what i'd like to do today is talkabout one of my favorite subjects, and that is the neuroscience of sleep. now, there is a sound -- (alarm clock) ah, it worked!
sex education un, a sound that is desperatelyfamiliar to most of us, and of course it's the soundof the alarm clock. and what that truly ghastly,awful sound does is stop the single most importantbehavioral experience
that we have, and that's sleep. if you're an average sort of person, 36 percent of your lifewill be spent asleep, which means that if you live to 90, then 32 years will havebeen spent entirely asleep. now what that 32 years is telling usis 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 todayis change your views, change your ideasand your thoughts about sleep. and the journeythat 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. (laughter) from the same time: "sleep is the golden chainthat 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 timeand a heritage from our cave days." bang! and if we also jump into the 1980s,some of you may remember that margaret thatcherwas reported to have said, "sleep is for wimps." and of course the infamous --what was his name? -- the infamous gordon gekkofrom "wall street" said, "money never sleeps."
what do we do in the 20thcentury about sleep? well, of course, we usethomas 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 perhapsmany of us think of sleep as an illness that needssome sort of a cure.
and our ignorance about sleepis really quite profound. why is it? why do we abandonsleep in our thoughts? well, it's because you don't do anythingmuch 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 incrediblyimportant part of our biology, and neuroscientistsare 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 whatit was or indeed, how to use it, so -- so i borrowed it.
i don't think they noticed. ok. the point i'm trying to makeis that when you're asleep, this thing doesn't shut down. in fact, some areas of the brainare actually more active during the sleep statethan during the wake state. the other thing that's reallyimportant about sleep is that it doesn't arise from a singlestructure within the brain, but is to some extent a network property. if we flip the brain on its back --
i love this little bitof spinal cord here -- this bit here is the hypothalamus, and right under there is a whole raftof interesting structures, not least the biological clock. the biological clock tells uswhen 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 areaswithin the hypothalamus, the lateral hypothalamus,the ventrolateral preoptic nuclei.
all of those combine, and they send projectionsdown 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 uswith our consciousness. so sleep arises from a whole raft of different interactionswithin the brain, and essentially,sleep is turned on and off
as a result of a rangeof interactions in here. ok. 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 explainedis what sleep is about. so why do we sleep? and it won't surpriseany of you that, of course, as scientists, we don't have a consensus. there are dozens of different ideasabout 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 stuffwe'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 shownis that within the brain, a whole raft of genes have been shownto be turned on only during sleep, and those genes are associatedwith restoration and metabolic pathways. so there's good evidencefor 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 individualwho has slept at night,
or stayed awakeand hasn't moved very much, the energy saving of sleepingis about 110 calories a night. now, that's the equivalentof a hot dog bun. now, i would say that a hot dog bun is kind of a meager return for such a complicatedand demanding behavior as sleep. so i'm less convincedby the energy conservation idea. but the third idea i'm quite attracted to, which is brain processingand 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 consolidationis also very important. however, it's not justthe laying down of memory and recalling it. what's turned out to be really exciting is that our ability to come upwith novel solutions to complex problems
is hugely enhanced by a night of sleep. in fact, it's been estimatedto give us a threefold advantage. sleeping at night enhances our creativity. and what seems to be going onis that, in the brain, those neural connectionsthat are important, those synaptic connectionsthat are important, are linked and strengthened, while those that are less importanttend to fade away and be less important. ok.
so we've had three explanationsfor why we might sleep, and i think the important thing to realizeis that the details will vary, and it's probable we sleepfor multiple different reasons. but sleep is not an indulgence. it's not some sort of thing that we cantake on board rather casually. i think that sleep was oncelikened to an upgrade from economy to business class,you know, the equivalent of. it's not even an upgradefrom economy to first class. the critical thing to realize is thatif you don't sleep,
you don't fly. essentially, you never get there. and what's extraordinaryabout much of our society these days is that we are desperately sleep-deprived. so let's now look at sleep deprivation. huge sectors of societyare sleep-deprived, and let's look at our sleep-o-meter. so in the 1950s, good datasuggests that most of us were getting around eight hoursof sleep a night.
