 Hi, and welcome back to the biological psychology video course in this video video 6.4 We're going to take a look at sleep and dreams Now so let's start with the very basic question. What is sleep sleep is characterized by low levels of physical activity Right, so if an animal or a human is sleeping generally speaking That person or animal doesn't do much Low body temperature your your your body temperature goes down if you're asleep and Reduced or perhaps an altered form of consciousness, right? There is something to be said for the idea that if you're sleeping Especially if you have vivid dreams that that is a level of consciousness But it is definitely very different from the consciousness that we have during alert wakefulness So why do we sleep that is a very Good question and one that we don't really have an answer to but there are a few possible functions so one function is That we sleep to allow the body to restore Now that's I think that is an answer that you will hear quite often But it is essentially a non-answer. I think it is it is kind of it Tricks you into thinking that it's an answer But it's not really because it leaves the question open of what it means to restore, right? What what exactly does it mean for our body to restore? I mean I understand that I can be tired and then when I sleep I wake up and I'm I'm I'm Rested again, but what exactly happened? What is this restoration process that happened? And why is it not possible to to restore while we're awake, right? So I can imagine that if you've been if you've exercised a lot of visual physical activity that your muscles need some time Maybe to restore whatever that may mean But why is it not enough to simply sit down in the chair wait for a little bit and then get up again, right? Why do we need to sleep in other words? I would say that allowing the body to restore as an answer to the question Why do we sleep is not a very satisfactory answer? Here's another answer Conserving energy during inefficient periods. That's kind of sounds kind of abstract, but the idea is very simple And I think it's actually very insightful insightful answer So the idea is for us the night is an inefficient period because in at night We are not going to hunt for food. We are not going to pick berries. We simply We're just wasting energy really, right? It is not a period for us in which we do anything that is useful for our existence So the best thing that we can do then if it is night is simply shut down and use as little energy as possible and That's why we go to sleep simply to conserve energy until it becomes light again And then we can start doing things again that makes sense, right? That help us survive right so essentially sleep is a way to skip those periods of the day that are not very useful to us Another function of sleep is memory consolidation now This is an answer To some extent it is certainly true that memory consolidation does happen during sleep So if you have learned something and then you sleep then you know that better when you wake up, right? You've learned it better when you wake up that no there's no doubt that that is the case The question is whether we would really well whether we really need sleep in order to do that or whether it would also Be impossible for us to have some form of Memory consolidation that does not require sleep right is memory consolidation really why we sleep you could say or Do we happen to perform memory consolidation during sleep because we were not doing much else during sleep to begin with? So I think memory consolidation is not really a very satisfactory answer to why we sleep Even though we clearly do exhibit memory consolidation during sleep So but we don't know why we sleep not really to me the the idea that we that it conserves energy during inefficient periods is the most Attractive idea, but honestly we don't really know But we do know that sleep is clearly important and that if you don't sleep enough That is very bad for you And if you really don't sleep enough eventually you will die right so sleeping is really an important Important aspect of life you should get enough sleep And you don't need to know why in order to do that Now sleep is often subdivided into different stages Two general stages are generally separated stages without rapid eye movement Non-RAM sleep so RAM stands for rapid eye movement and these this the rapid eye movements are literal right in the stages with rapid eye movement These are those stages are called such or that stage stage 5 is called such because our eyes really move rapidly And even though the eyes are closed you can see the eyes move rapidly behind the eyelids So in in stages 1 to 4 of sleep our eyes do not really move very rapidly and in stage 5 Our eyes do move very rapidly and that is an important distinction that we make And these stages are traversed in more or less a fixed order. So this is just an observation We don't really understand why and what that means, but clearly that is what happens So stage 1 of sleep is non-RAM. So we our eyes don't really move And it's kind of a transition between wakefulness and sleep very similar to just be being really relaxed and Characterized by a particular type of brain activity that is called alpha and theta waves Which are low frequency high amplitude brain waves So essentially if you would measure a lot of sleep research is done with EEG where we measure Electrical activity on the scalp and if you measure if you measure low frequency high amplitude brain waves Then you know the person may be in stage one Stage one sleep, even though we don't really know what that means or what that signifies Now if people are Woken during stage one sleep they often claim that they haven't slept right and this is actually quite common in sleep if People are very bad at knowing whether they slept or not and for example people who are exhibit insomnia Which is a very awful thing to suffer from sleep more than they then they claim right So if you for example, if you've had a very bad night and you feel like I haven't slept at all That's probably not true You probably did sleep a very large