Welcome back for our third session today titled Sleep A Tool for Maximizing health and Performance and its enhancement with slow oscillatory transcranial Direct Current electrical Simulation presented by Doctor Sarah E Alger and Doctor John David Hughes . Junior . Doctor Sarah E Alger is a Sleep research scientist and Chief of Scientific Planning in the Behavioral Biology Branch at the Walter Reed Army Institute of Research in Silver Spring , Maryland . Doctor John David Hughes junior is a research , a senior research neurologist at the Center for Military Psychiatry and Neuroscience at the Walter Reed Army Institute of Research in Silver Spring , Maryland . Please welcome Doctor Alger and Doctor Hughes to their presentation and presenters . I encourage you if you're able and willing to turn on your video cameras while you do your presentation over to you . Good morning . This is uh Doctor Sarah Alder . Let me just get a confirmation from someone that you guys can actually hear me . We can hear you . Yes . OK . Perfect . My , my microphone , my microphone was being a little delayed there . So I kept turning it on and off . But um it is such a pleasure to be here and I really thank you for letting Doctor Hughes and I speak today about one of our favorite topics which is sleep . Um So just to go through the disclosures first , um myself and Dr Hughes have no uh relevant financial or non-financial relationships to disclose uh related to the content of this activity . Um The views expressed in this presentation are those of ourselves and do not necessarily reflect the official policy or position of the dod or the US government . Um This continuing education activity is managed and accredited by the Defense Health Agency J seven Continuing Education Program office , DH AJ seven CPO ce pe O and all accrediting organizations do not support or endorse any product or service mentioned in this activity . And the DH AJ seven ce po staff as well as activity planners and reviewers have no relevant financial or non-financial interest to disclose and commercial support was not received for this activity . Uh Next slide , please . And this is our own disclaimer basically saying that whatever Doctor Hughes and I talk about today are our own opinions and assertions and don't necessarily reflect that of the dod or the army . Next slide , please . So we do have a few learning objectives today . Uh The first is to uh by the end of this talk , be able to identify the functions of the brain and the body that are impacted by sleep loss . Then to also describe strategies to manage fatigue when sufficient sleep is not possible to be able to analyze the physiological basis of the accumulation of homeostatic sleep drive during sustained wakefulness . Also to summarize the physiology of electroencephalogram or eeg sleep , slow waves and their role in sleeps resto restorative function . As well as to explain how slow oscillatory transcranial direct current stimulation can enhance the restorative properties of sleep . Next slide , please . So , uh I believe we have some poll questions that are gonna be included in here and these are the instructions . So , oh , let's see the , the poll instructions here . Uh , and this is the first poll question , what percentage of soldiers regularly obtain a sufficient amount of sleep during their duty week ? Getting the answers coming in here . So I think the overwhelming response here is only about 25% of soldiers regularly obtain a sufficient amount of sleep during the duty week . Um , and you know , by a lot of data that has come in that is , that is the correct answer there . Um , it is , it is quite low and it , it's what I want to talk about today because there are a lot of consequences in that and moving on to the next . Ok , we also have another questions . So for an for adults , uh , what is the recommended number of hours for daily sleep duration ? Yeah , I think everybody has heard that the recommendation is eight hours . So the , the overwhelming response here is , is eight hours and that , and that would be the correct answer . So we'll go through that and uh and look at exactly what that looks like uh in terms of the recommendations . Ok , great . So I want to start off our talk here . Um , essentially talking about why sleep matters the science of sleep . And uh what happens when you are getting the sufficient sleep that you need ? And what , what are the consequences when you aren't getting the sufficient sleep that you need ? Um Then I want to touch on some low level fatigue management strategies as well as tips for good sleep hygiene . Then I'm going to hand it over to my colleague , Doctor John Hughes , who will go into the physiology of sleep and how to use uh transcranial electrical stimulation and how that can help to modulate brain physiology , to improve performance and health . So to begin , I wanted to look at some of the stats from the 2021 health of the force data . Uh the report that came out , um there was actually a more recent one that came out but it uh happened within the last week or two . So I didn't get it onto the slides here , but we'll talk about the 2021 and health of the force because it says it's very interesting and it's enlightening about how poorly our soldiers are sleeping . So what we see in this figure on the left is that during the work or duty weeks , a little over one third of soldiers about 38% reported obtaining seven or more hours of sleep . Now , I know , uh , we could see in other data from our own group at rare that maybe even only 25% are , are getting the sufficient amount of sleep that they need . So that means that an overwhelming majority of soldiers are chronically sleep restricted , meaning they're getting less than the recommended seven hours of sleep per night . Um And this is in part because of unavoidable circumstances , is like having to do 24 hour duty , um which also creates this circadian misalignment from round the clock operations . Uh but also due to poor sleep environments and poor sleep hygiene and a lack of general understanding about what sleep does for you and what sleep does sleep loss does to you . That's what I wanna focus on today . We also see that um better sleep health is related to having healthy body compositions , positive health behaviors and greater fitness . And uh the health of the force also assessed the prevalence of sleep disorders like sleep apnea , insomnia , hypersomnia , circadian rhythm , sleep disorder and narcolepsy . And in this particular report , it found that 9% of soldiers had a sleep disorder . Um Now this 2021 data came uh primarily during the pandemic . So the numbers actually look quite , quite a bit bigger uh better than they had in previous years . And um I believe the most recent health of the force data that came out a couple of weeks ago , um , reflected that unfortunately , sleep got a little bit worse . Um , and that even , uh , more people about 14% were having , uh , sleep disorders . So , unfortunately , we're heading in the wrong direction . So we want to make sure