Scientist Explains Sleep in 5 Levels of Difficulty | WIRED

my name is Eric Prather and I'm a sleep scientist at UCSF I study that causes and consequences of insufficient sleep and I also carry out interventions to improve sleep among people with insomnia today I've been challenged to explain the topic of sleep at five different levels everybody knows a little bit about what is happening when they sleep but I think they'll be surprised that there's a lot of science in there Christopher hey Christopher and how old are you I'm 10 what great is that I think fifth think what is your favorite subject in science well

that's awesome because we're gonna be talking about science today cool hey you know we're gonna be talking about what sleep of the day mine too cuz I get to spend all day studying it cuz you know what sleep does for you body's like an electric car that's exactly right it kinda is like recharging your battery right and sleep is so critical for so many parts of our body in our mind right it plays a really important way that we learn and it helps us kind of recover from the day before it affects our immune system

and our metabolism all of these things that we need to kind of be healthy so today we're gonna talk about some animals and how they sleep so here's the first one what's that a giraffe have you ever seen a giraffe in person oh they're pretty cool right huh and so what's really cool about this is that giraffes need to sleep like everybody else and so the way that it does is it kind of kind of slumps over and it gets down on its legs and it kind of becomes this ball but what's crazy about the

whole thing is they only sleep for like 30 minutes a day 30 minutes because it can't waste any more time because it can't be vulnerable for any longer it can get eaten by lions and that kind of thing it is kind of evolved in a way that it can still survive and still get all the restoration it needs under such a short period of time like recharge really humans so we think it works the same way but maybe just like more efficiently and so we're still really learning about how this works sleep science itself is

kind of a new field I had to sleep over on Saturday and I didn't sleep at all and how did you feel tired really tired do you think you were a little crankier than usual yeah that's actually really interesting because what happens is humans and everything needs to sleep eventually and so you can't stay up indefinitely right what do you think happens if you don't sleep it affects what you can do in your daily life excellent so now I want to tell you about another animal and how they sleep okay so we have this one

what's that a hippo hippopotamus they have a different challenge they sleep underwater right right so how do they do it in the in the area that they live they need to stay cool right and so they spent a lot of time in the water and so then as a consequence they need to sleep in the water but how do they do it so it's really fascinating what they do is while they're sleeping they actually float back up to the surface and breathe without waking up they're able to go about their whole sleep cycles but still

able to breathe because their body has adapted in a way that they can still get the oxygen that they need it's it's it's a really amazing thing what do you think that's cool would it be cool to have that power oh yeah so now I want to talk about our last animal and I think this one is probably the most amazing of all okay so what's this oh I don't think a dolphin yes so dolphins kind of like hippos have to sleep in the water okay but because they're mammals right they need to breathe dolphins

breathe air they have to go up to the surface and breathe right and for an animal like that it can get eaten it needs to figure out a way that it can sleep but also still survive right you know what how dolphins sleep one half of their brain at a time so half of their brain goes to sleep and the other half stays awake so that they can continue to breathe and swim and they do it in this for hours at a time so like their right part of their brain sleeps they're able to go

up to the surface and breathe then the left part of their brain sleeps for four hours and it goes back and forth back and forth so that they can kind of maintain alertness still breathe and survive is that amazing or what that's cool so what'd you learn today I learn how other animals sleep what is important about sleeping sleep rests your body and you have to rest your body in order to do your daily things in life hey I'm Eric I'm doing nice teacher and how old are you doing I'm 16 years old okay where

do you go to school MacLaren's high school in Oakland California excellent and what's your favorite subject ap chemistry that's a serious scientist and good news we're talking about science today yeah in fact we're talking about sleep and sleep science do you sleep I do I try you try but we all gotta try you've probably heard about sleep as this kind of you know it's a biological process that happens in your brain it's really important to your body but it's it's a lot more complex than that sleep is made up of different parts and you know

when you think about sleep what do you think about resting relaxing really shutting down your brain taking some time off and a busy schedule and you know a work day but being off is just not being off there's lots of things that are happening we're gonna kind of talk about those different pieces of sleep okay so our sleep is is made up of different types okay the first one is called non rapid eye movement sleep or non REM okay or n REM and then the other one which is you know might not be a surprise