nowadays, we sleep one and a halfto two hours less every night, so we're in the six-and-a-half-hoursevery-night league. for teenagers, it's worse, much worse. they need nine hoursfor 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 sectorsof society -- the aged; if you are aged, then your abilityto 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 percentof the working population, and the body clock does not shiftto the demands of working at night. it's locked onto the samelight-dark cycle as the rest of us. so when the poor oldshift 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 sleepthat 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 millionsof people suffer from jet lag. so who here has jet lag? well, my goodness gracious. well, thank you very muchindeed for not falling asleep, because that's what your brain is craving. one of the things that the brain doesis indulge in micro-sleeps, this involuntary falling asleep,
and you have essentiallyno control over it. now, micro-sleeps can be sortof somewhat embarrassing, but they can also be deadly. it's been estimatedthat 31 percent of drivers will fall asleep at the wheelat least once in their life, and in the us, the statisticsare pretty good: 100,000 accidents on the freewayhave 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 tragicaccidents at chernobyl and indeed the space shuttle challenger, which was so tragically lost. and in the investigationsthat followed those disasters, poor judgment as a resultof extended shift work and loss of vigilance and tiredness was attributed to a big chunkof those disasters. 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. if you are a tired brain, the brain is craving things to wake it up. so drugs, stimulants. caffeine representsthe stimulant of choice across much of the western world.
much of the day is fueled by caffeine, and if you're a really naughtytired brain, nicotine. of course, you're fueling the waking statewith these stimulants, and then, of course, it getsto 11 o'clock at night, and the brain says to itself, "actually, i needto be asleep fairly shortly. what do we do about thatwhen i'm feeling completely wired?" well, of course,you then resort to alcohol. now alcohol, short-term,you know, once or twice,
to use to mildly sedate you,can be very useful. it can actually ease the sleep transition. but what you must be so aware ofis that alcohol doesn't provide sleep. a biological mimic for sleep, it sedates you. so it actually harmssome of the neural processing that's going on during memoryconsolidation and memory recall. so it's a short-term acute measure, but for goodness sake,
don't become addicted to alcohol as a way of getting to sleep every night. another connectionbetween loss of sleep is weight gain. if you sleep aroundabout five hours or less every night, then you have a 50 percentlikelihood of being obese. what's the connection here? well, sleep loss seems to give riseto the release of the hormone ghrelin, the hunger hormone. ghrelin is released.
it gets to the brain. the brain says, "i need carbohydrates," and what it does is seek out carbohydratesand particularly sugars. so there's a link between tiredness and the metabolic predispositionfor weight gain: stress. tired people are massively stressed. and one of the things of stress,of course, is loss of memory, which is what i sort of just thenhad a little lapse of. but stress is so much more.
so, if you're acutely stressed,not a great problem, but it's sustained stress associatedwith sleep loss that's the problem. sustained stress leadsto suppressed immunity. and so, tired people tend to havehigher rates of overall infection, and there's some very good studies showing that shift workers, for example,have higher rates of cancer. increased levels of stressthrow glucose into the circulation. glucose becomes a dominant partof the vasculature and essentially you becomeglucose intolerant.
therefore, diabetes 2. stress increases cardiovascular diseaseas a result of raising blood pressure. so there's a whole raft of thingsassociated with sleep loss that are more than justa mildly impaired brain, which is where i think most people thinkthat sleep loss resides. so at this point in the talk,this is a nice time to think, "well, do you think on the wholei'm getting enough sleep?" so a quick show of hands. who feels that they're gettingenough sleep here?
oh. well, that's pretty impressive. good. we'll talk more about that later,about what are your tips. so most of us, of course,ask the question, "how do i know whetheri'm getting enough sleep?" well, it's not rocket science. if you need an alarm clock to getyou out of bed in the morning, if you are taking a long time to get up, if you need lots of stimulants, if you're grumpy, if you're irritable,
if you're told by your work colleaguesthat you're looking tired and irritable, chances are you are sleep-deprived. listen to them. listen to yourself. what do you do? well -- and this is slightly offensive -- sleep for dummies. make your bedroom a haven for sleep. the first critical thing is make itas dark as you possibly can, and also make it slightly cool.
very important. actually, reduce your amountof light exposure at least half an hourbefore you go to bed. light increases levels of alertnessand will delay sleep. what's the last thing that most of usdo before we go to bed? we stand in a massively lit bathroom, looking into the mirrorcleaning our teeth. it's the worst thing we can possibly dobefore we go to sleep. turn off those mobile phones.turn off those computers.
turn off all of those thingsthat are also going to excite the brain. try not to drink caffeinetoo late in the day, ideally not after lunch. now, we've set about reducing lightexposure before you go to bed, but light exposure in the morning is very good at setting the biologicalclock to the light-dark cycle. so seek out morning light. basically, listen to yourself. wind down.