that we're always educating about the , the value of sleep here . Next slide , please . So , how much sleep do we need ? We , we mostly set in the polls eight hours and that is the average amount of sleep that you need um on a daily basis . And this is actually a range of 7 to 9 hours uh for adults . So we like to message at the Walter Reed Army Institute of Research in our sleep research center and in our operational research team that everyone needs to be trying to get seven or more hours per night or seven plus hours per night . Um And that's every night , um or , or every 24 hours because the uh night schedule is not always the schedule that you have to follow . So everyone has their own amount of sleep that is normal and healthy for them . So some people may be long sleepers . I know for myself if I am able to sleep without having to wake up to an alarm or Children , then I , I typically am a nine hour night sleeper and other people might be on the shorter range closer to seven hours a night . But there are very few people who are truly short sleepers , meaning they get less than seven hours of sleep a night consistently and perform at their optimum . Uh And so a lot of people who are , are , um , reporting that they can get by with maybe four hours a night every night are commonly subjectively judging themselves to be feeling perfectly normal and functioning fine . But if you were to objectively test them , say , using a , uh , psychomotor vigilance test , which is a test of uh sustained attention , they will be shown to be impaired . Um There's a lot going on uh that , that impairs people's ability to perceive how impaired that they are on other tasks when they are sleep deprived . Um And you'll notice from this chart from the National Sleep Foundation that the amount of sleep that you should be obtaining daily changes with age . So we know that babies and small Children uh sleep a good portion of the day and the night , they don't often sleep when you want them to be sleeping , but they are sleeping quite a bit , but this becomes more consolidated and more refined with age . And you'll notice that the recommendation as we get into our later years remains in that 7 to 8 hour range . But because of the aging brain , the amount that you'll get will likely be less than this amount or more broken up . Uh So it's really important to develop sleep habits now that are healthy because routinely getting poor sleep may have long lasting consequences that we in the sleep research field uh are still are still trying to figure out exactly . Um All that entails next slide , please . A comparison that really resonates with people is the connection between sleep loss and intoxication . And it really helps to understand why sleep loss can result in so many more accidents and injuries . So research has shown that when you've been awake continuously for around one full day . So 22 23 24 hours a day , um you are as cognitively impaired as you would be at the legal limit of 0.08 blood alcohol concentration . So what I'm showing you here on the screen , um in the figure on the left , we are showing performance on a test of hand eye coordination and so on the figure on the left , you can see that at a blood alcohol concentration of 0.08 performance is at about 0.95 and at that very same level of performance . And the figure on the right , you will see that that's where you're you are performing at at about 23 hours of wakefulness . So really , that's not a whole lot of sleep loss in the grand scheme of things . That's about one day of sleep loss . What does this look like ? Go to the next slide , please . So if you were to compare this to a blood alcohol concentration of 0.08 having about one day of sleep loss would look like having um altered moods . So your inhibitions are becoming lowered , you're taking more risks and engaging in more dangerous behavior . You're having impairments in focusing on and visually tracking objects . So you can see if you're trying to operate a vehicle in this circumstance , it'll be harder to avoid an accident . If there is one looming , you also have impaired alertness and reaction time and executive function . So your ability to reason to judge have self control , concentrate and make decisions is going to be impaired at this level . You also have impaired memory . So both the formation and consolidation of memory . So that means the uh that taking in new information and putting into long term storage are both affected by uh sleep loss , as well as the ability to retrieve that information from your memory banks . You also have less physical control over your body . So your gestures and your speech and your vision are all going to be um off from the from normal and baseline . So keep in mind , what we're looking at is only , you know , a day's worth of sleep loss about up to 0.08 blood alcohol concentration equivalency . And if you think about when a soldier has 24 hour duty , you have to add on the time it takes to get to their duty station , the time it takes to take care of their needs after their shift and to travel back home . And this is going to add up to well over 24 hours before they can get any more sleep . So essentially toward the end of this duty period , they are performing as if they were legally intoxicated . Now , keep in mind this is only continuous wakefulness that we're talking about here . And some people may be required to occasionally keep that kind of a schedule . But many of us , most of us I would say are chronically restricting our sleep over several days . Um as is evident with that health of the force data and as is evident if you've ever , you know , gone through , say a high school or um you know , had a , a work schedule that really requires you to be on a specific schedule where you're , you're shorting yourself during the week and then trying to binge sleep on the weekend . So what could that do to you next slide , please ? But we can see from this simple cognition task that I we have plotted out here that , you know , sleep restriction is far more common , like I mentioned and the more restricted your sleep is the more impairment there is . So if you looked at the , the dashed black line up top , if you get eight hours of sleep per night , you can maintain your performance on this cognitive task across a week . But the even at , you know , six hours of sleep per night , the dashed line in yellow there you will be looking at a 10% decrement by the end of the week . And of course , this gets worse , the more you restrict your sleep . Next slide , please . So , one thing that sleep is a crucial factor in is your ability to regulate your emotions . So , in a well rested state , the prefrontal cortex , which is the area in purple there that I've circled . Um that is the area of the brain that's involved in logic and reasoning and all these executive functions . And essentially it serves to keep your emotional center of your brain , which is your Amygdala , the smaller area that's circled there , keeps the activity in that area in check . It kind