it's called REM rapid eye movement sleep and those are the the two main types of sleep that happen the way that we measure that as a sleep scientist is we actually will bring people into the lab or they can do this at home where we put electrodes on their scalp while they're sleeping and then allows us to measure the brain activity that's going on during the night okay are you like able to tell how much sleep someone's getting or what their sleep schedule is by REM when we measure all of that we're able to see

you know how much time someone's asleep and how many how many times they wake up and stuff during the night you know we're also really interested in kind of the amount of non REM sleep that someone gets and the amount of REM sleep that someone gets because each part of those types of sleep do different things for the body and so it's important to get both of those and so within non REM sleep there are three stages ranging from n1 to n2 to end so not particularly clever in our naming but that's how we know

what stages they are and what they do is as it moves from lightest to deepest sleep okay and so an n1 it's more kind of light wakefulness sleep kind of kind of in and out of sleeping then you go into n2 which is where we spend 45 to 55 percent of our sleep and it's it's more this kind of light sleep but then we get into kind of the the really restorative sleep and that's n3 and in n3 when we look at someone's eg wave we see these big slow waves and it's called slow wave

sleep and so we spend about you know 20% of our sleep and in slow wave sleep though it can vary on a day to day ok when do you think you experience the most of Rama well I've heard that you don't really go in till I could deeper sleep so I'm guessing like in 3 or any of the ends that are really if you are on technology right before you go to sleep and also if you like if there's so much light or if you are listening to music while you're asleep or anything like that

like you're not experienced with deep sleep right you know some of that is is totally accurate that like you know when you your brains more engaged by being on your phone or you know doing things that you really enjoy or things that stress you out or any of those types of things it's harder to get to sleep and to kind of fall into that deeper levels of sleep most of the REM sleep this dreaming sleep happens in the second half of the night okay so we wake up a lot during the night and we just

don't remember it and then you'll go back down into deep sleep and then you know up again into REM and you know and the kind of these these cycles right do you ever take naps I do okay how long that how long are the naps that you take anywhere between 1 to 6 hours 1 to 6 hours yes that's a long nap ok usually we want to keep naps like like 20 or 30 minutes when people drop into deep sleep and then they're walkin up out of a nap most people report that they feel way

worse than they did before they took the nap and that's because you've been in deep sleep and it's this term called sleep inertia so what are what are the stages of sleep so in one being like light you know sleep still a lot of brain activity going I can imagine that that happens right after you fall asleep asleep and into being light moderate activity in your brain still sleep but still kind of consciously aware and then 3 being the deepest form of sleep I want to know if you agree sleep is the coolest thing you've

ever heard of it really is right now is definitely the coolest thing I've ever heard of so tell me you know where are you in school what do you study I'm a fourth year chemistry student at USF it's a pretty science II yes pretty science II excellent because today for this level we're talking about sleep great how much sleep do you get typically during the summer like German our turnout during the school year maybe five Wow yeah so how much do you think you need I mean I've read that six is ideal for people in

my age range turns out so for people that are between the ages of 18 and 65 the agreed upon amount of sleep that people should get is between seven and nine hours and it's really at least seven hours per night to maintain optimal health as an adult so at least seven hours when we look at across all of the the data that is available on like sleep and health and sleep in psychiatric illness and those types of things the largest risk is when people get five hours or less what do you think kind of is

responsible for driving kind of how much sleep you need and things like that I mean I know sleep is kind of regulated by the thalamus and the suprachiasmatic nucleus sending signals to the pineal gland which kind of secretes melatonin which tells us like when it's time to go to sleep and right you can do part of this level I will do the other part clearly got some expertise under your belt and so that's awesome because I think that everyone should know more about sleep and so the way that we think about what drives sleep are

two kind of independent but kind of related processes and so they have kind of lame names process s and process C ok what you've kind of described is process C and that's the master clock right and it helps Rea kind of the rhythms like all of your body all your cells and all those kind of things it drives the release of melatonin from the pineal gland and melatonin comes online under darkness so when the Sun Goes Down your brain knows okay it's it's time to start getting ready for sleep and so you start releasing melatonin

which really kind of sets the table for sleeping like I'm from Hawaii so we have very long days we have early sun rises late Sun sets does that signify like less sleep because we have a shorter amount of time for militant ends to be released yeah no that's a really great question and the same thing is true you know in places where the Sun never goes down during the summer and when it's dark all time during the winter it turns out that light isn't the only thing that kind of gates your circadian rhythm but I

