed it. I don't think they noticed. Okay.

  • (Laughter)

  • The point I'm trying to make is that when you're asleep,

  • this thing doesn't shut down.

  • In fact, some areas of the brain are actually more active

  • during the sleep state than during the wake state.

  • The other thing that's really important about sleep

  • is that it doesn't arise from a single structure within the brain,

  • but is to some extent a network property,

  • and if we flip the brain on its back --

  • I love this little bit of spinal cord here --

  • this bit here is the hypothalamus,

  • and right under there is a whole raft of interesting structures,

  • not least the biological clock.

  • The biological clock tells us when it's good to be up,

  • when it's good to be asleep,

  • and what that structure does is interact

  • with a whole raft of other areas within the hypothalamus,

  • the lateral hypothalamus, the ventrolateral preoptic nuclei.

  • All of those combine, and they send projections

  • down to the brain stem here.

  • The brain stem then projects forward

  • and bathes the cortex, this wonderfully wrinkly bit over here,

  • with neurotransmitters that keep us awake

  • and essentially provide us with our consciousness.

  • So sleep arises from a whole raft

  • of different interactions within the brain,

  • and essentially, sleep is turned on and off

  • as a result of a range of interactions in here.

  • Okay. So where have we got to?

  • We've said that sleep is complicated

  • and it takes 32 years of our life.

  • But what I haven't explained is what sleep is about.

  • So why do we sleep?

  • And it won't surprise any of you that, of course,

  • the scientists, we don't have a consensus.

  • There are dozens of different ideas about why we sleep,

  • and I'm going to outline three of those.

  • The first is sort of the restoration idea,

  • and it's somewhat intuitive.

  • Essentially, all the stuff we've burned up during the day,

  • we restore, we replace, we rebuild during the night.

  • And indeed, as an explanation,

  • it goes back to Aristotle,

  • so that's, what, 2,300 years ago.

  • It's gone in and out of fashion.

  • It's fashionable at the moment because what's been shown

  • is that within the brain, a whole raft of genes

  • have been shown to be turned on only during sleep,

  • and those genes are associated with restoration

  • and metabolic pathways.

  • So there's good evidence for the whole restoration hypothesis.

  • What about energy conservation?

  • Again, perhaps intuitive.

  • You essentially sleep to save calories.

  • Now, when you do the sums, though,

  • it doesn't really pan out.

  • If you compare an individual who has

  • slept at night, or stayed awake and hasn't moved very much,

  • the energy saving of sleeping is about 110 calories a night.

  • Now, that's the equivalent of a hot dog bun.

  • Now, I would say that a hot dog bun

  • is kind of a meager return for such a complicated

  • and demanding behavior as sleep.

  • So I'm less convinced by the energy conservation idea.

  • But the third idea I'm quite attracted to,

  • which is brain processing and memory consolidation.

  • What we know is that, if after you've tried to learn a task,

  • and you sleep-deprive individuals,

  • the ability to learn that task is smashed.

  • It's really hugely attenuated.

  • So sleep and memory consolidation is also very important.

  • However, it's not just the laying down of memory

  • and recalling it.

  • What's turned out to be really exciting

  • is that our ability to come up with novel solutions

  • to complex problems is hugely enhanced by a night of sleep.

  • In fact, it's been estimated to give us a threefold advantage.

  • Sleeping at night enhances our creativity.

  • And what seems to be going on is that, in the brain,

  • those neural connections that are important,

  • those synaptic connections that are important,

  • are linked and strengthened,

  • while those that are less important

  • tend to fade away and be less important.

  • Okay. So we've had three explanations for why we might sleep,

  • and I think the important thing to realize is that

  • the details will vary, and it's probable we sleep for multiple different reasons.

  • But sleep is not an indulgence.

  • It's not some sort of thing that we can take on board rather casually.

  • I think that sleep was once likened to an upgrade

  • from economy to business class, you know, the equiavlent of.

  • It's not even an upgrade from economy to first class.

  • The critical thing to realize is that

  • if you don't sleep, you don't fly.

  • Essentially, you never get there,

  • and what's extraordinary about much of our society these days

  • is that we are desperately sleep-deprived.

  • So let's now look at sleep deprivation.

  • Huge sectors of society are sleep-deprived,

  • and let's look at our sleep-o-meter.

  • So in the 1950s, good data suggests that most of us

  • were getting around about eight hours of sleep a night.

  • Nowadays, we sleep one and a half to two hours less every night,

  • so we're in the six-and-a-half-hours-every-night league.

  • For teenagers, it's worse, much worse.

  • They need nine hours for full brain performance,

  • and many of them, on a school night,

  • are only getting five hours of sleep.

  • It's simply not enough.

  • If we think about other sectors of society, the aged,

  • if you are aged, then your ability to sleep in a single block

  • is somewhat disrupted, and many sleep, again,

  • less than five hours a night.

  • Shift work. Shift work is extraordinary,

  • perhaps 20 percent of the working population,

  • and the body clock does not shift to the demands

  • of working at night.

  • It's locked onto the same light-dark cycle as the rest of us.

  • So when the poor old shift worker is going home

  • to try and sleep during the day, desperately tired,

  • the body clock is saying, "Wake up. This is the time to be awake."

  • So the quality of sleep that you get as a night shift worker

  • is usually very poor, again in that sort of five-hour region.

  • And then, of course, tens of millions of people

  • suffer from jet lag.

  • So who here has jet lag?

  • Well, my goodness gracious.

  • Well, thank you very much indeed for not falling asleep,

  • because that's what your brain is craving.

  • One of the things that the brain does

  • is indulge in micro-sleeps,

  • this involuntary falling asleep,

  • and you have essentially no control over it.

  • Now, micro-sleeps can be sort of somewhat embarrassing,

  • but they can also be deadly.

  • It's been estimated that 31 percent of drivers

  • will fall asleep at the wheel at least once in their life,

  • and in the U.S., the statistics are pretty good:

  • 100,000 accidents on the freeway

  • have been associated with tiredness,

  • loss of vigilance, and falling asleep.

  • A hundred thousand a year. It's extraordinary.

  • At another level of terror,

  • we dip into the tragic accidents at Chernobyl

  • and indeed the space shuttle Challenger,

  • which was so tragically lost.

  • And in the investigations that followed those disasters,

  • poor judgment as a result of extended shift work

  • and loss of vigilance and tiredness

  • was attributed to a big chunk of those disasters.

  • So when you're tired, and you lack sleep,

  • you have poor memory, you have poor creativity,

  • you have increased impulsiveness,

  • and you have overall poor judgment.

  • But my friends, it's so much worse than that.

  • (Laughter)

  • If you are a tired brain,

  • the brain is craving things to wake it up.

  • So drugs, stimulants. Caffeine represents

  • the stimulant of choice across much of the Western world.

  • Much of the day is fueled by caffeine,

  • and if you're a really naughty tired brain, nicotine.

  • And of course, you're fueling the waking state

  • with these stimulants,

  • and then of course it gets to 11 o'clock at night,

  • and the brain says to itself, "Ah, well actually,

  • I need to be asleep fairly shortly.

  • What do we do about that when I'm feeling completely wired?"

  • Well, of course, you then resort to alcohol.

  • Now alcohol, short-term, you know, once or