of puts the brakes on the activity in that emotional region and that allows you to be able to control your emotions and to react appropriately in situations . So with sleep loss , this top down control is impaired and it results in an overactive Amygdala and this overactive Amygdala results in exaggerated emotional responses . So that increases your stress response . And it notably makes you perceive and react to the world in a more negative way . So think about how you may be feeling when you haven't had a good night's sleep , you didn't get enough sleep . Uh you may wake up grumpy a little short tempered , you're snipping at people . But you know , in the worst case scenario , you could be really irrational in your reactions and explosive in your anger . Um towards situations , it can really get out of control very quickly . And also because of that impaired prefrontal cortex , you may be willing to take more risks and participate in risky or destructive behaviors when you are sleep deprived . So , and this is partly because of that impaired judgment center , but also because of that heightened emotional center , as well as heightened activity in reward seeking areas of the brain . Next slide please . So we can see this emotion disregulation in our military populations that we conduct research with as well . So we often work with the 75th Ranger Regiment in our operational research team and they've found that leaders and soldiers with more reported sleep issues reported that they were having higher anxiety , more depressive symptoms , higher alcohol consumption , uh generalized , lower satisfaction with life as well as participating in those risky behaviors . Now , while on the topic of emotion and mood , I always want to put out there that sleep is intrinsically involved in mental health disorders . So number one , it can just be a symptom of the disorder . Number two , it can be a factor that exacerbates other symptoms of this mental health disorder or number three , there's even a growing body of evidence that shows that some sleep disruptions can be a causal factor in the development of mental health conditions such as a really strong link between insomnia and the development of depressive symptoms . So I always want to emphasize that , you know , if anyone here in the audience believes that they have a sleep disorder or a mental health condition . Please seek the right professional help to uh to , to help sort the those conditions out because it can just uh compound and , and get worse . Uh Next slide , please . Now , with regard to your health and wellness , let's take a look at how sleep loss impacts how you eat and your weight . So think about how you're eating when you're tired . So again , I was , I use myself because I'm very susceptible to this when I'm tired . I don't want to cook . Um I especially don't want to go for healthy foods . So I every now and then will reach for , you know , a prepackaged frozen meal or something that's quick in the pantry or I'll go through the drive-through and get some fast food , uh which is not a good choice . And aside from , you know , choosing these foods just because you're simply feeling tired or low energy , sleep loss may actually change how you interact and react to food . So sleep loss leads to blood sugar changes and reduces insulin sensitivity . It can lead to poorer food choices . Like I've mentioned , like craving those high carb , high starch foods , a lack of sleep will actually facilitate a dysregulation in the hormones leptin , which signals when you feel full and Grein , which signals when you are hungry . Such that when you have sleep loss , you will have higher amounts of Grein and lower amounts of leptin supporting this feeling of increased hunger when you may not actually be hungry . So you start grazing , you start snacking on things when you might not actually be needing food to sustain yourself . And those who chronically sleep less than five hours per night are at 50% higher risk for obesity than those who sleep within the recommended range . Next slide please , there are also serious health risks uh for those with chronic sleep loss including uh an increase in elevated lipids , um a greater risk of stroke , more hypertension , a very large increase in heart attack and also an increased risk of diabetes . And moreover , sleep loss can lead to an increased risk of dementia and can age your brain so that it functions several years older than you actually are . So , one of the functions of sleep is to essentially wash the brain . So what I mean by that is that during sleep , you have this increase in cerebral spinal fluid that's moving through the spaces in your brain , the interstitial spaces and those spaces actually increase while you sleep as well , allowing more fluid to , to move through them . And that functions to wash away the toxins that built up as byproducts of brain activity across the waking day . This is your glymphatic system and it's really , really important these toxins are the same as what's seen to increase in the in neurodegenerative diseases like dementia and Alzheimer's disease . So , the sleep that you are getting today may set you up for your brain health as you continue to age either for the good or for the bad . Next slide , please . And we also see that lack of sleep has been linked to impaired inflammatory function in response to illness or injury , which can lengthen the time that it takes to regain your health as well as an increased susceptibility to disease . Insufficient sleep , reduces the ability to fight infections and its certainly decreases antibody response . Excuse me , including vaccine induced antibody response is necessary for protection from disease . Now , you can imagine this is vitally important to know , particularly considering the ongoing pan pandemic and the efforts to effectively vaccinate the population . We also see that people who average less than seven hours of sleep per night are at three times more susceptible to infections . Um and those who are sleeping less than five hours of sleep per night are 4.5 times more susceptible . So even shaving an hour off your sleep really compounds the impact that it has on your ability to protect yourself from disease . Next slide , please . So what do we do about this ? Um , aside from , you know , going back in time and getting more sleep , a lot of the times we are just not able to get enough consolidated sleep and we are faced having to be fatigued throughout the day and experiencing all of these consequences that I've just talked about . So what are some basic , low level fatigue management strategies that we can employ to mitigate some of those consequences . Pardon me ? Well , one of those strategies is to take a nap to get more sleep in a different kind of way . So when you can't get enough nighttime sleep , you can intentionally what we use , uh what we call a um , pardon me , a tactical nap . Uh in order to boost alertness and to help regulate your emotions and facilitate performance and productivity . Excuse me . So