think the thing that's really important is again there are two processes but the other one is the s process and that one's just kind of a really important driver of sleep and its formal name we call it like the homeostatic sleep drive kind of the longer you're awake the sleepier you get you stay up you get sleepy time goes by you get sleepy air time goes by you get sleep here but it's actually kind of a really fundamental principle for how sleep is regulated and it's really kind of a kin to like a balloon okay

so you know you wake up in the morning and your balloon is flat like you kind of like drained out all the sleepiness but then as you kind of go throughout the day it kind of fills up right so you can use your energy it gets filled up and it gets filled up more like as you get towards nighttime right and then when it's at like this optimal amount is when you kind of like go to sleep again this is really what underlies kind of wide napping can also be bad for you so napkins aren't

inherently bad but if you know you actually let out some of this air during the day it's gonna take longer for the balloon to get bigger right and where you feel sleepy right okay what did you learn about sleep today I learned about the two processes process and process see I learned about their circadian rhythm and how it doesn't only rely on like melatonin but it also relies on your eating and like a whole bunch of other factors that kind of affect your circadian rhythm hi I'm Eric maze thank you for joining us what do

you do or yet so I'm at UC Berkeley I'm a psychology student studying cognitive neuroscience and I just started my third year congratulations thank you so so a lot of brain stuff a lot of brain stuff great I'm biased because I study one of the others of critical parts of the brain the cerebellum so that's good because that's that's why you're here and so we're talking about sleep today and really about kind of what is the brain machinery through which we go from kind of consciousness to unconsciousness and that transition great okay the best way

to think about this transition is really called up it's a flip-flop switch okay and so this term comes from engineering and the idea is that in sleep you basically have kind of this all-or-nothing kind of experience you know certainly people kind of drift off to sleep but then also in your unconscious right so it seems like it's this flip-flop between kind of the arousal system and then the sleep promoting system and it's it's certainly regulated and well and we'll get a little bit into that but there's certainly kind of made up of two reciprocally inhibitory

processes okay so we have the ascending reticular activating system it originates in the brainstem and there's a dorsal and ventral arm to this and so the the dorsal arm has neurons cholinergic neurons that go up to the thalamus and then it you know projections into the forebrain and then there's the the ventral arm and this is comprised of a whole bunch of different types of neurons that are all monomineralic so there's kind of dopaminergic neurons that come from the periaqueductal gray serotonergic ones from the dorsal raphe nuclei histamine nergic neurons that come from the tuber

mammillary nucleus of the hypothalamus and then nor adrenergic neurons from the locus realice and so all of those are kind of working in tandem to kind of drive wake within the brain and you know so if we just think about kind of drugs that are available for inducing wakefulness we can you know it's certainly kind of the dopaminergic ones kind of jump out right so we have kind of in feta means that certainly kind of dry those signaling and then modafinil which is a wake promoting drug for people that have kind of excessive daytime sleepiness

that it maintains alertness throughout the day in terms of the dopamine is you know if you're taking amphetamines that's usually to promote as you said wakefulness but does that actually improve the quality of your sleep how reliable are those kinds of interventions the role that they play with respect to the sleep/wake system is really kind of amping up the weak system right and so certainly that has like downstream consequences for the sleep system because now the flip-flops which is kind of pushed you know in a much stronger direction and we have to kind of rely

on what regulates sleep to kind of get it pushed back to sleep and do we know much about why or which like which stages are the sleep Skycycle are affected you know if you take amphetamines as a sign when you go to sleep you're not able to transition through each of the different sleep periods or no I think that's what's clear in some ways you know getting back to this idea of this wake sleep system you know we have this sleep system that is kind of the counterpoint to to this wake arousal system and so

that the primary nucleus region is the ventral lateral preoptic nucleus they also called VLP oh and that has particular neuron outputs that release GABA and Gamelin which work in an inhibitory way on kind of the the weight promoting ones and so it's this kind of delicate balance of these two systems that are ongoing and your cognitive neuroscience training right it sounds like it's you know pretty specific and focus in a particular part of the brain the cerebellum and I one thing that I'm kind of interested in it's a you bring a participant into the study

have you ensured that they got a good night's sleep have you asked them about that in most studies probably it is advised for eight participants before they come in to get a good night's sleep so those would be recommendations that you would lay out you know in communication with the participant before they come in you know what we do in our studies is we actually track people for say a week and they have to kind of get in within this range of amount of sleep and then it has to be both amount of sleep and

then how kind of stable it is that variability can really impact it and certainly might have an packed on the machinery that's happening in the brain often think that people many people think that they can get by and very little sleep or less than average meant of sleep but from what I know from the research you know if you actually test those people on different batteries of cognitive tasks you'll often find that they their performance is is slightly worse than maybe they had anticipated yeah so what what did you learn about sleep today I guess