do those sorts of things that you know are going to ease you off into the honey-heavy dew of slumber. that's some facts. what about some myths? teenagers are lazy. no. poor things. they have a biological predispositionto go to bed late and get up late, so give them a break. we need eight hours of sleep a night.
that's an average. some people need more.some people need less. and what you need to dois listen to your body. do you need that much or do you need more? simple as that. old people need less sleep. not true. the sleep demands of the ageddo not go down. essentially, sleep fragmentsand becomes less robust,
but sleep requirements do not go down. and the fourth mythis early to bed, early to rise makes a man healthy, wealthy and wise. well, that's wrongat so many different levels. there is no evidence that getting up earlyand going to bed early gives you more wealth at all. there's no differencein socioeconomic status. in my experience, the only difference between morningpeople and evening people
is that those people that get upin the morning early are just horribly smug. (applause) so for the last few minutes, what i want to do is change gears and talk about some really new,breaking areas of neuroscience, which is the associationbetween mental health, mental illness and sleep disruption. we've known for 130 yearsthat in severe mental illness,
there is always, always sleep disruption, but it's been largely ignored. in the 1970s, when people startedto think about this again, they said, "yes, well, of course you havesleep disruption in schizophrenia, because they're on antipsychotics. it's the antipsychotics causingthe sleep problems," ignoring the fact thatfor a hundred years previously, sleep disruption had been reportedbefore antipsychotics. so what's going on?
several groups are studying conditions like depression,schizophrenia and bipolar and what's going onin terms of sleep disruption. we have a big study which we publishedlast year on schizophrenia, and the data were quite extraordinary. in those individuals with schizophrenia, much of the time, they were awakeduring the night phase and then they were asleep during the day. other groups showed no 24-hourpatterns whatsoever --
their sleep was absolutely smashed. and some had no ability to regulatetheir sleep by the light-dark cycle. they were getting up later and laterand later and later each night. it was smashed. and the really exciting news is that mental illness and sleepare not simply associated, but they are physically linkedwithin the brain. the neural networks that predisposeyou to normal sleep, give you normal sleep,
and those that give you normalmental health, are overlapping. and what's the evidence for that? well, genes that have been shown to be very importantin the generation of normal sleep, when mutated, when changed, also predispose individualsto mental health problems. and last year, we published a study which showed that a genethat's been linked to schizophrenia, when mutated, also smashes the sleep.
so we have evidenceof a genuine mechanistic overlap between these two important systems. other work flowed from these studies. the first was that sleep disruption actually precedes certain typesof mental illness, and we've shown thatin those young individuals who are at high riskof developing bipolar disorder, they already have a sleep abnormality prior to any clinicaldiagnosis of bipolar.
the other bit of datawas that sleep disruption may actually exacerbate, make worse,the mental illness state. my colleague dan freemanhas used a range of agents which have stabilized sleepand reduced levels of paranoia in those individuals by 50 percent. so what have we got? we've got, in these connections,some really exciting things. in terms of the neuroscience, by understanding these two systems,
we're really beginning to understandhow both sleep and mental illness are generated and regulatedwithin the brain. the second areais that if we can use sleep and sleep disruptionas an early warning signal, then we have the chance of going in. if we know these individualsare vulnerable, early intervention then becomes possible. and the third, which i thinkis the most exciting, is that we can thinkof the sleep centers within the brain
as a new therapeutic target. stabilize sleep in those individualswho are vulnerable, we can certainly make them healthier, but also alleviate some of the appallingsymptoms of mental illness. so let me just finish. what i started by saying is:take sleep seriously. our attitudes toward sleepare so very different from a pre-industrial age, when we were almost wrapped in a duvet.
we used to understand intuitivelythe importance of sleep. and this isn't some sortof crystal-waving nonsense. this is a pragmatic responseto good health. if you have good sleep,it increases your concentration, attention, decision-making,creativity, social skills, health. if you get sleep, it reducesyour mood changes, your stress, your levels of anger, your impulsivity, and your tendency to drink and take drugs. and we finished by saying
that an understandingof the neuroscience of sleep is really informing the way we think about some of the causesof mental illness, and indeed is providing us new ways to treat these incrediblydebilitating conditions. jim butcher, the fantasy writer, said, "sleep is god. go worship." and i can only recommendthat you do the same. thank you for your attention.