what you can do is you could take a 20 minute daytime nap , which we can call a power nap . Um And immediately you're going to see decreases in your subject of sleepiness , increased alertness , increased cognitive performance and improved mood . Then you could take a nice long , luxurious nap of maybe an hour to an hour and a half if you have that ability and you're going to get into those deeper processes like facilitating memory consolidation , enhancing your creativity , reducing stress and strengthening your immune immune function . You could also take naps somewhere in the middle . So 30 to 60 minute naps . Um while we do not discourage taking naps of that length , we also recommend to use them in , in , in combination with alerting strategies . And this is because if you take a 30 to 60 minute nap , you are more likely to wake up from what we call slow wave sleep or deep sleep . And in doing so , you can feel very groggy or disoriented um and have a lot of sleep inertia , which is that feeling that you want to just go right back to sleep . So if you use an alerting strategy , like getting bright light , going outside , getting some sunshine or using caffeine immediately afterward , we actually recommend using our caffeine gum because the gum is very fast acting . And uh you get , you know about , I think it's 80% of bioavailability within five minutes of chewing it . So it can really help to pay down that sleep inertia and to uh to get uh the the most benefit out of the nap as possible next time , please . So we know that there is um lingering stigma around napping being something that lazy people do uh particularly in environments where the sleep culture is framed more like sleep is for the week or I'll sleep when I'm dead . These are common things uh that we hear and uh that's something that we're trying to change in the culture . However , I would say in the last few years since the publication of Holistic health and fitness Field manual 7-22 which we were uh primary authors on the Sleep Readiness chapter strategic or tactical Mapping has really gained traction . So there's been publications in the mainstream media as well as military coverage . And it's something that we , we are actually actively researching in our lab right now . My own study is looking at different sleep strategies using the combination of nocturnal sleep and daytime napping to see what strategy may result in the best performance on various tasks as well as um emotions . So this is one of my favorite interventions uh that is recommended because nap research is near and dear to my heart . Next slide , please . Another strategy that we recommend is to use caffeine , which I just mentioned with our caffeine gum and this is for a temporary boost of energy and performance . So , the way that caffeine works is to essentially block a Denno from binding to its receptors . So denine builds up in the brain , the longer that you are awake and when it binds to the receptors , it can cause you to feel sleepy and increase your pressure to sleep . So caffeine can temporarily block this uh this process . But if you wanna make sure that you , you , you but you always want to make sure that you're using caffeine wisely . So you actually don't need caffeine when you are well rested . So if you've had that good night's sleep , you don't need to have a cup of coffee in the morning . However , I will always say that there is something to be said for if it is something that you always do . Um There's something to be said about the continuations of habits that psychologically connect you with your awakening and feeling like you're ready for the day and , and feeling energetic . So even if you technically don't require it , you need to know yourself and know how you operate with caffeine and , and how it benefits you . But we do have some general recommendations like making sure that you stop caffeine at least six hours before you are going to try to go to bed , to make sure it leaves your system and doesn't impact your ability to fall asleep . And you could optimize your caffeine usage with certain tools . So in combination with our colleagues at BHSA , I , we've developed what we call the to be alert algorithm and it can learn how susceptible you are to sleep loss . And it can also help to optimize your caffeine usage by optimizing the timing and dosage of caffeine um to be at your best . When you tell the program , you need to be at your best . So say you have like a presentation um at 10 50 in the morning and you need to be at your best . It'll tell you how much caffeine to use and when to use it . Next slide , please . Another strategy that we can always use is getting more sleep . And so what I mean by that is sleep banking , you can use sleep as a tool to improve your performance and prepare for periods of upcoming sleep loss . So this is in preparation for . So sleep banking is a strategy that leaders and soldiers can employ in preparation . So if you know there's an upcoming mission that will require you to have continuous operations to not get sleep or to restrict your sleep . Then prior to the mission , you want to increase the amount of sleep that you're getting beyond the recommended 7 to 9 hours a night . So maybe sleeping nine or 10 hours . And we do this in some of our studies to help uh people get ready for the experimental manipulations that we're going to be doing . So , this extended or banked sleep will essentially serve to pay down your existing sleep debt . We pretty much all carry around uh some level of sleep debt that is uh keeping us from being at our optimal performance . Uh And it can also slow the rate of decline in performance and cognitive uh physical and cognitive performance during the mission and help recover function more quickly after the mission . So this is a great tool to use next slide , please . So aside from napping , caffeine and sleep banking , there's just some other low level strategies that you can use to feel more alert . So just making sure you're taking frequent breaks throughout the day , especially if you're often working at a computer like I do . So , fatigue impacts sustained attention . There's plenty of research on this . So having frequent breaks can help combat that uh cognitive fatigue that can also build up , make sure you stay well hydrated because dehydrated cells don't function as well , which means you may feel sluggish and tired , be sure you get enough exercise because exercise increases heart rate and blood flow . But also we always recommend to keep exercise light when you're really fatigued because sleep loss also very much increases your risk for musculoskeletal injuries and use light to your advantage . I already um inferred referred to this earlier , but you wanna make sure you get plenty of sunlight in the morning because light is the primary environmental synchronizer to the environmental day light and especially sunlight um increases alertness and suppresses sleepiness because it suppresses melatonin , which is a hormone that uh is released to signal when you