It is my pleasure and honor to introduce our guest speaker today. We are very lucky to have Dr. Ruth Benca as our guest speaker in this class today. Dr. Benca, I'm going to share a very brief bio because otherwise, I'm going to be standing here for an hour introducing you. Dr. Benca went to Harvard for her undergrad studies and then she went to University of Chicago to get her MD and PhD. At University of Chicago, she also completed a residency in Psychiatry and a fellowship in Sleep Medicine or Sleep Sciences? Sleep Medicine. Dr. Benca is currently a Professor in School of Medicine and also the Chair of Psychiatry. She's going to talk to us about sleep medicine, sleep sciences, and the research that she has been doing for the past few decades. Thank you. Thank you. I'm glad you've heard about exercise and diet, and those are really important. But the third leg of that stool is sleep because diet and exercise don't work as well if you don't sleep, which we're going to talk about. Actually, some of the work we're doing is starting to suggest that one of the ways exercise helps your brain is through its effects on sleep and it works better when you sleep more. To get started, I just want to point out that this is data from the Bureau of Labor Statistics. Looking at the US life expectancy and how we spend our time, we spend more of our life asleep than doing any other one thing. Over a third of our life is spent sleeping. That's because, as I'm going to try to get across, sleep is a critically important function, not only for your brain but for the rest of your body and for your health in general. Then when we short change our sleep, we cause problems. Now, does anybody knows who this is? You're all too young, right? Anybody heard of Warren Zevon? No. Werewolves of London? No. I guess I'm dating myself. He was a very famous musician and he wrote this book, I'll Sleep When I'm Dead. In fact the message I want to get across to you, this is, I think the attitude of a lot of people, "I don't have time to sleep. I have much more important things to do. I'll sleep later. I'll sleep when I'm dead." If you don't sleep, you'll die. That's how I got into sleep research. I'm dating myself now. In the 1980s it was shown for the first time that when mammals are sleep deprived, they can't survive. This was work that was done by Dr. Alan [inaudible] and at the University of Chicago. He showed that if you sleep deprive a rat for about a week or so, it can't survive. Probably the same thing is true for us, but fortunately, we would probably have to be sleep-deprived a lot longer and we haven't done those experiments and won't. Today what I want to do just very briefly is talk about a couple of different things; what sleep is, why we sleep, and what happens when we don't sleep enough. We'll start out by talking about what sleep is. Sleep is an interesting behavioral state. First and foremost, it is characterized by reduced responsiveness to the environment. We generally sleep in a typical position, our anti-gravity muscles are relaxed and in fact, it's hard to sleep when you're standing up. We are not aware of what's going on around us, but it's a reversible state, meaning that we can be awakened with enough sensory input. It's different from being in a coma or from hibernating or some other type of state where we're still alive but we can't be aroused easily. I'm not going to go over this in great detail, but one of the things we do to detect whether people are sleeping or not in the way we study sleep is we look at brainwave activity. Our brain goes through different patterns of activity, the neurons fire differently when we're asleep. Some of these particular waveforms in sleep, I'm just going to point them out, this is a sleep spindle here, this little fast burst of activity or these deep, slow-waves, deep sleep, are really important for brain function. We have two kinds of sleep. The majority of our sleep, about three-quarters of our sleep is called non-rapid eye movement sleep and about a quarter of it is REM sleep, rapid eye movement sleep, sometimes called dreaming sleep because we do more dreaming when we're in REM sleep than in any other sleep stage; although you can dream in any stage of sleep. In a normal adult, sleep looks like something like this across the night, which is that you should fall asleep within about 15 minutes or so of closing your eyes and turning off the lights. You go into a period of non-REM sleep with deep sleep, deep non-REM sleep at the beginning of the night. Then about every 90 minutes, you cycle back and forth between non-REM and REM sleep. The two changes across the night as you have more deep sleep at the beginning of the night and your sleep lightens up to some extent as the night goes on and you have longer and more intense periods of REM sleep as the night goes on. That's why the dreams you have in the early morning just before you wake up are sometimes the longest and most intense. Now the thing that affects sleep the most is our age. There are dramatic changes across the lifespan and the amount and kinds of sleep we have. This is not a linear scale here. This is birth. This is two years old here, five, 10 years old here and then everything gets crunched after that. We know that sleep is critically important for brain development. Does anybody know when the brain finishes developing, what age? What? About 25. In the middle of your third decade, your brain finishes developing and your sleep changes throughout that time, and we can actually use sleep almost as a brain imaging tool to look at brain development and changes in sleep parallel to this change in brain development. That's why sleep, as you see from birth, a newborn spends about two-thirds of the time asleep. Then by the time we get to be into that third decade or so of life, we start to stabilize. Then as we get older, we sleep less, we have less REM sleep and we have less deep sleep, and we don't know whether it's that we don't need as much sleep as we get older or we're just not as able to sleep and it's probably a little bit of both. The next thing I want to talk about is why do we sleep? Sleep is one of the biggest mysteries in biology. We know a lot about many of the other behaviors we engage in, but it's only been fairly recently that we're starting to understand why we spend so much of our lives in such a vulnerable useless state, just lying there sleeping. So it's not surprising that sleep is critical for a number of vital functions. First and foremost, sleep is important for brain plasticity and that is in larger synaptic things. Why we can learn and remember. Our brain is different each day because of the experiences we have, and it's different every morning from how it was the night before. This was a theory that was developed by my colleagues when I was at the University of Wisconsin, doctors Giulio Tononi and Chiara Cirelli. You all know that there are neurons in the brain. We hear about neurons a little bit. Okay. Good. You know it. Your brain has neurons. These neurons talk to each other because they have synaptic connections. They have processes that touch each other and that's how they transmit information. As the day goes on while we're awake, we are learning all the time. Even when you don't think you're learning just by being awake and alert, you are learning about your environment and when you're studying you are learning even more. When you're exercising, you're learning, when you're playing sports you're learning. While we're learning, these synaptic connections become stronger. The problem is that if we just kept learning and we're awake all the time, our synaptic connections would keep getting stronger, and eventually, our brains wouldn't fit in our head. We'd have a big signal-to-noise ratio problem. We have all these connections that would be getting across. The other issue is that the more synaptic connections in the brain, the more energy is required and your brain actually uses a lot of energy. It's going to take up more space. It needs more fuel. What are the things that happen during sleep of a large majority of what's happening to your synapses, your brain connections? Is they are getting pruned. About 80 percent of what's going on at night is you're cleaning out or doing housekeeping and synapse is getting rid of synapses. By the same token, about 20 percent, you're strengthening synapses. As you keep learning new things, your brain can change. That's why actually, a lot of the function of sleep is important for memory. Many of the things that you need to learn are sleep-dependent. Not everything we learn a sleep-dependent but a lot of them are. Another thing we now know about sleep is that it's important for what some of us like to call brainwashing. That is, that there are a lot of toxic substances that accumulate in the brain, particularly substances that lead to conditions like Alzheimer's disease. We now know that during the night, the fluid that your brain sits in the cerebral spinal fluid washes through the brain during sleep because the spaces between the neurons and the spaces around the vessels open up and allow that fluid to flush through and some of the rhythmic brainwave activity pushes that fluid through and cleans up the garbage in your brain.