I learned that it's a system that is you know very heavily regulated and influenced by you know some of these older more conserved subcortical systems in the brain and that there's as you called it like a flip flop flop function between wakefulness and and sleep that's regulated by these specific like dopaminergic neurons energy like neurotransmitters that manifest in different sub critical parts of the brain so now we have sleep on your brain that was they all I wanted to hear good to see you again you a yes really glad that you could join us so

we've been talking about sleep today at various levels of complexity but now with you I really want to talk about kind of what do we know about sleep and the aging brain can you tell me a lot about some of the work that you've been doing in that area so I'm a pathologist so we do a lot of work on the epidemiology of sleep and development of neurodegenerative diseases including both Alzheimer's and Parkinson's disease so a dmpd we make me work on population studies we work on thousands and even millions of population and we use

statistical modeling to find out the association between different sleep disturbances and also genetics related to sleep disturbances and linked that to their risk of developing AD and Pt so how strong is the link our study has found really strong associations looking at these populations for example with sleep apnea we've done one meta-analysis and it showed that those with sleep apnea they have us ratio of one point two six which means that those have sleep apnea they have 26% elevated risk of developing Alzheimer's compared to those without sleep apnea well it's essentially cuz I so so

I also saw that there was a recent meta-analysis around sleep disturbances and dementia risk and in that study they looked at about 250,000 people in this meta-analysis and they followed them for around 10 years you know when they pulled all the samples together and they found there was a 1.2 fold risk increased risk for developing all cause dementia and so it sounds like both sleep apnea and then maybe sleep disturbances more generally are associated with increased risk for dementia when I think about that I think about how sleepily lives in the brain these nerds jenner

disease live in the brain and so what do we know about the causality of this could it be that individuals who have early onset of say Alzheimer's have then kind of poor sleep as a consequence of that yeah so I think what's really fascinating is all these bi-directional relationship that's being identified in animal studies especially sharing their sleep changes actually occur very early on in the disease process so it could be a proto normal stage of Parkinson's and also in transgenic mouse model of AD they are already showing a lot of circadian abnormalities in this

mouse so within dementia risk in particular Alzheimer's for instance there are kind of two clear features that seem to be part of the pathology right so there's kind of beta amyloid which accumulates in the brain and there's kind of these tangles this tau off at these right and so it sounds like you know sleep seems to be related to the tau off at these what about kind of beta amyloid yes in the transgenic mouse models of AD including those expressing human mutant amyloid precursor protein AP P tau of both so that's kind of showing the

sleep changes in those of these pathologies okay so there is this bi-directional piece but I think you know perhaps the most exciting thing that happened in this sleep field at least in my view has been understanding the role of sleep and it's clearance of beta amyloid brain this idea that sleep is like the dishwasher of the brain it seems like that you know a bat beta accumulates as we kind of use energy and you know it's it's kind of you know it's a waste product and the idea that if you don't clear it out then

it's going to build up and accumulate so the thing I'm most excited about sleep research is I think first of all this complexity of the daytime nighttime sleep what sleep is really doing to our body and to our brain and then is really from the epidemiologic or public health perspective how we can best use sleep as a tool for the detection and Prevention of neuro degeneration in the long-term I'm excited about the kind of the future of sleep medicine I think there are incredible innovations that are happening in the basic sciences kind of really starting

to understand what are the clear biological processes that underlie some of these things as they relate to disease risk and what is the true function of sleep kind of the why we sleep phenomenon right so this was certainly a challenge today everyone knew a little bit about sleep and I think that's great because sleep is incredibly important but there was also a lot of misinformation around kind of how sleep works and people doing sleep behaviors that may not be the most adaptive for them we're still uncovering new things every day about how sleep works but

despite that all of us know that sleep is fundamental to our health and so I'm excited for sleep to kind of raise its profile among other health behaviors and get the investment and care that it needs [Music]