should feel sleepy . Next slide , please . So we've developed uh what we call our habits for healthy sleep , which is our general sleep hygiene recommendations . So I'll go through some of these , we have our dos and our don't in our dos , we would say try as much as possible to keep a regular sleep schedule . So you wanna try to go to bed and wake up at the same time every day , even off duty days to keep that routine going so that your body and your brain know when to start preparing for sleep . And you always want to try to schedule enough time to get enough sleep , get your seven or more hours of sleep per night . It seems intuitive , but sometimes you forget that you have to be getting up at say six in the morning and you need to work your schedule backwards to be in bed and to be actually sleepy and ready to fall asleep by a certain time , you want to establish a routine . So to be able to , to get into that place where you can fall asleep , you wanna do activities that help your body and your brain signal that it's , it's time to start feeling sleepy . So maybe um you know , taking a bath or reading a book or whatever works to help calm the body in the brain . You also want to make sure you're , you're using your bed for sleep and not for work or entertainment . So not taking your laptop into your bed and finishing up some last minute things uh for work . Uh and uh or , or watching a movie on your phone or something like that . Uh Again , we've talked about the exercise . Uh I also want to emphasize that you need to get out of bed if you can't fall asleep to avoid connecting your bed with stress . So this is a great technique um where we talk about in a in cognitive behavioral therapy for insomnia , you wanna make sure that you're not in bed if you're not ready to sleep . So if you're tossing and turning , get out of bed , go to a different room . Um and don't return to bed until you're really feeling tired enough that you could fall asleep uh because you don't want to make those associations . So for our , don't we always recommend not to use electronic devices in bed or within an hour of bedtime . This is difficult for a lot of people to do including myself . So that means that um you don't want to have your phone in bed with you scrolling through tiktok . And this is really for two reasons that that um are the most prevalent reasons . One is because these electrons product devices emit blue light and blue light suppresses melatonin production . And this of course , will kind of push back um your , your need or desire to go to sleep . And so if you can use at the very least a blue light blocking filter , um which most devices have nowadays , just make sure yours is on so that if you are gonna have your tablet or your phone with you , um if you can kind of cut down on the impact that that blue light , blue light has , the other reason we recommend not having your devices in bed is because you can get sucked into activities that are going to unintentionally cut into the time that you should have preserved for sleep . So like getting stuck in a , at a tiktok , you know , scroll or Instagram or whatever , where you find yourself uh losing time without really intention intending to do so go to bed comfortable . So don't not too hungry or thirsty or too full . Um We already talked about the caffeine consumption with regard to alcohol . People think that um alcohol will help you fall asleep and it , it it actually does help you fall asleep , but it actually very much disrupts your healthy cycling through the different sleep stages , which Doctor Hughes will refer to um what all the different sleep stages are . Um And it also specifically cut into your ability to have healthy rapid eye movement sleep . So you'll find yourself maybe waking up really early in the morning if you've had too much alcohol , because it really disrupts that particular stage of sleep , which is very much prevalent in the later part of your , your night of sleep . With regard to napping . While I'm a , a big proponent of napping , you don't wanna have naps too late , too close to bedtime , um too long , especially if you have trouble sleeping at night . So if you have any symptoms of insomnia or other sleep disorders , you , you very much want to um you very much wanna not , not because you want to build up that sleep pressure and then finally , don't focus as much as possible on not being able to fall asleep . So that means if you have a clock in your room , turn your , turn your clock off . And so , um you're not looking at the time , especially if you know , you have to get up at a certain time . You're not uh kind of ruminating on the fact that the hours are going by and you're not able to fall asleep . All right , next slide , please . So we also want you to check your sleep slant . And so what I mean by this is that if you have the ability to improve your sleeping environment , we recommend that you do so in order to make an ideal space to get the best sleep that you can . So check your surface , your light , the air quality noise and temperature or your slant . And so some simple fixes for this would be to use darkening shades or an eye mask if your environment is too light , um try to reduce the noise by using a white noise machine or using earplugs . Um anywhere that you can have a simple solution in order to improve the environment is going to help improve your sleep quality . Um and hopefully your sleep quantity as well . Next slide please . So to end my part of the the talk today , one of my favorite quotes is from Colonel Burke , uh who said sleep is not only critical for ensuring our lethality on the battlefield , but for ensuring the safety of our crews and aircraft . And to that end , sleep is truly a weapon and I can't echo this enough in the military context . Sleep is our force multiplier . It is truly a weapon that we can all use . So I'll be happy to take questions later at the end of the session . But right now I'll transition over to my colleague , Doctor John Hughes . Doctor Hughes , can you please unmute yourself and turn on your camera ? I think I did . Can people hear me ? Yes . I can hear you . Thanks . Well , thank you very much for the introduction . Uh Doctor Alder , um what I'm gonna be talking about um in my half of this is um uh actually the neural physiological basis for sleeps restorative or recuperative function . And then I'm gonna talk about a study that we've conducted recently at the rare Sleep research center um to in attempting to enhance sleeps restorative function using a form of transcranial electrical stimulation referred to as um SOTD CS or slow oscillatory transcranial direct current stimulation . Uh Next . So we've actually known for many decades that there is a homeostatic or sustained wakefulness induced drive for sleep that accumulates over a period of sustained wakefulness . And we see that with the upward sloping uh curve during the white or waking part of the , the figure and that uh sleep drive is then gradually dissipated during a subsequent sleep period . And we