proportion of the night It's just that you slept very poorly and you didn't really rest very well, right? Now then we have stage 2 sleep stage 2 sleep is again non-RAM sleep and if you measure EEG It is characterized by theta waves interrupted by brief bursts of activity Then we have states 3 and 4 slow wave sleep a very similar right there distinguished for a reason that to me is not clear But they are very similar stages of sleep again non-RAM Characterized by so-called delta waves, which are even more low frequency and high amplitude than the alpha and theta waves And if you wake someone up during stage 3 or 4 sleep they often feel very groggy Right, so it is really a type of sleep You should not wake up during stage 3 or 4 sleep makes you feel bad for whatever reason and Then we have stage 5 sleep and that's the REM sleep and that's the most famous form of sleep Sometimes also called paradoxical sleep when it was studied first with with animals people tended to call it paradoxical sleep Nowadays people tend to call it REM sleep, but it's the same thing and It's accompanied by eye movements with the eyes closed and the brain activity is very similar to Your brain activity during wakefulness and it's strongly associated with dreaming So it seems to be the case to some extent at least that during REM sleep stage 5 sleep You are basically conscious to some extent in your dreams and you're doing all kinds of things and your eye movements reflect that Right, so you're essentially looking around in your dreams. You could say and in real life your eyes also move The rest of your body is paralyzed And that is presumably why you are not actually moving right so your your body movements are Inhibited you are paralyzed so that you don't really exercise your dreams Which would be very dangerous of course, but the exception being your eyes because you can freely move your eyes, right? That's not dangerous. So presumably that's why your eyes are not paralyzed during REM sleep That's the idea So it used to be Said that dreaming was exclusive to REM sleep nowadays I think it's clear that dreaming occurs to some extent in other stages of sleep as well Although they might be different forms of dreaming. So for example REM sleep I have is really that kind of storytelling narrative Dreaming where you really have some kind of adventure, right? You're experiencing something vivid dream Whereas dreams in the other stages of sleep may be more Emotions or pictures, right? So for example, the feeling that you're falling is not really story. That's unfolding Right, it's not really what you would dream during REM sleep But it may be an it's a dream of sorts nevertheless and it probably happens during different types of different stages of sleep Now now that we've talked a little bit about dreaming. What are dreams really dreams are these well They are these narratives that happen when you're asleep, right or feelings that you have when you're asleep We know very little about dreams Best we know dreams are essentially pretty much random activity that is based on recent experiences, right? So we tend to dream about recent experience or Experiences or thoughts if we have if you've experienced something that was quite salient during the day You're quite likely to dream about it if you have been on your phone On Facebook messaging your messenger until 3 3 a.m. Before you all fall asleep You're quite likely to dream about that right because that's then very salient and on your mind Now the idea is that basically this happens because Activity that you that you had in your brain before you were asleep is very easily activated So basically if you have some if you were thinking about a person that person is already kind of have activated in your in your brain And then when there is some random activation that person becomes really active and you start dreaming about that person Right that does not really answer the question why also for example There are a lot of very stereotype dreams right that that things like dreaming that you are naked in a socially inappropriate situation Dreaming that you have things in your mouth dreaming, you know, very there are very various quite stereotype dreams that a lot of people have Why that is is to as far as I know not not not really known Now when we talk about dreams, I think we cannot not talk about Sigmund Freud However much I would like to not talk about Sigmund Freud because Sigmund Freud famously proposed that dreams have a deeper meaning Right, so in he talked about the manifest content Which is what the dream really was so you might for example dream that your teeth are loose in your mouth That's another very common dream that people have and then according to Freud that that dream is not really about your teeth being Losing your mouth, but it conveys some kind of deeper meaning. There's some latent content And for example in this case that might mean that you have very little self-confidence, right? So according to Sigmund Freud and other people Your dreams are like symbols and if you know how to interpret those symbols, you can sort of figure out what's on someone's mind now Dreams do kind of represent something, but I think they represent something in fairly trivial ways in the sense that they represent To some degree what is has been on your mind But the idea even though this is still a popular belief the idea that dreams reflect in any meaningful way Something else than what they manifestly are is as far as I know completely unsupported by any evidence It's probably complete nonsense. So don't start interpreting your dreams in this kind of with these dream interpretation things They don't really mean anything if you if you dream that you you stand in front of your class naked Then that is a form of embarrassment that's probably been on your mind But there's not some kind of very deeper meaning there that you can disentangle by by by some kind of Freudian Logic right dreams are probably quite trivial in that in that respect Now with that we've arrived at the end of this section on on attention and consciousness. Thank you very much for your attention