see the sort of downsloping um uh curve during the shaded uh part of the figure which is sleep now mechanistically , though what we've really had very little idea about is what exactly is happening to accumulate that sleep drive over a period of sustained wakefulness . And what exactly is sleep doing to restore um the degradation of cognitive function that occurs over that sustained period of wakefulness . It's really only been within the past 10 or 20 years that we've gained any significant insight into that . Um But we're trying to leverage the insight that we've gained over that time at the Sleep Research Center to try to enhance sleep restorative function . Next . So I guess we have a full question . Now , the true false rapid eye movement rem sleep is the most recuperative stage of sleep . Ok . Well , it looks like we have some divided answers uh Here , about uh 67% say , think that's true actually , that's false . Um And non rapid eye movement sleep is really the restorative um part of sleep . I actually um rem sleep , recent evidence suggests it may be anti restorative uh but I won't get in , I I won't get into that . Um And , and , but we'll , I'll be talking in great depth about how non rem sleep uh provides restoration . OK . And next slide , OK . So , um in order to understand um sleeps are sort of function , uh we have to kind of orient you a little bit to the eeg during different uh during different um brain states . And the e the eeg um is characterized by uh prominent oscillations of electrical potential of the surface of the brain recorded on the scalp over a very broad range of frequencies of these oscillations . Um Now , the information processing and cognitive um processing during wakefulness uh requires pretty fast oscillations greater than 20 Hertz or 20 cycles per second , a very low amplitude . And we really see that um at the top of this uh figure during wakefulness quite to the contrary , uh during non rem sleep . And particularly during the most restorative , the deepest part of sleep , which is N three non rapid eye movement sleep . We see actually very high amplitude activity with extremes of positive and negative uh uh potentials on the surface of the brain really uh slow waves , uh less than two Hertz . And really the majority of them are less than one Hertz or one cycle uh per second . And this is a really a a crucial aspect of sleep . The lighter stages of non rem sleep stages , one and two have much less , much sparser slow wave activity as uh as you can see the next slide . Now , the amount of , of uh slow wave activity that we see during a fixed period of sleep in a particular individual is really directly proportional to the amount of time spent a week prior to that to that sleep period . So , in this case here , if you look at an eight hour period of sleep , this occurred after a 48 hour period of or I'm sorry , 48 40 per hour period of total sleep deprivation . As in the bottom part of the , this uh figure , you would expect to see a significantly greater amount of slow wave activity compared to um the upper part of the figure in which these eight hour sleep periods are are occurring after a normal 16 hour period uh of wakefulness . And this strong relationship between um sleep drive , you can see , the sleep drive is much higher in the , in the bottom part of the figure . Uh And uh and slow and slow wave power really suggests a potentially an important role of slow wave activity in sleeps restorative function . Next . Well , a full night of sleep uh consists of a series of sleep cycles with Alternations between non rapid eye movement and rapid eye movement , sleep . Um Each cycle starts with a progressive deepening of non rapid eye movement sleep from lighter and N one and N two stages , culminating in the deepest part of sleep , the most restorative part of sleep and three , and that deepening consists of progressively increasing density of slow wave activity . And then we see N three sleep and then each uh each , each period of non rem sleep is then followed by a period of rem sleep uh which you can see in the green and rem rem sleep actually has very fast activity very similar to uh to wakefulness . So , so very different from the , from uh non rem sleep with the , the slow waves which we believe are really convey the restorative aspects uh uh to sleep . Now , as , as we see with each cycle , the duration of the deep N three uh period decreases as sleep drive is slowly dissipated during the course of the night . Overall , only about 20% of a full night of sleep really represents this deep restorative sleep or N three sleep . And , and actually the amount of slow wave activity during N three really varies from individual to individual . But even in the , in the , in uh individuals with the greatest density even of uh slow waves . In N three sleep , there's still plenty of room to increase uh or enhance slow wave activity even in that deep part of sea . Uh Next slide , please . Uh So let's take a little uh a little closer look at individual slow waves . So each , each cycle of the slow oscillation or slow wave activity in sleep consists of two distinct phases . The so-called upstate which is early periods of uh positive polarity , neuronal excitation and firing of action potentials or um electrical potentials uh similar to wakefulness actually . And this lasts for a period of 4 to 500 milliseconds . And each upstate is then followed by a so-called downstate a , a period of deep negative potential hyper polarization in which all neurons in the uh in the cortex are completely silent , complete neuronal inhibition . So slow , slow waves alternate between these up and down states um which are highly synchronized among all neurons across the cortex and next slide . Uh So the , the , the uh top of this uh uh figure uh depicts um a few cycles of the slow oscillation in deep N three sleep . And the bottom part actually depicts the electrical activity of a single neuron during that same time frame . And we can see an arrow please . And we can see during the upstate , this neuron is firing action potentials . Those are those upward , very brief spikes of depolarization kind of like wakefulness . But what what we see is they're interrupted periodically every few 100 milliseconds by these deep um periods of hyper polarization where there's where negative periods where the uh the neurons are completely electrically silent . And that's really the characteristic of uh non rem sleep and particularly um deep non rem sleep . Now , when millions or even tens of millions of neurons are synchronized um in this activity . So , there are these down states , these periods of um normal silence are co occurring . Uh We actually see that reflected in the surface eeg with , with those upward deflections . Um The polarity is reversed with the the actual surface eeg . So um negative polarity events are upward deflections that's just to confuse uh beginning electroencephalographer . But we , we can see that each downstate in the neuron um is reflected by a downstate um over the whole population of neurons in the eeg . Next slide . Another poll question . So how many stages of sleep are there ? I think I've probably already given this way a bit . This is kind of a trick question because um a little about uh 15 years ago , uh there was sort of an update on sleep scoring and sleep stages . So the correct answer is yes , most of you have it is four a next thick slide . Um I think we're missing a , a slide here , there was a slide uh showing um sleep stages and sleep cycles . No , I guess it's gone . So we'll , we'll skip that if you could go back to the previous slide . Well , I there was a slide that showed a hypno gram which is the sleep architecture during the course of the night . And there are indeed four stages of uh a sleep rem sleep and then three stages of non rem sleep . For those who said five , there used to be four stages of non rem sleep , but they were condensed stages , three and four were condensed into uh into N three . And basically the , the um but , but , but basically , there are several cycles , sleep cycles throughout the course of the night , alternating between rem and non rem sleep with uh with a progressive deepening of sleep . Now , um the question may , may come up as um what exactly and what I want to address here with the physiology of sleep is um what , what actually causes the homeostatic drive for sleep ? That is to say , why do we need uh sleep slow waves ? The sleep , slow waves are indeed what , what conveys uh their shortest properties to sleep ? Well , um two things in particular that I like to touch on . One is uh neuronal damage with sustained wakefulness . You increasingly get damage to DNA and other organelles uh in neurons that require repair . Now , the down states of electrical silence are , are really what um provides an opportunity for repair because a neuron can't repair itself while it's actively firing action potentials or while it's um a receiving excitation from other neurons . So that 400 millisecond down state is really what is necessary uh for , for neuronal repair . And it's really the only time in , in one day is the only and sleep is the only brain state that can provide that electrical silence . Now , a one down state is only about 400 milliseconds . But over the course of an eight hour period of sleep and hundreds or thousands of slow waves , one actually has about 15 to 20 minutes of electrical silence to perform this this repair operation . Now , the other thing that um drives the need for sleep slow waves is the sensory experience that we um that we have throughout the day , we're constantly bombarded with information from our environment that these increased excitatory synaptic connectivity in the cortex learning . And this consists of increased connections among the neurons or synapses as well as an increased increase in the strength of individual connections or synapses . And this increased connectivity progressively leads to a a , an a an impairment in information processing once it gets above a particular range . And also it leads to increased excitability that ultimately can predispose to uh seizure activity . Now , it turns out that the alternation between up and down states of slow wave activity weakens syna synapses that have not been tagged for retention due to the salience of the information that's encoded in that in the new synapse or in the increasing strength of the synapse , the next slide . So this , this uh yeah , actually , if you can go back to that . So if we think about the increase in the homos static drive during wakefulness and its dissipation during sleep , we can sort of think of this as an increase in synaptic strength , synaptic potentiation that's , that's corrected by synaptic downscaling that takes place during sleep or reduction in synaptic strength . Ex uh Next . So if we go sort of go back to um look at uh the eeg during different brain states and then normal activity during those brain states . Here , we have wakefulness with the eeg on the top again , low voltage fast activity and then the uh the the electrical firing properties of six neurons across the six rows below with each little tick mark representing an action potential . Each of the six rows , six different neurons , we can see they fire at different rates . But what we see is , and we're looking in the upper left here . But what we see is uh that there are never any coordinated brakes , synchronized brakes and firing . And that's wakefulness . There's really sustained activity throughout that period of wakefulness leading to damage to , to the neuron itself as well as increased connectivity . Uh Next . Uh Next . Well , here we have uh the same eeg and the same six neurons during deep non rim uh sleep stage N three sleep , what we can see is intermittent firing during the what correlate with upstate and , and periodic sustained uh synchronized rates in firing amongst all six neurons that are reflected in the eeg as these upward deflections of surface negativity or so-called downstate . OK . Uh Next . Now , with insufficient sleep or with sustained wakefulness as an early sleep deprivation , the need for these uh slow waves , these downstate for normal repair and neuronal pruning um is is so profound that these downstate start to intrude on wakefulness and that interferes with information processing processing . It interferes with cognition next . And if we stay out , if , if sleep deprivation continues , this gets dramatically worse , more and more of these these breaks um in the in in uh neural firing that are synchronized um and , and interfere with uh information processing . And in fact , the eeg of late sleep deprivation looks very similar to the eeg of deep non RM sleep or N three sleep . And in fact , one is really half asleep uh during , you know , a prolonged period of sleep deprivation . OK . Next slide . So what if we could find or devise some sort of methodology to enhance slow wave activity during a restricted period of uh of sleep so that we could potentially enhance the restorative value of that sleep and and make those individuals less vulnerable to the negative effects of having uh insufficient sleep , the negative effects on cognition . Next . Well , this would benefit both active duty service personnel who regularly experience restricted sleep opportunity as well as a host of uh patients with various neurological and psychiatric disorders that are associated with reduced slow wave activity . Next . So this is just a partial list of neurological disorders associated with varying degrees of decreased uh slow wave activity during sleep , uh traumatic brain injury , stroke , multiple sclerosis and Alzheimer's disease . Next , as well as psychiatric disease . PTSD depression and schizophrenia . Next slide . So we hypothesized at uh at the rare Sleep Research Center , could we conceivably use transcranial electrical stimulation or specifically ? So , oscillatory transcranial direct current stimulation without getting into what exactly what that is to administer a weak current through scalp electrodes . This current oscillating at the peak frequency of the endogenous uh slow oscillation or slow wave activity of 0.7 Hertz in order to stimulate or entra neurons of the cerebral cortex to oscillate with that current and therefore increase uh slow wave activity in the brain and therefore enhancing or accelerating sleep's restorative process . But by essentially transitioning light sleep into deeper N three sleep by creating uh exogenously uh slow wave activity there and also enhancing the power of slow wave activity during deep n three sleep . Uh Next slide . And this is a little schematic of our uh study designed to use TES to enhance slow wave activity . Um Each bar represents one night in the study with uh the height of the bar uh representing approximately the duration uh uh of sleep . And we randomized 27 healthy adults into one of two groups . A stimulation group receiving the slow oscillatory transplanting electrical stimulation or a sham group that didn't receive the stimulation . The first phase of the study with the blue bars that consists of seven days at home in which we recorded the uh sleep wake activity of participants uh and had them sleep at least eight hours in bed per night to make sure they didn't come in with a whopping sleep debt . Second part of the phase with the , with the green bars was uh three nights of 10 hours in bed uh in the sleep lab , which we call sleep satiation to further reduce any residual sleep debt that may have existed . Coming into the lab on the fourth night in lab , uh participants got only a two hour sleep opportunity between 11 , 100 and 0 100 . And during the second hour of that , uh of that two hour period received either the slow oscillatory stimulation or a sham stimulation . And then immediately after that two hour period of sleep , uh these participants were were subjected to a 48 hour or 46 hour period of total sleep deprivation in lab . Uh And then this was followed up by two consecutive eight hour nights of recovery sleep . Uh Also in the lab . Now , performance uh was tested with a an intentional vigilance task every 75 minutes while awake during the last five in lab uh days of the study , the baseline day before the two hour uh sleep opportunity with simulation during the two days of sleep deprivation . And the two days after the two recovery nights of sleep next slide and just some more details about the stimulation procedure itself . So , the stimulation consisted of 60 minutes of stimulation at 0.75 Hertz of an oscillation um with five minutes , five minute periods of stimulation , alternating with one minute periods of interstimulus intervals . And the oscillation had this trapezoid trapezoidal um shaped meant to um mimic the endogen , the shape of the endogen endogenous . So , oscillation and oscillated between zero and 260 micro amps of current , which is a very weak current . In fact , um you wouldn't be able to feel 260 micro aps of current . Uh If you were awake , the sham stimulation uh consists of a , a 60 minute period of stimulation at zero amps of current . And the uh electrode uh circuit uh is bihemispheric with um a bilateral an Anno electrodes in the frontal regions of the brain with positive current injected into those anote electrodes . And then the circus is completed with the current traveling through the brain . The cathode electrodes located in the mastoid or behind the ears uh again by hemispherical and next slide . So we assessed cognitive function attention with our psychomotor vigilance test or PV T Um and this was administered , as I mentioned every 75 minutes while in the lab and while awake , and this uh test consists of targets appearing on a computer screen at varying interstim stimulus intervals for a 10 minute period . And participants are required to press a key immediately or as fast as possible when they perceive a target . And again , this is determined , this this takes , takes place over a 10 minute period And reaction times are calculated in terms of the time to detect these stimuli and reaction times are very sensitive to , to sleep loss . As you might imagine these down states occurring . Um If that , if that occurs , uh if do , if that occurs right before or during one of these targets , clearly , it's gonna dramatically affect uh reaction time . My next . So you have two minutes remaining in the presentation . Yeah . OK . And here are the results of the study . Um And we can , we can and ba basically what this uh figure uh shows are um average reaction times for each of the two groups um over for , for each uh time point during the study in which um the PV TD data was collected during the two baseline days , the two sleep deprivation days and during the two recovery days after the night of the , the two recovery nights of sleep , the gold arrow indicates the um period of stimulation at the end of the baseline day . The blue line represents data for the sham group and the red line for the stem group . And what we can see we're here really is that the stem group is really outperforming the sham group um at all points after the , after the period uh of stimulation that's really quite robust during the second uh days of um sleep deprivation where um where the reaction times are really quadrupled uh for the sham group , but they are only modestly increased for the stem group . Next slide . And here is that same data that collapsed uh uh across each day showing again that the student group is outperforming the Shan group and every day and is statistically significant on the second day of sleep deprivation next slide . Um and we can skip this slide and I'll just go to the uh to the conclusion . So the conclusion here is that this , this mechanism , this methodology soto trans pain , direct current stimulation during a portion of her period of sleep enhances sleep restorative properties and thus accelerates the dissipation of sleep drive . So that less sleep duration is required to attain a certain level of recuperation or to maintain a certain level of performance during subsequent wakefulness . And uh SOTD CS also allows less post uh sleep deprivation , recovery sleep to return to return performance to baseline . And finally , in addition to um its potentially use in our active duty service members with uh restricted sleep , um SOTD CS may have the therapeutic beneficial to treat a whole host of neurological and psychiatric conditions character characterized by reduced slow wave power , including M TB I and PTSD . So I guess we're at the end here . So you can uh peruse the uh overall takeaways on your own . Doctor Hughes and Doctor Alger . I do just want to say thank you so much for this presentation and to help share with us the critical role that sleep plays in not only our health but our everyday performance . So , unfortunately , you're correct . We are at the end of the time and we unfortunately don't have time for questions . There are however , questions in the chat . So if either one of you are able to type responses in the chat , that would be greatly appreciated , I believe by our audience .